Hello
I'm trying to control a small dc motor through arduino using PWM. The dc motor will run off its own 3v 1A power supply. Originally I wanted to go with transistor s8050, but when I plugged the power supply and checked the current being drawn by the motor, it showed 1.1 Amps. So s8050 will not work (unless I'm wrong) because the collector can handle max of 700mA.
At this point don't know what is the best choice for this fast switching application. Should there be a transistor used or maybe mosfet or is there a third option?
If you already have the transistor you mentioned laying around, try using it, maybe it can handle the current, maybe magic smoke starts coming out. These transistors are cheap, so it's worth a shot.
For your application any NPN-Transistor is fine, as long as it can handle the current.
If you want to use a MOSFET, it needs to be a logiclevel-type, preferably N-Channel.
I did a google image search of . The first three hits explain pretty clearly what you need to drive a mosfet
Similarly a google image search on reviles schematics that show useful information.
When I was getting to know the uno I used what I had laying around to do this but there are chips that will do all this for you. Also several shields that can provide a wide variety of driver capacities.
The S8050 is a poor choice, it has a saturation voltage of over 1V at 0.5A (50mA on base), so don't expect it
to turn the motor very fast driven from an Arduino pin (40mA to the base would be starting to overload the
Arduino).
You can always parallel them in pairs to Double the Load.
Also as a Driver, you could use a 2222 Transistor to drive the s8550 and s8050 at Collector and Emitter of the 2222 for one Motor Lead. And, build a second circuit with 2222 and s8550 and s8050 - for the second Motor Lead. You need this H-Bridge circuit anyway for Transistors.
jlsilicon:
You can always parallel them in pairs to Double the Load.
If the load is more than about 0.5A you have the problem that an Arduino pin can't drive a BJT properly into
saturation.
For saturation the base current needs to be 5 to 10% of the load current for a BJT, and since 40mA is
the absolute maximum I'd suggest limiting base current to 25mA for reliability - hence 0.5A gets to be the
cutoff point. Doubling up transistors is not going to help.
Darlingtons and MOSFETs are the options for higher current, but darlingtons lose 1 to 2V which isn't great for
low voltage loads.