Wednesday, May 02, 2007

Improvisation

For those of you who hang upon my lips, you'll know our narrowboat has been converted to electric drive - with an on-board diesel generator charging the drive batteries as needed...

What you may not know is the the generator has a "VCS" - "Voltage Control System" - a box of electronics that is supposed to keep the output voltage of the generator constant so that - if need be - the batteries recharge at fantastic rate (up to 60 Amps) for their ideal charging voltage (about 87 Volts) AND, conversely, if the batteries are nearly charged the generator doesn't speed up.... in our case anything over 90V would speedily wreck them and, indeed, prolonged over-high voltage could cause them to explode (yes, really!!)

Well, I had a gut feeling the batteries weren't recharging as fast as planned and hoped and - when they were nearly charged - the voltage did merrily get up to 90V (no higher because I hastily turned the generator off and wiped the sweat from my brow whilst imagining popping noises...)

You've guessed it. Our VCS as supplied (second hand) wasn't working. So I fiddled around.. and fiddled around... and fiddled around... and consulted the chief engineer, Chris Baker, at Fischer-Panda (the make of the generator) - he's intrigued about our conversion and kindly answers all my questions but... it still didn't work....

I was slightly in despair. BUT I had discovered the "actuator" on the generator worked fine - it's a neat (and very simple) thing where an electric motor effectively operates the generator's accelerator. You drive it with little 12 volt pulses - voltage one way round for "faster", other way around for "slower". Indeed, being a belt & braces man I wired up a switch to check... yes, pulse the one way, generator got faster, other way, slower. So wonderfully simple I could have sat there all day - and ACTUALLY we don't need a VCS - just me flicking the switch whilst watching the voltmeter!!!!

I shall cut my pet homily to the bone that I don't really go for all this automated stuff if something can be done by hand - human consideration tends to be vastly superior to automated stuff, especially if something unexpected happens!

Nevertheless, I did realise that with all my hobby electronics I could probably dream up a substitute VCS... even better, I had ALL the components I needed (some people collect postcards - I accumulate electronic bits... not particularly intentionally, I've just got reams of stuff left over from previous experiments... and may I recommend electronics as a hobby for the impoverished, most components only cost a few pence each! And getting them to work as you want can take DAYS - it's a really cheap way of filling one's day! And terribly satisfying when things work...)

So, the photo above is my trial circuit at that moment - merrily producing pulses to (notionally) speed the generator up and pulses to set the accelerator to "low" upon switching the generator off. Since then, another little group of bits added to that blank bit of plugboard and, wow, it all seems to work. Pulse, pulse pulse to (notionally) accelerate the generator if the voltage drops by less than a volt, pulse, pulse, pulse to (notionally) slow the generator if the voltage rises by less than half a volt. Don't ask me why, the effects aren't symmetrical. I mean, by the way, don't ask me why or I'll tell you - that would take an hour or more and probably longer for the uninitiated. ....

Before you all applaud loudly (some hope!), I now have to convert this trial circuit into solidly-soldered form. Of all things, I happen to have a bit of PCB (printed circuit board) will fit into the same box the original VCS came in... so, unless I tell people, nobody will actually know we haven't got a Fischer-Panda VCS!! Don't think I'm so modest, I'll tell just everybody (relevant) EVEN if they didn't want to know...

Oh, I'm supposed to be a house developer - that's OK, apparently - plans should be approved June 7th. Yawn... we have to wait a MONTH sitting on our backsides not able to do a thing?

Anyway, my news from nowhere is that the boat is likely to be working A1 OK - Waterways World have already agreed they'd like an article or two - in about two days I'll be ready to do proper tests. House stuff, June 7th to start.

I do wish people would realise what FUN it is to make a functional electronic circuit - unlike history or anything people can argue about, it simply works. No argument.


2 comments:

  1. Whoever goes through your "little brown suitcase" when the sad day comes in about 100 years is going to have a very interesting time.

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  2. I think they'll say "what the hell is all that? - He wasn't still using that stuff, was he?, that went out of date at least two years ago."

    Actually, same transistors, just re-numbered, such is progress...

    Hey ho, musn't become a grumpy old man... tempting though it is...

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