Diode good idea?

[TGTool]

A friend of mine wants to start dabbling in CNC, bought a bunch of components and dropped them off asking if I could wire them up. I approach wiring like a mechanic, not an electronics technician, but these things all have documentation and it looks like he has all the essentials and maybe a little more. X-Y-Z is a breakout board and Gecko drivers which are pretty straightforward so it's going together.

I have one question though, in terms of his experimentation and startup. The Gecko docs warn against reverse polarity and I can color code and label well enough, but I'm wondering if adding a diode so he can't accidentally reverse the power supply inputs is a good, bad, or impractical idea for some reason. I just don't have enough experience to know.

What is the real experience and opinion?

[MaxHeadRoom]

Usually not a good idea to place a rectifier in the DC supply, fuse the AC side preferably.
Is this in the supply to the drives?
Actually Gecko do not recommend you fuse the DC supply side, but if you must, wire a diode in reverse, (reverse biased) across the fuse, this allows BEMF to dump into the power supply capacitors should a fuse blow at high motor current leaving the back EMF no where to go if no diode present.
There is a Gecko section in the Cnczone forum also for lots of info.
Max.

[arcs_n_sparks]

Not going to hurt anything putting a diode in. Just be aware that you will drop about 0.7 volts, diode must be sized for the current, and must be able to dissipate the heat generated (0.7 x amps).

[MaxHeadRoom]

TGTool, drop an email to Mariss at Gecko, he will be able to confirm it for you.
Max.

[TGTool]

Thanks, good suggestions all. I'm just concerned that if my buddy wasn't comfortable wiring it himself I'm not sure what to count on when he's on his own. I'd like to include whatever safety I can before he does something accidental or stupid and fries his nice parts.

I took a quick scan of the CNCZone and marked the place for more contemplation. Posing my worry to Gecko is probably a good suggestion too since they've probably seen it all by now.

[macona]

Nothing to gain by doing it. Its not hard, don't worry about it.

[MaxHeadRoom]

One thing to note if you have individual drives is to feed each one individually from the Power supply and not daisy-chain them.
Max.

[sch]

Not going to hurt anything putting a diode in. Just be aware that you will drop about 0.7 volts, diode must be sized for the current, and must be able to dissipate the heat generated (0.7 x amps).

Absolutely correct, and if you think your friend is so ham handed as to
potentially reverse polarity on the PS this is a fail safe way to protect
the geckos and BOBd, though some thought will be needed on where to
put the diode(s), so as to not compromise a single source DC + to multiple
geckos.

[TGTool]

Macona,
I'm not sure I understand the thrust of your comment. Could you elaborate a little please?

Sch,
I've got terminal strips for power supply so there are individual feeds to each driver. My thought was to have the diode feed the strip before subsequent distribution. I haven't gotten to looking for diode specifics yet, but there's room for heat sink and isolation if necessary. Do you have more specific recommendations or cautions?

I don't know my friend's capabilities well enough, but IIRC he was trying to set up some motor on one of his machines and smoked it. OTOH, he does have several machines in his garage that run satisfactorily AFAIK, though that would all be AC single phase wiring.

[macona]

There is just no reason to add a diode. just something else to fail and heat up.

Use color coded wiring when hooking it up. Red positive, black negative. Double check when you are done. Simple as that.

Don't make a mountain out of a molehill.

Even if you do toast a drive by doing something stupid Mariss will repair them often no charge.

If you are that worried about it get a set of the "Vampire" gecko drives. They are (supposedly) unkillable.