DIY PSU build query...

[Desertboy]

This here is exactly why you shouldn't buy anything until you fully understand what's been said and why.!

My suggestion to that person to use a toroidal over a the 6A PSU would have been based on them using both the secondary coils.

Building a PSU isn't difficult and the best choice for a CNC machine but you can't just guess at it.

My strong advice is DONT buy anything until you have researched exactly what your building and what components your going to use. Even then the electronics are best left until the end of the build.

If your not sure what you need then ASK don't read posts taking bits from here and there because often you'll put 2 & 2 and end up at 6 because there are so many different ways of doing this it's easy to misunderstand, even if you think you do.! So Unless your 100% sure it's correct for your needs then just ASK for a second opinion before buying.

Wise man that Jazz you should listen to him.

[Clive S]

I was hoping that the PSU would be something that it was possible to get started on, and that it would be possible to 'spec' one up that could work across a variety of motor choices, and also still be usable in the future on possibly a larger machine. So essentially an over engineered/spec'ed one.

You still haven't answered post #5 What will the drives take as max voltage and will the drives take AC and well as DC

You have not said what drives you want to use as a lot of drive these day only need AC input ie just a toroidal

[Desertboy]

You still haven't answered post #5 What will the drives take as max voltage and will the drives take AC and well as DC

You have not said what drives you want to use as a lot of drive these day only need AC input ie just a toroidal

That's the $64000 question isn't it.

I built a 70v PSU which means if I change my drivers they would have to be in that range or I need a new transformer.

I think mine is 1kva so I think I could run pretty much anything in the Nema23 profile on all 3 axis (4 motors) without blinking.

[JAZZCNC]

That's the $64000 question isn't it.

I built a 70v PSU which means if I change my drivers they would have to be in that range or I need a new transformer.

I think mine is 1kva so I think I could run pretty much anything in the Nema23 profile on all 3 axis (4 motors) without blinking.

First let me say I'm not having a go at you or anyone with this post, it's just to make my point.!

Posts like these are what confuse folks and lead them to add up the wrong numbers. The Va rating won't kill your drives but choosing the wrong Voltage will fry them in a heartbeat.

Likewise, some of the other posts that are overly technical and made by people who know electricity don't always help either and add to the confusion because they talk in technical jargon that the person seeking information doesn't understand, or really needs to know to build a PSU suitable for CNC.

Sometimes I just wish those posting would take into consideration the knowledge level of the person seeking help and answer accordingly, in ways that don't blow people's minds. Or at least try to find the persons knowledge level and then explain in such ways that explain the technical jargon.

We all try to help with the best of intentions, which is great, but I do think that often the more technical minded could answer in simpler ways. This is why often some of my posts can bang on a bit because I'm always trying to answer in the simplest ways possible mindful that for every 1 person asking the questions there will be 10+ silently watching who say nothing. It's these people who often fall foul of misunderstandings because we can't know there knowledge level and answer accordingly.
Yes it's there fault not ours, they should speak up, but we can keep the jargon to a minimum, or at least explain it clearly so there's no confusion.

So ASK is the message to all those reading who never speak up.! . . . . . But to all you clever bugger who know it all just keeps it simple please and the jargon down.

[joe.ninety]

You still haven't answered post #5 What will the drives take as max voltage and will the drives take AC and well as DC

You have not said what drives you want to use as a lot of drive these day only need AC input ie just a toroidal

I've haven't said because I don't yet know I thought me saying the bit about making something that was over 'spec'ed' and that could work with a variety of choices would make that clear but I guess not and I'm sorry for misleading you. It would seem Desertboy in #14 has done exactly the sort of thing I was alluding to.
Anyway, I'm not going to ask any more questions until I've put more flesh on the bones, but that in itself is difficult if i don't know what I've got in mind is possible. I'm just trying to gather some underlying info and knowledge that means I don't end up wasting either my time or others in coming up with designs that don't have a hope of being good.

Cheers

[Doddy]

Wiring secondaries in parallel is a perfectly acceptable solution - just remember you need to make sure the phase of each secondary is matched (you normally find one end of each secondary marked on any schematic with a 'dot' - wire dot-to-dots and non-dots-to-non-dots... if that makes sense). Don't worry, if you get it wrong your fuse will politely inform you.

The only issue to consider is that the power loss in a system rises as a square of the current drawn - you'll have less losses for a given wiring CSA if you can distribute your load across individual secondaries, rather than wiring everything to parallel secondaries. But, provided you over-spec the wiring, and/or avoid daisy-chains on the power distribution then you shouldn't have problems.

[Desertboy]

I built my own PSU there was nothing to it just a transformer, bridge rectifier and 3 capacitors.

It sounds far scarier than it actually is took about an hour including time to smoke cigs and drink tea.

I have since quit smoking so I think 30 mins is realistic.

[AndyUK]

Yeah, it's not difficult just be aware of the safety.

Plus, if you get AC drivers it's just the torrodial. Nothing else.

Doing it beforehand however is not your best plan, bit of a false economy because you'll end up with something that isn't quite right or you'll make compromises on the rest of the build to suit.

First, figure out what you want to cut. Materials, sizes.
Then work out your physical constraints on machine size.
Then find a similar build log and start CADing. As you come up against different problems look to other build logs for solutions then add your own twist. It's just not worth spending time and money until you know what you want and have speced it out across the board.

[dazp1976]

I would forget places like zapp automation. The u.k. has some junk available.
If I did my mill again I would:
1. Go closed loop.
2. I'd get AC powered drivers 20-80vac like:
https://www.ebay.co.uk/itm/EU-Ship-W...-/223484030824
3. Get 2 toroidal 35vac supplies wired in series for 70vac (7.14A) and wire them direct to 2 drivers each for 4 axis. These would leave headroom as the idle voltage would be above 80v. like:
https://uk.rs-online.com/web/p/toroi...ormers/1233994

[Desertboy]

I should just link the Clive S build it's how I built mine, 2 years ago bad memory.

Whatever I did I did it right I just copied Clive S's build, 3 capacitors to smooth the DC.

This is what it tests out at without load