How to make a wall-avoiding robot with the BS2 board

How to make a Della-WAHR



Do you have a BS2 board, possibly the one found at radioshack, and are now saying "Well, that was fun. Now what do I do?". Well, you should make a Della-WAHR! For around only $40! This robot is easy to construct and can be easily programmed with the PBASIC language or code from



In this tutorial I will show you how to make a Wall-Avoiding robot with the BS2 board. Other things you will need are:

1) 2 modified Hitec HS-311 servos (

2) a PING)) rangefinder (Radioshack or

3) 1" Diameter PVC pipe (get about 2 ft to be safe) and T joint

4) a good supply of cardboard

5) twist ties (about 6)

6) rubber bands and lots of tape

7) a small caster (home depot)

8) Velcro

9) obviously a BS2 Board of Education (found at or can be found on ebay for half the price)

10) PING)) mounting bracket and servo combo, which is actually a good price (Buy Here)


The tools you will need are:

1) hacksaw

2) scissors

3) different sized screw drivers

4) box cutter (knife)

5) some type of vise (not required but helps a lot)

6) wire cutter / pliers (also not required but helps)


Our first step is to cut the PVC to length. You will need three 2 1/2" long sections of pipe. Now, you will need to cut groves into them for servos.

On 2 of the sections, cut groves like this with your hacksaw. The servo should go in about a cm less than all the way and must fit snuggly.

Real photo:



How to cut out that black part:


Now the next thing to do is cut the slot for the other section. This one will be for our vertical 180 degree rotation servo. It should go at least 3/4 of the way down the pipe. And this  one should fit snugly too.

Real photo:



How to cut out that black part:

Now that we have cut the pipe sections, arrange them like this with the T joint.

Real photo:


Now we move on to step #2. Here we will make the platform for the BS2 board to rest on. First cut out a cardboard piece like this and twist tie it onto your frame.


Step three is where we make the wheels and attach them to our HS-311 modified servos (2). We will make our wheels (2) out of cardboard, with a 6" diameter (a large Ovaltine cap works well). Poke a hole in the middle for the servo horn screw.

Real photo:

You may want to add some reinforcements to the wheels (bent paperclips or wooden sticks).

Now take the screw off of the servo horn and put it through the hole (you may want to add a washer) and into your wheel. You may also want to tape it on too. Take your servo with wheel and put it into its slots on the pieces of PVC. If it is loose tape the servo in too.



Step four is adding our PING)) servo combo (the ping is connected to the mounting bracket and the bracket is connected to our servo. put the 180 degree servo into its slot and if necessary and tape.

I secured mine with Velcro and rubber bands since the screws were stripped but you probably wont have to do so.


Now step five is to add the 4xAA pack that came with the BS2 board. Add Velcro to its back and to the bottom of the frame and stick them together.


Step 6 is to position our BS2 board on the robot. it will be on it like so.

( It will hang off the edge but that is ok. You can also add some more cardboad in the back if you like so it doesn't)      Twist tie the front onto the cardboard through the front 2 screw holes and then attach all of the sensors/servos into the following ports on the BS2 board:

right servo  12

left servo    13

PING servo 14

PING           15


The final step is to add your small caster. Position it under the PING)) servo and tape it on WELL (you may also add rubber bands) if it is too short and the robot leans forward on the caster then add some small scraps of wood on top of the caster then tape it on.


CONGRATULATIONS!!!!! just plug in the battery pack to your board, upload the attached code and you have a finished the wall avoiding robot for the BS2 board.


Code modified from code downloaded from


Thanks to everyone at Society of Robots for answering all of my questions on mechanics and electronics.

I never would have been able to do this without you guys.



My robots shake test: 



RoamingWithPING-V1.0.zip2.57 KB



Well If I used a dremel (which I dont own (darn)) it would just add another tool to the list, but good Idea!

dremel tool

Just a side note, a rotary tool (such as a Dremel) will make quick work of PVC. A file can clean up any edges.