SSR with Android - Do i need a resistor here?

Using Arduino General Electronics
#1

Hi everyone! I just got a SSR in the mail, that i was planing to use with my Arduino. The problem is, that i'm getting a bit nervous about if I should use a resistor. I got the SSR from ebay, and the only information on the page is this:

Solid state relays SSR 48-480V AC Load voltage: 48-480V AC Load Current: 25A Control Voltage: 3-32VDC Control Current: DC 3-25mA

I'm not sure how to read this. Dose it mean that the SSR draws no more then 25mA but could use as little as 3mA? Or dose it mean that, depending on the control voltage, it draws somewhere between 3-25mA?

Any help is appreciated.

Thanks in advance

#2

Dose it mean that the SSR draws no more then 25mA but could use as little as 3mA?

Yes. It depends on the input voltage which can be from 3 to 32V. The more voltage the more input current it will take.

You don't need an input resistor.

#3

Thanks! I didn't want to risk frying my Mega2560 ^^

Just for any future questions like this, dose it harm to add an resistor (like 100ohm) if in doubt? :)

#4

No harm will result from adding a resistor when you're unsure. And better that than the way so many around here go about things.

#5

Not completely true, adding series resistance will increase the minimum required control voltage, and if it drops below the arduino HIGH output pin voltage then the SSR will fail to turn on. I see no advantage to adding such an external resistor, just disadvantages.

#6

retrolefty: Not completely true, adding series resistance will increase the minimum required control voltage, and if it drops below the arduino HIGH output pin voltage then the SSR will fail to turn on. I see no advantage to adding such an external resistor, just disadvantages.

It's absolutely true, without qualification - no [u]HARM[/u] will result.

EndLessMind: Just for any future questions like this, dose it harm to add an resistor (like 100ohm) if in doubt? :)

Going with some precautionary resistance in case of "doubt" makes a lot of sense, ELM.

When discussing your circuitry, in any event, fully disclose your situation. Don't present a textbook example for discussion and keep the mess on the kitchen table a secret.

#7

[quote author=Runaway Pancake link=topic=215130.msg1574323#msg1574323 date=1391435598] No harm will result from adding a resistor when you're unsure. And better that than the way so many around here go about things.

[/quote]

So there is no instance where adding a resistor can cause harm?

I bet it could, thinking along the lines of sensors used for safety, eg if you used one on a distance or heat sensor you could stop it working or go weird and a robot connected or car, could then screw up and kill you by not seeing you...

#8

cjdelphi: So there is no instance where adding a resistor can cause harm?

I bet it could, thinking along the lines of sensors used for safety, eg if you used one on a distance or heat sensor you could stop it working or go weird and a robot connected or car, could then screw up and kill you by not seeing you...

Absurd. Nobody should add resistors or anything else in a safety-related situation and then blindly turn that loose on the world. But that's not the situation. In the context of the OP's concern - no harm: zero.

#9