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Dorifto_Shoes's picture

Thanks OddBot.  Yeah, my current setup is definitely less than efficient.  I'll look into the DAGU setup.  At this point I'm not even using the encoders.  I wanted to get this basic setup working then I was going to expand on it from there.

Dorifto_Shoes's picture

Oh, I forgot to mention that I'm running 4 motors.

OddBot's picture

Ok, you are using 8x Alkaline batteries to get 12V. The motors are rated for 7.2V which is what you get if you use 6x AA NiMh batteries.

Your "H" bridge IC's will drop a few volts but all up this is not a good combination as a lot of battery power is wasted as heat by both the "H" bridges and your 5V regulator.

At the very least, piggybacking your "H" bridge IC's to handle the current and changing to 6x AA NiMh (rechargeable) will make a big improvement in running cost, motor life and heat dissapation.

DAGU has designed a 4 channel FET "H" bridge that is especially designed for the Rover 5 chassis and includes encoder support. If you cannot find a distributor that sells it then you can contact Claudia to buy directly from DAGU.

Because 4 motors and 4 encoders require a lot of control pins you really need an Arduino Mega or a compatible board like the Spider to get full benifits of the chassis.

Dorifto_Shoes's picture

Will I see much of a voltage drop acros the FET H bridges?

OddBot's picture

The reason FET's are prefered for "H" bridges is because they have a very low "on" resistance, usually less than 100mΩ. This means they can handle much higher currents with much less heat being generated.

BJT's are often used in toys because they are cheaper and can work at lower voltages.

Dorifto_Shoes's picture

Thanks OddBot!  Yeah that's something I was worried about.  I forgot to mention in the article but I swapped out the L293Ds for SN754410s.  I also have two additional SN754410s that I can piggy back on top if need be.  Would you suggest putting the additional ones on there?

Put a fuse or PTC fuse in series with the SN754410's power supply.
Razvan's picture

Hi, I've got the same setup: rover 5 ( 2motors +2encoders) and adafruit motor shield. Could you give more details about the fuse?

OddBot's picture

Very nice.

Just be careful though. the motor sheild your using isn't rated for those motors and will probably burn out. The stall current for your motors is 2.5 amps.

Are you using a 4 motor or 2 motor Rover 5 chassis?