Let's Make Robots!

Robot Number 3

Autonomous robot with US navigation with IR obstacle and depth detectors

Robot No1 was the LMR kit and came about as part of my desire to learn about microprocessors. It was no good simply reading about code I had to write and play with it to understand it and robots seemed like a fun way of doing this.

Robot No2 was the old Picaxe "Mr General" kit which provided many hours of "education" and by then I was ready for No3.

Robot No3 was custom made using Picaxe 40X2 and 08 microprocessors, SRF06 ultra sound for the main proximity sensor (on a servo so it could look from side to side) and a host of other IR sensors to detect drops and low edges which I had discovered caused havoc if you only had the main forward looking proxinity sensor.

I found a few goodlooking "bicycle" wheels on a model pennyfarthing bike then gave the robot a "head" with a flashing (RGB) "brain" all made from acrylic. The RGB LED in the brain is driven by the Picaxe08. It started out with green for forward and red for turning but I thought it looked better with RGB sequence.

Code is similar to the LMR kit with extra subroutines to interface with the additional sensors. It also has variable forward speed depending on the "free range" ahead. It slows as it gets closer to an obstacle similar to the Mr General robot.

Another feature is an easy to use "kill" switch which stops the operator having to grab the robot to turn it off. I've added an IR sensor looking above the robot. All you have to do to stop this robot is hold your hand over it. Much easier (and less traumatic for the robot) than trying to hit an OFF switch while it is on the move.

In response to a request from fpictor a photo of the "Motherboard"



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Thanis for adding the follow up. This is a really nice looking bot.

Lessons learned.

I thought I’d add a postscript to this build. It’s a couple of years overdue but might help some “new” builder from making the same mistake I made. After all one of the massive advantages of LMR is the collected knowledge and experience of its members.

The story….

Robot Number 3 was a “hit” from the start and did many demos BUT it became apparent that from time to time it would get “confused” and erratic. This occurred in areas of high IR light, for example inside, on a table top, in a room with lots of windows and sunlight +++.

The IR “side and depth” detectors were sensitive to ambient sunlight and their erratic input under this condition played havoc with the robot.. The end came with a 2 metre plunge from a high ledge (it was showing off at the time). Both acrylic “front feelers” were broken and it sat in the junk box for several months waiting rebuild.

It was rebuilt as Robot Number 3B and the only difference was a new black acrylic chassis and Sharp IR proximity sensors (to replace the simple inexpensive  ones) which are fairly resistant to ambient IR and work very well even when angled at 45 degrees to the target zone.

Robot Number 3B

Proximity Detectors

The “lessons learned”….

  1. Simple IR proximity sensors have limitations especially in areas of ambient IR. See OddBot’s “Compound Eye” for a discussion of this and some clever software techniques.

  2. Don’t show off.

wheels of the robot are very nice...

nice robot... looking great...


This is a really interesting looking robot, with some cool design and nice features.

Great work 1 what =)

The IR sensors on Robot 3 are: Edge and Drop (Cliff) sensors  

The low front obstruction sensor http://yourduino.com/sunshop2/index.php?l=product_detail&p=47

The turn off sensor – you could use either of the first 2 but I used


Photo of the Picaxe processors follows. It’s not too tidy and reflects the “dynamic” nature of the development of this project (read as “multiple variations along the way!”)


The “translucent pipes” are acrylic tube and you shape it with a hot air gun. It can be glued with acrylic cement. There should be a lot of hits if you Google “bend acrylic”. I’ve used it a lot as conduit in projects – bends easily and looks great.


Very nice manufacturing.

You put a lot of care at the finishing.

I like your wheels too.

Can you tell me what kind of IR sensor you used ?

What are the translucid pipes you use for "conveying" your cable ? How do you "shape" those pipes and fix onto your frame ?

Can you post a picture of your "moterboard" with your 2 Picaxe ?


Thanks Guys.

A very kind response to my first post.

Wait till you see Robot # 4!

I have to admit I spent a lot of time searching for large cool wheels. I was after looks as well as big diameter = speed.

Chris - just for you - http://lilfishes.com/id215.html

Cheers, 1 what.

Very sweet looking bot! Very creative design with function as well and quick thing as well. Nice work. Stephen

Those are really cool wheels.  Nice bot, too!