... without blowing up my arduino uno, of course
As a hobby project I'd like to make my my old hot air heater arudino controllable. I will to control two SSRs need, one which powers the fan and a second one which powers the heating coil.
This is the SSR I have found (LINK) and I am wondering if I can control these directly from an digital output of an Arduino UNO (or maybe even a nano?). What confuses me is that the ebay page says the control current is 3-25mA. Depending on what?
Thanks!
Yes, you can drive this SSR directly by a digital output.
The ad says:
Steuerspannung: 3 - 32 V DC
Which means "control voltage: 3-32 V DC".
I had a similar question. The data sheets I saw all had an internal current limiting resistor for the LED.
Paul
There has to be an internal current limiting resistor, if a control voltage of 32 VDC is allowed.
It is very wise to measure the actual current drawn by putting a DVM in series with the input, and applying 5V.
Uh-oh! In our "post-truth" and "fake news" world, my guess is "fake relay".
You should ask the eBay seller if it is counterfeit.
jremington:
You should ask the eBay seller if it is counterfeit.
12€ for 4 SSRs... yeah, I am pretty sure it is a counterfeit 
dlloyd:
Uh-oh! In our "post-truth" and "fake news" world, my guess is "fake relay".
Wow! Really useful links. Now the question is if its really a completely bad product, or if it can handle about half the current as written in the first link. Because my application (fan + heating coil) will never go above 2kW which is 2000W/230V = 8.7A total for the both. I really dont need 25A, just less than 8.7A.
Yeah, I would make sure the current is lower than 50% of rating. I used one about 15 years ago and also found that a control voltage of 12V is needed to reliably turn on the output. I guess you could consider the input control range as being 12-32V.
Best to throw those away and buy reliable SSRs. Think of it as a 12 Euro learning experience!
I am curious, how large a heat sink are these being mounted on?
Paul
jremington:
Best to throw those away and buy reliable SSRs. Think of it as a 12 Euro learning experience!
True... but if they can operate at half the current then 4 for €12 is still a bargain, so I am thinking about buying them.
Paul_KD7HB:
I am curious, how large a heat sink are these being mounted on?
Duh... didnt think about this. Can you recommend a documentation to understand how big the heatsink should be?
Istvanb:
Duh... didnt think about this. Can you recommend a documentation to understand how big the heatsink should be?
That's why I am asking. In testing on a 500 watt drying oven I am attempting to control with an Arduino, I can feel the base of the relay getting warm.
Paul