Electronics > PCB/EDA/CAD

solid state relay module

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mblyman89:
Cool beans, my bad. Thank you for the help, I’m still learning how it all works.

floobydust:
It's not going to work - you only have at most 3.3V from a RPi DO and the PhotoMOS LED uses ~1.25V and then a red LED is ~1.8V so the 1k resistor will give almost nothing for current.
I don't think that SSR is tough enough, 1A is its max rating and cold nichrome has much lower resistance longer than 100msec.

https://www.eevblog.com/forum/projects/my-arduino-powered-firework-sequencer-this-is-gonna-be-a-blast/

mblyman89:
thanks for the reply! the link you posted is broken. I used a resistor calculator to figure out the resistor value, so it was my best guess. If I remove the 1k resistor, will that provide enough current for both leds? the data sheet says it's rated for 3A pulses, how long is a pulse? the minimum on time for the relays will be .25 seconds, at most they will be on for 2 seconds. I am using talon ignitors, and while using a 12v battery and a regular em relay, .25 seconds was the minimum amount of on time to light the fuse I found. the data sheet also states the min voltage on input is 1.7V I think, or something like that, is that something the RPi can handle, or is it just because I have a 1k resistor in series with the two leds and all I need to do is remove the 1k resistor? I don't really know what I am doing, just stumbling around in the dark!   

mblyman89:
I went back to the data sheet of the led I am using as an indicator light. it has a minimum forward voltage of 1.7v, normal 2.0 and max of 2.5v. the data sheet of the relay says the min forward voltage of the led is 1.25, max 1.5v. if I take out the 1K resistor, will that be enough to power both leds with a 3.3v supply? or would I be better off leaving the 1k resistor and removing the indicator led?

ledtester:
Just put the LED in parallel with the SSR each having their own current limiting resistor.

The meaning of the LED changes slightly -- it now indicates if the MCU is trying to activate the relay rather than if current is going through the relay's LED -- but it still will be a useful indicator.

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