Author Topic: Power supply issues  (Read 11840 times)

arvydas

  • Jr. Member
  • **
  • Posts: 51
    • View Profile
Re: Power supply issues
« Reply #15 on: July 15, 2016, 03:50:03 PM »
Just installed new power supplies. Rewired pretty much everything power related ensuring that the PSUs get beefy supply wires and 20 AWG for the motors from PSUs.

PSU1 - X axis
PSU2 - Y axis
PSU3 - R + Z axis

What a difference! The machine runs smoothly and so quiet now! I used to get annoying buzzing just by using test controls to move the arm by 1500 and now it's gone.

Need to sort out the LED power supply and all should be done and dusted. BTW, the veroboard powered the LEDs both for fiducial correction and vertical facing static camera.

Thanks for all your help! Will be doing board placement next week to put the machine to a real test.

Mike

  • Administrator
  • Hero Member
  • *****
  • Posts: 536
    • View Profile
Re: Power supply issues
« Reply #16 on: July 15, 2016, 06:23:36 PM »
I think I've got the veroboard reverse engineered now. It's basically a DC-DC power converter that drops the 36V to 12V for the LEDs on the fiducial correction camera. That's pretty much it. The motor controllers essentially don't use any of this. They are powered like this:

Mains Power -> Toroid -> diode bridge -> 12000uF cap -> motor controllers

 :( :o ??? >:(

Mains power in the nineties must have been very stable when they were designing this machine...
The motor drivers should work in constant-current mode, so supply voltage variation shouldn't be a big deal as long as it is high enough.

Mike

  • Administrator
  • Hero Member
  • *****
  • Posts: 536
    • View Profile
Re: Power supply issues
« Reply #17 on: July 19, 2016, 12:22:18 PM »
Mine has 2 big toroids, maybe this was the solution they used to improve things. During motion the voltage doesn't drop below 33v

arvydas

  • Jr. Member
  • **
  • Posts: 51
    • View Profile
Re: Power supply issues
« Reply #18 on: July 19, 2016, 12:37:55 PM »
Mike, I noticed your two toroids in one of your videos. Guess if it works for you then there is no point in upgrading.  :)

Replaced the veroboard with a proper 12V power supply for the LEDs which seems to work great. Doing final update to the machine and installing fast blow fuses as per your recommendation in one of the threads. Measured all axis power draw and here are the MAX readings:

Z - 0.97A
X - 2.32A
Y - 2.23A
R - 0.90A

Bought a bunch of fast blow fuses from Maplin with the following ratings: 1.6A, 2A, 2.5A, 3.15A, 4A and 5A. Which ones would you recommend placing on each axis? Don't want to go too low in case my measurements were incorrect, but would also like to be on the safe side in case of a short to ground like you had. Going to be placing fuses on each axis separately.

This actually raises anther concern. Let's say one of the fuses on Z axis blows for any reason. Then the whole Z axis will drop and the head could start smashing into anything on the machine while X and Y are still operational. Same thing applies pretty much on any of the axis. Is there any way to detect that a fuse has blown and there is not power supplied for the controller in order to shut down ALL axis immediately?

Mike

  • Administrator
  • Hero Member
  • *****
  • Posts: 536
    • View Profile
Re: Power supply issues
« Reply #19 on: July 19, 2016, 02:02:59 PM »
A crude but effective way would to be to put a relay powered by the fused Z supply and have the contacts disconnect the step inputs to the X & Y axes.
TBH i'm not sure I'd bother with fuses, especially with a switchmode supply, as that  will shut down pretty quickly if overloaded.
The only reason I added fuses is that I had a blown hybrid that looked like it was probably caused by a wiring short but I never found the root cause, so it was just insurance against that. Also at the time I didn't have the stock of replacement hybrids I have now.
I'm not aware of enyone else seeing blown hybrids , so adding a fuse could actually be more risky, unless you add protection to stop the other axes. 

arvydas

  • Jr. Member
  • **
  • Posts: 51
    • View Profile
Re: Power supply issues
« Reply #20 on: July 19, 2016, 02:24:28 PM »
Hm... wish I had your advise before I installed the fuses :)

I currently have 1.5A on the R and Z each and 3.15A on X and Y each. Just ran the warmup procedure and all seems well, but the risk exists. Will try to find out if I can find some sort of safeguard to shut everything off automatically if any of the fuses blow. I'm currently looking into using an Arduino with three relays. I would rather have the fuses in place just because each PSU is rated at 9A and the total drawn from each one looks like not going to be more than 2.3A. If I understand correctly when there is a problem, PSUs would shut down only after the current reaches 9A and I certainly don't want that!


