and you may find plenty of circuits for it. However these circuits do not
guarantee consistent torque levels at lower motor speeds, making the functioning
Moreover at very low speeds due to insufficient torque, the
motor tends to stall. Another serious drawback is that, there’s no motor reversal
feature included with these circuits. The proposed circuit is completely free
from the above shortcomings and is able to generate and sustain high torque
levels even at lowest possible speeds.
to learn the simpler alternative which is not so efficient, yet may be
considered reasonably good as long as the load over the motor is not high and
as long as the speed is not reduced to minimum levels.
controlling DC motor speed, we won’t go into the details, the only notable
drawback of this configuration is that the torque is directly proportional to
the speed of the motor.
ICs instead of one or rather a single IC 556 that contains two 555 ICs in one
Briefly the proposed DC motor controller includes the
following interesting features:
constant even at minimum speed levels.
fraction of second.
One sections is configures as an astable multivibrator generating 100 Hz square
wave clocks which is fed to the preceding 555 section inside the package.
frequency of the PWM.
which keeps the adjoining capacitor at its collector arm charged.
which is compared inside the 556 IC with the sample voltage applied externally
over over the shown pin-out.
derived from a simple 0-12V variable voltage power supply circuit.
voltage applied to the 556 IC is used to vary the PWM of the pulses at the output
and which eventually is used for the speed regulation of the connected motor.
direction whenever required.
The above circuit was inspired from the following circuit which was published long back in elecktor electronic India magazine.
The first diagram can be much simplified by using a DPDT switch for the motor reversal operation, and by using an emitter follower transistor for the speed control implementation, as shown below: