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Topic: What transistor should be used for a bipolar stepper? (Read 406 times) previous topic - next topic


Jun 25, 2015, 10:17 pm Last Edit: Jun 25, 2015, 10:30 pm by electricviolin
Going by the first schematic on this page, what is the transistor really used for? If that transistor is being used for the motor supply at all, I will need to use a more powerful transistor. If it is being used as a signal transistor, I will just use a 2n2222.

Also, could I use the second schematic with the l293D? From what I know from h-bridges, the transistor in the first schematic is being used to avoid the use of two more arduino pins.
"To invent, you need a good imagination and a pile of junk" -Thomas Edison


I just found this for anyone who is having a similar problem. Moderator - delete the thread if needed
"To invent, you need a good imagination and a pile of junk" -Thomas Edison


The transistor is used as an inverter.
It inverts the "control" input.
When 1-in is "low", 2-in is "high", etc.
The transistor has a 10k collector resistor, so it only has to switch 0.5mA.
Any small NPN transistor will do.


If you use an H-bridge like the L293D you do not need any transistors at all. Just connect the inputs directly to your Arduono board (maybe using 1K resistors for protection)
If you bought the original Arduino starter kit you will have the L293D chip and a circuit example in the user guide.

If your questions are not precise, nobody can help you.

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