Converting from 30V to 5V or less

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

 

[John Fields]

On Fri, 19 Sep 2008 16:15:13 +0300, spam_filter@invalid.nil wrote:

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

---
View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND


JF

 

[Stephen J. Rush]

On Fri, 19 Sep 2008 16:15:13 +0300, spam_filter wrote:

I'm using a computer to gather data using LPT1 port. The input pins of
the lpt accept 0-5V.

I want to know when three utility motors using 30V start and when they
end. When a motor starts it gets 30V. Actually they should get 24V but
occasional bursts to 30V are normal. The motors themself can handle the
extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've
done simple electronics but a simple schematic would be great. I want to
know when each of the motors start.

The safest way to couple signal from a "dirty" source -motors are
notorious sources of noise and spikes- into a logic circuit is to use an
optoisolator, a device with a lamp (usually an LED) on the dirty side and
a phototransistor on the logic side. These are common parts, available
from any of the online distributors. You connect the phototransistor
side between a logic input and ground, with a pullup resistor. The LED
side goes across the motor, with a series resistor whose value depends on
the motor voltage and the current required by the LED.

Another approach is a simple 6:1 resistive voltage divider, but you have
to protect the logic input from overvoltage and from the negative voltage
you get when you switch the motor off. Two diodes may be enough: one
from the logic input to ground (anode to ground) to catch the negative
back EMF from the motor, and one from the logic input to the 5V logic
supply (anode to the logic input) to dump any overvoltage spikes into the
5V supply's filter capacitors. The optoisolator is safer. They
typically offer several hundred volts of isolation.

 

[Jamie]

spam_filter@invalid.nil wrote:

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Using a Photo coupler is the safest method that I know of.
Just pull one of the input pins of your port using the photo output
transistor.

Since you stated 30 V's maybe the max at times I would use ~ 2 thirds
of the LED (If) which is ~ 45 ma.
R = (30-1.2)=(28.8)/0.045 = 640 ohms.
W = 0.045*1.2 = 0.054 watts.

http://www.qsl.net/n4xy/PDFs/Semiconductor_Data_Sheets/4n35_37.pdf

P.S.
Might be advisable to use a zener diode of around 30 volts so
that it can be protected from reverse voltage exceeding (Vr)
6 and forward voltages exceeding 30 volts.

If this is a brushed motor, it can generate inductive energy that
isn't safe even for the coupler. A cheap zener diode helps this out in
minor cases and the photo coupler helps in major cases to protect the
computer.



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

 

[John Fields]

On Fri, 19 Sep 2008 18:52:46 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

spam_filter@invalid.nil wrote:

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Using a Photo coupler is the safest method that I know of.
Just pull one of the input pins of your port using the photo output
transistor.

Since you stated 30 V's maybe the max at times I would use ~ 2 thirds
of the LED (If) which is ~ 45 ma.
R = (30-1.2)=(28.8)/0.045 = 640 ohms.
W = 0.045*1.2 = 0.054 watts.

---

P = Iled (Vin - Vled) = 0.045A * (30V - 1.2V) ~ 1.3 watts

---

http://www.qsl.net/n4xy/PDFs/Semiconductor_Data_Sheets/4n35_37.pdf

P.S.
Might be advisable to use a zener diode of around 30 volts so
that it can be protected from reverse voltage exceeding (Vr)
6 and forward voltages exceeding 30 volts.

---
Missed this, did you:?

View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

JF

 

[Jamie]

John Fields wrote:

On Fri, 19 Sep 2008 18:52:46 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


spam_filter@invalid.nil wrote:


I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Using a Photo coupler is the safest method that I know of.
Just pull one of the input pins of your port using the photo output
transistor.

Since you stated 30 V's maybe the max at times I would use ~ 2 thirds
of the LED (If) which is ~ 45 ma.
R = (30-1.2)=(28.8)/0.045 = 640 ohms.
W = 0.045*1.2 = 0.054 watts.


