First Week of April 1999
We have started working on Miss Struts electronics. From the experiments we did last week it was the intention of using a TV line drive transistor to power the hydraulic solenoids, unfortunately the gain of these transistors is quite low ( 30 ) and we ended up using more power than we can afford, to switch them. So have reverted back to the MOSFETS. The driver circuit for the MOSFETS has been modified so that there is better immunity from the back emf generated by the hydraulic solenoids on switch off. We did lots of drilling and cutting and now have the housing for the electronics, and have started mounted and wiring the electronic components into it.
This weekend we completed the system box by installing the missing fuse holder and did some tests on it. Not bad, we had two dry joints on the cables to the LEDS and the output enables on two of the latch chips held to the wrong rail, so we are quite pleased. We then made up the solenoid cables and have installed them in Miss Struts, we also made a start on mounting the system box in Miss Struts, this is not complete.
We did not complete the mounting of the system box as some of the fixings are missing, but we did enough to continue with the cabling and have now terminated all the solenoid cables into the system box. We also fitted the fuel tank, and the radio receiver. By having the batteries sitting on the ground we were able to do some basic testing. We started the engine and started some rudimentary tests, Miss Struts limbs twitched. Well we managed to move all the legs and attracted a few of our neighbours. We then stopped the engine made some minor adjustments to some of the hydraulic hoses and topped up the hydraulic oil. We then ran the engine again and had another go at moving all the legs, the left rear leg would only move forward, and the left hand controls operated the right legs and vice-versa. Apart from the inverted control all went reasonable well. The inverted controls can be easily fixed as it is a minor error in the software. We got some frothing of the oil in the hydraulic tank so will probably have to have another go at this.
The left rear leg was only working in one direction because an opto-isolator had failed this was quickly replaced and okay.
This weekend we continued to, and apart from final adjustments, mounted the backwards and forwards position sensors. We then spent the rest of the day running cables and terminating them from the sensors to the system box.
We finally did a balance check which was quite entertaining, and from this sorted out the final positioning of the batteries. After the balance testing we tried weighing Miss Struts by having her suspended on the end of a scaffold tube and me the heaviest dangling at the other with the fulcrum been a very tall trestle I made for cutting our hedge. When we calculated the weight it was suspiciously low so we do not trust this measurement.
We then spent the rest of day mounting the batteries, and fitting and cabling the cut off switch.