How to Avoid Back EMF

Back electromotive force, or EMF, essentially is current flowing in the wrong direction on a circuit path. Back EMF can damage sensitive components and circuity, without the use of a blocking device. When installed, these devices act as one-way transducers that only allow current to flow in one direction. When using small motors, solenoids, or relays, adding a blocking device is nearly always useful and often essential.

Things You'll Need

• Circuit board schematic
• IN4001 diode
• Soldering iron
• Lead-free solder

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Instructions

1. • 1

     Find the primary transistor that leads to a switching relay controlling the activation of the motor, or other device, generating back EMF. Consult the schematic for the device, if necessary.

   • 2

     Apply a small bead of solder to the small legs on the diode to power.

   • 3

     Apply a second bead of solder to the leg of the EMF-blocking diode -- to the point bridging the primary relay and transistor. The transistor should lead from the primary switching relay to ground for EMF avoidance.