Today we tried to build an H-bridge to control the motors.
An H-bridge is a circuit that makes it easy to control a motor to go backward or forward, for example from an Arduino.
We used TIP120 and TIP127 transistors and built the following circuit using 5V as VCC:
It did not work.
We are not sure if there was a problem with the connections – or if the circuit design itself as the problem.
What’s next?
Until next time, I will check the connections of the circuit and do some measurements. Eduardo will look at simulations to see if he can find any problems with the circuit there.
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We’ll meet up in one week to continue building the robot.
Check out week 3 of the build >>
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nope; the Vce and Vbe of the tip120 is too high to run it on 5V like this; both transistors are saturated above 2Vce, leaving you with less than 1V across the motor, if any.
http://everycircuit.com/circuit/4714217155592192
the arduino does not have the current to drive these transistors either.
at this low voltage, BJTs aren’t going to be very helpful. even low saturation transistors have a Vce around 700mV to 1V.
look at using a L293 IC to drive instead, or look at how 7V remote control cars use a mosfet HBridge to run their motors
Yep. That’s what I found too. Only 1V left for the motor. I found a cheap H-bridge module at a local shop here, so we’re gonna use that one.
But would like to make it work, so I have to take a look at the transistor selection at the local shop to see if I find something suitable.
Oyvind