Help me hijack a brushless DC motor from a cordless drill

[gladiataar]

Hi Everyone,

I'm new to this forum and this is my first post, so apologies in advance if I didn't select the right place for this question.

My question involves the use of a brushless DC motor (my first!) in a hobbiest project. The tight area constraints of this project required a motor with the smallest possible footprint, so one of the these fancy brushless 18v DC Makita drills really seemed to fit the bill. However, after tinkering with brushed motors all my life, I'm struggling a bit trying to figure out how I'm going to adapt this motor to my project.

So far, I opened up the drill, and pushed the battery and trigger switch aside. Then carefully cut the entire plastic handle portion off, leaving the motor mounted within the remaining portion of it's housing, and all electrical connections still intact. Voila! I now have a very compact and powerful cylindrical motor assembly with a geared socket wrench for an axis.

In this project, I need to control motor direction and speed through two SEPARATE external switches placed around 6ft away from the motor. To do this, I purchased a 30A brushless DC motor controller, with the intent of using it's appropriate wire breakouts for said switches. It's a nice controller by the way. Lots of wire breakouts to control a number of motor functions.

The problem I ran into was that in addition to the traditional 3 thick wires used to power a brushless motor, there are an additional seven ~30 awg wires coming off this motor assembly: Yellow, red, blue, and two black and white pairs. All seven wires run directly into the drill's onboard controller. Now, I'm guessing that the two black and white wire pairs are for hall effect sensors, because I can see the circuit board they're soldered to, and it's positioned around the motor shaft. I'm also guessing that the red wire may power this small circuit board, but what are the other two wires for? The fact that one of them is blue -- the same color as one of the three motor power supply lines -- makes me nervous enough to wonder if they are necessary for actual functionality of the motor itself. So my question is, can I cut these smaller wires off from the drill's onboard controller and still use this motor via my own independent, external controller? Or are these smaller wires somehow necessary to a brushless motor's functionality and need to remain intact?

As a side note, in case you're wondering why I don't leave the onboard motor controller intact and just replace the trigger switch with my own switches, there are problems with that approach as well. First, there are (again!) five small 30 awg wires running from the drill's onboard motor controller to the trigger switch and I have no idea what they do. Secondly, the drill's trigger is a COMBO multi-function (motor speed and direction) switch. Maybe that explains all the extra small wires??? In my application, these two functions (speed and direction) need to be controlled by two SEPARATE switches located 6 ft away.

Any input or advice as to whether or not cutting these additional small wires will directly affect the motor's overall functionality would be greatly appreciated.

Best regards,
Ken

 

[Minder]

Almost impossible to speculate from a distance, if you can locate the three hall sensors and their supply then it should be possible to use practically any common BLDC controller that receives hall sensors.
Probabally some more reverse engineering is needed!
M.

 

[gladiataar]

OK, you'll have to pardon my ignorance here, as this is my first brushless motor. Do I even need hall sensors to run a brushless motor? Are there different kinds of brushless motors? It does say in the picture "for motors without hall ..."

I've attached a picture of the motor controller that I purchased. It does have a hall sensors connector, but I thought that this was for OUTPUT, like if I wanted to monitor the motor's rpm, or maybe use counts to start and stop the motor at a certain position.

 

[debe]

With BLDC type of after market drivers, the ones i got were slightly different circuits betwean one that uses Hall sensors & ones that dont. The drivers that are for non Hall sensor motors generate there own drive (bit like a 3 phase square wave motor drive). The drivers that use Hall sensors are different as they use the Hall sensors to tell the circuit where the rotor is (bit like a DC motor commutator). I have used an after market BLDC driver for a Danfoss BLDC fridge compressor (non hall sensor type). Hope my simplistic description is of some help.

 

[Minder]

There are BLDC and ECM motors that operate without physical sensor, they generally exercise the motor at power up to sense rotor position and from then on detect electronically.
The typical ECM motors used in HVAC blower systems operate this way.
The most definite way, is the hall sensor.
M.

 

[gladiataar]

I appreciate the replies. I had no idea there were two different kinds of commonly used brushless motors (i.e. with and without hall sensors). Your responses inspired me to do more digging into the sensored version because I knew for sure this drill had a hall sensor board.

This is what I've come up with so far:

+ In a Makita 18V DC brushless drill, there are 10 wires coming out of the controller board that feed up the handle toward the motor.
+ Three of the wires are medium 14 gauge. These are obviously used to physically drive the motor.
+ The remaining seven wires are a very small 28-30awg.
+ Two of these small wires -- one black and one white -- are taped together. This pair is actually used to power the LED light and have nothing to do with the motor.
+ The remaining five small wires (red, black, yellow, white, blue) do continue on into the hall sensor board. From my research (not actual testing!) I've been told that one of them is 5V (probably the red wire), one is ground (probably the black wire), and the remaining three wires are used for hall sensors a, b, c. I also read somewhere that there is a standard orientation for the pins contained within a flat 5-pin hall sensor connector. The two outside pins are 5v and ground. The three inside pins are hall sensors a, b, c.

It's also worth mentioning that in order to use this motor and its onboard controller board together, you will probably end up using the trigger switch as well. It's a two-speed trigger button -- and motor direction controller -- contained within one switch. Unfortunately, five low-current 28awg wires are used to communicate each combination of trigger position and motor direction into the controller board. I tried unplugging this 5-pin logic connector entirely from the trigger switch, but the onboard controller board wouldn't let me run the motor in either direction without it.


The above information might be useful for others looking to use a Makita brushless drill motor for their project, so I thought it appropriate to record my findings/research here.