Grounding metal enclosure and fusing powersupply for driver box?

[autobot]

I am thinking of buying some cheap stepper drivers and buying a separate power supply to power the drivers.

I want to use something like an old PC case which is all aluminum. The voltage supply Im eyeing is rated for high voltage output and obviously the voltage from the jack is standard 110V.

I dont know much and learning about power electronics.

Do I need to ground the metal enclosure for safety in case there is short circuit? If so do I just wire out something and connect the enclosure to the ground terminal for the power jack that goes into the wall?

Also, the power supply probably doesnt have a fuse. Should I be putting a fast/slow acting fuse on the power supply between the powersupply and the jack? If so how do I hook this up? The standard power jack has 3 connectors. do I need a fuse on both the remaining hot ends?

What other precautions do i need to take? I heard some AC fans have good power output. How do I hook that up to the right voltage so I dont damage the fan and that it turns on when I turn the driver box on? I think the power source has DC output. So do I hook the AC fan to the AC side in parallel perhaps with the power supply block?

[Al_The_Man]

There are many previous posts on grounding, it may be more fruitful to do a search for bonding.
http://www.cnczone.com/forums/phase_...und_issue.html
All power supplies should be fused preferably.
Only fuse the live side if using 120v 1ph, do not fuse the neutral.
Al.

[autobot]

Do you know of any pictures of people's homebuilt driver boxes and how everything is laid out and connected? Im asking practical stuff like, do you have to drill a hole and bolt down the grounding wire or do you use electrical tape (obviously not but thats the sort of solution I want to see from others)?

What about what gauge wire should you use? (I know there are recommendations based on on current etc)

Any other safety hazards and protection of the electronics?

If my power supply is rated at say 12A, and 3 steppers each draw 3A load, Is it ok to put a 9A fuse between the power supply and the wall outlet? How do I wire an AC fan to the rig (since the power block outputs DC)?

[Al_The_Man]

The fuse should be at least the rating of the power supply.
For an AC fan, presuming it is a 120vac type, then this could be wired to the 120v supply where it enters the enclosure.
This article is mainly aimed at industrial applications, but many of the principles apply and should be followed for a successful instal.
http://www.automation.siemens.com/do.../emv_r.pdf?p=1
Al.

[doorknob]

Originally Posted by autobot If my power supply is rated at say 12A, and 3 steppers each draw 3A load, Is it ok to put a 9A fuse between the power supply and the wall outlet? How do I wire an AC fan to the rig (since the power block outputs DC)?

The fuse that you are describing goes inline with the AC power input to the power supply.

The 12A current rating is for the DC output from the power supply. The AC input current will usually be different from the DC output current (ignoring some finer details, a simplified way of looking at this is to figure out approximately how much power in watts will be handled by the power supply during normal operation, leaving some safety factor - since power is calculated as volts times amps, and the AC line voltage is higher than the output voltage, you will need less amps on the input than you will need on the output for a given power - again, that is oversimplified).

You might consider getting one of these chassis-mount IEC power jacks with a built-in fuse holder, which should simplify your wiring:

IEC Power Jack Chassis Mount with 10A Fuse Holder 090-443

That jack will have a ground lug that you would normally connect to the equipment chassis through a short wire, and two other wires for the power (one for 'line', the other for 'neutral'). You will probably want to wire a power on/off switch in line with the 'line' wire. Then you can wire up the leads to the AC fan with one lead going to the switched line terminal of the on/off switch, and the other lead going to the neutral terminal.

Some people may disagree with the power cord jack approach, because the power cord will be removable, just like the type used with typical desktop PCs, and so it's possible that you could inadvertently unplug the power to the controller in the middle of a job, but since the same thing is true of the wall plug, I wouldn't worry too much about it.

[autobot]

I am wondering will lab power supplies work just as well?

Most of the controller boards from hobbycnc use dc input right?

So if I get a lab type dc power supply with the variable controls, is that ok?