HCPL0631 is not functioning properly please help!!

[justinycc]

To adminitrator,

I am trying to use the HCPL0631 optocoupler for my simulation. However, this optocoupler will not function properly and will not give me a good result.

I have attached the circuit diagram in the attachment, please let me know what is wrong with my circuit causing the components to fail.

thank you for your kind attention

 

Message Edited by justinycc on 04-11-2009 06:40 AM

Message Edited by justinycc on 04-11-2009 06:41 AM

[justinycc]

Sorry I am mistake the printscreen of my circuit

here is an updated one

[yyao]

Hi there,

 I think the current limiting resistor connected to the diode input is too large. Try using a resistor between 100 and 200 ohms on the input.

[justinycc]

hi yi,

if you can see my second message in this post, i have already tried using a resistor of 180ohms in the input and it still gives me a flat DC signal for the output. I have also tried other values as well but it still wouldn't work. I have been going to the optocouple list in multisim and can't find any other model that has an amplifier inside the optocoupler apart from this HCLP0631. Please advice me what other options can I use or solutions to my problem. Let me know thanx

[yyao]

Ahh, I see you problem. Take a look at the datasheet. The outputs of the optocoupler has an open collector NPN driver. The resistor R1 should be a pull up resistor connected between the output and your power rail, not a pull down resistor like the way you've connected it.

[yyao · Accepted solution]

Actually, never mind about that, the model for the HCPL0631 isn't very good. It doesn't actual have a open collector output. It also has a built in VCC of 5V, so the power supply that you are attaching isn't really being used. Your problem is grounding. Multisim constructs mesh current and node voltage equations for simulation and can't do it accurately if you don't specify the ground for your circuit.

Try adding a ground to the GND terminal of the optoisolator. You should also have a ground attached to the cathode of the optoisolator or neutral wire of the function generator. The GROUND component is in the Master Database in the Sources group and in the POWER_SOURCES family.

[justinycc]

hi yi,

thank you for your help. I have added a ground on the right have side of the circuit and it worked.

However,  I am experiencing a similar problem if I replace the input with another signal. It worked for the TIL191 model but not for the HCPL0631. Will it be possible for you to tell me where have gone wrong in my circuit below?

 

Message Edited by justinycc on 04-15-2009 11:14 AM

[yyao]

I wouldn't be able to tell you as the circuit looks a bit complex. I bet that you can figure it out if you debugged the circuit by tracing the signal from the circuit's input to its output. A lot of other people are on this forum and it may help everyone if you attached your Multisim file.

[segunbabs]

Your circuit is wrong.