Introduction: Resistor Motor Driver 2

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In this Instructable you will be making a motor driver 2.

Although I used a 9 V power supply in the video, testing proved that my low current motor could spin at just 3 V (two AAA batteries).

In this circuit, the diode protects the power sources from reverse currents from the motor. I used Schottky diode that has low forward bias voltage and thus to maximises the voltage supplied to the motor.

Warning:

1. When you connect the circuit make sure that you do not short the positive and negative terminals with the switch.

2. Be very careful if you connect this circuit to USB power supply. I advise you not to do it. You can short the USB power supply due to poor wiring and high current consumption from the motor and probably even resistors alone..

I suggest that you also read a similar Instructable made by Simple Circuits:

https://www.instructables.com/id/Resistor-Motor-Dr...

Supplies

Components: Low current DC motor, 6 V power source maximum (AA or AAA batteries), battery harness, high power variable 1 kohm potentiometer. on SPST switch, wires.

Tools: screwdriver, pliers, wire stripper, scissors.

Option components: box cardboard/plastic, bolts/nuts/washers/wire terminals, high power diode - 2, crocodile clips, simulation software.

Optional tools: soldering iron.

Step 1: Draw the Circuit

I have drawn the circuit via Easy Eda software (https://easyeda.com).

You need high power resistor for this circuit.

Ro is used for short circuit protection.

I am not sure if a typical 1 kohm variable resistor can handle the high currents in this circuit. Usually, high power potentiometers are produced as low as 500-ohm in resistance.

In real life, a motor is made from coils. Not resistors. However, all coils have resistance in practice.

When the motor is stationary (motor movement is halted or impeded by physical/mechanical means) the motor resistance is approximately zero and the current across Ro and Rv is maximum:
ImaxRo = (Vs - Vd) / Ro = (3 V - 0.7 V) / 10 ohms = 2.3 V / 10 ohms = 230 mA (We are assuming that Rv is set to maximum setting).

Step 2: Make the Circuit

You can see that I used two high power Schottky diodes in parallel to reduce power dissipation for each diode.

The 10 ohm Ro resistor should have been 5 ohms because I noticed that my device is not moving the motor when connected to 1.5 V battery and needs at least 3 V.

Step 3: Encasement

I used blue tack to cover the hole in the box. Initially I drilled the hole for a typical potentiometer. However, when the potentiometer arrived in the mail it so big that I had to move the potentiometer to the centre of the box, thus leaving the hole in the plastic box encasement.

The 1 kohm potentiometer is a high power variable resistors from Rockby Electronics and produce in Melbourne, Victoria, Australia. I paid $9. I could have used a cheaper 1 kohm potentiometer. However, I was worried about burning the potentiometer.

Step 4: Testing

You can try shorting the diodes and reducing the value of the Ro resistor. Then motor might spin when only one AAA battery is connected, suppling the device with only 1.5 V.