L9110 motor driver IC issues.

So I’ve had a little RC car lying around, that stopped working, so I decided to take it apart and see what made it tick. After examining the internals, I decided to pick it up as a project, and make it autonomous, with an AVR and a simple infrared distance sensor.

It has a really small DC motor at the back, and a coil at the front. The rod, which connects the front wheels, has 2 pretty strong magnets in it, offset from the center of the coil, so depending on the polarity the two wires are connected, the direction of the magnetic field shifts, and dragging either one or the other magnet in front of itself, making the little car steer. A small spring makes sure, that when there is no current applied, the wheels return to the middle position.

Now at first, I wanted to make a simple H-bridge out of some NPNs, but a friend of mine pointed out, that whenever I’d disconnect the current from the little coil at the front, it’d generate an opposing current, which would harm the transistors, rendering my solution useless.

So I decided to look for a way which had a solution to this problem. Said friend also pointed out, that I’d be much better off using an H-bridge IC instead of making my own, so after I looked, I found the L9110 IC, which is perfect layout and feature-wise for my project. Its ‘datasheet’ can be found here:

Basically it really stood out from all the other H bridges, as it didn’t need a 5V logic voltage, it can work off of the voltage intended for the motors, up to 12V. So I ordered a couple of them and they arrived recently.

Now I tried it out with an Arduino, and it doesn’t work even though I wired everything up correctly. I was supplying it with the 5V off of the Arduino. I tried it out with some generic LEDs, and to my suprise it worked as intended. The thing I noticed, that the LEDs were much less brighter when connected to the 5V of the Arduino (with an 1K resistor). Judging from this, I thought that the IC might be dropping too much voltage, but no, it still outputs a solid 4.5V at it’s motor connections. The motor is really really tiny, and it had no problem working off of the 3.3V the Arduino provides, and it ran pretty fast with it.

I’m thinking that the motor isn’t getting enough current to run, and that’s why the LEDs are dimmer than hooking up them directly. If this is the case though, I don’t have any ideas on how to solve it, so any help would be greatly appreciated! :slight_smile:

You just need diodes across all 4 switches in an H-bridge to safely pass the inductive
current.

If you use MOSFETs these are built in already.

What supply voltage? Building an H-bridge of just NPN means bootstrapping the
base drive for the high-side drivers, its usual to use PNP high side switches and
NPN low side.

By the way that chip drops a total of 2V or so under load, and its only rated at 800mA,
so not up to most motors. What current does your motor take at 3V or 5V?

Just a quick question about de l9110...I've bought a tchang dd1-1 track set from dx and it seems to work with a l9110.. Can I power it with a 12v lipo battery?