Makeing a barebone somo robot controller/driver, what does it need?


I'm makeing a "simple" atmega328pu card with a 7805 voltage regulator and a l293d double H-bridge for my mini sumo robot.

The atmega is clocked using a creamic 16MHz resonator. Programming is done using ICSP, not usb. I would have used a usb if I could solder smd's. The pins that is not used by the h-bridge is breaked out using male pinheaders for use with servos and sensors.

The 7805 is decoupled with a pair of 10uF cap's and the 5v on the l293d is decoupled with a 100uF cap. Should I change the size og the caps, or add more?

I'm still having problems with noise resetting the atmega. But I haven't decoupled the motor's yet, and thats the next on my list.

I tok a lot of care to try to separate the motor and the controller signals when routing in eagle so they dont interfer with each other.

I'm sending the pcb to "production" soon, and it's annoying to find yet another thing I should have done to the pcb design.

Is there more I should do before sending the pcb design to china? More cap's?

This is my first ever microcontroller pcb, and one of my first pcb's in 20-25 years, so please advise me!


Is there no one with a little info for me? Please?!!

People like to look at things. If you want them to comment on a PCB design, you could post it.

Thats a wery good point bigred! Thanks!

Hope this helps someone to give me some suggestions!

(this is one of my first design using Eagle, so please don't be to cruel :stuck_out_tongue: )

Still no one?

First I've seen this.
You need 0.1uF decoupling caps - one on the power pin of each IC. If a chip has multiple power pins, use multiple caps.
Do not connect Aref to +5; connect a 0.1uf cap from Aref to Gnd.
Diode across R2 will also help - anode to Reset pin, cathode to +5. This will keep any spikes from the reset switch out, so the chip doesn't go into high voltage programming mode and looking hung.

Thanks CrossRoads!

Like this? I added a few cap's and a diode. Should I have a small cap in paralell with C1? I have seen a few design that uses that, but I don't know what that should accompish..