Trying to replace a brushed motor with a brusheless one in an old tape recorder. Naturally it requires a controller so I wonder if this could be built on Arduino and how complicated would it be. The most important question for me is
How accurately a microcontroller managed brusheless motor can keep the rotation speed? Talking about a sound related device, the wow and flutter is of absolute importance. I met some cases where the rotation adjustments happen too slow or too late resulting in rythmically floating sound.
Here is the technical part I have to deal with:
24v input power (both for controller and for the motor)
I bought such a controller, it was ok on the paper but then it came out that my rpm were too low for it and the way it was correcting the revs was unacceptable.
So while I still admit there might be a better match out there (and I keep googling with my left hand) I still would like to ask what would be the disatvantage of assembling a DIY controller? Cost, inefficiency, reliability?...
Yes, I have. But many similar topics are treating much more advanced details while I was looking for a hint - which arduino model would be enough for this task, so I could start buying it and experimenting.
Just curious, what is the problem with the original motor? Used to occasionally see a tape deck where the takeup reel motors operated too slowly because dust from the brushes had filled the gaps between the commutator segments and was shunting current around the motor winding.
A DIY solution will include 3 half bridges, i.e. 9 output pins and 3 input pins for the sensors - no problem with any (8 bit) Arduino. But if 3 phase shifted PWM outputs are required then a Mega may be the best choice. As long as the code will be fast enough.
You should have a more precise idea of your hard- and software and timing requirements before choosing a controller.
Know that too. It's about a Teac X1000R, I took all motors apart, cleaned commutators, refreshed the brushes, replaced capacitors, coils and resistors and lubricated, and reassembled. The reel motors came out of this very well and they are fully operational, while the capstan is driving me crazy. It won't spin at all, if powered from an external power supply, and , if powered from the original driver unit, it spins extremely slow and weak, so that a light touch of a finger stops it. I can't get the reason, because the service manual doesn't include the diagram of the capstan controller PCB, and I have no clue where to start from. So I started to chew this idea of replacing it with a brushless motor, to solve the issue once forever.
Very unlikely this is your problem, but years ago when I was working at an electronics repair shop, we had a tape deck that had a similar problem. Finally noticed that if you put a little drag on the supply reel with your hand, the speed would increase and it would play properly. Turned out to be a purely mechanical problem - there is a small tension arm below each reel, that has an optical position sensor that serves as part of the feedback to the motors. Each of those tension arms has a spring, and one of the springs was broken.
Yes, it seems a bit different. This capstan motor refuses to spin with no relation to the supply or take-up reels. It is not even connected to the capstan fly-wheels, so there is definitely something wrong with it or with the driver. But anyway, thanks for reaching out!!