---

P = Iled (Vin - Vled) = 0.045A * (30V - 1.2V) ~ 1.3 watts

---

Yes, I made a mistake there. got my 1.2 mixed up with my 28.8.

http://www.qsl.net/n4xy/PDFs/Semiconductor_Data_Sheets/4n35_37.pdf

P.S.
Might be advisable to use a zener diode of around 30 volts so
that it can be protected from reverse voltage exceeding (Vr)
6 and forward voltages exceeding 30 volts.


---
Missed this, did you:?
No, I didn't miss it.

I just wouldn't subject the PC port
to a motor circuit. Although you
have covered all bases as far as over voltage
and reverse voltage, you didn't account for
current loops on the ground path between the devices which loves to
make PC's miss behave.
Motors are notorious for generating such currents if
improper installation is performed.

View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

JF

To each, his own.

 

[John Fields]

On Fri, 19 Sep 2008 19:56:43 -0400, Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

John Fields wrote:

On Fri, 19 Sep 2008 18:52:46 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


spam_filter@invalid.nil wrote:


I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Using a Photo coupler is the safest method that I know of.
Just pull one of the input pins of your port using the photo output
transistor.

Since you stated 30 V's maybe the max at times I would use ~ 2 thirds
of the LED (If) which is ~ 45 ma.
R = (30-1.2)=(28.8)/0.045 = 640 ohms.
W = 0.045*1.2 = 0.054 watts.


---

P = Iled (Vin - Vled) = 0.045A * (30V - 1.2V) ~ 1.3 watts

---

Yes, I made a mistake there. got my 1.2 mixed up with my 28.8.

http://www.qsl.net/n4xy/PDFs/Semiconductor_Data_Sheets/4n35_37.pdf

P.S.
Might be advisable to use a zener diode of around 30 volts so
that it can be protected from reverse voltage exceeding (Vr)
6 and forward voltages exceeding 30 volts.


---
Missed this, did you:?

View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

JF

No, I didn't miss it.

I just wouldn't subject the PC port
to a motor circuit. Although you
have covered all bases as far as over voltage
and reverse voltage, you didn't account for
current loops on the ground path between the devices which loves to
make PC's miss behave.
Motors are notorious for generating such currents if
improper installation is performed.

---
The OP didn't ask for installation instructions, he asked for the
_simplest_ way to get ~ to 5V to his printer port when the motor was
running, and my circuit will get it for him.

I don't think you can get much simpler than a resistor and a Zener.

Well, maybe a two resistor voltage divider, but that won't provide much
protection...
---

To each, his own.

---
Yeah, but what you're trying to do is make my solution seem flawed
because of some trepidation you feel about mythical ground currents in
an equipment arrangement you've never seen and yet feel competent to
judge.

Just for grins, why don't you describe how a current loop in the ground
side of the circuit could cause a data error between MOTOR ON and MOTOR
OFF and how long it would last?

JF

 

[Jasen Betts]

On 2008-09-19, spam_filter@invalid.nil <spam_filter@invalid.nil> wrote:

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Just changing the voltage is possibly not enough, things like ground
loops cour damage your pc or stop the other equipment from working.

the easiest way is use a 24V relay, or to use optocouplers.

The parallel port inputs have internal pull-ups so you only need to
connect them to the pc's digital ground or disconnect them - you don't
need to provide a 5v signal.

Bye.
Jasen

 

[Jasen Betts]

On 2008-09-20, John Fields <jfields@austininstruments.com> wrote:

View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND


---
The OP didn't ask for installation instructions, he asked for the
_simplest_ way to get ~ to 5V to his printer port when the motor was
running, and my circuit will get it for him.

He asked for that, but what he wants is a way to get 0V to the printer
port. the input pins have interal pull-ups.

For it to read zero the motor must have sufficiently low voltage
drop to ground the data pin through your 1K resistor...

