28 Feb 2007 slap.fish   » (Journeyer)

Steady progress on 48k's electronics - the card cage backplane is mechanically complete, and partially wired - and I now have 3 of the cards complete.

The first is a PSU/standby/timer card, which has two MCUs - this will monitor the PSU voltages and create recharge requests to the main CPU, and oversee the recharging once the robot has 'docked' and the main CPU relinquished control and the robot powered down (standby mode).

The second complete card is the MCU for handling the compressed air supply - a deceptively complex task. The problem with an on-board compressor is the large surge of power required to start it when the reservoir is already pressurised - there are two air valves which need to be carefully controlled, as well as the main compressor motor. I thought this would be a simple card to program.. wrong!

Third up is the card (containing 4 MCUs) which will handle the steering and drive motor controls - lots of quadrature encoders to keep track of, but ultimately an exercise in position/speed control.

Did get some time to do some initial experiments with I2C communications - and although it's a little more software intensive with PICs than I'd anticipated, it'll do the job of providing a main communication channel between all the cards quite well.

..still plenty to do before I can really get down to properely programming it all though.

- My lathe is now up and running again, upgraded with a 3 phase motor + inverter instead of the unreliable standard DC motor (burnt out the second one before xmas). As any machinist knows, small Chinese metalworking tools are good value - but don't ever rely for heavy use - at least until you've 'debugged' them and made improvements.. my little 7x12 has had many hours spent on it (a project in itself), and is quite literally a different machine. I've a few changes to the mill in mind as well! I tested out the new motor making up some parts for my fathers model R/C boat that I offered to install the motor/R/C equipment etc. into - no shortage of power now. The soft start is useful as well - but sadly, games of 'dodge the chuck key' are no longer possible - it just falls out safely instead of hurtling at your head like an enraged 5 ounce metal wasp that's smelt your ice cream. I feel I can live without that though.

Back onto robotics now - A Boebot joined the throng of projects competing for spare time. This is my first experience of the Basic Stamp (version 2), and I must say I'm really impressed me with the speed and ease with which you can have it doing some clever stuff. I liked it so much I've now got a second one to experiment with. They're very difficult to beat in terms of ease of use - and it's nice to be able to play around and get real results quickly.. something that programming PICs in ASM definitely isn't.

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