Let's Make Robots!

any schematic design for brainless/no PIC/no microcontroller. avoiding obstacle robot??

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hmm.. should i use 2n2222 and 2n2907..?? 


ill buy a DC motor maybe tommorow. 6v DC motor right?? 

Yes, try those transistors.

And look for a lower current motor, similar to the pololu one I linked to above. Stall current of around 800mA, etc.

Good luck!

my only problem now is. synchronizing the motor speed.. haha.. its hard to adjust it.. whew..
The motors should be running at the same speed. I've edited my reply above.
its all working now..im using 4AA batteries. the motor i used is only a generic DC motor from the twin gearbox of tamiya.. but the two outputs does not sync in speed.. and it is too slow.. i think it cant support the mobot. but well see..

Hey, I'm glad it's working ok.

 Regarding the motors, I was checking out the twin-gearbox specs over here:


The motors appear to be low voltage (3 - 6 volts) but draw a fair whack of current, certainly more than the 3904/3906 can handle. Check the specs in the Mabuchi motors pdf, referenced on the same page.

I think you'll need to beef up the transistors in your h-bridge.

You could also look at swapping out the high current motors in the gearbox with something like this:


Used to be able to buy a similar motor called a P9000. Maybe check your local electronics suppliers for motor with specs approximately that of the pololu motor.

question. i used trimmer on P1 and P2. is it advisable?

Yes. Use a trimmer. But, where is P2? There should only be P1, used to adjust the voltage at pin 2 of the LM393.

 edited: It's official - I'm an idiot. P2 is the pot for the second sensor! Duh.

i used the first design and its working on the breadboad. but its really hard to adjust the potentios. and the motor output  its kinda low i think its because of the transistors?? i used 2x 2n3904 and 2x 2n3906 and 1k ohms every base pins on the H-BRIDGE.. but its a progress to our project thanks.. 

You could add a visual indicator to show when the sensor is triggered:


D3 just stops the LED/resistor combination from affectting the delay time.