Re: [CAD_CAM_EDM_DRO] G201 death/repair/questions/problems (long post)

Chris Brick wrote:

>I don't have any fuses between the G201s and the power supply. I was
>under the impression that this wasn't necessary but will install them if
>it will help. Any thoughts?
>
>

Let me get this straight - TWO G201s blew up at the same moment?
Something is definitely
wrong! Fuses probably will not save them before damage, but it may
reduce the "collateral
damage" to one or two components, rather than making everything smoke.
you are supposed
to put an external capacitor at the power terminals of the Gecko drive
if you use fuses.

>I only have 10,000uF of capacitor on the power supply. When I built the
>supply a year ago, I remember doing the math to make sure it was within
>the specs in the Gecko literature. Will a high ripple voltage cause
>damage to the Geckos?
>
>

Maybe. how high is high? With 10 V of ripple or more, that elevates
the peak voltage
the drive sees.

>I do not have the disable pin connected on the G201s. Is this something
>that should be pulled to ground until everything is powered up and I'm
>ready to move motors? I was planning to do this but haven't yet.
>
>

Yes, this is a very good idea. I think the drive has an internal delay
that keeps the
power transistors off until the drive's logic has powered up and stabilized.

>Voltage spikes? I've done tests with my power supply that suggest there
>are no spikes when it is switched on. Any thoughts?
>
>Is there a correct power up sequence? I've been leaving my parallel
>port connected and the software running while only turning off the power
>supply/Geckos/motors.
>
>

That should not matter, as the inputs are optoisolated.

>I'm hoping someone has seen this or a similar issue and can help me find
>the problem prior to me making more smoke.
>
>Now on to repairing the Geckos. (Thanks tons to those of you that
>helped out last week when I posted)
>
>

If only one drive had fried, I would strongly suspect a motor with an
intermittent short.
I wonder if there is a possibility that a very sudden power down when
one drive shorts
out could cause the other drive to fail?

>Are there any tests I can do on the motors that will tell me if they
>have problems?
>
>

An impedance bridge could be used to measure inductance. Also, a precision
ohmmeter with kelvin leads could be used to measure resistance. but, most
people don't have that sort of gear.

Jon