Let's Make Robots!

Quick mock-up of IR obstacle avoider.

What is it?

This is a quick mockup used to test the IR obstacle detection circuit which came out of this forum topic:


It uses this circuit:


In the forum topic I mention the problems using a 1 Meg resistor in the delay components caused. Switching to 100k solved them, but the real solution was attaching one end of the delay capacitor to the second inverter, as you see above. This provides  positive feedback which forces the capacitor to reset at the end of the delay. If you need to use a 1 Meg resistor for a longer delay, with this configuration it is ok.

At the moment it uses this h-bridge:


but I intend to trial a couple of changes with an L293D. It is powered by four AA batteries.


I got it together in around half an hour using a few old CDs and some double-sided tape. Most of that time was spent populating the breadboard!

It basically a multi-layer sandwich of a CD, some tape, motors, more tape, another CD, some tape, a battery pack, some tape, another CD, yet more tape, and a breadboard with components. 

The circuit seems to work quite well, but would obviously benefit from better sensor placement. Possibly could do with lowering the value of the IR LED's resistor, too. Might try pulsing it at a low duty cycle and increase the LED current.

Anyway, it was a really quick and easy way to construct a mobile test-bed.

I used these motors:


I used these phototransistors:




Note the old LEDs superglued to both ends of the undercarriage to act as skids.



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Love your design! :D

Hey, thanks fritsl!

Yep, only the best engineering standards are good enough here at Jo's Dodgy 'Bots Shop.  :)


  can i have the full systematic lay-out of your obstacle robot that your posting pls??

   i am a tollaly noob in this ,, and i cant see clear the breadboard stemualation..

    i need to make this project in 2 months .. tnx in advance bro...



(and an idea I'm bound to steal, since it totally fits into my design ethic)


And you went way beyond the call of duty in that forum thread, nice one.

Oh no! Don't tell me you're starting a PhilBot's Dodgy 'Bots Emporium!!  :D

Once I started in the forum I sort of got a bit carried away with it all ...

Cheers, mate!

The other day I made a cat feeder out of a stick I found on our driveway and an old salt container. But the sad truth is it would probably take me weeks just to replicate your cool little CD-bot. Heh, I love the dog in the video, I tie ribbons to one of my bots to get the cat playing with it. Anyway, at this stage it's more like PhilBot's Dodgy 'Bots Honesty Box, I'll have to build up to Emporium status ;)

hey jo. were done now. we already passed our project. and got a good mark. thanks again :))

That's great, aidzmana.

I hope you all had a bit of fun and learned something along the way. I know I did!