Using small motors with arduino

Hi

I have two small motors from an old broken helicopter and I need some help for connecting them to my arduino duemilanove board. You can find some pictures attached.

From what I’ve read, for bigger motors, the recommended way to use them is by using a transistor and an external battery but in my case both helicopter motors were powered by a 3.7V battery and I think they are small enough to be powered directly by arduino board.
I would like to know if I can safely connect them to the arduino board or should I use the following approach: Motor Speed Controller - Arduino~Soapy29

Also, these motors don’t have serials or identification numbers and I cant find any specifications for them. Do you know a way to find more details about them?

Thank you,
Costin

I think they are small enough to be powered directly by arduino board.

I don't

costin-zaharia: but in my case both helicopter motors were powered by a 3.7V battery and I think they are small enough to be powered directly by arduino board.

If you could fly a helicopter on 40mA and 3.7V life would be so simple!

No, that motor will require far larger currents than that, and at low voltage a MOSFET or MOSFET-based H-bridge is indicated. First task is to measure the current consumption with a multimeter under realistic load conditions.

Take another look at that PCB. It has 2 transistors of which the type can't be read because of the glue that is on it. Remove the glue and you will be able to identify them. They are connected to the blue and to the brown wire of your motors. Because the donor didn't need direction reversal, they were able to use just 1 transistor per motor. If you want reversal, you'll need more.

It has 2 transistors of which the type can't be read because of the glue that is on it. Remove the glue and you will be able to identify them.

I removed the glue and tried to figure out the transistors type. It seems that on them is typed Y1. I tried to find them on the internet (http://www.s-manuals.com/smd/y1) but I can't really understand the specifications.

In the meantime I also tried to measure the current with my multimeter by connecting the motor to 2x1.6v bateries. The measured current was 36mA.

As you can see, I'm a complete beginner but I really want to learn so any advice will be appreciated :)

Thanks, Costin

I also powered the motor from the original battery (3.7V) and the measured current is 45mA.

Cheers, Costin

I googled "smd transistor y1" (don't pay attention to the smart ass but rather funny remark) and found in the first result what you are looking for. The component's package (the shape it has) looks to be SOT23, and we may assume it is not a (zener) diode. It would be nice if you would know the manufacturer, but how would you know.

So i just tried to see what results are there. I clicked on the first link that mentions 1 type of transistor (NPN) and took a peek at the pinouts and the way the parts on your print are connected. It's quite likely that that pinout is correct. Measuring at it will tell more about this, but holding the measuring pins at my monitor didn't give a good result aside from some scratches ;).

The current you measured, probably was the free running current. That means the motor was running, but there was no load to that running. The current under load will be more The stall current is the current that you see when the motor is powered, but has a too large load so that the motor does not turn (hence "stall"), it will burn when this lasts too long.