Mike

  • Administrator
  • Hero Member
  • *****
  • Posts: 536
    • View Profile
Re: Power supply issues
« Reply #21 on: July 20, 2016, 12:12:58 PM »
Hm... wish I had your advise before I installed the fuses :)

I currently have 1.5A on the R and Z each and 3.15A on X and Y each. Just ran the warmup procedure and all seems well, but the risk exists. Will try to find out if I can find some sort of safeguard to shut everything off automatically if any of the fuses blow. I'm currently looking into using an Arduino with three relays. I would rather have the fuses in place just because each PSU is rated at 9A and the total drawn from each one looks like not going to be more than 2.3A. If I understand correctly when there is a problem, PSUs would shut down only after the current reaches 9A and I certainly don't want that!

Why the arduino ?
Keep it simple - just use relays to interrupt the step signals. make sure you use relays designed for signal levels and not power.

arvydas

  • Jr. Member
  • **
  • Posts: 51
    • View Profile
Re: Power supply issues
« Reply #22 on: July 20, 2016, 12:48:35 PM »
Interesting idea. Mine was pretty much the same, except I wanted to cut the power with relays to each VCC-X, VCC-Y, VCC-RZ. Is this what you have in mind?

IN - signal wires coming from the connector to the computer
OUT - signal wires going into the Sanyo-Denki boards
VCC1, VCC2, VCC3 - separate PSUs I have
VCC-X, VCC-Y, VCC-RZ - power supply wires to Sanyo-Denki control boards


Jason

  • Jr. Member
  • **
  • Posts: 84
    • View Profile
Re: Power supply issues
« Reply #23 on: July 22, 2016, 07:14:55 AM »
Why not just put the relay output in series with the door interlock?

Mike

  • Administrator
  • Hero Member
  • *****
  • Posts: 536
    • View Profile
Re: Power supply issues
« Reply #24 on: July 22, 2016, 10:14:59 AM »
No need to do anything with the R axis.
I suggested interrupting the step line rather than the power to the drivers to avoid anything that might cause power issues or contacts sticking.
Totally forgot about the interlock (has anyone not bypassed this ? ) Not sure what it controls - it can be overridden by the software for setup so probably not ideal.

arvydas

  • Jr. Member
  • **
  • Posts: 51
    • View Profile
Re: Power supply issues
« Reply #25 on: July 22, 2016, 02:15:19 PM »
Jason, mine has only a switch for the front door which lifts up to access the pick and place area and that only slows the machine down, but does not stop it so not ideal. It does not have any other door interlocks.

Mike, makes sense regarding contacts sticking. I would go with very high quality relays anyway.

On a side note, placed more than 6000 components yesterday with absolutely perfect placement at full speed! Had so many issues and now they are all gone: I can just start the machine and leave it to do it's job while I'm working on other stuff instead of constantly standing next to it and monitoring.

I have a few things still on my list to do:

* Rewire the connector on the box for feeders. The 220V wires going inside the box directly to the feeders are just too thin. I think the whole machine was wired with something like 28AWG for power and data wires. Already received the parts and crimps from RS so that's going to be my next mod before working on the next batch of PCBs.
* Feeders need servicing. Already received new O rings suggested by Mike so hoping that it will improve the performance. Will do some cleaning too. Feeder disassembly is a bit of a pain. Will see how they perform after I rewire the connector though. Current symptoms are: failing to pull back the cover tape, jumping back after index.
* Do the power shut down mod when fuse or PSU fails.
* Not sure if needed, but I would like to add a few PC cooling fans inside the box to cool down stepper motor drivers. They do seem to get very very hot... Machine works fine though.

BTW, this is how the main wires to the diode bridge looked like before I decided to start modding the hell out of that box...


Jason

  • Jr. Member
  • **
  • Posts: 84
    • View Profile
Re: Power supply issues
« Reply #26 on: July 24, 2016, 09:26:23 AM »
Totally forgot about the interlock (has anyone not bypassed this ? )

Hehe, mine is bypassed so I forgot it's only a slowdown not a stop.
I would suggest in series with the emergency stop but then the Z is likely to drop.
Breaking the step lines might not help in a overcurrent situation.

I'm just about redo all the power on mine as I'm still not happy with it.