Re: Mean Well power supply question

Joe Zeglinski


Good idea about "isolating " your Mean Well power supply with wood and a plastic enclosure, so you no longer (?) have a leaky ground return to the GFCI, from it.

If the "Euro Safety Regulations", as recently noted by Rolando, require tying power supply DC Returns to chassis/earth ground - dumb idea, unsafe for electronics even with a nearby storm just miles away - and the chassis ground on the 120 AC side of the power supply case and power cord's earth return (third pin) is also tied to house neutral in the fuse box through plumbing or copper ground rod, then why wouldn't the GFCI not trip, when it senses even a few milliamps, (or perhaps just micro amps), supplied by the CPx controller's serial port housing? That's true for many other controllers anywhere on the scope besides just AP's). In such case, the (slightly) leaky chassis ground return is tied to the GFCI circuit protected socket.

The GFCI would naturally trip to protect you from being (potentially) electrocuted by electronics with a chassis ground tied to the pier.
Seems logical. Probably nothing you can do to prevent it, except replace the GFCI outlet for the pier, with a non-fused one. However, your home fuse box panel might also be wired with GFCI breakers. It probably isn't, or you would have a room full of lights drop out every time you power up the telescope electronics, using a normal outlet. GFCI breakers are very sensitive, if they do their job right.

You can likely prove the possibility of the pier chassis leaking current to your GFCI protected AC power cord, supplying your telescope. Using an ohmmeter , check the resistance (continuity) between scope electrical system and GFCI supply - on the unpowered telescope - by touching the probe to the bare serial port screw on the CPx, and the other probe to the earth safety ground pin in the AC socket at the telescope. A meter with a "continuity buzzer" would be easier to use than looking at a reading.

A few milliamps of chassis current won't hurt you, but it is reassuring that the GFCI would protect you from a major short circuit from something at the pier. But, the GFCI can be a nuisance for typically minor amps from pier equipment.

Joe Z.

-----Original Message-----
From: Mike Dodd
Sent: Friday, November 8, 2019 11:09 PM
Subject: Re: [ap-gto] Mean Well power supply question

On 11/8/2019 9:55 PM, Don Anderson via Groups.Io wrote:
Hi Mike
Did you try the Alinco on another outlet?
No; the one that tripped was the one powering the pier equipment, so
that's the one I tested.

No matter. I have the Mean Well mounted on a board, and enclosed on
three sides with a plastic shield that extends over the ends, so I'm
ready to use that one.

--- Mike

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