Let's Make Robots!

Yet another h-bridge question

I've been reading a lot about h-bridges, but I can't seem to find specifically what I need. I have a toy that I am hacking, and it contains two small DC motors. The toy is powered by a single AAA battery, and the motors receive almost the full supply voltage when they are turning (difference is about 0.02V). Their resistance is 2.6 Ohms, for a stall current of about  0.58 amps.

Now the control board of the toy has two SMD chips which I presume are the drivers for the motors. The numbers on these chips are "HF2025C" (first line) and "1130P" (second line). There is no manufacturer name or logo or any other lettering or logo on the chips. So far, I have come up with absolutely no info for this type, so if anyone knows how to find a datasheet for these things, I'd love to hear about it.

Second though, I am looking at making an alternative control circuit to drive these motors, but I have been unable to find an integrated h-bridge chip or a DIY circuit that works with a supply voltage of 1.5V, and can drive the motors with almost that entire voltage.

Any help is appreciated. If you need more information, please let me know.

Thanks in advance,

Jeroen

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If you want to stick to 1.5V then you can use a simple H bridge like the one below but what processor did you want to use. I think the lowest voltage for an ATmega is 1.8V and that is at a clock frequency of 4MHz or less.

Perhaps the best solution to your problem is to get a AAA sized Li-Ion battery. This will fit in the existing battery holder and give you enough voltage to run an Arduino Pro Mini which is small and comes in a 3.3V version. If the higher voltage is too much for the motors then you can use PWM to slow them down.

Alternatively you could use a Micro Magician V2 which is a bit bigger (30mm x 60mm) but has a dual "H" bridge with electronic brakes built in as well as a 3-axis accelerometer and IR receiver. This controller will run from a single  Li-Ion, LiPo or LiFe cell.

Thanks for that! You're right in that I want to use an AVR processor, preferably something like the atmega328 so I can reuse the Arduino libs. For some reason I thought these would work at 1.5 V, but the datasheet indeed clearly states 1.8V. In that case a 3.3V AAA-sized Li-Ion cell is probably my best be, which also simplifies finding a suitable integrated dual H-bridge chip.

 

 

Thanks for the reply. I'll check out those chips.

But if you always need at least 2.7v, how does the original control circuit manage to get away with a single 1.5V AAA battery, including running both motors both ways? I don't think they use a voltage step-up, as the voltage driving the motors pretty much follows the supply voltage.

Not arguing here, just trying to understand :)

Jeroen

That is just the voltage needs for the Step Up/Down regulator I linked out to, not necessarily related to your circuit.

No clue how it runs off the 1.5 but I would bet somewhere there is a step up piece in there.

Have you measured voltage points to see what they area around the board with a DVM?

Just curious...

The only links I find for that 2025 chip that makes sense is here:

http://www.flickr.com/photos/qdot76367/6296272375/

Related to the My Keepon bot I guess...

-Stephen

Yep, I found that picture as well, and those are indeed almost the same 2025 chip I found on the PCB. Only mine are 1130P instead of 1128P (but I don't know what that signifies).

I'm not working on a Keepon bot though, but an AirSwimmer.

You'll need 3.3 or 5v to run whatever you're going to control right? That voltage will be needed torun the logic side of the h-bridge but the motor driver voltage is independent of the logic voltage. I've driven 3.0 volts on a 754110 without problems. You MAY be able to use a step up/down regulator like http://www.pololu.com/catalog/product/798 but you'll need at least 2.7v or so even then and the output diminishes with the lower voltage and won't be enough to drive the motors by may drive the logic. Just an opinion... Stephen