UC3844 base motor speed controller

UC3844 is a popular current mode controller which is commonly found on DC-to-DC converter circuits and switch mode power supplies. This motor speed controller is also based on UC3844 and it is specifically designed to drive 20V - 24V DC motors.

In this given configuration UC3844 produces (approx.) 50kHz to 240kHz PWM output and this range can be adjusted by changing the value of C2 timing capacitor. As per the datasheet, UC3844 is capable to produce PWM output frequency up to 1MHz.

This circuit is quite sensitive to the noises, and to get the accurate output to construct this circuit on PCB. As per our observations, long wires on the oscillator circuit may change the stability of the output signal.

According to the ON semiconductors, UC3844 has now discontinued product but it is still commonly available in the market for less than Rs. 40.00 (LKR). For this circuit either DIP (UC3844N) or SMD (UC3844D1) version of UC3844 can be used but the PCB design available with this article is based on DIP version of UC3844.

The schematic and PCB layout for this motor controller is available to download at google drive.

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