Brushed 12v DC motor active speed control (no arduino)

Thread Starter

alpha027

Joined Oct 17, 2020
5
Hi,

I want to actively control DC motor speed and I am looking for some hints on the corresponding control circuit.

What I have found till now is classical control schems with Potentiometers (mechanical), however, this is not convenient for my use case.

I am looking for a circuit that I can program with my own function (taking speed feedback from the motor through the encoder) and then actively changing the motor's speed.

I look for your help !

Thanks
 

Alec_t

Joined Sep 17, 2013
12,148
Welcome to AAC!
What have you got against using an Arduino? Code for motor control is already freely available and could surely be adapted for your purpose.
Do you have experience with programming any other microcontroller?
 

Thread Starter

alpha027

Joined Oct 17, 2020
5
Thanks for your reply.
Of course Arduino is very suited for this use case and I have nothing against it.
Till now, my only microcontroller programming experience has been with Arduino.
The thing is that I want to build a custom PCB and have 10 copies of the same project. Therefore, I am struggling to build the circuit from scratch, or find alternatives on the web -not found till now-. Or, second alternative is to replicate the same arduino circuit in a custom PCB.

Feel free to give recommendations or useful links for built up circuits.
 

s14rs4

Joined Sep 15, 2016
73
If you are familiar with the Arduino, and can program it to do the functions you want, why don't you use an Arduino Uno with the ATMEGA328P DIP package in a socket, program it, then remove the IC and incorporate into your own PCB without all the unused peripherals.
 

MaxHeadRoom

Joined Jul 18, 2013
23,341
Your title requests no Arduino, as I posted it can be done with a small pic, The last boards I put together are 8 pin pic and the board is 50mm x 50mm.
Max.
 
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Reloadron

Joined Jan 15, 2015
5,992
Much of what you are asking also depends on the motor be it a fractional horsepower DC motor to a larger HP DC motor. Then there is the type of DC motor to consider. Most people will suggest using a uC (micro-controller) simply because regardless of motor size and type the uC is the common approach, if nothing else to reduce parts count and subsequently cost. A very popular fractional HP variable speed DC motor for years was made by Bodine, they made an endless array of DC motors and AC too. Most had armature and field windings labeled A1 and A2 followed by F1 and F2 where a fixed DC voltage of about 130 VDC was used and an adjustable DC voltage. It was just how it was done before we had nicer permanent magnet variable speed DC motors and now most speed control, depending on motor type, use a simple PIC chip as Max points out. Lower parts count and lower cost. Anyway this starts with how large of a DC motor (HP) and what type DC motor?

Ron
 

KeithWalker

Joined Jul 10, 2017
1,850
I have no idea what size motor you will be using but I designed and built this speed controller when my record turntable died. It still works well after 9 years of use. It uses the back EMF of the motor to monitor the speed. As you can see, the speed can be pre-set with the resistors on the left.
Initially, to set it up, the 1Mohm pot is adjusted with the motor stalled to give 0V at the output of the bottom left op-amp.
I used an LM324 op-amp with a dual +/- 12V supply and a 2N3904 transistor. You are welcome to use any part of the design if you wish.
For the purists, yes, there are no dots at the junctions of the lines in the circuit but that does not cause any compromises so I am not going to re-draw it for you. :)
Regards,
Keith
Phono Speed Copntroller Schematic.jpg
 
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jpanhalt

Joined Jan 18, 2008
11,088
Today, it might be hard to find ways to do that that do not use microcontrollers. In any event, you will need some way to monitor the rpm. Digital makes that easy. However, if you have a voltage that is proportional to speed, here are some links from my files that might help.

Lots of good stuff here on voltage (or pot) controlled PWM drives:
http://www.4qdtec.com/pwm-01.html
http://www.4qdtec.com/#mot

One example of a voltage controlled PWM chip (TPIC2101):
https://www.digikey.be/htmldatasheets/production/261671/0/0/1/tpic2101.html

EDIT: The TPIC2101 is now obsolete but is available for sources that specialize in older stuff and eBay. You can also search on voltage-controlled motor controllers.
 
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