Comments sought on new build: A CNC Router for RC Gliders and Planes

[Wobblycogs]

The advice I was given was to get a 2x24V transformer and having measured the output and input voltage I'd definitely say that's the best advice. The power to my house at least tends to be a few volts over 230V so a 2x25V transformer + back EMF would probably push it over the magic 80V.

I went for a 1000VA transformer in case I ever added a fifth axis, to be honest though I reckon I could probably add a 9th axis it's so over kill. At 625VA you should be fine with just three steppers, you may or may not need to put together an inrush limiter, you'll probably get away with a Type C or D breaker though - a type D breaker would stay in occasionally for me.

For capacitors I used 4 of these: http://www.ebay.co.uk/itm/1-NEW-NIPP...-/280934713637 Multiple small caps were a lot cheaper than one big one.

I have a bleed resistor which will bleed the capacitors in a few minutes if steppers aren't attached, if steppers are attached they bleed in seconds. I forget what rating it is but it's a lot less than 10.8W, 0.5W rings a bell. I know the recommendation is to bleed the caps in so many seconds but it was a play off between safety and heat produced in the case. To improve safety I fitted a UV style meter to the front of the case to tell me cap voltage and fitted a cover over the capacitors, total cost about £5.

I think you'll want more bootlace ferrules than that and I used a mile of single core cable (can't remember if it was 0.75mm or 1.0). You can get jumper bars for the DIN terminals to make them one large block which came in handy.

[Clive S]

Neil Have I missed the rectifier? The cable for the limit switches can be as small as you like as there is practically no current to speak of.
I have used 25 -25 with no problem and my personal opinion is that the bleed resistor is not needed. ..Clve

[njhussey]

Neil Have I missed the rectifier? The cable for the limit switches can be as small as you like as there is practically no current to speak of.
I have used 25 -25 with no problem and my personal opinion is that the bleed resistor is not needed. ..Clve

Yes you've missed it.....I'm going for a 35A 200V one from Rapidonline....

I'll get some 0.75 tri core shielded cable then for the limit switches.

I think I'll measure the supply voltage here and see what it is out of interest.