Motor Drivers

Introduction: Motor Drivers

About: Our circuits are designed in Philippines and tested in Australia.

This Instructable teaches you about motor driving circuits.

Nowadays there are a number of motor driving ICs (integrated circuits) sold at:

However, because sparks can jump between the IC contacts for DC motors you might need to use transistors unless the IC is produced in an appropriate metal can package. Also, if a particular IC is not longer produced you will no be able to fix the circuit.

The values of resistors and capacitors depend on:

- type of motor that you are using (inductance, current consumption) - will affect transistor type, heat sink, capacitor power/voltage/current rating, Ro resistance/power rating, Vs voltage, diode voltage/current/power rating,

- motor EMI (electromagnetic interference) that you are trying to filter with C1 capacitor - affect the value of the capacitor.

- device lifetime (component power ratings and component lifetimes in specifications),

- maximum temperature (component power ratings).

This circuit needs to be connected to a pulse width modulator (PWM) that will control the motor speed.

The diodes are used to protect the transistors from motor discharge current.
The capacitor is used to filter high frequencies in the circuit that can cause EMI. Large capacitors can filter lower EMI signals. However, they cannot filter high EMI signals. Thus you might need two capacitors if you are building this circuit.


Simulation Software. This could be online and software that you download and install. I used old PSpice Student Simulation software only to reduce the circuit drawing due to keyboard short cuts that modern software does not allow.

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Step 1: Draw MOSFET Circuit

Old PSpice software was used to reduce time due to keyboard short cuts.

Step 2: Simulate MOSFET Circuit

Simulations show a fast response time of MOSFET circuit.

Step 3: Draw BJT Circuit

I have drawn a BJT circuit because some MOSFET have low maximum gate-source voltage. This is probably the only advantage that a BJT transistor has over MOSFET for those particular applications.

Step 4: Simulate BJT Circuit

Simulations show a fast response time of BJT circuit.

You are now done.

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