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Using 4N33 optocoupler to feed solid state relay

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Brain Damage

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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

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4n33 optocoupler

Brain Damage said:
What is the best way to connect the 4N33 to acheive the desired result?
Use this kind of circuit


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 : http://www.epanorama.net/circuits/parallel_output.html#relaycontrol
 

Brain Damage

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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

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4n33 circuits

Brain Damage said:
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

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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
 

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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.
 

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