Question about three wire dc motor

Thread Starter

johnboyman

Joined Jun 1, 2019
32
Hello. I am found a 3 wire dc motor that is in brand new condition. I tried hooking it up with a dc power source its a dc motor. It has three wires and green black and red. the number ldc on my 36 volt power supply flickers so i think the power cables are not hooked up properly. I know what 3 phase ac motors are and how they work but i do not know much about a 3 wire dc motor. I read around and heard you need a micro controller to control a 3 wire dc motor. Does anyone know how to make a or get a simple controller for one of these motors or anything about them. Thanks.
 

Reloadron

Joined Jan 15, 2015
5,370
Using an ohmmeter I would measure between motor frame (case) and the green wire. If you have continuity then red and black are your DC lines with red being likely positive. Should there be no continuity (open circuit) then see post #2 above.
Hello. I am found a 3 wire dc motor that is in brand new condition.
That's nice and you fail to mention if the motor has any name plate data or model number or manufacturer?

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
20,471
Also does the motor have brushes? If not and If continuity between all three conductors then it is BLDC, but the odds are it is DC brushed and the green is frame ground..
Max.
 

Reloadron

Joined Jan 15, 2015
5,370
I found this article now that i have the keyword BLDC.

https://elabz.com/brushless-dc-motor-with-arduino/

It shows how to run a 3 phase dc motor with an Arduino. That is the wierdest thing ever. I have to make this work now. Thanks for the advice.
That is not weird. You have a motor which runs on an unknown voltage drawing an unknown current. The unknowns here will make running this motor a little difficult. You will need an interface between the Arduino (or micro-Controller of your choice) and that interface will require you knowing at least something about the voltage and current ratings of the motor. Read into this no Arduino will directly drive much of a BLDC motor.

Ron
 

MaxHeadRoom

Joined Jul 18, 2013
20,471
I have never used Arduino, but the Pic's have a PWM module built in, this gives you the form of programmable speed control, then you need a 3ph bridge controller, usually consisting of Mosfets and dedicated driver IC's.
Then also you need to decide if you need bi-directional motor control.
If your motor does not come with commutation sensors, which it sounds as though it doesn't, then you will require some method of initially detecting rotor position.
Max.
 

djsfantasi

Joined Apr 11, 2010
6,367
I have never used Arduino, but the Pic's have a PWM module built in, this gives you the form of programmable speed control, then you need a 3ph bridge controller, usually consisting of Mosfets and dedicated driver IC's.
Then also you need to decide if you need bi-directional motor control.
If your motor does not come with commutation sensors, which it sounds as though it doesn't, then you will require some method of initially detecting rotor position.
Max.
@MaxHeadRoom All Arduinos have at least some PWM pins. How many depend on the model/ μP of the unit.
 

Reloadron

Joined Jan 15, 2015
5,370
A Google of BLDC Arduino will likely bring up a dozen hits using an older Arduino Duemillenova (Arduino 2009) or Arduino Uno or Arduiino Mega and the list of uC possibilities goes on. There are solutions for motors which have hall effect feedback (like a motor yanked from an old hard drive) to basic BLDC motors having only 3 wires. There is no limit to BLDC controllers out there and including ESC (Electronic Speed Control) or using a uC one can roll their own.

Before anything can happen be it any driver or uC one needs some data on the motor, things like voltage and current would help. :)

Ron
 

djsfantasi

Joined Apr 11, 2010
6,367
I assume you are referring to RC servo's? ;)
The 3 wire (BLDC) motors I use are also Servo's.
Max.
Ok, but are all BLDC motors servos?

In other words, do some three wire motors use the third wire as a control wire and how many different control systems are there in this case?
 

MaxHeadRoom

Joined Jul 18, 2013
20,471
Many posts are made using the word Servo, where in fact the poster intends to refer to an RC servo, which of course IS a servo, but there are all kinds of motors and mechanisms that can be termed 'Servo', for example, typically industrial servo's have been, and are derived using DC, BLDC, Stepper motors etc. With various means of feedback for positioning, or in the case of a stepper, no F.B. (open loop).
Max.

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MisterBill2

Joined Jan 23, 2018
5,804
Hello. I am found a 3 wire dc motor that is in brand new condition. I tried hooking it up with a dc power source its a dc motor. It has three wires and green black and red. the number ldc on my 36 volt power supply flickers so i think the power cables are not hooked up properly. I know what 3 phase ac motors are and how they work but i do not know much about a 3 wire dc motor. I read around and heard you need a micro controller to control a 3 wire dc motor. Does anyone know how to make a or get a simple controller for one of these motors or anything about them. Thanks.
Before assembling a controller for the motor you need to verify that it is actually usable as a motor. No mention at all as to if it turned and ran when the DC power was connected. No mention of what voltage or what current was used. And there was no mention of any identification on a tag on the motor. In addition there was no mention of size of the motor.
The result is that I will make no mention of anything until more information is provided.
 
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