cap didn't pop

Hi Marriss,

I have to disagree with your statement that caps blows up with the
sound of a firecracker. It was not too loud, and not too much
smoke. What scared me the most were the sparks from the 201.

I just put together a huge power supply, 68,000 uF cap and a 10 amp
transformer, connected a 201 to a NEMA23, 6V, 0.85a stepper Vexta
stepper, and used a 6.19K ohm set resistor. ( talk about overkill )

I connected the PC's 5 volt to the #10 pin and used an aluminum
470uF cap with about 18 inches of leads from the power supply to the
201. I cut the 470's leads to about 1/2 inch. I had a 6 amp fuse
(one of my many mistakes) in the +V line. I wish that blew first, or
at all.

I started testing the table with running 5 inch jogs on a 400 step
motor, with a 1/2-13 all thread rod.

At 10,000 maximum steps, the motor started missing, although I was
not sure if it was during acceleration or where it started.
Acceleration was 200 steps in TurboCNC.

I reduced to 5,000 maximum steps/sec and it worked fine. I increased
to 8,000 and increased the acceleration to 2,000 and during the ramp
period, it started missing steps. I stopped the step command when I
heard the missing, and shortly thereafter heard the first pop.

I turned off the 110 to the transformer, but have no fast dump for
the cap. Since I do not have any drain on the 68kuF cap, it keeps on
going... and going... and going...

I looked at the 201 and within a second I could see the sparks as it
was releasing all kinds of magic smoke.

At that time I was pulling the wall plug.

With some quick overview, the major destruction was the catastrophic
freeing of electrons in such a way that all components that used to
occupy the space between the pot and the angled resistor have been
liberated and have joined Elvis in the hereafter.

The pictures are not too good, but you might get the overall idea of
the location.

Oddly enough, there was also some heat transfer grease liberated from
under the opposite corner, just under the #12 connection.

I connected the stepper to the 201 with about 30 feet of #18ga wire,
that was coiled on the floor. That means there was 4 feet to the
stepper and 4 ft straight to the 201 and a sizeable coil on the floor.

No e-stop.

All that said, my questions now come towards not repeating the
performance and clean-up.

#1) immediate handling, how aggressive is the fluid from the cap ?
do I need to scrub everything or just wipe down the stuff that is
easy to get to ?

Now, the simple stuff, what else did I do wrong ?

I put a photo in the photo's section under the Daves Unit folder.
(I web read, not e-mail, so I don't know how to attach a photo)


Dave
(again stepless in NJ)