I don't think you can get much simpler than a resistor and a Zener.

If it's a (for example) a brushless DC motor the voltage drop
may be sufficient to present as logic high with the DC supply
disconnected.

I'd add a resistor in parallel with the zener to provide a reliable
path for the off-state signal current, 470 ohms would be a good choice.

Bye.
Jasen

 

[Test]

Thanks guys, I'll try either way.

John Fields <jfields@austininstruments.com> wrote:

On Fri, 19 Sep 2008 19:56:43 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:

John Fields wrote:

On Fri, 19 Sep 2008 18:52:46 -0400, Jamie
jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote:


spam_filter@invalid.nil wrote:


I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Using a Photo coupler is the safest method that I know of.
Just pull one of the input pins of your port using the photo output
transistor.

Since you stated 30 V's maybe the max at times I would use ~ 2 thirds
of the LED (If) which is ~ 45 ma.
R = (30-1.2)=(28.8)/0.045 = 640 ohms.
W = 0.045*1.2 = 0.054 watts.


---

P = Iled (Vin - Vled) = 0.045A * (30V - 1.2V) ~ 1.3 watts

---

Yes, I made a mistake there. got my 1.2 mixed up with my 28.8.

http://www.qsl.net/n4xy/PDFs/Semiconductor_Data_Sheets/4n35_37.pdf

P.S.
Might be advisable to use a zener diode of around 30 volts so
that it can be protected from reverse voltage exceeding (Vr)
6 and forward voltages exceeding 30 volts.


---
Missed this, did you:?

View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

JF

No, I didn't miss it.

I just wouldn't subject the PC port
to a motor circuit. Although you
have covered all bases as far as over voltage
and reverse voltage, you didn't account for
current loops on the ground path between the devices which loves to
make PC's miss behave.
Motors are notorious for generating such currents if
improper installation is performed.

---
The OP didn't ask for installation instructions, he asked for the
_simplest_ way to get ~ to 5V to his printer port when the motor was
running, and my circuit will get it for him.

I don't think you can get much simpler than a resistor and a Zener.

Well, maybe a two resistor voltage divider, but that won't provide much
protection...
---

To each, his own.

---
Yeah, but what you're trying to do is make my solution seem flawed
because of some trepidation you feel about mythical ground currents in
an equipment arrangement you've never seen and yet feel competent to
judge.

Just for grins, why don't you describe how a current loop in the ground
side of the circuit could cause a data error between MOTOR ON and MOTOR
OFF and how long it would last?

JF

 

[John Fields]

On 20 Sep 2008 02:37:25 GMT, Jasen Betts <jasen@xnet.co.nz> wrote:

On 2008-09-20, John Fields <jfields@austininstruments.com> wrote:
View in Courier:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |K
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND


---
The OP didn't ask for installation instructions, he asked for the
_simplest_ way to get ~ to 5V to his printer port when the motor was
running, and my circuit will get it for him.

He asked for that, but what he wants is a way to get 0V to the printer
port. the input pins have interal pull-ups.

For it to read zero the motor must have sufficiently low voltage
drop to ground the data pin through your 1K resistor...

I don't think you can get much simpler than a resistor and a Zener.

If it's a (for example) a brushless DC motor the voltage drop
may be sufficient to present as logic high with the DC supply
disconnected.

I'd add a resistor in parallel with the zener to provide a reliable
path for the off-state signal current, 470 ohms would be a good choice.

---
You're right; I didn't think about the pullup. :-(

Thanks.

JF

 

[Test]

Jasen Betts <jasen@xnet.co.nz> wrote:

On 2008-09-19, spam_filter@invalid.nil <spam_filter@invalid.nil> wrote:
I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

Just changing the voltage is possibly not enough, things like ground
loops cour damage your pc or stop the other equipment from working.

the easiest way is use a 24V relay, or to use optocouplers.

The parallel port inputs have internal pull-ups so you only need to
connect them to the pc's digital ground or disconnect them - you don't
need to provide a 5v signal.

Bye.
Jasen

What is a "pull up"? How would I connect this to my printer pins? The 30V is btw
AC (just found out).

Right now I have John Field's:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+


My aim is to find out when the motor is powered up. In above the voltage is
dropped to <5V for the relay not to fry.

What about the current? I don't know what the current is.

 

[John Fields]

On Sat, 20 Sep 2008 15:40:41 +0300, Test <test@.nil.invalid.com> wrote:

What is a "pull up"? How would I connect this to my printer pins?

---
It's a resistor connected to the logic supply positive rail, and you
don't have do anything; it's already connected internally.
---

The 30V is btw AC (just found out).

---
Aarghhhhh!!!
---

Right now I have John Field's:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+


My aim is to find out when the motor is powered up. In above the voltage is
dropped to <5V for the relay not to fry.

---
Forget it.

If you're going to use a relay, you'll need one with signal contacts,
but they're hard to find with AC coils, so you'll need to rectify the
24VAC and feed the relay's coil with it, like this:


24VAC>----+-----+----------+
| |K |A
| [2N4001] [2N4001]
| | |
| | +-----+ O----> || PORT PIN?
| | | | |
[MOTOR] | | [COIL]- -|
| | | | O-> |
| +----------|-----+ |
| | | +--------> || PORT PIN 25
| [2N4001] [2N4001]
| |K |A
24VAC>----+-----+----------+

---

What about the current? I don't know what the current is.

It's going to be very low, so you'll need a relay with precious metal
contacts.

This one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=255-1064-ND

would work well, and here's its data sheet:

http://pewa.panasonic.com/pcsd/product/sign/pdf/mech_eng_ds.pdf

JF

 

[Test]

John Fields <jfields@austininstruments.com> wrote:

On Sat, 20 Sep 2008 15:40:41 +0300, Test <test@.nil.invalid.com> wrote:

What is a "pull up"? How would I connect this to my printer pins?

---
It's a resistor connected to the logic supply positive rail, and you
don't have do anything; it's already connected internally.
---

The 30V is btw AC (just found out).

---
Aarghhhhh!!!
---

Right now I have John Field's:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+


My aim is to find out when the motor is powered up. In above the voltage is
dropped to <5V for the relay not to fry.

---
Forget it.

If you're going to use a relay, you'll need one with signal contacts,
but they're hard to find with AC coils, so you'll need to rectify the
24VAC and feed the relay's coil with it, like this:


24VAC>----+-----+----------+
| |K |A
| [2N4001] [2N4001]
| | |
| | +-----+ O----> || PORT PIN?
| | | | |
[MOTOR] | | [COIL]- -|
| | | | O-> |
| +----------|-----+ |
| | | +--------> || PORT PIN 25
| [2N4001] [2N4001]
| |K |A
24VAC>----+-----+----------+

---

What about the current? I don't know what the current is.

It's going to be very low, so you'll need a relay with precious metal
contacts.

This one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=255-1064-ND

would work well, and here's its data sheet:

http://pewa.panasonic.com/pcsd/product/sign/pdf/mech_eng_ds.pdf

JF

Thanks. I was rather surprised for the AC. I was testing teh first simple setup
with another transformer that was DC.
I'll have to rethink the system over again.

Thank you for your time.

 

[Jamie]

Test wrote:

John Fields <jfields@austininstruments.com> wrote:


On Sat, 20 Sep 2008 15:40:41 +0300, Test <test@.nil.invalid.com> wrote:


What is a "pull up"? How would I connect this to my printer pins?

---
It's a resistor connected to the logic supply positive rail, and you
don't have do anything; it's already connected internally.
---


The 30V is btw AC (just found out).

---
Aarghhhhh!!!
---


Right now I have John Field's:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+


My aim is to find out when the motor is powered up. In above the voltage is
dropped to <5V for the relay not to fry.

