Add-on CNC build log

[bikepete]

Minor progress last night - opened up one of my donated Dell ATX PSUs and armed with a multimeter started looking around for the ground-to-case connection as per the various instructions around e.g. here. Aiming to link three PSUs to give a 36V 10A supply.

Turned out to take about ten seconds - just follow the black wires back down to the PCB and there was an obvious jumper (J23) over to the case via a screw. Bit awkward getting in to cut it so ended up desoldering and pulling it out with needle nose pliers. Checking after with meter revealed it did the trick, so I did the second one as well.

Still a bit of wiring to sort and need to get some power resistors to provide a bit of load for them to go at but that's the main hurdle over I think as far as the PSU goes.

[irving2008]

Minor progress last night - opened up one of my donated Dell ATX PSUs and armed with a multimeter started looking around for the ground-to-case connection as per the various instructions around e.g. here. Aiming to link three PSUs to give a 36V 10A supply.

Turned out to take about ten seconds - just follow the black wires back down to the PCB and there was an obvious jumper (J23) over to the case via a screw. Bit awkward getting in to cut it so ended up desoldering and pulling it out with needle nose pliers. Checking after with meter revealed it did the trick, so I did the second one as well.

Still a bit of wiring to sort and need to get some power resistors to provide a bit of load for them to go at but that's the main hurdle over I think as far as the PSU goes.

Doesn't need much of a load. 100mA on each +5V rail is usually sufficient (50 ohm, 2W).

[irving2008]

Minor progress last night - opened up one of my donated Dell ATX PSUs and armed with a multimeter started looking around for the ground-to-case connection as per the various instructions around e.g. here. Aiming to link three PSUs to give a 36V 10A supply.

Just a note for anyone else planning to do this... a safety point that is not stated in the article referenced:

When connecting two or more supplies in series to give 24, 36, etc volts - the one that isn't modified (i.e. still has the case connected to the negative output) MUST be the bottom one in the stack. I know its probably obvious but its not explicitly stated and is a big omission IMHO..