Hey guys!
Im currently working with small dc motors and the typical pwm mosfet speed controller.
But in the low range of pwm signal, like 1-20, the motor does not spin, it just make a sound, and I thought it is normal but recently a saw a video in which a guy says that it can be solved with a decupling or bypass capacitor, and recently while taking apart a tool that uses the same type of motor, i found a small ceramic capacitor solded in parallel with the motor and I dont know what is it for. Maybe it is yor this? Can a motor start spinning from the start of the pwm range with a capacitor? And witch type the capacitor I should use?
Are you changing the width of the + part of the signal, or are you only changing the frequency?
I suggest you tell us what you are using to power the motor and what you are using to control the power. A typical device does not convey any information, as you are the only one that can see it. A data sheet for the motor, the controller and a schematic would bring a lot more help.
Paul
Im changing the width of the pwm. The control is a simple irl44z mosfet and the motor is a regular 12V brushed dc motor
There is a minimum PWM value that a motor will start at, that value depends on the motor, how heavily the motor is loaded, voltage, etc. Please describe a "regular" DC motor. Post a diagram of your wiring.
That cannot "always" be solved with capacitors.
Some motors require a set voltage to actually turn and of course the required amps too.
Find the minimum needed to turn it and that is the start point anything less and you should turn off the mosfet.
I generally call the lowest number a tickover point and add to it by a small margin so if the tickover was 10 I would set the minimum at maybe 12.
So many 12 volt motors with so many different aspects to them.
Maybe a few will benefit from a large capacitor to give them a boost but one the charge in the cap dissipates that's it you will be back at a stall point.
tycobrae:
Hey guys!
Im currently working with small dc motors and the typical pwm mosfet speed controller.
But in the low range of pwm signal, like 1-20, the motor does not spin, it just make a sound, and I thought it is normal but recently a saw a video in which a guy says that it can be solved with a decupling or bypass capacitor,
no, that's not the case. For low speed with good control a servo loop is necessary. Brushed motors in particular have a lot of static friction in the brushes to overcome, and at low current they just stop. Some sort of active feedback loop is needed to allow for this.
and recently while taking apart a tool that uses the same type of motor, i found a small ceramic capacitor solded in parallel with the motor and I dont know what is it for. Maybe it is yor this?
No, it reduces EMI so that nearby radios don't become unusable.
Can a motor start spinning from the start of the pwm range with a capacitor? And witch type the capacitor I should use?
No, if you need good control at low speed you either need more reduction gearing or a servo-loop.