---
Forget it.

If you're going to use a relay, you'll need one with signal contacts,
but they're hard to find with AC coils, so you'll need to rectify the
24VAC and feed the relay's coil with it, like this:


24VAC>----+-----+----------+
| |K |A
| [2N4001] [2N4001]
| | |
| | +-----+ O----> || PORT PIN?
| | | | |
[MOTOR] | | [COIL]- -|
| | | | O-> |
| +----------|-----+ |
| | | +--------> || PORT PIN 25
| [2N4001] [2N4001]
| |K |A
24VAC>----+-----+----------+

---


What about the current? I don't know what the current is.

It's going to be very low, so you'll need a relay with precious metal
contacts.

This one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=255-1064-ND

would work well, and here's its data sheet:

http://pewa.panasonic.com/pcsd/product/sign/pdf/mech_eng_ds.pdf

JF


Thanks. I was rather surprised for the AC. I was testing teh first simple setup
with another transformer that was DC.
I'll have to rethink the system over again.

Thank you for your time.

This is what you need to make it simple and still safe for

AC work. You only too use a cap on the port side so you
don't get a pulse on the pin.

http://www.toshiba.com/taec/components2/Datasheet_Sync//206/4215.pdf

This is an AC input version much like the one's used in the front ends
of PLC cards that accept AC as the input type.

Found at digikey.. as

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=TLP620GRFT-ND

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

 

[Robert Monsen]

On Fri, 19 Sep 2008 16:15:13 +0300, spam_filter@invalid.nil wrote:

I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

What is the simplest way lower the voltage to 5V for my LPT port? I've done
simple electronics but a simple schematic would be great. I want to know when
each of the motors start.

I would not bet on the fact that your motors are referenced with the
same ground. If you connect the wrong wire to your PC parallel port,
and you have ground issues, you can destroy your mainboard.

You can test this by using a DC voltmeter between the ground at the
parallel port and the ground at the motor.

FYI

Regards,
Bob Monsen

 

[Jasen Betts]

On 2008-09-20, Test <test@> wrote:

Jasen Betts <jasen@xnet.co.nz> wrote:

On 2008-09-19, spam_filter@invalid.nil <spam_filter@invalid.nil> wrote:
I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

The parallel port inputs have internal pull-ups so you only need to
connect them to the pc's digital ground or disconnect them - you don't
need to provide a 5v signal.

What is a "pull up"?

a resistor used to increase the voltage at a point in a circuit whenever
it's not connected to any input signal.

what this means is that you don't need to provide 5v to the printer
port, you need to take it away from the printer port.

How would I connect this to my printer pins? The 30V is btw
AC (just found out).

I had suspicion it might be...

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+

you'll just need to change that a adding a rectifier so
that the relay gets DC, and a capacitor to stop it switching off while
the AC voltage altenates, and reduce the resistor so that the relay
gets enough power....


An opto-coupler will use less power than a relay and is less fussy
about how much power it gets which makes the design easier (cheaper
and more reliable too)

1N4002 .------.
--+-------->|---+---[3300]--[|o \/ |] PC
| | | |
| 10uF=== .---[| 4N25 |]-- pin 10/12/13
30VAC (M) 50V |- | | |
| | | [| |]-- pin 20
--+-------------+-------' `------'

the diode can be 1N4002 to 1n4010, the capacitor should be rated
for atleast 50V (more than 50V is fine)

with those pins (pick one of 10/12/13) it'll come up as the bit
6/5/4 on port 0x379.

What about the current? I don't know what the current is.

which current?

Bye.
Jasen

 

[Test]

Jasen Betts <jasen@xnet.co.nz> wrote:

On 2008-09-20, Test <test@> wrote:
Jasen Betts <jasen@xnet.co.nz> wrote:

On 2008-09-19, spam_filter@invalid.nil <spam_filter@invalid.nil> wrote:
I'm using a computer to gather data using LPT1 port. The input pins of the lpt
accept 0-5V.

