H-Bridge motor control

Discussion in 'Homebrew and Kit Projects' started by KB1LQC, Nov 25, 2008.

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  1. KB1LQC

    KB1LQC Guest

    I figured I would let everyone in on a quick project I have been working on during this fall break from RIT (we get two weeks off). Since I accidentally left my Software Defined Radio project and a good amount of my tools :( at school back in Rochester, I could not work on those projects. So I decided to play around with the Arduino (Brent has his other post about that on this forum) controlling motors and other devices.

    I first built a simple switch amplifier or whatever you want to call it (i forget :( ) consisting simply of a TIP120 Darlington array, a diode and a 1k ohm resistor. Worked very well. Then I decided to explore an H-bridge which allows both forward and reverse control of a motor.

    Simple switch with TIP 120:

    A good description:

    I built a version based on this following project:

    The only differences were that I substituted with different optoisolators and instead of the TIP107 PNP Darlington arrays I used some D41K PNP Darlington arrays since they were on hand. The circuit seemed to work but the D41K's were just not going to work with the TIP120... under a almost 2 amp load from a 12v lightbulb the D41K's were heating up quickly while the TIP120's were warm if anything. I know that the D41K are maxed out around 1.8 or 2 watts of power but this is experimenting to see if the circuit worked so what the heck :)

    H-bridge Top:

    H-Bridge Bottom:

    One or both of the D41K's was damaged when I switched the circuit into reverse, Ill have to check the wiring and replace PNP Darlingtons with a TIP equivalent or something while I am at it. It has definitly beed a cool proof of concept project ( and a good learning experience with RadShack prototyping solder boards :( , was not fun hehe). This could eventually be turned into both forward and reverse control of a remote control device if I wanted to. Something like it may even be implimented into the RIT Blimp! I will post pictures later when I get home. Anyone else experiment with projects such as this?

    Last edited by a moderator: Nov 26, 2008
  2. VA7AAX

    VA7AAX Ham Member QRZ Page


    I dont know much the project you are working on because most of my electronics tinkering tends to be on the RF side:

    I do want to comment on the Radio Shack pototyping boards/per boards/matrix board,etc.

    I absolutely dont like working with those. I tried using them a couple of times but found it was really hard to work with. So I went back over to good old ugly style groundplane construction(copper board unetched with parts directly soldered where ground and the rest just soldered together)
  3. AE5JU

    AE5JU Ham Member QRZ Page

    This would be similar to R/C car/boat electronic speed controls.

    The TIP35 (NPN) and TIP36(PNP) with TIP31 drivers work well in this application. The TIP35 and 36 are rated about 25 amps continuous, 40 am surge.

    The forward TIP36 and reverse TIP35 can be mounted on one heat shink with no insulators. That heat shink can be connected to one side of the motor.

    The reverse TIP 36 and forward TIP35 can be mounted on a separate single heatsink with no insulators. That heat shink can be connected to the other side of the motor.

    The two TIP31's don't need to be heatsinked.

    The diodes protect the transistors from back emf when the power is turned off and the motor is still spinning. In addition, they provide "dynamic braking" and help the motor stop quickly. Get some healty rated one. Depends on the motor, of course.

    The 47 ohm resistors, probably anything up to 120 ohms will work there. For these, 2-5w resistors. The 1k's can be 1/4 w.

    This bridge should be able to handle up to 10-15 amps for short periods. For higher operating voltages, increase the resistor values proportionately.

    By applying a pulsed input to the bases of either of the TIP31's, increasing or decreasing the pulse width, you can control speed of the motor.

    I've changed up the direction switching by adding a center-off switch, so that Forward and Reverse cannot both be activated at the same time. This keeps the magic smoke from leaking out of the transistors.

    Last edited: Dec 7, 2008
  4. K9FV

    K9FV Ham Member QRZ Page

    I like this thread - just the starting ticket for a reversing motor to tune a remote roller tuner I've been thinking about.

    Thanks for the ideas.

  5. AE5JU

    AE5JU Ham Member QRZ Page

    Any way you can come up with for a computer to turn on either of the TIP31's will work this bridge.

    If you can generate squarewave pulses, and vary the width of the pulses, you can contol speed.
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