# can i get more power from this?

i'am building a robot based on the beetlebot with 3v motors,
i modified it to run with an arduino but now my motors seem to weak i use a p2n2222a transistor to control the motors is there a way to get more power from my motors without using very expensive things (this is a school project and is due in a week so i need your help please)
i have a TIP 41A transistor should this allow for a greater current so a greater torque from my 3V motors

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timothy demaegdt (author) 5 years ago
PS it is an open hardware project so if i get it to work i will make an instructables to make your own watersearching turtlebot XD
hope you guys can help me
5 years ago
I guess its just a "coincidence" that there is also a robot building contest on right now... ;)
timothy demaegdt (author)  canucksgirl5 years ago
actually it is a coincidence XD
but i think the instructables will be for after my finals
steveastrouk5 years ago
What current do the motors take on a 3V supply ?
Quercus austrina5 years ago
Well, I started to write this several hours ago (when the question was only about 25 min. old) but had to step out. Now for my reply:

My design software says that the P2N2222A is good for 500mW or 800mA. The datasheet says 625mW. Not sure how you have the driver set up, but if you use the P2N2222a as a pre driver for the TIP41A (basically a darlington transistor setup), you'll be able to push many amps through to the motor(s). You will also need to up the operating voltage to the motors to account for voltage drop in the supply chain. Also, you may need to bias the p2n2222a in order to get it close enough to conduction in order to make it come on as soon as a signal is present. Shoot for around 0.55 volts or so. You can try a variable resistor (50K - 100k linear) from +V to Gnd and use the wiper tap connected to the base of the transistor. Start at Gnd and slowly move up. Monitor voltage at C or E and when it turns on, back it off just a bit til it turns off. Measure both sides of the VR (- to wiper and + to wiper) and use standard values close to those measurements. Double check to make sure it still works the same - change the value of 1 or both resistors to get it closer if need be. Also, you should know the current draw of the motors under load to make sure the transistor can handle it. If you need less than 500 mA, just use the p2n2222a.

Let us know if you need more help.

Qa
steveastrouk5 years ago
Changing the transistor won't make any difference, assuming that the motors are seeing around 3V when the transistor is "on" ?

Steve
bwrussell5 years ago
Get a motor shield. They have places to attach a second external power source so the Arduino doesn't have to power them. This also means you can use higher voltages than the Arduino allows, although that point isn't too helpful if you only have 3V motors.