Sunday, 28 February 2010
The buggy started life as a toy Lamborghini running on 2 6-volt motors, one driving each rear wheel. When we moved house I took the opportunity to ditch the upper body which had seen better days leaving a bucket chassis.
It has 2 6-volt emergency lighting lead-acid batteries wired in parallel to give a whopping 20 Ah. Most of these electric toys have batteries around 6-8 Ah. It doesn't go any faster, but this gives a much extended running time.
These are the new wheels on the buggy up close. I got these hand-truck pneumatic wheels on eBay for £15 and my colleague Johnny kindly helped me adapt them to fit on the buggy. I finally got time to drill holes in the axles for cotter pins to make sure the wheels won't fall off. It's unlikely this would happen because the washers behind them are a very tight fit, but better to be sure where children are concerned.
Friday, 26 February 2010
I got a little more work done on the Psion 2 interface board, but I'm getting some spurious results on the input port, so I'll concentrate on finishing the output port tomorrow by adding the 2 H-bridge ICs to drive the Lego motors.
Thursday, 25 February 2010
A kind donor gave me a broken car DVD player set with 2 nice 7 inch monitors. A bit of re-wiring and they now have simple 5-pin DIN plugs carrying power, video and audio. I then acquired an old VGA-to-Video adaptor that had lost its leads and power supply, but that was easy to sort out and here we have a test bar graph application running from an old laptop. The program was written in C using the OpenGL graphics libraries and runs under DOS.
I've re-created this in Linux, but DOS has a lot going for it in simple applications like this, most of all the fact it runs in RAM so is ideal if you're using a compact flash card as an alternative hard disk drive. Fewer writes to the card the better.
Wednesday, 24 February 2010
JAL is similar to Pascal in feel, but so easy to learn that any competent programmer should be able to master it in an evening.
Speaking of which, I may be getting back into web programming, which really stretches the mind if (as I did) you do everything from first principals.
Many thanks to Nathan for donating some servos for me to play with, here are the first results...
This is a simple start to driving servos from a PIC using the venerable 16F84. On power up, the PIC resets the servo to the mid position and then waits for one of two input pins to go low. One makes the servo swing to the right and the other to the left. The total range of movement is sub-divided into 100 steps so accuracy is good.
I'd like to use this in a scanning security camera application with some sort of simple motion sensing using maybe ultrasonics.
This device uses a KS0108 graphical display driven by a nice I2C interface to display the voltages read by a 16F873 PIC on 4 of its A/D pins. The display is just a horizontal bar with a label for the engine parameter being measured - boost (forced induction engine), oxygen (lambda sensor), engine speed and fuelling level.
The strange item on the right is the steering column stereo control from a scrapped Renault Laguna. This is wired as a 3 x 3 matrix with only 7 switches implemented. Two of these switches, [Vol +] and [Vol -], are used here to cycle up and down through the 4 engine parameters being measured so the driver can change this from the steering column.