Powering 6 motors

Hi guys

I'm kinda new to arduino and currently working on my first project- hexacopter. I'm trying to power up 6 small dc motors (150 mA operating current) with TIP120 transistors (PWM to control their speed), arduino nano and a 3.7v lipo battery (500 mAh).

Problem is that the motors don't go as fast as they should. I don't know where in my configuration is the problem- if it's current draw from the arduino itself, or from the power supply? should i change one of them? and basically, i would appreciate very much if you can try and explain how to choose parts for something like that.

Thanks!

That small battery can't supply enough current for six motors. You need a larger one, with high discharge current capability (measured in units of C, where your battery has C = 500mA).

Keep in mind that the startup current for a motor is 5-10x the running current.

In general, motor speed is proportional to the supply voltage.

I suspect there is a significant ON resistance in the TIP120s. MOSFETs generally have much lower ON resistance.

I suspect your 500mAh LiPo would be sufficient for testing - although it would run down very quickly.

Are motors that only consume 150mA capable of lifting their own weight?

...R

Thanks for replying.
I’ve just ordered 3.7V and 7.4V batteries with higher capacity, hope they will do.

If not, i’ll consider replacing the motors
(this is what i have right now, their purpose is for quadcopters so i figured they will be sufficient).

Thanks again!

150mA isn’t likely to lift you off the ground, even the small slotless/coreless motors take 2A or so.

Also the TIP120 is a darlington, so completely inappropriate. MOSFET or superbeta is required, you can't afford to lose 1.5V in the driving device.

What kind of MOSFET? I’ve tried several and they all heated up real quickly…

oops, my bad, got confused by all the transistors i have tried out.
The one i’m using is actually the IRFZ44N power MOSFET.

At 3.7V you need a MOSFET which works with 3.7V gate voltage, which will be surface mount in all probability I'm afraid.

IRFZ44 is 10V gate drive, completely useless here.

Mark, maybe you know a specific MOSFET you can recommend? got lost in the search, there are so many..