davidbuckley.net
home  >  Double Vision < Beeber > First-Step 20 August 2023
Beeber - by David Buckley 1986
Beeber was designed in 1986 and is the prototype for a simple robot vehicle to be controlled from a BBC-B User-Port and is equipped with two bumper sensors for obstacle detection and two light dependent resistor (LDR) eyes to be able to seek or avoid light.
It can also hold a standard Berol pen to draw Logo style graphics.
Drive is by the two electric motors, the two wheel-axles are hinged so they can move slightly up and down and the motor shafts bear directly on the tires being kept in place by the weight of Beeber. Each motor is controlled by two relays in a normal 'H' bridge arrangement and mounted at the back. Each relay and LED is switched by a transistor.
5v power for the electronics and relays was to be provided from the User-Port, and power for the motors from two C-cells in holders underneath between the wheels.
The metal brackets for the Bumpers rest on wire loops in the PCB and are held in place by the nylon clips, as soon as a Bumper is pressed the contact is broken which gives a very low activation pressure for the Bumpers.
The shelf under the front was to hold sensors to detect lines and table edges but non was fitted. 
    D0 - Right Motor forwards  + Green LED
    D1 - Right Motor backwards + Red LED
    D2 - Left  Motor forwards  + Green LED
    D3 - Left  Motor backwards + Red LED
    D4 - Right Bumper - pressed =1
    D5 - Left  Bumper - pressed =1
    D6 - Right Eye (LDR) - bright =1
    D7 - Left  Eye (LDR) - bright =1

    The umbilical is 10-way ribbon cable terminated in 2x5 IDC connectors.
    
       D1 D3 D5 D7 5v
    [1]D0 D2 D4 D6 0v

    The white box between the User-Port cable and the 10-way umbilical holds a 74LS241 dual quad schmitt 3-state buffer.

It was intended to sell Beeber as a kit but my domestic circumstances brought work on Beeber to an end and when circumstances were better the market had changed, so Beeber was abandoned. All that was incomplete were the wheels which never got beyond simple wooden discs.

However during the 2020 Corona Virus lockdown I decided to finish Beeber. I cleaned up the wheels, bushed the bores with brass tube so they fitted the axles, turned a groove in each rim to take an 'O' ring tire, and sanding sealered and spray painted them.
Then for the first time I could test Beeber using a switch box I have. Since I didn't have any C-cells I made C-cell sized tubes from rolled-up paper to hold AA cells which are the same length as C-cells. Beeber drove very well, quite spritely, quiet and was very controllable.

On 13 July 2020 I wrote a simple Basic-Stamp-2 program (Beeber.bs2.txt) for Beeber. It works so well I might make more similar vehicles with additional sensors and onboard computers.