Back EMF Precautions when using MIDI Solutions Relays to Drive Inductive Loads

Protecting MIDI Solutions Relays from Back EMF Generated by Inductive Loads

When switching external loads with MIDI Solutions relays there is the potential for back EMF to be generated. Back EMF arises whenever current is removed from an inductive load (such as a coil in a larger relay or solenoid). The current wants to continue to flow through the load and so a reverse voltage builds up which can spark across the contacts of the relays in the MIDI Solutions product, causing them to stick or even causing permanent damage if the spike in voltage is high enough. The solution is to add a diode across the load in the opposite direction that the current normally flows, then when the current tries to flow in the opposite direction it is shunted by the diode. Most common diodes and rectifiers will work, e.g. 1N4001, 1N4002, 1N400x, etc.

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