Reducing the space in my garage.

[Rich]

Yes but, no but, yes but, no but, yes but ......... )

And I did include the phrase 'distinction between projected and real world', covering all my bases! You're just being selective.

[EddyCurrent]

This might explain better; http://www.mycncuk.com/threads/2148-...2975#post62975

[Rich]

Jazz, I get the point. Using a spreadsheet doesn't distract from the issue of build quality. If the error rate between projected and real world is 20% and I've used all the right parts (as detailed clearly within the forum), then the figures will tell me I can't build a thing worth a damn. My issue, the things I need to be realistic about. I haven't used all the right parts, but then I'm a novic and likely to break, bend and drop things. So I design with this in mind. I have two key issue to resolve within this design. The first is to learn everything I can from it, the second it to buy the electronic responsibly so that don't end up dumped in a foreign country. If I do it right, the worst thing that will happen is the aluminium rail with travel 5 miles to the local smelter.

BTW: I've not quite finished reading all your posts )

[Rich]

Could someone please let me know what the answer is here - I just need to have these thing clear in my mind as all the calculations can be a bit confusing!

The PSU based on the following transformer is quoted within the forum (building a PSU is a risky business) :

http://www.airlinktransformers.com/c...nge/CM0625250/

When wiring in parallel, the output is +/-70vdc at 12amps, providing 840 watts. This is just less than double the 430watts, measured while a machine was in motion.

An alternative transformer appears to be:

http://www.airlinktransformers.com/c...nge/CM0500220/

When wired in series, it makes available 700watts (56volts/12.5amps). The figure I have for the motors suggest vmax for the motors at 57 volts (4.2amps,3.2mH).

So why would I build the PSU using the a larger transformer? It affects the number of capacitors required? I'm just running calculation ...

C = 0.1 * A/V for a 5% ripple = 0.1 * 12.5/56 = .022F = 22,000uF with a voltage rating of at least 100V and a ripple rating of 12.5A.

I read somewhere that voltage, in this instance, is like pressure in the system, its re-supplying the motor. I understand there is an issue of impedance, but there are capacitors and back EMF resupplying the circuit. I'm assuming the transformer in continuous use will heat up and so the rate at which is can provide power will slow. Is that the point?

Another point, the BOB (OPPB v.3). Just checking I don't need to worry about its maximum voltage or current unless I am running ancillary items via the BOB. It's not part of the power circuit, its just pulsing the steppers with go/stop signals?

[JAZZCNC]

You're just being selective.

No it's called being realistic.!!