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How to Wire a Brushless DC Motor with Integrated Commutation Electronics

November 20, 2012 2 Comments

Yesterday, I gave a brief explanation of just what is a brushless DC motor with integrated commutation electronics. While noting they represent a compact, simple good value motion solution, their ease of installation was recognized as another benefit. Today, I’ll show just how simple and easy it is to wire up a brushless DC motor with integrated commutation electronics. But first, let’s take a quick look at the more complex older way of doing it.

brushless DC motor and control BLDC

Typical brushless DC motor and separate speed control.

A conventional brushless DC motor (BLDC) will have from 8 to 10 leads that need to be connected to the separate speed control in order for the motor shaft to turn. Three of those leads connect to the motor phases and five of the leads connect to the Hall sensors in the motor and are wired back to the commutation logic on the controller board. A couple more leads would be for grounding of the motor frame and cable shield, if used. So, as you can see from the photo above the separate BLDC motor and control not only take up quite a bit of room, but it’s also time-consuming to wire up all those leads. In addition, you have to find somewhere to mount the control board.

Dunkermotor BG42KI Brushless DC motor

Dunkermotor BG42 Brushless DC motor: without integrated commutation electronics wiring on left and with integrated commutation electronics wiring on right

You’ll note from the above illustration that the conventional Dunkermotor BLDC motor has 8 leads (3 motor, 3 Halls, 2 Halls power and ground). However, the KI (integrated commutation electronics) version on the right has 5 leads — but 3 of those can almost be considered optional extras that you use only if needed. In that regard, take a look at the wiring example below.

Dunkermotor BG32KI BLDC brushless DC motor wiring example

Dunkermotor BG32KI Brushless DC motor wiring example

It’s pretty simple. Your DC voltage and ground are the red and blue connections, respectively. The yellow and green legs are there in case you want to switch direction of the motor with digital inputs. If you’re only going to run in one direction you could just connect one of those directly to your DC voltage. You would then effectively have two-wire operation of your brushless DC motor. Not to forget that brown leg above. It’s another nice feature you can use at your option as described below.

BLDC Brushless DC motor Hall Output for speed or position monitoring

If you wish, the Hall digital output can be used to monitor speed or position, as an integrated transistor in the motor switches the applied voltage 4 times per revolution to ground. A pull-up resistor is required and its value is adapted to the voltage supply source so that the current at the Hall input does not exceed 10mA.

This is meant to be a fairly nontechnical explanation of what’s involved in wiring up a brushless DC motor with integrated commutation electronics so that one can put its benefits into perspective with the traditional way of employing a BLDC motor with a separate speed control and the necessary cabling. In this case, the wonders of modern electronics and German engineering all come together to make life easier and more reliable.

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About the Author:

John Morehead is an experienced marketing, sales and business development leader. He’s passionate about motion control and advanced motor technology and shares that enthusiastically with those he encounters and many more through his myriad marketing initiatives. This blog is one more tool to be able to spread the word about news, information and insights on the motion control, electric motors, drives and automation fields. Your comments or questions on posts are welcome.

Comments (2)

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  1. Mark J Vera says:

    John,

    I salvaged a hand full of very small 12v dc brushless blowers off of a defective digital projector. Each one of these blowers have three wires coming out of them. They all have “12v dc” nomonclature but have no other electrical information, I want to use two of these blowers as cooling fans for my fridge coil in my camper. I have no Idea how to wire these or what I need in the way of electronic drivers to run these fans. Can you advise?

    Thanks,
    Mark J Vera

    • John Morehead says:

      Thanks for asking, Mark, but this blog isn’t meant to be a technical Q&A reference. However, I’ll try to offer some advice. There are many different styles and types of small brushless air moving motors and not knowing the specifics of the manufacturer, model, etc. one would only be taking a stab in the dark at getting it to rotate. However, with 3 wires it’s quite likely the motors were driven by an electronic speed control (ESC) that was built into the projector’s control board. It’s unlikely that in such a wall-powered consumer electronics device with a built-in control board that it would use brushless motors with integral commutation electronics. You’d be wasting time and money trying to find the correct type of ESC to run the salvaged motors in another application like a 12 volt refrigerator. For example, you’ll need an ESC that operates with 12 volts in and provides 12 volts out and the correct commutation to turn the motors you have — and it would also need to have adequate current capability. It would be quicker, easier and cheaper in the long run to source a 12 volt blower that runs direct from a battery or comes with a built-in ESC. Sorry it’s not an easy fix.

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