Designing a circuit to control dc motor speed

Thread Starter

NickAK

Joined Apr 29, 2024
2
Hi everyone,
I'm very much a beginner at designing circuits, and am having trouble researching how to create 3 speed modes +on/off for a small dc motor,
operated only by a push button. The only online results I have found online use an Arduino but I want to create this as an embedded circuit for a small project I'm working on. The closest thing I can find is the control board for a usb fan, but again I've struggled finding any pcb diagrams or anything that explains how it works online.
Any thoughts?
 

LowQCab

Joined Nov 6, 2012
4,290
Does the Motor-Speed need to be regulated to a specific RPM-range ?

What is the Load that the Motor is driving ?

How much Current does the Motor require, and at what DC-Voltage ?

Is this project Battery-Powered ?, or Mains-Powered ?

A "One-Button" requirement complicates things a lot, making a Micro-Controller the best choice.
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ElectricSpidey

Joined Dec 2, 2017
2,880
If it's just a small DC motor and the control is not that important, you could configure a counter chip to vary the voltage divider of a simple transistor follower circuit.

Details are needed.
 

Thread Starter

NickAK

Joined Apr 29, 2024
2
Hi everyone,
I'm very much a beginner at designing circuits, and am having trouble researching how to create 3 speed modes +on/off for a small dc motor,
operated only by a push button. The only online results I have found online use an Arduino but I want to create this as an embedded circuit for a small project I'm working on. The closest thing I can find is the control board for a usb fan, but again I've struggled finding any pcb diagrams or anything that explains how it works online.
Any thoughts?
Thanks for your responses
Finer details :
Battery powered, 7.4V
The motor that I am looking at using is 12v dc with max current draw ~0.5A, the motor should be able to drive up to 0.15kg/cm ideally.
It is very possible that I will need to revise these details, I would like to learn how to design a system that incorporates this so I can iterate and improve from somewhere.
IMG_7960.JPGAttached is my notes on the basic functions I was mapping out. I'm confident I can design and produce circuits to safely charge the battery and power LEDs to tell the user if the device is on/off and charge status.
The main problem I've had is from taking a single voltage input and being able to switch between 3 output voltage modes, there isn't much relevant information online that I can find.
Any pointers on where I can look would be super useful !
thanks
 
Hi everyone,
I'm very much a beginner at designing circuits, and am having trouble researching how to create 3 speed modes +on/off for a small dc motor,
operated only by a push button. The only online results I have found online use an Arduino but I want to create this as an embedded circuit for a small project I'm working on. The closest thing I can find is the control board for a usb fan, but again I've struggled finding any pcb diagrams or anything that explains how it works online.
Any thoughts?
Take a look at this:
 

LowQCab

Joined Nov 6, 2012
4,290
"" The motor that I am looking at using is 12v dc with max current draw ~0.5A, ......... ""

"" the motor should be able to drive up to 0.15kg/cm ideally. ""
What kind of measurement is this ?

"" It is very possible that I will need to revise these details, ............. ""

It would appear that You are pursuing this project completely backwards.

What is the overall-purpose, or "Valuable-Final-Product", of this project ?

Please explain what You are trying to do, in as much detail as possible.
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MisterBill2

Joined Jan 23, 2018
19,366
The very simplest scheme for multiple speeds for a DC motor is a copy of the heater blower speed control that was used in cars back until after the 1960's It was a simple switch that controlled how much resistance was connected between the motor and the power source. Fairly cheap, very reliable, and terribly inefficient. But it served many thousands of people quite well for many years.
 

Audioguru again

Joined Oct 21, 2019
6,778
Don't you want to regulate the RPMs of the motor? Then you need a tachometer and error amplifier.
I am thinking about a portable cassette tape recorder invented in 1968.
 

MisterBill2

Joined Jan 23, 2018
19,366
Certainly there is a question as to the application and the degree of control required. With the three speeds given it seems that there will need to be a stage of reduction because mostly small/medium DC motors spin in the thousands of RPM, although some will run smoothly at slower speeds.
the 0.15Kg/cm is a metric TORQUE specification that tells me the motor is in the 1 1/2 to 2 inch diameter class.

And we still do not know if the requirement is for regulated speeds or just "Fast-medium-slow control."
 
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