[Coco] The most bizarre thing

[Gene Heskett]

On Wednesday 15 May 2013 13:30:55 T. Franklin did opine:

> That would explain the large caps but even then, the caps seem like they
> were just what was laying around the garage (as the entire
> Frankin-Project looks).

Hey, my place resembles that remark, but whoever said that was a big 
honking power supply hasn't seen some of my cobble jobs.  I cheated and 
used a surplus medical grade 28 volt 12 amp supply to run the steppers on 
my milling machine, but since I only had 2 main motors on the lathe, I 
cobbled up a 7 amp at 39 volt supply for it.

Back in analog TV days, we had some 1.5kw cement block sized switchers that 
just the 5 volt line was rated at 300 amps. 3 of them in a digital effects 
unit.  Now you can understand the requirement that the AC HAD to work, even 
if it was -25F outside.  I finally found an AC tech that understood that 
and he cobbled up a variable speed condenser fan based on the compressors 
high side pressure to modulate its speed.  Wierd, stepping out for a smoke, 
the compressor was running nicely, and the fan was turning maybe 75 RPM.  
Then he quit, and the next time I called that dealer, the guy he sent 
didn't grok it at all, so before he fixed the problem, which was a bad run 
controller on the compressor, the idiot tore it all back out, he didn't 
appreciate it a bit with me standing there telling him how dumb he was 
while he put it all back, wrong of course.  So I had to dig the schematics 
back out of the snow where he threw them because he couldn't read them and 
finish the job myself.  In the meantime we've got every back door open and 
several 18" stand fans blowing the cold air into the control room trying to 
keep it below 80F.  And failing.

Now you know why I don't like to suffer idiots with enthusiasm.  In the 
meantime, because I didn't get something else fixed, we lost several thou 
in production fees we couldn't bill, I really did have better things to do 
than trying to educate an idiot about the finer points of the thermal world 
when he was the one being paid to do it.  Guy's like that usually find I 
have about a 1 oz trigger.

I am ATM, in the process of designing a 12 to 15 amp current sink, to be 
connected across a 1hp motor when the motor is to be stopped.  A simple 
circuit really, based on almost all motors are also generators except the 
common universal AC motors.  This one has a PM field, with a top rpm of 
about 7 grand, and if not braked, will coast for a couple minutes after 
power removal.  But that Permanent Magnet field also means its a great 
generator, often used in home sized wind power projects.  Hang a current 
draw of about 10 amps on it and it will be stopped in 2 or 3 seconds since 
generating that 10 amps pulls the energy stored in that spinning flywheel 
back out, converting it into heat in the current sinks parts.  And since it 
is not continuous, but only to brake the motor, no fancy finned heat sink 
is needed, just bolt the bugs to a good sized block of alu, it will have 
plenty of time to cool in between doing its thing.  I have a leftover block 
of alu an inch thick, and about 2.5"x3.15" that should be more than enough 
mass to absorb and radiate away a kilowatt seconds worth of heat once a 
minute.  Total cost, under 5 bucks.

Cheers, Gene
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