Using 4N33 optocoupler to feed solid state relay

[Brain Damage]

4n33 circuit

I have a computer device that sends a 3.3v dc signal when the computer is actively recording audio. I want to connect this device to a record light circuit that uses a solid state relay that (when activated) sends 120V ac to our On-Air lights.

even thought the solid state relay claims a 3-24V input trigger range I have had problems with any signal lower than 7 volts actually triggering the Solid State Relay (SSR).

I either need to boost the 3.3v to around 8-10v or ...
The Computer device manufacturer suggests using an optocoupler in between my computer and the SSR. I have a 4N33 in my parts bin.

What is the best way to connect the 4N33 to acheive the desired result?

Thanks, Brain Damage

 

[silvio]

4n33 optocoupler

What is the best way to connect the 4N33 to acheive the desired result?

Use this kind of circuit
**broken link removed**

Decrease the value of 1K resistor according to your 3,3v input if the 2N3906 transistor is not able to provide enough current to activate the relay.
The"+" control input is tied to your 3,3v output and "-" to the computer gnd.

Alternatively read this tutorial : https://www.epanorama.net/circuits/parallel_output.html#relaycontrol

 

[Brain Damage]

optocoupler relay

Thanks Silvio I will bread-board it early next week. One question There is a component on the output (in parallel with the diode) that is unlabeled. I assume this is a load resistor. If so what value?

The output will be connected to 2 diodes in front of the Solid State Relay (that way I can input multiple signals and not back feed the trigger voltage to other sending devices.

Thanks,
Brain Damage

 

[silvio]

4n33 circuits

There is a component on the output (in parallel with the diode) that is unlabeled. I assume this is a load resistor. If so what value?

The component is exactly your coil relay.

 

[Brain Damage]

optocoupler 4n33

Okay !


Thanks,
Brian

 

[Brain Damage]

circuits using 4n33

silvio

I bread boarded both of the test circuits you provided and I didn't have any output.

I had 3.24 volts DC on the input and nothing on the output. It looks llike the 4N33 is not triggering. Just in case I had a bad chip I tried 2 others. I don't get it. Any ideas?????


Thanks,
Brain

 

[silvio]

what is part# 4n33 used for

Assuming that you've used the circuit from the Figure 2 above:
If the diode inside 4N33 is driven by an ouput pin of LPT then check the following:
- the voltage of CONTROL INPUT (you said 3.24v)
- the voltage between pins 1 and 2 of optocoupler
- the voltage between pins 4 and 5 of optocoupler
- your SUPPLY voltage for relay
- the voltage across diode D1 connected in parallel with your relay for a given SUPPLY.

Take all those measurements at once for a given CONTROL INPUT (you said 3.24v)

You may need to use a darlington transistor rather than 2N3906 if decreasing of 1k resistor will not be enough to arm your relay.

Don't connect "-" COMMON with "-" CONTROL INPUT since will defeat the purpose of optocoupler.