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How It Works

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12 Volt
24 Volt Modifications

Quick Reference

Dump Controller - How It Works

The ZM33064 (ZM) is a tiny voltage controlled switch.

The Zener diode (ZD1) and potentiometer (pot) is an adjustable voltage divider. This feeds a portion of the battery voltage to the ZM.

If the voltage to the ZM is higher than approximately 4.6V the switch is open, current through the resistor RX makes a voltage of 5.1V at the gate of the 2N7000 (N-fet) turning it on. The N-fet pulls the BSS92 (P-fet) gate to ground, turning it on. The P-fet sends power to the LED and the power N-fet gate, turning them on. The IRFZ44N power N-fet turns on the dump load.

If the voltage to the ZM is below 4.6V, the ZM is closed, grounding the gate of the N-fet. The N-fet is off and the rest of the circuit is off.

  • The capacitor (C1) provides a very short minimum time delay between switching cycles to prevent the circuit from running too fast.
  • The adjustment of the pot determines at what battery voltage the circuit will turn on.
  • Resistor RX determines the hysteresis (the difference between the voltages/when the circuit turns on and off).
  • The diode 1N4007 (D1) protects the circuit from reverse voltage.
  • LED1 simply indicates the circuit is connected to the battery.
  • LED2 indicates the dump load is on.
  • Resistors R1 and R2 limit the current through the LEDs.
  • R4 limits current through the P-fet to the gate of the power N-fet.
  • R5 pulls the power N-fet gate to ground when the circuit is off.