I want to know when three utility motors using 30V start and when they end. When
a motor starts it gets 30V. Actually they should get 24V but occasional bursts to
30V are normal. The motors themself can handle the extra voltage.

The parallel port inputs have internal pull-ups so you only need to
connect them to the pc's digital ground or disconnect them - you don't
need to provide a 5v signal.

What is a "pull up"?

a resistor used to increase the voltage at a point in a circuit whenever
it's not connected to any input signal.

what this means is that you don't need to provide 5v to the printer
port, you need to take it away from the printer port.

How would I connect this to my printer pins? The 30V is btw
AC (just found out).

I had suspicion it might be...

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+

you'll just need to change that a adding a rectifier so
that the relay gets DC, and a capacitor to stop it switching off while
the AC voltage altenates, and reduce the resistor so that the relay
gets enough power....


An opto-coupler will use less power than a relay and is less fussy
about how much power it gets which makes the design easier (cheaper
and more reliable too)

1N4002 .------.
--+-------->|---+---[3300]--[|o \/ |] PC
| | | |
| 10uF=== .---[| 4N25 |]-- pin 10/12/13
30VAC (M) 50V |- | | |
| | | [| |]-- pin 20
--+-------------+-------' `------'

the diode can be 1N4002 to 1n4010, the capacitor should be rated
for atleast 50V (more than 50V is fine)

with those pins (pick one of 10/12/13) it'll come up as the bit
6/5/4 on port 0x379.

What about the current? I don't know what the current is.

which current?

Bye.
Jasen

Thanks.

 

[John Fields]

On Sat, 20 Sep 2008 22:09:48 +0300, Test <test@.nil.invalid.com> wrote:

John Fields <jfields@austininstruments.com> wrote:

On Sat, 20 Sep 2008 15:40:41 +0300, Test <test@.nil.invalid.com> wrote:

What is a "pull up"? How would I connect this to my printer pins?

---
It's a resistor connected to the logic supply positive rail, and you
don't have do anything; it's already connected internally.
---

The 30V is btw AC (just found out).

---
Aarghhhhh!!!
---

Right now I have John Field's:

1/2 WATT
30V----+--[1000]--+------>4.7V
| |
[MOTOR] [1N5230B]
| |
GND>---+----------+------>GND

Just to be safe I'll do this:

30V----+--[1000]--+------+ +---------+
| | +---+ +----> pin? in LPTport
[MOTOR] [1N5230B] | 5V relay|
| | +---+ +----> pin? in LPTport
GND>---+----------+------+ +---------+


My aim is to find out when the motor is powered up. In above the voltage is
dropped to <5V for the relay not to fry.

---
Forget it.

If you're going to use a relay, you'll need one with signal contacts,
but they're hard to find with AC coils, so you'll need to rectify the
24VAC and feed the relay's coil with it, like this:


24VAC>----+-----+----------+
| |K |A
| [2N4001] [2N4001]
| | |
| | +-----+ O----> || PORT PIN?
| | | | |
[MOTOR] | | [COIL]- -|
| | | | O-> |
| +----------|-----+ |
| | | +--------> || PORT PIN 25
| [2N4001] [2N4001]
| |K |A
24VAC>----+-----+----------+

---

What about the current? I don't know what the current is.

It's going to be very low, so you'll need a relay with precious metal
contacts.

This one:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=255-1064-ND

would work well, and here's its data sheet:

http://pewa.panasonic.com/pcsd/product/sign/pdf/mech_eng_ds.pdf

JF

Thanks. I was rather surprised for the AC. I was testing teh first simple setup
with another transformer that was DC.

---
Transformers don't put out DC, they put out AC.

What you were using is called a "DC power supply" or an "AC to DC
converter."
---

I'll have to rethink the system over again.

---
OK.
---

Thank you for your time.

---
My pleasure.

JF