L293 H Driver

I ordered a couple of these the other day to use with a kit I purchased. I intended to get the L293D, but when they arrived I had actually ordered the L293NE.

I'm only using 3 volts (2 double A batteries). I know I should use diodes, but I'm wondering if this is enough power to potentially hurt the arduino if I go ahead an hook it up now without them. It will be a few days before I can get the correct part since I have to order online. It sucks having it all together and not being able to use it.

If you read the datasheet of the L293D or the L293NE, you see that the minimal voltage is 4.5V.
This is a serious problem with the L293D, it can be used to drive 12V motors. I'm sorry to say, but 3V motors will not work.

About your question about the diodes: you should never underestimate the voltage spikes caused by an inductance (the motor in this case), so yes, you need the diodes.
With a H-bridge, things are a little different. I think your Arduino board will not get hurt. But I cann't guarantee it.

Can you tell us which Arduino board you have, what kind of motors (link to the motor please) and what you want to do.

Thanks for the reply Erdin

Would you believe that I read the datasheet, but that hadn't even occurred to me? I was so busy looking at the differences between the two that the voltage just never registered with me. Thanks.

The kit is this http://www.tamiyausa.com/product/item.php?product-id=70108

I got the dual motor gearbox to replace the single one that comes with the kit so I can turn the vehicle. It has the same motors though. They're just small 3v mabuchi motors. I don't see anything on the motor or the package that would identify the model.

I guess the reason I was looking at the L293D is because that is what's used on the adafruit shield and I've seen a lot of demos of this kit being driven by it. It also has the diodes built in.

I have both an Uno and a Leonardo. I will probably be using the Leonardo on this because I want to control it via bluetooth, and being able to use the RX and TX pins without an extra library is convenient while programming it. I could use either though.

I did set the motor up with the Driver using LEDs as temporary diodes, and it will run the motor off a 3v source.

There are 3V motor drivers.
The mosfet motor drivers mostly require 5V as minimum.
With transistor output it should be possible make it work for 1.5V.
I can only only find expensive motor drivers, I'm sure there must be cheap 3V motor drivers good enough for that funny little Tamiya chassis.

For example TI has low-voltage motor drivers, DRV8832 data sheet, product information and support | TI.com

How will you run the Uno or Leonardo at 3V ?

If you want to run everything at 3V, perhaps an Arduino Lilipad can be used.

And perhaps you have to build two H-bridges yourself with normal transistors (not darlington transistors).

thanks
I was going to run the leonardo off a 9v battery and use the AA for the motor.

I found a low voltage motor driver from TI for about $4, but the shipping was around $55. :fearful:

I managed to find the datasheet for the motor on pololu http://www.pololu.com/file/download/fa_130ra.pdf?file_id=0J11

I may buy a higher voltage 130 sized motor. That solves the driver problem, and I can probably get away with a single power supply.
I'm looking at the one on adafruit, but not sure how interchangeable they will be. DC Toy / Hobby Motor - 130 Size : ID 711 : $1.95 : Adafruit Industries, Unique & fun DIY electronics and kits

If not, there's a higher rpm motor on amazon that is about the same price. I just have a few other things I'd like to get from adafruit at the same time.

As another alternative, could I temporarily use a voltage divider at the motor wires to drop it down to 3? It wouldn't be an ideal solution, but I want to play with this thing now danglit! XD

The driver has to be able to supply the stall current.
According to the datasheet that would be 2.2 or 2.1 or 0.9A

You can't use a voltage divider for the motor.
Also using the L293 at a higher voltage might damage the motor.

If you are willing to take a risk, run the L293 at 5V. The motors should do something.

Using 9V for the Leonardo makes things easier.
You could always change to a Lilypad or a Mini Pro at 3V.

As far as I know these motor drivers have free wheeling diodes which automatically bypasses the voltage spikes and back emf to motors to ground. You do not need to add external diodes.