Let's Make Robots!

Little 8

Very cheap but fun little beginners robot. It think' it has a brains within a Picaxe 8


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Edit: Check out this nice clone: http://letsmakerobots.com/node/8386

From building big, nasty, with large shovel, 2 cores, multiple sensors, soundsystem etc, I got tired of that.. and decided to see what fun I could have with a little Picaxe 8 on a board ($16, total prize for robot is about $40).

Version II of this fella here: http://letsmakerobots.com/node/101

I have since recieved some interest in how to build this extremely easy and cheap robot, and so I hereby transform this post to a small and simple tutorial:

Shopping list:

Can be bought from Picaxe:

You can get this from anywhere:

  • 1 9V battery
  • Some sticks and something to cut them
  • Screwdriver
  • Soldering iron and led
  • Some pieces of wire and something to cut it with
  • Some different types of glue or tape etc
  • a table-tennis ball and a knife to cut it
- And then you need some motors with wheels. I recomend these, used in my robot.


I like the challenge of only having 8 pins and 128 bytes of code etc. But be aware; you get a funny robot, but it is blind, can only sense a bumper in front, and you really do not have much memory in it etc.

What I did after building this, was i set it up with Easy Radio serial wireless input on the only pin left for anything. This made it possible to control this little robot by another robot, which opens new windows etc.

Some friends and i in our local club also had a contest of making it draw the number 8 on a piece of paper with a marker glued to its back.. Good fun little fast and chep robot!


A stick, some switches, and a sliced up table-tennis-sized ball for "the third wheel"


To get the 9V down to 5V, I use a voltage regulator.

I was just mounting with some glue, the strips just tohold things in place..


An angle grinder may look like an extreme tool for such a small job - but I use it quite often. Just turn it on, hold it steady against something, and anything you stick in there is just vanishing, nice and smooth - compared to cutting such small parts. I also use it for acrylic (Plexiglass), again it is perfect to make little cuts and markings.


Just follow the instructions that comes with the board - it cannot be more simple, hook up the 2 motors.

The motors I recomend are incredible! Fast and strong, even though I only feed them 3.5V due to the 1.5V drop from the Motor Driver. So I actually had to make a "tale-bumper" (red square) as it was lifting the front a little too much :D With the bumper on it turned out quite cool, as it is just as capable of navigating on only the rear-wheels.. there is nothing else but a glider in front anyway.


All needed now is some code and the battery.

TIP: Get rechargeable batteries (and a recharger) - Or you will soon have used as much on batteries as on the Robot itself!

REMEMBER: If you make anything like this, to take a picture and show me :)

Here is the code used in the robot on the video. Don't mind that the names of the sub-routines does not make sense to you. Fact is that nothing in this code makes much sense, it was just the fun I had at the time when I shoot the video :)

I will have a closer look at this soon, but on request, here the code from the video:

symbol fw = 20
symbol bc = 200

b0= 175


random w5

for w3 = 0 to w5
if pin3 = 1 then
gosub bum
end if
next w3

b0= b0 +1
random w5
if b0 < w5 then goto hest

random w5
if w5 > fw then
high 1 low 0'ForwardRight

random w5
if w5 > fw then
high 4 low 2'ForwardLeft


random w5
if w5 > bc then
high 2 low 4'ReverseLeft

random w5
if w5 > bc then
high 0 low 1'ReverseRight

goto dav

w4 = 32212

high 2 low 4 high 0 low 1'Reverse
pause 300
if b0 > 175 then
high 1 low 0'ForwardRight
high 2 low 4'ReverseLeft
high 4 low 2'ForwardLeft
high 0 low 1'ReverseRight
end if
pause 300

b0 = 175

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Without seeing the switch, it's hard to say for sure, but you will probably be fine.

A 'limit switch' is just a regular switch that is used to indicate when some mechanism has reached (or is about to reach) its mechanical limit. You might use a switch as a limit switch on a rotating mechanism, if you don't want it to rotate more than 360 degrees, for example.

So what you hav bought is not a 'limit switch'. It is only a limit switch if that is what you use if for.

A 'bump switch' is also just a regular momentary switch that is used to detect when an object has been bumped into. As long as the switch can be activated by the pressure of your robot bumping into something, and then released when your robot backs up, you can use it as a bump switch.

That should be fine. There are probably three electrical contacts. One is 'common', often marked with a 'C'; one is 'normally open', often marked with a 'NO'; and one is 'normally closed', often marked with a 'NC'.

The switch will normally have the common contact connected to 'normally closed'. If you depress the switch lever, the common contact will now be connected to 'normally open'.

Hi , im new to robotics and im going to build this robot as my very first bot , ive a got a question though , is this the complete quide to build this bot n make it work? is there any instruction in more details ? cause im a complete noob in robotics ~ for instance what are those metal sticks in front of the bot , and what device are they connected to , and how are those connected to the board ? can u please provide in detailed instruction ? let me know.

best regards.

Welcome to LMR! I'm glad you want to jump in and start building something. It's the best way to learn.

Little 8 is a pretty simple robot, and not a bad place to start. If you read Frits' post carefully, you can see that those two metal sticks are switches.

However, if you want some really clear instructions on building a robot, try the start here robot, which is intentionally designed with the first time robot builder in mind. Even if you deside to build something more like Little 8 instead of the SHR, a careful reading of that post will teach you everything you need to get started.

If you decide to build the start here robot, you will have a basic platform with some room to grow. That's something to consider before you make your purchase.

ty for the response , yup those are bumper switches , wasnt paying attention to the description ~ ive got another problem though , i live in malaysia and im gonna have to order the parts from US and it'll take weeks till i receive em , that's gonna suck big time :(

Search around for other dealers. Shipping costs will kill you if you are not careful. Search around and you may find distributors with better deals.

do u recommend any good site i can purchase from ?

Sorry, but I'm in the US. Most of the places I shop online probably would ship to you... for a cost. You'd be better off doing some research on your own.

Fristl, could you post the schematic?  i am making something similar.


see ya !!