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An On and Off Motor Controller with Brake

An On and Off Motor Controller with Brake

This Motor Controller with Brake controller has the following specifications the size ranging from 1.5 inch L x 1.3 inch W x 1 inch H.It weights approximately 1oz. Current consumption is 10A nominal and 20A for maximum recommended. Voltage ranges from 7.2V to 12V . No power-on glitch and Throttle stays off when transmitter is off.
The Circuit
The circuit for the controller begins with a buffer, consisting of R1, R2, R3, and Z1A, which isolates the receiver from the rest of the circuit and makes operation of the circuit independent of the exact signal levels from the receiver.
R4, R5, and C1 form an integrator. Whenever a pulse comes in, Z1A inverts it, and discharges C1 through R5. In the space between pulses, C1 recharges through R4 and R5. The longer the pulse, the lower C1 will discharge.
The comparator stage, consisting of Z1B and Z1C wired in parallel (to provide a larger current sink for C2) detects if C1 ever drops below a threshold (set by R2 and R3). If it does, C2 is quickly discharged during the time that C1 is below the threshold. Between these discharge times, C2 is slowly charged through R6. C2, R6, and Z1D form a missing pulse detector. As long as C1 periodically goes below the threshold, C2 will be discharged and also remain below the threshold, thereby keeping the output of Z1D low. If C1 stops going below the threshold (because the pulses have become shorter), C2 will recharge, and Z1D will go high.
The final stage, consisting of R7, R8, and Q1 turns on the relay whenever the output of Z1D is low. So, short pulses from the receiver will leave the relay turned off, and long pulses will keep it turned on.
The arming switch is wired between the motor battery positive side and Q1. When the switch is open, no current can flow through Q1, and consequently, the relay cannot be turned on.

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