How can I get a relay (relays) to work on an Arduino uno the output between ground and the pin is 2.5 volts. Thank you
google "arduino relay circuit"
If you ever try to drive an inductive load like a relay directly from an Arduino
pin you will likely destroy the Arduino pin (or the whole chip, or even the board).
You must use a flyback diode across relay contacts and you must not draw more
than about 25mA from any Arduino pin (40mA absolute maximum one-time exposure).
A relay coil can push back 100's or 1000's of volts if you switch it without appropriate
protection (such as flyback diode).