Re: [CAD_CAM_EDM_DRO] SPC-type DRO scale tale

On Sun, 20 Apr 2003 11:16:39 -0700, you wrote:

>
>Well, it's mostly done.

<snip>

>Right up until I turned the spindle on, at which point the readouts went nuts,
>both the little LCDs on the readers as well as the LEDs on the main display,
>jittering away like crazy, even with the table stationary.
>
>Interestingly, upon turning the spindle off, both the readers and the main
>display showed the same ( wild ) numbers, indicating that the communication
>between them all was working correctly.

I would guess that the spindle power surge spiked the readouts enough
that they came up "confused".

>
>Now, some time ago, I'd added a VFD to the machine and they're notorious for
>LARGE amounts of electrical noise. I shielded everything from the VFD well,
>( although not the DRO leads ) but I guess there was still enough noise to be
>causing problems.
>
>Powering the whole system from batteries did not solve the problem, indicating
>it was not noise sneaking in along the power line.
>
>But putting the batteries back into the readers did fix things !

Which says that the batteries in the readouts were acting like big
filter caps, and were keeping the readouts from being reset by a power
dropout.

>
>So it seemed as if noise was being induced into the power lines from the reader
>to the display.
>
>My first thought for a fit was to lower the impedence of the system and add
>some filtering. To that end, I paralleled a 100 ohm resistor, a .01uf ceramic
>cap and a 47uf tantalum cap. These I soldered up into as small a bundle as
>I could, and then soldered this bundle to the battery leads. ( No going back
>now )

Yep, the 47UF cap probably did it.

>
>And this solved the problem.
>
>Now, which of the three items was actually responsible for the fix, I didn't
>take the time to investigate. I'm just happy to have it working.
>
>Now the problem of all these cables; three motor cables, three DRO cables,
>three limit/home switch cables, three cables from the (remote) VFD to the
>motors and switches.

I will eventually know that feeling, but not for a bit...

Trying to make the pcboards for the drivers... L298 and L297... At the
"put the pattern on the copper" stage. I think I don't like tek200
film....

Harvey

>
>It's starting to look like an octopus ...

spiral wrapping stuff can be your friend....

H.

>
>
>Alan