NE555 versus TLC555 ??

[Dave, I can't do that]

Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

Thanks

Dave

 

[John Fields]

On Sun, 3 Aug 2008 11:35:17 -0700 (PDT), "Dave, I can't do that"
<davenpete@gmail.com> wrote:

Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

---
It depends on the circuit.

Post it somewhere and let's have a look.

JF

 

[Tim Wescott]

Tom Biasi wrote:

"Dave, I can't do that" <davenpete@gmail.com> wrote in message
news:a7607a2f-07b6-4055-8199-e40ddd95f423@a21g2000prf.googlegroups.com...
Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

Thanks

Dave

I don't know why, I can't see your circuit.
NE needs 5 Volts and has a lower Fmax. if that matters.

Tom

And the TTL version's output won't necessarily go all the way up to 5V,

or even be symmetrical about 2.5V. At least one of the 555 circuits
suggested recently in this group depended on the property of CMOS 555's
to go all the way to 0V and VCC (and the poster said as much).

So, post the circuit somewhere, and post a link here, and let us take a
look.

--

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

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[Bob Monsen]

"Dave, I can't do that" <davenpete@gmail.com> wrote in message
news:a7607a2f-07b6-4055-8199-e40ddd95f423@a21g2000prf.googlegroups.com...

Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

Thanks

Dave

You can use them! Why not?

The differences are:

1) they probably don't have 'rail-to-rail' outputs
2) they use about 100 times as much power
3) they require lots more current to trigger
4) they have a slightly lower Vmax
5) NE555 will drive more current on the output

Regards,
Bob Monsen

 

[Jamie]

Dave, I can't do that wrote:

Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

Thanks

Dave
I don't know why? Maybe you need lower voltage rating

part? supply (I) lower? Closer to the rails, higher freq maybe? If
those aren't a problem then use
the NE version.



http://webpages.charter.net/jamie_5"

 

[Tim Wescott]

Dave, I can't do that wrote:

On Aug 4, 6:00 am, NoS...@daqarta.com (Bob Masta) wrote:

Thanks Bob and everyone else who replied. OK, so no breaking news here
about me being a newbie. <grin> I didn't think the circuit would have
much bearing on the case other than lower power needed by the CMOS
version.

I didn't bother with a link to the circuit since low power is not an
issue with my application.

However I do need an operating frequency of 5KHz and 1-uS pulse width
at the lowest setting.

Here's the schematic...
http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm

Thanks

Dave

That circuit uses the output voltage to feed the threshold and trigger
pins. My (ancient) TI data book lists the NE555 as having a guaranteed
maximum output voltage of 3.3V with VCC = 5V, and a threshold voltage
that can go as high as 4.2V -- which means that if you get this
combination you'll never get there from here.

OTOH, CMOS pretty much goes to the power rail.

I wouldn't do this with a TTL part. I would either use a circuit that
works off of the 'official' discharge output, or I would use one 555 as
an astable multivibrator to establish the frequency, and another one as
a monostable multivibrator to establish the on (or off) time.

--

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

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[Dave, I can't do that]

On Aug 4, 6:00 am, NoS...@daqarta.com (Bob Masta) wrote:

Thanks Bob and everyone else who replied. OK, so no breaking news here
about me being a newbie. <grin> I didn't think the circuit would have
much bearing on the case other than lower power needed by the CMOS
version.

I didn't bother with a link to the circuit since low power is not an
issue with my application.

However I do need an operating frequency of 5KHz and 1-uS pulse width
at the lowest setting.

Here's the schematic...
http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm

Thanks

Dave

 

[John Fields]

On Mon, 4 Aug 2008 19:34:11 -0400, "Paul E. Schoen" <pstech@smart.net>
wrote:

"Tim Wescott" <tim@seemywebsite.com> wrote in message
news:JMCdnfRlvZCk2QrVnZ2dnUVZ_t7inZ2d@web-ster.com...
Dave, I can't do that wrote:
On Aug 4, 6:00 am, NoS...@daqarta.com (Bob Masta) wrote:

Thanks Bob and everyone else who replied. OK, so no breaking news here
about me being a newbie. <grin> I didn't think the circuit would have
much bearing on the case other than lower power needed by the CMOS
version.

I didn't bother with a link to the circuit since low power is not an
issue with my application.

However I do need an operating frequency of 5KHz and 1-uS pulse width
at the lowest setting.

Here's the schematic...
http://www.discovercircuits.com/DJ-Circuits/simplepwm2.htm

Thanks

Dave

That circuit uses the output voltage to feed the threshold and trigger
pins. My (ancient) TI data book lists the NE555 as having a guaranteed
maximum output voltage of 3.3V with VCC = 5V, and a threshold voltage
that can go as high as 4.2V -- which means that if you get this
combination you'll never get there from here.

OTOH, CMOS pretty much goes to the power rail.

I wouldn't do this with a TTL part. I would either use a circuit that
works off of the 'official' discharge output, or I would use one 555 as
an astable multivibrator to establish the frequency, and another one as a
monostable multivibrator to establish the on (or off) time.

You can get around the limited output voltage swing by adding a 1k resistor
from pin 3 to +5V.

---
Indeed.
---

Also, the supply voltage needs to be bypassed near the
IC with a small 100nF or so capacitor in addition to the 100 uF shown. And
a similar bypass capacitor from pin 5 to GND is recommended for control
voltage stability,

---
That's generally not needed unless noise on that floating pin becomes
a problem.
---

and you can add a resistor to GND to lower the threshold
and trigger to work better with the reduced output swing.

---
Yup, but then you lose the isothermal benefits of the internal string.
---

An even better circuit for motor control is the H-bridge, an example of
which is referenced in a link on the website you listed:
http://library.solarbotics.net/circuits/driver_4varHbridge.html

I have a DC motor control demo board from Microchip that uses an H-bridge
with PWM to accomplish forward and reverse motor operation and dynamic
braking (which the 555 circuit does not have). It uses four MOSFETs and a
PIC16F684, and can even be controlled via a PC serial port and a simple
Windows GUI:
http://ww1.microchip.com/downloads/en/AppNotes/00893a.pdf
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2125&param=en026704

Good luck,

Paul

JF

 

[Dave, I can't do that]

Thanks again to everyone who has contributed but you guys are starting
to get way out of my knowledge-depth.

I think I will order some CMOS, I only asked as I don't have any on
hand but I have plenty of NE555.

Dave

 

[Dave]

Paul E. Schoen wrote:

I only suggested the Microchip parts because PICs and similar uPs are often

Hi Paul,

Thanks, I too have an S-Corp and a garage full of metalworking machines,
some with CNC but I am pretty much a newbie with electronics.

Over the years, I have made many kits and have programmed PCs for many
years but never quite got into the uP field.

Might be time to take a closer look. I like the idea of being able to
change frequency and duty cycle without soldering parts.

Dave
I am using an account with http://www.usenet4all.se/ to weed out the
bullshit and spam. If you are responding from within Google Groups I
will not see your reply. Try usenet4all I think you will like it. It is
Usenet the way it used to be. Yes, I am THAT old! <grin>

 

[Jasen Betts]

On 2008-08-03, Dave, I can't do that <davenpete@gmail.com> wrote:

Hi,

I have a circuit that calls for TLC555 and I have about a zillion
NE555.

Why couldn't I use the NE in place of the CMOS version?

There are many points of difference between the two.
there is certasinly a chance that the NE is suitable.

some points to consider

operating voltage
output current
power consumption

Bye.
Jasen