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Topic: Using positive 12v as switch input instead of 0v (Read 275 times) previous topic - next topic


Hi All

Here is the first stage of what i'm trying to do

I already have a pre-made controller that has an output of positive 12v which i'm trying to connect to a relay board. The problem that i'm having is that the relay board requires a connection to ground to switch the relay instead of the positive 12v that my pre-made controller is outputting

does anyone know how i can reverse this on the relay board so that when i put +12v onto the input of the relay board it will switch instead on 0v

if you know of a way to do this via the arduino or directly to the board id be glad to hear it. I can try and provide more information if its confusing. :smiley-confuse:


Mrs Drew
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If I've understood it correctly from your description, you need a NPN transistor between the relay coil  and ground.
Look up: Transistor Switch Low Side.
If you are using a relay module, some have a jumper to change the trigger from HIGH to LOW.
Post a link to the relay or relay module you are using and maybe you get some better answers.


Does your pre-made controller have a specification for current sourcing?  Perhaps it can drive the coil of a 12V relay directly.  Check the specification of the relay to find out the required coil voltage and current.
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