Adjustable Voltage motor controller

Posted on Feb 6, 2014

The problem is how to control the speed of the motor. One way is to use the plane, radio, and speed control with the motor in it. That`s no fun! Mount the motor on the bench and just plug the batteryinto the motor. That`s even worse! It`s hard on the motor and gearbox. To solve the `It`s hard on the motor and gearbox` problem I made myself an Adjustable Voltage Control unit (speed control)

Adjustable Voltage motor controller
Click here to download the full size of the above Circuit.

so I can slowly bring the motor up to speed. VR1 is used as a voltage divider to drive Q5, Q5 then drives Q1, Q2, Q3, and Q4. As VR1 is turned clockwise the voltage increases on the base of Q5. Q5 then increases the voltage on Q1, Q2, Q3, and Q4. As the base voltage increases on the on Q1, Q2, Q3, and Q4 the voltage will increases to the motor. As Q1, Q2, Q3, and Q4 are used in parallel. 1 ohm resistors are placed on the output of the 3055s to make an attempt to balance the load between them. The 12 volt regulator is used to supply a constant 12 volts to the fan when using voltage above 12 Prototype of the Adjustable Voltage Control. Note the 12" of 14 awg used for. 1 ohm resistors (red wire). To help keep the 12 volt regulator cool I mounted it on the exhaust side of the Heatsink. (not shown) I have tested this Adjustable Voltage Control and have found that the 3055s generate quit a bit of heat, even mounted to a large fan cooled Heatsink. The voltage drop across the voltage in to voltage out is about. 10 volt per amp or 1 volt for every 10 amps. To make up for the voltage loss I made a series connector to run two battery packs to double the input voltage.

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