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BLDC Monitor Boards for a build?

Hi Blue Robotics Team,

Firstly can I just say I’m a big fan of all your work and enjoyed watching the brand grow over the last couple of years. My name is Chris and I’m an ambitious amateur builder, mainly multi-rotor builds and racing quads. But I recently turned my attention to ROVs and found a useful release on GIThub relating to a BLDC Monitor board GIT BLDC_Monitor. After reviewing the eagle files I am keen to incorporate these boards in my latest project.

I was hoping you might be able to answer a couple of questions for me, before I go any further and seek to re-create these. Apologies if the below questions seem a bit obvious but I’m more of a mechanical guy :grinning:
1.) Am I correct in understanding that the BLDC Monitor board does away with the need for a Power distribution board as typically / conventionally used in multi-rotor / quad copter builds?
2.) The build I have in mind makes use of 4 off T100 thrusters, so was planning on commissioning a friend (Electronics Engineer) to build me 3 off BLDC Monitor boards from the details provided by Rusty on GIT. Effectively leaving me with one spare board, should I make a mistake. The thing I’m struggling with is the wiring of the ESC’s to the board? Do you have a wiring diagram?
a. I think 2 phases of the motors A & B go to P$1 Tach-A/B and P$1 Tech+A/B?
b. With the Black (-) and the Red (+) ESC wires going to P$1 ESC+A and GND and Conversely for Motor ESC B P$1 ESC+B and GND?
c. The ESC-Third-A and ESC-Third-B Pads have me stumped?
d. Guessing P$1 Power+ and P$1 PWR GND are the battery bower (12V) and ground?
If there are any details or wiring advise you can provide me, I would be extremely grateful.
3.) Final question, am I correct in thinking these boards can be flashed or have the appropriate code put on them using an FTDI?
Sorry to take up your time and hope you can help me out?

Thanks for taking the time to read this and look forward to your input.

1 Like

Hi Christian,

Thanks for the message and welcome to the forums!

The BLDC monitor was something we built when first testing our thrusters about four year ago. We haven’t used it much since and I would be hesitant to recommend it to you. It only worked okay. I can answer your questions still:

  1. It does distribute power but I wouldn’t count on it to handle very high current.

  2. The tachometer just attaches to one of the three wires and tries to count pulses. The other pads are just there for wiring convenience but have no effect.

  3. Yes, an FTDI cable would work for flashing.

Hope that helps!


1 Like

Thanks Rusty, much appreciated. Just curious as to hesitancy reason? Was it a bit flaky, or would you advise an alternative?

Think I’ll run with it for now.



Hi Chris,

Yeah, the RPM sensing on the board is not very reliable, which is the main reason I’m hesitant. I don’t have any alternatives to suggest, though!


Hi Chris,

There are off the shelf RPM monitors now that would probably do a better job. Check this out:


Do you have any experience with these RPM sensor(s)? We want to read out the RPM of our T-200 as well, but I believe this sensor is made to be connected to a Hobbywing receiver/controller/ESC right? So how do we read this pin? Thanks a lot!

Hi @Thymen,

These sensors just output a high/low 5v signal as the thruster commutates, you can read this signal with an Arduino or other microcontroller and calculate the RPM.