Let's say I have a very minimal project that wants to run a motor at a preset speed in a single direction, nice and simple. But I have limited space to play with, so the smaller the better.
I could use an L298 motor driver, but the ones I've looked at all seem rather big, and often have huge screw-down contacts that I don't need. Is there a smaller option that I can use for a really tiny (long-and-thin) circuit? It'll probably be a rat's nest job.
I also managed to find a very, very tiny and weak motor - 4.5v, 0.12 watts - and, since it doesn't need to drive anything heavy or mechanical, this might just do the job. Could I safely run this directly from an output pin without burning out the chip, provided that I put a diode in to protect against back-EMF?
Thanks!
Unidirectional never needs a motor driver, an N-channel mosfet will do nicely. What Arduino or other device did you have in mind?
And, for what you describe, what is wrong with a simple push button or Toggle switch?
See, all kinds of questions arise when you don't follow the how-to instructions...
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Hi,
4.5V 0.12W
P = V x I
I = P / V = 0.12 / 4.5 = 0.026A = 26mA.
I would use a MOSFET as you have starting current to consider also.
A SMD type would be ideal.
What is your project?
Thanks.... Tom.... 
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Even if it seems like the Arduino can handle the power, I'd still use an external driver. The inrush current can be much higher than the nominal value when the motor is spinning.
The DRV8833 breakouts are fairly small but ultimately the smallest is going to be something you custom design. KOOBOOK 5Pcs DRV8833 Motor Drive Module 1.5A Dual H Bridge DC Gear Motor Driver Controller Board - Amazon.com
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Pololu is a great resource for motor drivers with pictures for size and sample circuits, check the DRV8833 or TB6612FNG at Pololu
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@camsysca it has to be pretty small. At the moment I'm using an ATtiny85 for testing purposes. I may move up to a larger version later, but I'm trying to make do with that. Due to space requirements, it'll have to be something that I don't need to micro solder as I won't have room for a breakout board and a custom circuit board is beyond my means right now.
I could just run it off a push-switch, but the switch will also trigger sound and light elements which require a microcontroller. No reason why it can't do both. On the other hand it would be nice to have the option to experiment with PWM via the microcontroller too, if that's feasible, it's just not necessary for the MVP.
@TomGeorge it's a simple motorised toy with light and sound features, however the motorised portion is just a lightweight slow-spinning refractor and the only load it will bear is the weight of the refractor - maybe clear resin or, if the motor can handle it and it looks better, a small quartz crystal.
@cedarlakeinstruments if the testing goes well I may need to put together a custom electronics board, and then I'll be able to think about building a driver into it. Right now I'm only at the proof-of-concept level.
Doesn't hurt to think of the future, but right now I am concentrating on size.
More concerned with size, he can NOT use the direction pin. But like the OP said,
@TomGeorge looking in the ol' electronics spares box, I reckon I've got some through-hole MOSFET's already. They're chunky compared to surface-mount options and I'll need to cocoon them in electrical tape, but they'll do for a prototype.
Ensure they are logic level fets.
Ah, my mistake, these are voltage regulators. They look about the same. Alas the only transistor in my box is a lonely little BC548B.
Then if reversing may be a future requirement, seek out a suitable motor driver. Miniaturization may demand that you breadboard, or even design your own pcb.
@camsysca that may be the eventual goal, though it might be a bit tricky to fit everything I want into a 15mm circuitboard.
Another driver you can look into is the L9110, which can be bought from Digikey.
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@LarryD Currently it's not been decided, but I'm trying to keep it below 15mm wide and 100mm long (⅝" x 4")
Power source will be battery. I'm flexible on what kind, but due to the size limitations it'll probably be coin cells, one or two CR2's or, if I can squeeze in a charger circuit, a suitably-sized li-ion cell. I kinda wish I could use a BA5800 but they're likely to be too chunky.
@HazardsMind I think that'll prove to be a bit too wide for the space available, but it might fit. I'll keep it in mind.
The chip is about 8x9mm, so it should fit with the rest of your circuit. its the same size as a standard 555 timer IC.
Perhaps something like ESC's (Electric-Speed-Controller) for brushed motors.
https://de.aliexpress.com/item/1005007060330812.html
This tiny stuff is often used in micro models.
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