Driving SSR

Can the imp drive this SSR directly?

Based upon a quick look at the SSR specs, I believe it will draw 7.5mA, which is more than the imp can handle. I’d suggest putting something like a 2n2222 in play to better handle the current required by the device. It’s low cost and will safeguard the imp.

Connect the output pin of the imp to something like a 1K resistor which connects to the base of the transistor. The emitter should be tied to ground. Connect a 680 ohm resistor to +5Vdc and the other side to a terminal on the SSR input. The other other side of the SSR gets connected to the collector of the transistor. This should provide the required 7.5 mA when turned on (you’re really just lighting LEDs inside the device)

This is all suggested quickly to help, so I’m hoping someone else will chime in if I’ve said something amiss.

For the EI folks, it might be very handy to have a few simple circuits drawn out with recommended component parts for the basics that lots of people might be considering (lighting LEDs, turning on heavier current loads, thermistors, etc.). I know there’s a wealth of information on the site, but quick guides may be helpful.

Thank you so much.
What resistor should I use to connect the transistor to 12 V?

Not sure why you want to do that, but 12/0.0075 = 1600 ohms. 1.5K and 1.8K are standard values around this. There is ~1.5v drop across the LED inside the SSR, but the above gets you in range. I’m really being a bit too casual with the advice, but this should get you close. FWIW, I usually supply 5Vdc to my imp boards (April or P3V3) and have this readily available, assuming I’ve sized my power supply adequately.

the reason is that I also have to power a 12V water pump, and I thought this was the easiest way to power the imp and the pump with one power source, assuming you can power an Aprilboard with 12V


Sorry. I’m just used to powering my breakout boards with 5Vdc. Assuming the 12V is DC, you should be OK.

Hmmm…the SSR is for AC loads. Now I’m a bit confused as to what you’re trying to accomplish. Can you detail how you’re planning to connect this? Is the pump AC or DC?

Sure, the SSR is for switching the heat element for my Sous Vide cooker that I’m building. The water pump (DC) is to get a turning flow in the water of the cooker to level the water temperature. I want the PID controller to be an Imp, so I can control the system with my Android, which saves me a lot of switches and a display.