Safe to drive directly? (Lownoise dc motor)

I was just down picking up some heatshrink and noticed that there was a pile of old-stock "Solar Motor Modules". This place is phasing out their components, and these look to be from some circa 1999 solar kits.

Its a Low noise.. "efficent, clean, lightweight dc motor designed to be directly driven from small hobby solar modules".

Designed for 1.5-3.0V at 25ma or higher w/ a max speed of 3600rpm..

I picked a couple up becaue at $2.90 each I figured I could afford to let the magic smoke escape on a few and not care ;D

My question is - being so low-current/low-voltage, do I need to worry about anything other than a diode for some signal protection on the Arduino ? I was thinking either directly wiring it to a PWM pin with a diode, or running it via a BC5XX PNP/NPN transitor. Obviously a relay isn't needed for current switching reasons...

So any advice ?

(incidentally, anyone else in Australia who may be interested in some for giggles, I got it them from Dick Smith Electronics P8980)...

do I need to worry about anything other than a diode for some signal protection on the Arduino ?

Yes. They may draw more than 40ma continuous when run on 5 volts. Also note that the peak current when starting will be much higher than the continuous current that you would measure with a multimeter. It may work but it could also damage an arduino pin.

Driving off a transistor then is ok, or should I relay switch them still ? Or just follow the playground stuff and treat it as a normal motor ?

What if I run them off a seperate 3.3V supply I have??

A transistor should be fine. The motors will probably be happier with the seperate 3.3 volt supply

In order to protect the Arduino properly, you'll need a resistor to the pin as well.

The motor is spec'd at 25ma, but will pull more depending on load. Transistor control is preferred method for this reason.

I have some that draw around 50ma hanging in the air, but as high as 200ma under weight of a small 'bot chassis.

If you need to reverse it as well, look into an "H-Bridge"

Would it work (electrically) to have a transistor like this:

3.3v | | motor | | C D-Pin---B--| ) | E | Both grounds

Yes, but you need a series base resistor between the I/O pin and the base to set the maximum base current.

Lefty