Optocoupler, Relay, or Both

[btvarner]

I have apparently been laboring under a false assumption. I have been creating a simple PCB to close a circuit that isolates input current from output current using a JQC-3F relay. The problem is that I am unable to get to a low enough milliamp current to safely connect to the initial triggering device and still be able to close the relay. It was suggested by several that I should abandon the relay in favor of an optocoupler. The 6N137 was suggested. My false assumption came about when I assumed that the optocoupler would simply replace the relay. After pulling my hair out not understanding why this did not occur, I am now apparently saddled with the realization that the 6N137 optocoupler only outputs a current, not really just “closing” my existing circuit at all. Asking for help on what would be the best approach to solving this problem.

Requirements:
1) The initial button push that activates the closure of the DC high amperage circuit cannot directly connect to the button push device because that device only accepts very low amperage.
2) Input circuit (DC Circuit that closes when button pushed.) must be below 6V and 10mA or below.
3) Output circuit (DC High amperage circuit to be closed.) is only 3V but has very high short burst amperage.
4) Both push button device and the high amperage device are portable, therefore the solution must be portable.
5) The time from button push to high amperage circuit closure should be less than 20mS if possible.

This is not a device to be mass produced, therefore component cost is not a factor.

The Question:
Can I close the high amperage circuit using the 6N137 without the optocoupler in turn having to trigger a relay? If so, how.

Thanks!

 

[barry]

High amperage? 66 million amps? Portable? I can carry 50 pounds, is that good?. You can't just throw vague specifications around and expect people to give you a sensible answer.

The 6N137 is an open-collector device, it could drive a relay with about 50mA. But you could also just use a solid state relay, which is essentially an optocoupler on the input.

 

[btvarner]

Thanks Barry,
Can't say how high the amperage. The component is an old flash bulb flash. I do not have an oscilloscope. I just know it is considerable.... I can carry 50 lbs also. 50# is good.

Is voltage out of Vo (Pin 6) going to be the same as the Voo voltage going in?

One last thing. Are you confirming that the 6N137 can or cannot trigger the circuit without a separate relay?

I am looking into the solid state relay now. Odd that no one I have spoken with to this point has mentioned this possibility.

- - - Updated - - -

I just found what I was looking for. The "high amperage" amounts to 10 amps, but for only milliseconds....

Will an SSR handle that?

 

[barry]

There's no way i can tell if the 6n137 will trigger your circuit, because i have no idea what your circuit is. But the 6n137 is not a voltage output; as I mentioned,it is open-collector.

SSRs are rated in amps. I would use a 25 amp part, just to be safe. Same size as a 10 amp, just more costly.

 

[btvarner]

Ok, I am sure I am not making myself clear enough. Sorry. My first post stated that the input requirement was not more than 6V & must be less than 10mA. I do not find any SSR's that can handle such a large amperage load on the output and still able to trigger the SSR with that small of amperage on the input side.

Maybe I am reading the datasheets wrong. Please let me know. Thanks!

 

[Kajunbee]

If I am understanding your requirements correctly the crydom dc100d20 may work for you. This is a mosfet based ssr and according to datasheet can be parraled for higher current capabilities.

 

[barry]

then again, you could just use a logic-level MOSFET. .

 

[btvarner]

Thanks all! The dc100d20 seemed like it would fit the bill, except it is large enough to choke a horse. So I looked up logic-level MOSFET's and found the FQP30N06L. I ordered a couple of these and I am going to see if it works for me on a breadboard. I will provide a response after I test it......... Thanks again!

By the way. Are people interested on completed circuits? Should I post when I complete the circuit, or is that not of interest to the group. Do not what to break rules.

 

[KlausST]

Hi,

By the way. Are people interested on completed circuits? Should I post when I complete the circuit, or is that not of interest to the group. Do not what to break rules.

We have a section for this: Hardware and PCB Design --> Show your DIY

Klaus