Theory··9 min
Understanding Back EMF in Pulse Motors
What back EMF is, why it matters, how to measure it, and how to build a BEMF recovery circuit.
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Back EMF is the reverse voltage spike produced when current through a coil is interrupted. The collapsing field induces a high-voltage pulse — often many times the supply.
Why it matters
- Without a path, spikes destroy transistors
- With a recovery diode and secondary battery, you capture energy that would be wasted as heat
- It's efficiency engineering, not magic
Practical tips
- Always use a flyback/recovery diode rated for the spike
- Scope the collector node if you have an oscilloscope
- Compare primary draw vs secondary charge carefully over time
See also: Oscilloscope Readings.
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