I need help figuring out if I got mains voltage or DC temperature controller.

Thread Starter


Joined Nov 8, 2018
I ordered a while ago temperature controller from china. It was supposed to be AC 220 volt version but when I received it the back of the device said it was 12 volt DC. The item number was right on the packing so I got curious and opened it. the insides looked different from the insides of a 12 volt version that I saw on a youtube video. this has transformer in it and this led driver http://www.datasheetcafe.com/bp9022a-datasheet-led-driver/
I couldn't find any rectifier bridge in it. Here are some photos of the thing.



Joined Aug 12, 2014
One simple way to find out would be trying to power it with 12VDC. I'm guessing it actually is a 12V model, but if not, I seriously doubt that 12VDC will do any harm to a high voltage model.

If it runs on 12VDC, there's your answer.


Joined Sep 17, 2013
Perhaps the main board is a 12V powered one and the daughter board with the transformer is a mains-to-12V adapter? If only half-wave rectification is used you won't see a bridge rectifier.


Joined Apr 2, 2009
But it does have a 400V cap at the input side.
My guess is 220VAC input.
But tht's just me.

I would use a auto tx and power it up.

Thread Starter


Joined Nov 8, 2018
I just tested it with 12 VDC and it didn't start up. Then I took some readings from the circuit with multimeter and it showed that 12volts at diode what the current hits first and 12volts at primary of that transformer but secondary of the transformer gave only readings of millivolts. I am still trying to gather the courage to hook it to mains power and see if it will work with that or was there something else I missed.


Joined Jan 23, 2018
If you have a reasonable ohm meter, measure the resistance across the two power input terminals, then reverse the connections and not the resistance reading. If the two values are exactly the same, then it is probably a device intended for AC power. But if the resistance in opposite directions is different, then probably DC. One more thought is to use the ohm meter from one of the power leads and see if it connects to the transformer. A DC input will not connect to the transformer.