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