I've received a DC motor to use as a drill for M-Bot, when I got the motor I didn't know how much power it would require, driving a 8mm to drill bit in a log is kinda hard to size. So I used common sense, and looked at my drill and the size (literal size) of the motor, and thought I'd pretty much need the same one.
I wasn't wrong, I think the motor works quite well, 150-200W is enough power drill a hole slowly, I wanted something that would punch a whole like it's nothing, but realistically it's driving a hole as I would.
Well I'm saying it works, it does at 160W, not at 50W power. And if you haven't guessed that the power of a brushed DC motor is given by the magnetic fields, which is driven by the current going through the coil, which depends on the resistance of the coil, and guess what the Voltage. It's called Ohm's law.
The current voltage level I was using, which I liked, was 12V, because it's easy, and I've it installed in the workshop. However I probably need 24V, or at least 22, a 6S Lipo battery would work well.
Ok, so I need to change the voltage level, "no big deal" you might say.
Well, well, well... My current needs (pun very much intended) : - 3.3V : 0.5A (1.5W) : Led display and other sensors - 5V : 1A (5W) : Servo and uC - 12V : 4A (50W) 2 x Nema 17 - 24V : 8A (200W) Drill and Nema 23
So a total of around ~10A at 24V (not everything will run at the same time).
So here is my revised plan :
1) 24 Volts come in.
2) Two DC-DC converter for 12V, so the Amps for each stay under 1.8 A, and if I blow one, it can easily be replaced. Why not 1 big one, I've already got many tiny 1.8 A max converters, so it's easier to source, and making my own DC-DC converter is a bit of a pain, and not worth my time.
3) One DC-DC converters to go to the servo motor and the uCs and other sensors.
4) Use the internal LDO of the uC to get 3V3 where needed, as the initial plan.
5) Use 3 P-MOSFET to drive the DC Motor. The spec says they are rated to 3.5A each continuous, so I am 1.5x to 2x above this. I'll probably add another MOSFET footprint just in case.
Well I think that's a plan. I need to take measurements of the footprints, and design all of this.
An update on M-BOT, I've been designing the piece that would grab the dowels. My current issue is the Modulus of the gear of the belt is too small, and the print quality a bit terrible, so when bending around the tight radius the gear only works on a portion of the belt. The plan is to increase to M2 or something above.