mach3 wont reset keeps saying external emg stop requested

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Originally Posted by Kitwn

If you decide to install a 12V supply rated at 240W instead, the maximum current it can supply rises to 20A. ALL the following results, including electricity used and waste heat stay the same. The only changes are that the supply will be physically bigger and cost more.

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There is NO misunderstanding Kit we know this very well, the point was why use an oversized PSU that costs more money when not coming close to using the maximum output of the original.?
Regards your and DazP # of PSU's, which was the other point of my objection, you are still producing heat and burning electricity that isn't required. Heat is the enemy of electronics so anything that lowers it can only be good.!

. . . . Next you will all be telling people Bigger steppers are better.! :joker:

I would presume that an SMPS when off load only draws enough input power to keep the output stage at voltage. Off load the efficiency will therefore be 0. The current drawn from the mains will be enough to compensate for leakage in the output capacitor(s) and this will depend on the design of the unit and the quality of the output stage electrolytics (in the main).

Similarly in a transformer based supply, in an off load situation the self inductance of the primary will limit the input current, but not as much as an SMPS in the same state. Again the idle current will be dependant on the transformer design.

Are these valid assumptions?

Rob.

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Originally Posted by JAZZCNC

. . . . Next you will all be telling people Bigger steppers are better.! :joker:

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I have got a couple of Nema 17 steppers fron a 3D printer extruder bar, will these be OK if I build that steel tubed gantry mill? :confusion::confusion:

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Originally Posted by cropwell

I have got a couple of Nema 17 steppers fron a 3D printer extruder bar, will these be OK if I build that steel tubed gantry mill? :confusion::confusion:

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Depends on the tube wall thickness.? Anything below 0.3mm and you'll be fine...:whistle:

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Originally Posted by JAZZCNC

There is NO misunderstanding Kit we know this very well, the point was why use an oversized PSU that costs more money when not coming close to using the maximum output of the original.?
Regards your and DazP # of PSU's, which was the other point of my objection, you are still producing heat and burning electricity that isn't required. Heat is the enemy of electronics so anything that lowers it can only be good.!

. . . . Next you will all be telling people Bigger steppers are better.! :joker:

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Nooooooo. :smile: Bigger steppers are crap! unless you supply them with a very large voltage. Especially those 1700oz things with 8mh inductance from China. Seen a few make that mistake.

As for the PSU I don't see many of them that have failed unless they're running close to or over capacity. If the machine has car type relays in use and/or a few of them, then they may suck life out of it. If this is the case you're either replacing all the relays or going with a bigger supply (what's cheaper). (At least I only went 38w more! lol) Trace your wires and check what's in use.

My point about automotive relays is that they draw a lot of current, some of them nearly 1 amp. That may damage the electronics that feed the coil. I am not concerned about PSU capacities, more than the BoB. In this case I do not know where the relay is fed from.

In fact I have spotted two of the little buggers in the photos, there may be more.

Gods I'm bored being home-bound. Bored enough to look on Farnell and RS at both power relays and automotive - to be honest there's not an awful lot in it - which looks to be more around the switching capacity (not really surprising) and what you could imagine the associated switch gear and return springs, and with most of the 50A relays around the 90R coil resistance (around 130mA). Automotive are likely more suited to the environment (high vibration, humidity and corrosion resistance) as well as providing economic switching of the high capacity PSUs we all tend to have knocking about.

afternoon all hope you are all keeping well
psu arrived lunchtime all wired up machine working as it should
many many thanks to jazzcnc and Clive your persistance with me has now got my machine up and running sorry i was a pain but with your help and knowledge we got there when all this lockdown is over if you are down my way Barton on sea give me a shout i owe you guys a beer or two
Great Forum
thanks Geoff

Your Welcome Geoff pleased your making chips again. Take care and stay safe.

thanks jazz