In this post we discuss a simple, accurate, high torque treadmill motor speed controller circuit which may be effectively installed in similar units for acquiring PWM controlled variable speed feature. The idea was requested by Mr. Samuel.
The Circuit Request
I've a treadmill whose power failed completely...it had been imported from china and it's like they can't help after negotiating with them..guarantee is only meant in their x-try.
So, am asking, how would you assist me in designing a power supply that will control speed and change of direction of the treadmill movement as well. I'm and forever will be glad for your work.
Looking into the specs of the unit, the switching relays are specified with 10A ratings. I also had a view of the motor and it was written 180Volts on it.
This is the information i got sir. They also had a cautionary notice that the T.Mill shouldn't be run beyond 2hrs continuously. I hope I've given the best for the best.Thanks sir. Stay blessed now and forever! best moments!
The Circuit Design
Here's a simple PWM based motor speed controller circuit which can be used for controlling a treadmill speed right from zero to maximum.
The circuit also provides an instant bidirectional stop and reversal of the motor rotation by a single flick of a given switch.
Another interesting feature of this circuit is its capability of sustaining and balancing optimal torque even at lower speeds ensuring a continuous working of the motor without stalling it during extreme low speeds.
The circuit of the proposed treadmill motor speed controller may be understood with the help of the following points:
Here the two 555 ICs are configured as PWM generator/optimizer for acquiring the required speed control of the connected motor.
IC1 works as a frequency generator and is rigged at around 80Hz, any other value would also do and is not anyway critical.
The above frequency from pin#3 of IC1 is fed to pin#2 of IC2 which is wired as a standard monostable. IC2 responds and starts oscillating at this frequency, forcing equivalent triangle wave frequency at its pin2/6.
The above triangle waves is instantly compared by the set potential at pin#5 of IC2 creating an equivalent level of chopped PWM at its pin#3
The preset or a pot positioned at pin#5 of IC2 forms a potential divider network for a selectable fixing of any voltage from zero to maximum supply voltage at pin5 of IC2. This level is directly translated through optimized PWMs at pin#3 of the same IC as explained above.
The PWMs are fed across two sets of NOT gates via an SPDT toggle switch.
The NOT gates which act as inverters provide the feature of instant toggling of the motors rotational direction by a mere flick of the SPDT switch.
The resultant PWMs from the selected NOT gates finally reach the transistorized bridge network that holds the motor between them for implementing all the specified features discussed above.
These transistors should be rated as per the motor specifications, and the voltage across this bridge should also be as per the motor requirements.
As rightly suggested by one of the dedicated readers of this blog, Mr. Ivan, a 180 V treadmill motor can be simply controlled through mains phase chopping concept, normally incorporated in all commercial dimmer switches for regulating home fan speed.
Using A Dimmer Phase Chopper Circuit
Shown below is a modified dimmer switch circuit design which can be effectively used for regulating a 180 V treadmill motor from zero to max: