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L293D question

I´m trying to make my own motor driver, and this is what i could do until now by following some tutorials.

Happens that i can drive the motor in both ways with no problem!

If i connect the servo, and the motor, they both run for a couple of seconds and then stops... i think i should use a power supply for the motor but i´m lost in here..





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Here is another text-explanation, since I don't have the time to do a drawing right now.

Take a look at http://www.datasheetcatalog.org/datasheets/228/390068_DS.pdf page 21 top drawing. Create two of those. One will be the power supply for the logics, the other for the motors. The input for both circuits is the battery. The ground is common for both, so connect them together.

So, you have + from the battery going to the left side f both circuits. - from the battery going to ground on both circuits and ground on both circuits tied together (which is obvious, since - from the battery goes to both).

Now, take a look at  http://www.datasheetcatalog.org/datasheet/texasinstruments/l293d.pdf page 1-4. It might not be totally obvious, but there are two power inputs, VCC1 and VCC2. Now, connect the ground from both regulators to pin 4, 5, 12 and 13. Connect the positive output from regulator 1 to pin 16 (VCC1) and the positive output from regulator 2 to pin 8 (VCC2).

Regulator 1 is our logic  power supplay, so we are going to use this for the CPU and other chips as well, so the common ground goes to the other chips GND pin and the positive output from regulator 1 to VCC.

Regulator 2 can be used to power other "noisy" components like servos etc.


Does this make sense at all? It's just two regulators and 4 capacitors. If you still have problems, you can put capacitors on the CPU and other chips. Ask if you need help with that.


yes! it doesn´t seem so complicated at all..     :)      a schematic would also be great!!!!

i will only be able to get 0.33uf caps on monday!!  

hi jka! I apreciate your suggestion, but I would like to keep this simple, just because I am giving my first steps on electronics stuff..

I find robologist suggestion a lot simplier...

Belive me, it is simple. I'll make a schematic for you tomorrow (it's 20:17 in Copenhagen right now). It might be, that my way of explaining this is more complicated than it realy is.
Don't be so quick to dimiss jka's idea. My first 12-channel servo controller needed 4 voltage regulators: One for each group of 4 servos and a seperate one for the microcontroller. Otherwise, the microcontroller browned out.
it´s wasn´t my idea to dissmiss jka idea. it seemed very correct.. and also a bit complicated to me.
i need to take one step at a time  :)    and this is being far more complicated than i expected!! :)
Your diagram looks like you are poweing the motor driver and the microchip from the 5volt regulator. Wouldn't the positive connecting from the regulator and motor driver be seperate from the microchip power? Same ground, but different sets of batteries?
One battery could be a problem. You would need 2 regulators one going to the microchip and one going to the motor driver. Otherwise when you powered the motors the 5volts would drop enough to either not power the motors or reset your chip.

With the size of the motor and the fact that the driver only pulls a little over half an amp (600mah per channel and 1.2 at peak), I don't think he'd have to worry about it.

From what it looks like, he's also running a 7.2v RC battery which minmally would be around 1200mah(back in the day at least)  most now I think are up around 1500- 2200mah.... plenty of current for one motor and some electronics. This is how a lot of the RC car stuff is done...and actually, one of the leads would be directly connected to the motor.

Just need to make sure you have some ceramic caps on the motor to smooth out any spiking. 


thnx voodoobot! I never understood what was the function of ceramic caps on motors!

I´m using that motor only for test purposes, in the future I plan to use any kind of motor..