Open the (mosfet) gate!

[Jim Thompson]

On Thu, 1 Jun 2017 08:16:08 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

Thanks,

Michael

What level is your initial signal source, 0->5V, or 0->15V ?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:

On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C

 

On Thursday, June 1, 2017 at 8:28:01 AM UTC-7, Jim Thompson wrote:

On Thu, 1 Jun 2017 08:16:08 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

Thanks,

Michael

What level is your initial signal source, 0->5V, or 0->15V ?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

5v (Arduino PWM output port).

 

On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C

Ok thanks. I'll look into the common collector circuit then.

Michael

 

[George Herold]

On Thursday, June 1, 2017 at 12:37:17 PM UTC-4, mrda...@gmail.com wrote:

On Thursday, June 1, 2017 at 8:28:01 AM UTC-7, Jim Thompson wrote:
On Thu, 1 Jun 2017 08:16:08 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

Thanks,

Michael

What level is your initial signal source, 0->5V, or 0->15V ?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie


5v (Arduino PWM output port).

Just drive it with the Arduino output. That should be fine.

George H.

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:

On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?

The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?

--

Rick C

 

On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?

Ah. That explains a lot. No.

The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?

To make it fun, and to learn something new.

I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

Thanks,

Michael

 

On Thursday, June 1, 2017 at 10:04:14 AM UTC-7, George Herold wrote:

....

5v (Arduino PWM output port).

Just drive it with the Arduino output. That should be fine.

George H.

That's what I'm doing now, with an IRLZ34N.

Yeah, perhaps adding a PN2222 to amplify the voltage will introduce more losses than the Rds,on loss I'm taking by operating at just 5V (below Vgs,max).

I found this. Pretty. $0.57 for one, Rds,on = 6.2 mOhm (~10 mOhm at 5v).
http://www.mouser.com/ProductDetail/ON-Semiconductor/NTD4858N-35G/?qs=sGAEpiMZZMshyDBzk1%2fWixfVkyZTkH1qmpZ0twx7Ko0%3d

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:

On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


> I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?

--

Rick C

 

On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?

It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:

On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C

 

On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C

Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 6:25 PM:

On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C


Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Not really. If you are driving this with a PWM signal, that is just on or
off with variable timing. That would normally be driven by writing a one
or a zero to an I/O pin. Writing an integer to a DAC gives signal with many
values that will turn the drive on to a range of strengths which is pretty
much the opposite of PWM. Or are you calculating a value of 0 or 255 and
nothing in between to drive the DAC?

--

Rick C

 

On Thursday, June 1, 2017 at 3:34:29 PM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 6:25 PM:
On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C


Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Not really. If you are driving this with a PWM signal, that is just on or
off with variable timing. That would normally be driven by writing a one
or a zero to an I/O pin. Writing an integer to a DAC gives signal with many
values that will turn the drive on to a range of strengths which is pretty
much the opposite of PWM. Or are you calculating a value of 0 or 255 and
nothing in between to drive the DAC?

--

Rick C

Oh, I guess the Arduino is unique then.

Here's a description of analogWrite.
https://www.arduino.cc/en/Reference/analogWrite

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/1/2017 6:46 PM:

On Thursday, June 1, 2017 at 3:34:29 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 6:25 PM:
On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C


Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Not really. If you are driving this with a PWM signal, that is just on or
off with variable timing. That would normally be driven by writing a one
or a zero to an I/O pin. Writing an integer to a DAC gives signal with many
values that will turn the drive on to a range of strengths which is pretty
much the opposite of PWM. Or are you calculating a value of 0 or 255 and
nothing in between to drive the DAC?

--

Rick C


Oh, I guess the Arduino is unique then.

Here's a description of analogWrite.
https://www.arduino.cc/en/Reference/analogWrite

No, it's not unique, I'm just not familiar with the libraries for the
Arduino. This one is called "analog" when it is actually PWM. I expect it
uses PWM hardware built into the MCU chip you are using. There is no DAC,
it is a counter/timer instead.

--

Rick C

 

On Thursday, June 1, 2017 at 5:55:50 PM UTC-7, rickman wrote:

mrdarrett@gmail.com wrote on 6/1/2017 6:46 PM:
On Thursday, June 1, 2017 at 3:34:29 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 6:25 PM:
On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C


Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Not really. If you are driving this with a PWM signal, that is just on or
off with variable timing. That would normally be driven by writing a one
or a zero to an I/O pin. Writing an integer to a DAC gives signal with many
values that will turn the drive on to a range of strengths which is pretty
much the opposite of PWM. Or are you calculating a value of 0 or 255 and
nothing in between to drive the DAC?

--

Rick C


Oh, I guess the Arduino is unique then.

Here's a description of analogWrite.
https://www.arduino.cc/en/Reference/analogWrite

No, it's not unique, I'm just not familiar with the libraries for the
Arduino. This one is called "analog" when it is actually PWM. I expect it
uses PWM hardware built into the MCU chip you are using. There is no DAC,
it is a counter/timer instead.

