Let's Make Robots!

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

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haha. sorry. i should call you jo then.


just to confirm i will use the the 9,8  and 11,10 pin of UC2 for the second motor h brigde input 1 and 2..  RIGHT??


we're very thankful to you joC..


dont know how to pay you for helping me and my groupmates..  maybe almost all of my classmates.. 

No worries. I hope you all have some fun, and get it working.

You can use those pins for sure, or the others. Pin 9 is an input and 8 is the corresponding output. Likewise, pin 11 is the input and 10 is the output.

As for the other pins, 13 is input and 12 is output. Pin 5 is input and 6 is output.

Max voltage for the 74HC14 is 7 volts, 6 volts to be safe. If that's no good, there is a cmos chip that handles a higher voltage, the 74C14, I think, but don't quote me. You want the schmitt trigger inputs for snappy changes from the output to the input of the h-bridge.

For the two inverters you don't use, please tie the inputs to ground. I mean like the negative battery line. If you're using pins 9/8 and 11/10, then tie pins 13 and 5 to ground.

Anyway, have some fun, check out some stuff on the web. It's 10.30 here in Melbourne; past this old guy's bedtime. G'night!

 EDIT: Actually, you could probably about halve the value of R1, depending on the voltage you're running at. If you're running at 6volts you could go under 200 ohms for R1 with no probs. 330 is probably too high. Maybe try about 180 ohms first.

dude,,, i suggest this schematic than the 1st 1 




Hey, cool, now I'm a dude. Whatever ... Still have to do the switcheroo on the contacts to reverse a motor.
thanks a lot.. you're a big help..

i will be using the twin gear motor which u can buy in tamiya..




im thinking if i can use this circuit as a sensors.. see the link


Apologies for the delay. As soon as I said I would help all these tasks raised their ugly heads, and apparently I'm the only person in the universe who can deal with them! (No pay rise, though ... )

 This is just a simple sensor arrangement which will cause the motor to which it is attached to reverse for a certain amount of time. This time is set by R3 and C1.

 R1 feeds D1 which is an IR LED. You may wish to lower the value of R1 to increase the range. These are, obviously, used to trigger Q1, the phototransistor, when IR light hits an obstacle.

The phototransistor will have to be shielded from ambient, and stray IR, light. Under the corner of the 'bot sounds good.

Set potentionmeter, P1, so that the output of U1, the LM393, is high. Adjust the pot until the output goes low, then readjust until it just goes high again.

When an obstacle is detected the voltage at the junction of Q1 and R2 will decrease. When it falls below the voltage at the inverting input of the LM393 (pin 2), the output will go low, and reverse the motor. When the output goes low it will charge C1. The motor will continue to reverse until  C1 discharges.


Maybe breadboard the circuit and see how it goes for you.

You may, of course, want to use a 38kHz detector, but that would be a bit more work.

Any questions, please ask. Should I be a bit tardy with answers, others here may help.

If anyone has any improvements to offer, please feel free to have at it!


Been very busy with work and stuff. I will post a part schematic later today.



how about this 1? ill change the bump switch into this comparator? can u help me?



That is more like what you want.

What sort of motors do you have? Have you got any components yet? We may be able to make something with parts you have already.

Is this for a small robot, like one that will run around on a tabletop, or must it be able to go on the floor, cope with carpets or whatever?

Please give me some idea of what you have in mind.

Also, what knowledge of electronics do you have? I don't want to explain things that you already know.

I do not have a lot of time, but I am happy to help you if and when I can.

And, please don't call me sir. :-)