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Topic: 12vdc input to 5vdc for Arduino (Read 143 times) previous topic - next topic


Gents How can I get a 12vdc signal from a laser eye down to 5vdc for Arduino Uno?




Resistor divider



Sep 25, 2018, 07:26 pm Last Edit: Sep 25, 2018, 07:31 pm by DVDdoug
A voltage divider (2 resistors) is probably the easiest solution.   The resistor values are not critical but if they sum-up to around 10K Ohms, that's good.  (The ratio is important!)

Another easy option is an over-voltage protection circuit.   This is better (safer for the Arduino) if the 12V is not regulated, but it only works with  zero or 12V digital signals.   It won't work with zero to 12V analog signals.    (I'd recommend changing the current-limiting resistor to about 1K).

...The opto-isolator (or relay) is very safe because the 12V is electrically isolated from the Arduino, and the transistor method also provides over-voltage protection (assuming it's wired correctly, etc.).


If that 12V signal is push/pull a simple diode pointing away from the Arduino is all you need. Enable the internal pull-up for a reliable high, whenever the signal goes low it pulls the pin low through the diode.
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