H-Bridge for Dummies: How It Works and How to Make Your Own




Introduction: H-Bridge for Dummies: How It Works and How to Make Your Own

As a high school who loves electronics with a free summer, I started playing with arduinos, and one of my first questions was, "how can I spin a motor backwards?" A quick google search led me to the H-Bridge, one of the simplest and most common ways to obtain bidirectional control of a motor. the first tim I saw this, I assumed it was one of those complicated things I wouldn't worry about, but when I saw the diagram, I was surpirised by its simplicity and ingenuity and couldn't help, but nake one myself. In this instructable, I will guide you through the process of making an easy, fun, and working(ish) H-Bridge with components you probably already have, and hopefully, you will gain an understanding of the component along the way.

Disclaimer: Don't expect to plug this into an arduino and control motors. this device is purely for learning purposes.

Disclaimer: (Last one)I neither am responsible for nor can guarantee any effects from this instructable- good or bad.

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Step 1: Parts

If you are even slightly into hobby level electronics, you probably already have these. If not, you can get these quite cheap online.

1) Breadboard and jumper cables
2) 2 AA batteries and holder
3) 4 pushbutton switches
4) 2 leds- ideally different colors

1) You

Step 2: Put the Buttons In

Since the vertical columns in a breadboard(perpendicular to the red line) are in parallel, you must be careful how you place the buttons. Make sure the positive and negative pins are in different collumns. The type I used have 4 pins(2 pos 2 neg or vice versa), so I tested them with a voltmeter to see which ones were continuous.

1) Place the buttons (as described above) in a square formation. The formation isn't that important, but it looks nice:)

Step 3: Place the Jumper Cables

Please use the pictures, they will make it a lot easier

1) Connect the 2 inner pins of two adjacent switches
2) Repeat with the switches accross from them.
3) Connect the 2 outer pins, one from each of the pairs you just connected, so this jumper is perpendicular with the ones from steps 1 and 2. This will be where you connect the positive wire from the batteries.
4) Repeat with the switches accross. This will be where you plug in the negative wire from the batteries.

Step 4: Place the LEDs

1) Place the first led, between the two switches connected by the positive jumper(red in the picture), in the pins parallel to the jumpers perpendicular to the the positive jumper. (Just look at the pictures if you don't get it) You can choose either polarity, but remember which one.

2) Place the second led, the exact same way, but on the other side, in the opposite polarity of the first one

If you are already comfortable with electronics, you will realize that, since those parts of the pins are connected by jumpers, the leds are in parallel. Therefore, depending on which way you allow the electricity to pass through, only one of the leds will light up at a time.

Step 5: Plug the Battery In

Before you plug the power source in, double check your wiring for any mistakes, which can lead to shorts. If you followed the instructions it should look kind of like a clover leaf like the picture above.

1) Plug the black wire next to the ground jumper

2)Plug the red wire next to the positive jumper

Step 6: Play With It

1) Choose any two diagonal switches and press them and see what happens

2) Do not press press any adjacent pins, this can lead to a short

3) Press the other two diagonal switches and see what happens

For a demonstration, watch: [Play Video]

Each pair of switches will light a different led; since they are diodes and wired parallel in opposite polarities, only one of them will light at a time. This will be more apparent if you choose different color leds. This is how an H bridge works. The controller (often an arduino) decides which of the two switches (mosfet transistors) are closed to control the direction of current across the load.

Well that's it, I hope you know know how an H-Bridge works and one have to play with. If you have any questions, don't hesitate to leave a comment.

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    2 Discussions


    3 years ago

    Not exactly an H-bridge if there aren't any transistors...


    3 years ago

    Could add some information on timing?

    How fast can they be switched with the controller?