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daq-and-datalogging:documents:relay-control-from-digital-out [2023/06/13 15:52] – created Scandiwebdaq-and-datalogging:documents:relay-control-from-digital-out [2023/07/28 00:56] (current) – Arthur Brown
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-====== Controlling a relay or solenoid from a digital out ======+====== Controlling a Relay or Solenoid From a Digital Out ======
  
 Most digital IO of MCC products are control signals meaning they are TTL levels, but very low current. Most digital IO of MCC products are control signals meaning they are TTL levels, but very low current.
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 Here is the circuit I used: Here is the circuit I used:
  
-{{https://files.digilent.com/resources/measurement-computing/Reference Images/Circuit2.png?467x300}}+{{https://files.digilent.com/reference-images/Circuit2.png?467x300}}
  
 NOTE: be sure your relay has a back EMF diode (a.k.a. flyback diode) built in, or add one externally.  To add one externally, use a diode such as a 1N914, 1N4148 or 1N4004 installed across the relay’s coil terminals such that the cathode is attached to the same terminal as the power supply.  This will allow it to conduct current in a circular loop from the positive potential at the bottom of the relay coil to the negative potential at the top when the relay is de-energized. NOTE: be sure your relay has a back EMF diode (a.k.a. flyback diode) built in, or add one externally.  To add one externally, use a diode such as a 1N914, 1N4148 or 1N4004 installed across the relay’s coil terminals such that the cathode is attached to the same terminal as the power supply.  This will allow it to conduct current in a circular loop from the positive potential at the bottom of the relay coil to the negative potential at the top when the relay is de-energized.