--

Rick C

To get a PWM frequency of greater than ~500 Hz, I might have to use these functions anyway

https://www.arduino.cc/en/Reference/DelayMicroseconds

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/2/2017 11:22 AM:

On Thursday, June 1, 2017 at 5:55:50 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 6:46 PM:
On Thursday, June 1, 2017 at 3:34:29 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 6:25 PM:
On Thursday, June 1, 2017 at 2:40:03 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 4:30 PM:
On Thursday, June 1, 2017 at 12:58:16 PM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 1:24 PM:
On Thursday, June 1, 2017 at 10:17:01 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 12:37 PM:
On Thursday, June 1, 2017 at 9:21:59 AM UTC-7, rickman wrote:
mrdarrett@gmail.com wrote on 6/1/2017 11:16 AM:
On Wednesday, May 31, 2017 at 4:58:32 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 13:11:02 -0700 (PDT), mrdarrett@gmail.com wrote:

On Wednesday, May 31, 2017 at 12:22:00 PM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson


How slow is slow? Operation would be restricted to below 30kHz, 1kHz, ???

Would increasing the resistor to 47k improve anything?

Michael

Frequency isn't the main event, it's risetime. You'd have to simulate
with a known MOSFET AND defined load.

...Jim Thompson


Since the NPN gate driver inverts the input signal, is there a PNP solution that won't invert it?

When used in the same configuration, both NPN and PNP will invert the
signal. Inversion is a function of circuit topology. A common emitter
circuit inverts. The common base and common collector circuits do not invert.

--

Rick C


Ok thanks. I'll look into the common collector circuit then.

The common collector configuration provides no voltage gain, only current
gain. Will that work for you?


Ah. That explains a lot. No.


The common emitter configuration provides no current gain, but provides
voltage gain.

The bottom line is driving MOSFETs has been done before and optimized. Why
reinvent the wheel?


To make it fun, and to learn something new.

That is certainly a valid reason.


I suppose I'll try using the inverting common emitter and just update my Arduino code with analogWrite( 255 - value ).

I'm a bit confused. Is this a discrete control or a proportional control?
What exactly is this controlling?


It's controlling a coolant pump motor. If I look over at the thermometer and the temperature is too high, I type say for instance a "6" on my laptop, and it sends a 60% PWM duty cycle to the pump motor to send cooling water. It's laughable for now, but it took me a year to get the dang thing built, and it works for now. Someday I'll get around to getting a thermistor (maybe from the car's coolant sensor) and installing it, and getting some PID control in there. Someday.

Where does the analog output come in?

--

Rick C


Does this clarify?
http://mrdarrett.5gbfree.com/pwm.jpg

Not really. If you are driving this with a PWM signal, that is just on or
off with variable timing. That would normally be driven by writing a one
or a zero to an I/O pin. Writing an integer to a DAC gives signal with many
values that will turn the drive on to a range of strengths which is pretty
much the opposite of PWM. Or are you calculating a value of 0 or 255 and
nothing in between to drive the DAC?

--

Rick C


Oh, I guess the Arduino is unique then.

Here's a description of analogWrite.
https://www.arduino.cc/en/Reference/analogWrite

No, it's not unique, I'm just not familiar with the libraries for the
Arduino. This one is called "analog" when it is actually PWM. I expect it
uses PWM hardware built into the MCU chip you are using. There is no DAC,
it is a counter/timer instead.

--

Rick C


To get a PWM frequency of greater than ~500 Hz, I might have to use these functions anyway

https://www.arduino.cc/en/Reference/DelayMicroseconds

I can't imagine a PWM timer would only work up to 500 Hz. Rather than
relying on canned I/O routines, I suggest you read the data sheet for your
device and program the PWM counter directly. I think the library code is
leaving out a *lot* of capability.

--

Rick C

 

[Jim Thompson]

On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |

Thinking outside the box... producing elegant solutions.

"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie

 

On Friday, June 2, 2017 at 10:34:19 AM UTC-7, Jim Thompson wrote:

On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson

It looks like 20 mA per pin. The Arduino Uno that I'm using uses an ATmega328p.
https://www.arduino.cc/en/main/arduinoBoardUno

Michael

 

[rickman]

mrdarrett@gmail.com wrote on 6/2/2017 3:08 PM:

On Friday, June 2, 2017 at 10:34:19 AM UTC-7, Jim Thompson wrote:
On Wed, 31 May 2017 12:21:52 -0700, Jim Thompson
To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

On Wed, 31 May 2017 11:41:33 -0700 (PDT), mrdarrett@gmail.com wrote:

On Tuesday, May 30, 2017 at 8:06:00 PM UTC-7, Tim Wescott wrote:
On Tue, 30 May 2017 13:37:10 -0700, mrdarrett wrote:

[snip]

I'm wondering if a voltage amplifier could be used to shove 15V or so to
the gate... and I could use a cheaper IRF530 / standard MOSFET.

If you're just switching the thing on and off, and if you have 12 or 15V
available, you want a gate driver. There's a plethora of them out
there. And lots and lots, too.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com


A gate driver would work, but how about this?
https://arduinodiy.files.wordpress.com/2012/05/fet2.gif

Michael

That works, sort of... beware the slow risetime of the gate voltage,
10K and the gate capacitance might result in substantial dissipation
during turn-on.

...Jim Thompson

What are the source/sink current specs on the Arduino output pin?

...Jim Thompson


It looks like 20 mA per pin. The Arduino Uno that I'm using uses an ATmega328p.
https://www.arduino.cc/en/main/arduinoBoardUno

I don't think that is the relevant spec. That number if a guaranteed spec
for continuous operation. To determine the rise/fall time of the gate
voltage you need to know the *actual* current over the range of voltage as
the gate capacitance charges. They may have a curve showing this, but it
won't be a single number.

--

Rick C