DC MOTOR CONTROLLER

[Jherms]

Does anyone know how to make a DC MOTOR CONTROLLER? Need help for my final project. If anyone has made one already, may i see the diagram and its processes? Help anyone. Thanks in advance.

[Staigen]

Hi there Jherms, velcome to this board

There are many ways to do this! We need moore input! Constant RPM? Constant torque? Proportional? One direction or both? Voltage? Current? Stall current? What is it supposed to do? Moore?

//Staigen

[audioguru]

Hi Staigen,
Have you seen this "PWM" motor speed control circuit in our projects section?
http://www.electronics-lab.com/projects/motor_light/033/index.html
It looks like just a variable frequency oscillator to me. I think the motor's speed would remain the same about half, but it would buzz at a low setting and squeal when high.

I think adding a diode across a resistor would turn it into a real PWM motor speed controller. ;D

[Staigen]

Hi

No, i havent seen this before, got me a good laughter :) :D ;D

I think adding a diode across a resistor would turn it into a real PWM motor speed controller.

Yepp, across R2!

Only 6 Volt for the gate? I havent read the data for the mosfet, but isn't that a little low? And the gate connected to a Cmos, dont they have drive capability on the low side a bit? And no stopper? :( :D

//Staigen

[audioguru]

Only 6 Volt for the gate? I havent read the data for the mosfet, but isn't that a little low?

I think the author likes warm Mosfets.

And the gate connected to a Cmos, dont they have drive capability on the low side a bit?

Cmos operating with a supply of only 6V has an output current of about only 2mA. It will take a long time for only 2mA to fully charge the high gate capacitance of a power Mosfet. I think the author likes hot Mosfets.

And no stopper?

I think the author likes melted Mosfets (on rye bread). ;D ;D

[Guest Alun]

Come on, use your common sense, 6V is fine if you're only using it to power a low current 6V motor that uses less than an amp or so and it depends on the MOSFET too, the NTE2980 can switch quite a big load with only 6V at the gate. ;D

[Staigen]

Come on Alun, use your common sense, the project is not a PWM controller, its only a variable cmos oscillator, driving a power mosfet, thats driving a DC motor! It have errors, stating it is a PWM controller, amongst others. And the parts list states IRF511 or IRF620 and the notes says that the motor can draw up to the max current of the mosfet.


//Staigen

[Staigen]

I belive we came a little bit offtopic, hehe, back into the line again! ;D ;D

//Staigen

[Guest Alun]

Fair enough I stand corrected, I deserved that flaming, it isn't a PWM controller it is a variable CMOS oscilator and with the MOSFETs on the parts list only a motor can be used.

[Staigen]

It's okay Alun, i also make mistakes, often much bigger than this, sorry if you felt jumped on, not my intensions

//Staigen

[audioguru]

Hi Guys,
If the circuit is corrected by adding a diode, by using the spare gates in the Cmos IC in parallel with the existing one to drive the Mosfet with much more current and using a 12V supply, it will control the speed of a powerful motor and will also make a pretty good lamp dimmer.
No stopper? Don't stall the motor. A polyfuse would protect it and the Mosfet. ;D

[Shahriar]

There is a good one in the project section with this topic
"PWM Motor/Light Controller "
here is the schematic:


I have a MCU base PWM Controller with LCD and keyboard. IF you know programming I can send it to you.

[audioguru]

I used that motor speed control circuit in my electric model airplane and it works very well.

[Guest Alun]

Or you could save yourself a couple of op-amps. ;D

[audioguru]

Hi Alun,
Deja vu?
I used a voltage regulator for my circuit's PWM oscillator so that the motor's speed would remain constant as the battery voltage ran down, then a 3rd opamp as its comparator operating at the full supply voltage for plenty of Mosfet gate voltage.
Your circuit would also need a 3rd opamp for my application. ;D