November 2003

Sunday 2nd November 2003

Now that I had removed some of the pneumatics valves, I had some spare driver circuits with which I could light some status LEDs. I made a bracket and mounted three LEDs on it that I wired through to the motor controller.

Three status LEDs

I had given it a bit of thought over the past couple of days, and decided to make one of the LEDs light whenever the power failsafe relay was activated following a valid radio signal.

The second LED I decided to make light whenever the gyro was selected from the transmitter. Because I had a spare control switch on the transmitter I used this to enable or disable the gyro action, but it was nice to know that the Hog was actually detecting this and selecting the gyro when I flicked the switch.

The third LED I decided to make a "heartbeat" indicator. Under normal conditions with a valid radio signal, the LED would flash on and off once a second. If there was interference, or a loss of signal, the LED would flash four times a second. This was useful just as a "confidence booster" of the signal quality the Hog was receiving. I had to modify the motor controller software to perform these functions, but after a few hours of work, the LEDs were working as planned.

I had also made changes to the pneumatic routines now that the 5/3 valve was no longer in circuit, but I wasn't able to try the flipper out in anger because of the monsoon weather we were having today. It would have been nice to know that all the pneumatic changes I'd been making recently were worth the effort, but I suppose I will have to wait until a dryer day.

A few people had shown interest in my motor controller, or more correctly "Robot Controller Circuit", so I may add a new section to the web site explaining a few of its features. Watch this space for more details!

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Sunday 9th November 2003

I am planning to take part in the Worthing event on 6th December and thought it would be a good idea to check out the pneumatic modifications I have made.

My CO2 bottle was almost empty so I vented what remained to the atmosphere, and then charged it up from my filler bottle. Venting gas from the bottle cools it dramatically and also means that you can then get a better fill. In the past I have always found it hard to get a full fill into the bottle, but today because I had vented/cooled the bottle first, I managed to get a more or less full bottle.

What I wanted to test today was that the flipper would close quickly under the 2 bar (approx) pressure I was feeding the return side of the ram. I operated the flipper a few times, but on each subsequent flip, it moved slower and slower until it stopped working altogether after about 8 flips. I noticed that all the pipes had frosted up, and presumed that they were blocked with ice. I closed the gas bottle valve, opened the dump valve and waited for the pipes to thaw out.

After a few minutes I closed the dump valve and re-opened the gas bottle. I noticed liquid running along all the pneumatic pipes, which was a bit of a surprise. This was the first time I had noticed this, but found it a bit strange because I had a dip tube in the CO2 bottle that was bent upwards so that it wouldn't allow liquid CO2 into the system unless the bottle was inverted. I tested the flipper out again, but it froze up with a few flips as before.

I removed the bottle and vented it to the atmosphere while holding it in a number of orientations. Each time liquid was present which made me suspect that there was something wrong with the dip tube within the bottle. Maybe the tube had become dislodged after the jolts I had received in the Series 7 battles, so I unscrewed the valve and withdrew the dip tube, only to find that it was completely straight! The people who had fitted the valve for me had obviously forgotten to bend the pipe when they re-assembled it. This would explain the problems I had during Series 7 when the pneumatics completely froze up as well, and Derrick Foxell was less than impressed with not being able to dump the system quickly from the dump valve alone.

It was strange that I hadn't experienced this problem before in all the time I had been testing the flipper. The reason, I think, was that I had never before had a full bottle of CO2. Having cooled the bottle before filling it today, meant that for the first time I had managed to put enough liquid CO2 it to be above the dip tube. Likewise at Series 7, the filling station people knew what they were doing and also managed to get a full fill in.

It was a fairly simple task to heat the dip tube over the kitchen cooker and bend it at right angles before reassembling it back in the bottle. I tried the flipper out again with a full bottle, and it performed a whole lot better without freezing up. It also closed a lot quicker that it did under gravity, but I backed off the low pressure regulator until it was just enough to close the flipper each time. In this way I hoped to make the most efficient use of the gas without wasting it by needlessly "slamming" the flipper closed each time.

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Wednesday 12th November 2003

I received my appearance money for Series 7 today, which came to the princely sum of 50 pounds!

Appearance money from Series 7
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Last updated 9th January