Hi friends,
First post. I have a quick question. All I am looking for is a motor controller to control 4 wheels. I thought of putting together 2 L293D ic's, but asking your help to suggest other IC's which can reduce a couple of pins. Also the current requirement is too high in L293 IC's.
If someone has experimented with other motor drivers (commonly available) and suggest me, that would be helpful.
Requirement:
Control: To control 4 motors
Voltage: Should work between 5-12 Volts
Please let me know if you need additional inputs.
Thanks,
Praveen
www.robotplatform.com
Hi Praveen. We need to know
Hi Praveen. We need to know the current requirements of your motors.
I don’t know a driver that supports four motors. You can use two motor driver chips to drive four motors like you mentioned with the l293d. If the l293d doesn’t have enough current, there are higher current chips like:
You can also stack some chips on top of each other to get higher output (people have done this with the l293d and SN754410).
Another option is to build your own h-bridge. There are example designs on the H-Bridge Matrix page.
I am sorry, I think I should
I am sorry, I think I should have been more specific and clear. I did not mean that they do not give out enough current, but they sink in more current. This eats up my battery soon. The very reason I was wondering if there is any IC which combines two L293 IC’s into one so that the current taken by two IC’s will reduce to one.
Also, building a circuit with one IC is more simpler than putting two ic’s and also require less space.
I have a couple of H-bridges, but each transistor sinking in 0.7 volts would cost me a lot, especially if they need to drive 4 motors which would mean 16 x 0.7V = 11 Volts and at any time it would eat up atleast 5.5 volts and the robot runs on 7.4 volts 
Cheers,
Praveen
Either I don’t understand,
Either I don’t understand, or you are not making sense.
Any H-bridge is going to drop some voltage. Inside the motor driver chip are transistors. They will drop voltage no mater what. So if you feed in 7.4V, the motors will actually get less than that.
But the drop isn’t additive. Each H-bridge gets 7.4V. Let’s say the h-bridge drops 1.5V, so your motor gets about 6V. All your motors get 6V, you don’t drop 1.5V for each driver!
Also, the major current consumption is going to be a function of your motors. Some current will always be lost as heat (inefficiency) in the chip, but you can’t help that. If your batteries are getting used up too quickly, it is probably because of your motors, not your driver chip.
Please correct me if I am
Please correct me if I am wrong. Suppose I have a motor driver L293 which sinks in 1.5 Volts for two motors. Now If I find another driver from the same L29* family which runs four motors instead of two, does it sink in 3 volts or less than that? Just my vague assumption that it might end up taking less.
Also I know that if things does not work as intended, then I need to add-in a higher powered battery, but just checking the options.
Anyways, thanks for your kind response. I better add up two drivers in that case. 
If you happen to find a chip
If you happen to find a chip that drives four motors, inside will just be a two copies of what you would find in a two-motor chip. Each h-bridge operates separately. Each h-bridge gets 7.4V in and about 6V out. There’s no difference, except that it would all be in one package.
Look at it this way. You need one h-bridge to drive one motor. The l293 and similar chips helpfully package two h-bridges in one chip, since many people want to drive two motors bi-directionally. Maybe you’ll find someone who packaged four h-bridges together, but that’s pretty special and you may have trouble finding it or it may be very expensive.
Unless you are extremely concerned about space on your board, don’t worry about using two chips.
No. I am not "extremely"
No. I am not “extremely” concerned with the space, but that was a thought. I guess I will add two separate drivers as per your suggestion. It is just that I wanted to confirm for sure that there is no easier way from experienced guys like you.
Thanks for the response ignoblegnome.
Cheers,
Praveen
www.robotplatform.com
** I have a problem to find**
I have a problem finding motor driver to supply 5A per channel. I looked up L298 and here is what I found:
L 298 :: Driver, Multiwatt-15 = L 298N
It can only do 2.5A per channel repetitive. So not close to 4A at all It is kind of unclear whether is it L298 or L298N or the are both the same.
I was thinking just buying 2 ESC. What do you think about this one:
http://cgi.ebay.de/RC-ESC-20A-Brushed-Car-Motor-Speed-Controller-1-16-1-18-/250844624496?pt=RC_Modellbau&hash=item3a67813670#ht_2760wt_905
Hey RoboSerg,You should
Hey RoboSerg,
You should probably post your own question, rather than hijacking this one. However…
The DAGU Wild Thumper motor driver will provide 15A per channel. That might be overkill for your needs.
I’m honestly not too familiar with ESCs. I’ve never used one. The specs on the one you listed seem more than adequate for your current needs. I believe that many ESCs are designed for brushless DC motors. If you are using standard DC motors, I’m not sure it is appropriate to use an ESC, but I’m really not sure.
If you do use an ESC, you will have to control it much as you would control a servo. This is different than controlling a normal h-bridge.
More info on ESCs can be found here.
Transistor voltage drop across collector emitter
Hi Praveen,
Bear in mind, voltage drop is not current sunk. It does not cost you anything till a current runs through it.
If you are looking for a hBridge design from descrete components, look at FETs/HEXFETs. If you are not doing any high freq PWM, they are essentially a free ride ( energy wise). Zero voltage drop across th input and output, no current needed to switch them on, just apply a voltage.
If you do go this way make sure you use logic compatible ones, as driving a FET to be only half on is a recipe for voltage drop & lots of heat.
I use the Pololu motor drivers.
One other thing
Voltage drop across the collector&emitter is generally tiny,
An approximation of 0 or .2v would be a better estimate.
http://www.physics.unlv.edu/~bill/PHYS483/transbas.pdf
they only accumulate on the switched on parts of the h bridge, so left side may drop .4v, which is pretty I significant.
