I need to narrow things down a little - is it the drive PSU upsetting the BOB or is it the BOB PSU ?
The BOB pulls 150mA including the three sensors.
Will be back soon with some results, the BIG worrying me is the radio interference - the plasma is fully grounded etc and works perfectly BUT it pumps out RF like billy!
Maybe I need to ditch the SMPS's and go linear.
Off for some tests.....
Well, I am just about ready to give up for the day! And I hate shutting up shop on a negative position. :(
It works fine if i run off the variable bench PSU but not on the little SMPS, but i don't think it's needed to spend £110 on a PSU just for the BOB!
Here's a video showing the result on the SMPS...
And here's one showing what I expected and indeed what I get on the bench PSU...
Now the big question is WHAT DO I DO??
Obviously I will be throwing this at CNC4YOU as it's all their components but they usually blame the setup or the earthing or the wiring blah, blah, blah...
The drive PSU & drives wipe out FM radio when engaged.
The BOB PSU does not work with my sensors.
The sensors appear fine when on a different PSU.
I am a bit p1ssed off at present as this little setup should have been easy ;)
Just about ready to pour a big one.
Well look at it has good result it's just not the one you wanted.!! . . Good because you know the cause and not ending not knowing the reason.
The fact the bob works with bench supply shows it's working so PSU would be my first choice.
The drives affecting radio is a little concerning because shows dirty system (or Crap drives) so i'd be looking at this while i'm at it. Personanly it's no brainer to me I'd dump the SMPS and go with toroidal setup. 15mins work to man of your calibre.!!
Is there a preferred circuit or supplier of parts for a suitable linear supply?
Need 48v at up to 10A.
Keep the BOB on the SMPS?
The radio interference has been nagging me since i got the plasma going - same drives, motors and PSU again, no help at all from CNC4YOU of course.
I always use shielded motor cables, grounded at the drive end, and even used shielded wire for the step/dir signals on the plasma.
No objections to building a psu but cant risk over-volting the drives by building it wrong, they are ok up to 50v
Plasma by it's nature is dirty business so no surprise when that fires up but drives them selfs shouldn't be messing with radio.
So many things could be in play here like you know but I'd certainly start by getting rid of the SMPS for the drives. Nothing to them really just toroidal transformer Caps and bridge rectifier.
Size wise then it gets tricky with 50v because standard transformers either compute very close to 50vdc or just a little lower than needed.
The transformer I would use is this one with 2 x 33Vac secondery's giving 300va because. While it's less than 48vdc it's safer than next option which would close to 50vdc.
Normally I'd wire secondery coils in series which adds the volts together but keeps the amps same and use lower voltage seconderys. But in this case the nearist available which is 2 x 15Vac computes to low Ending up around 40Vdc after being recified.
Next option is 2 x 18Vac which takes too close to 50vdc.
So in this case going with 2 x 33Vac and wiring in parallel will give around 44Vdc and add the amps together giving 9A. This is much safer option and won't cost any performance. The way Toridal works then 9A is more than enough for 4 drives.
Then you'll need 3 x Caps around 4700uf 63v wired in parallel these will do nicely
Then 25A bridge and your sorted.
Last edited by JAZZCNC; 13-03-2016 at 05:24 PM.
I was leaning towards 30v secondary but that one does fit well, have got caps and bridge so the transformer is on order now.
If that works I'll ditch the PSU in the plasma too - note that it's not the PLASMA that kills the radio, it's the CNC drives again, as soon as i take Mach out of reset.
Hopefully this will move us along again, fingers crossed.
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