Power supply issues

[arvydas]

So I have this very old RV1S with toroidal transformer and veroboard based power supply circuitry. If you remember I mentioned that I have issues with random rotation of placed components. Been placing about 12 panels yesterday with about 200 components each and most of them had random rotation issues especially with 0603 caps. Came in today and the machine has been placing 4 5 panels so far with 0 issues and correct component angles. The only difference between yesterday and today is that I am working alone in a rather large office building.

Mike mentioned in one of his post that toroids work just fine unless mains voltage is unstable and I think I do have unstable mains when office building is full. What would be the best option to mitigate this issue? I'm thinking of either replacing the toroid and veroboard with a couple of high quality switch mode PSUs of just buy a high quality UPS that would also act as backup power in case of power failure.

I would probably prefer a UPS solution as it's very easy to install and I wouldn't have to bother with PSU rewiring. From what I've read on the internet, I need a high quality PSU that would also stabilize the mains power. Would any of you have suggestions on what I should purchase?

Thanks in advance for your help!

Arvy

[Mike]

Might be worth replacing the electrolytics first.Also beefing up the internal supply wiring - someone mentioned the supply is wire point-to-point through all the driver boards with the crappy IDC connectors - may be a simple case of star-wiring back to the caps  with better connectors.
 For UPS check it's happy driving a big transformer - you'd probably need a proper sinewave one, online so it acts a a voltage stabiliser.
 

[arvydas]

Already replaced the electrolytics on the power board and did the rewiring, but that didn't help much. Placed almost 4000 components today with minimal rotation issues. Yesterday with identical setup had componwnts rotated all over the place...

[phonoplug]

Personally I think you're barking up the wrong tree. I'd check the air hole through the tool is completely clear. Any small obstruction that reduces vacuum pressure can result in random rotations, and I've found this primarily affects ceramic capacitors (I work with 0603 mostly).

I use one or two (if they fit) strands of 7/02 wire to clear out the hole.

[Mike]

Wouldn't hurt to stick a DMM on the DC rail on min/max record.
Seems like the rotate axis is the one least likely to be affected by power issues as it's carrying no real load.
If the stepper is slipping, you'd also see tool unload failures.
 

[arvydas]

Decided to get to the bottom of this as I have been using the machine a lot more recently. I still have this annoying buzzing sound as mentioned a while back especially when the machine goes full speed. I beefed up all power cables (like to an insane level), replaced all electrolytics, checked all the wiring, tested hybrids with multimeter and everything seems in a solid shape however the buzzing just wouldn't go away! Hooked up main power rail to a scope and just as Jason reported in one of my other threads I have a nice 4V ripple and a voltage drop of 7V on occasions just by running warm up procedure. Can't hook it up to a bench PSU to test the theory as mine goes only up to 20V. I want to completely get rid of the toroid and the crappy veroboard and replace them with proper switch mode PSUs.

• Do any of you guys have a spare power module for sale? If not I might reuse the veroboard, but I don't have much faith in it :-)
• I remember one of you mentioning that newer models have two switch mode PSUs. Maybe somebody would be able to provide me with model numbers of those? Thay are supposed to be rated at 36V if I understand correctly, but what is the amp rating on them?
• How are they connected to the controller boards? X+R and Y+Z or something similar?

Thanks for all your help!

[phonoplug]

The power supplies are long obsolete. I checked them out a while back. Made by Lambda, part number ZWS120PPF-36. I'll attach the datasheet. No doubt you can find something similar but the only thing to watch out is how well any replacement handles the surge requirements the motors may need. From experience that's not something you can glean from datasheets, you just have to try it and see.

The machines that use them do indeed have two. From what I can tell each one powers one high power drive (presumably X and Y) and one low power drive (presumably R and Z) but I don't know that combination it is. I may have something sketched on paper somewhere.

[arvydas]

phonoplug, thanks! You are amazing

I ordered a 10A lab power supply yesterday just to test the theory that PSU is causing all my troubles. Have been shopping for a permanent solution around so thanks very much for the tips! I'm even thinking of getting 3 power supplies: one for X, one for Y and one for R+Z. My only concern is whether I need any additional set of circuitry which is on the veroboard between each PSU and motor drivers. I'm good at MCUs, but motor drivers and their power supplies is something new to me.

[phonoplug]

I'm not entirely sure that that bit of veroboard circuit is exactly. I've got something similar in my machine though they did manage to progress to a proper bit of PCB by the time mine was built (hurrah!). What I would say is that the Sanyo-Denki motor control boards do all the clever stuff so I wouldn't worry too much. The power from your 36V power supplies goes straight to these drive boards so this little extra circuit is probably providing relatively low current power for other parts of the machine (quite possibly power for the arm control board and fid LED ring, but don't quote me on that).

[arvydas]

Yes, I think you are right! I'll reverse engineer the veroboard to make any sense out of the circuit.

[arvydas]

Ok, looked through the datasheets. One of the amazing features is "Low Cost!!" Wonder why just two exclamation marks?

Anyway, found a few power supplies that should be suitable. They are rated at 9A nominal output current and have way more advanced features. The ones that originally came in your machine seem to have a feature for "Applicable to peak output wattage 200%" which sounds dodgy... There is also a limitation of 10s duration at peak current. I think that's why they are sort of suitable for the machine as all steppers do not run at 100% all the time and you just get power spikes when the arm moves around.

If I stick power supplies with nominal current way above required by the machine I think I should be on the safe side. Plus I'll be putting 3 PSUs instead of just two.

Having had so many power supply wiring problems with this very old model I just want to completely get rid of this issue and have the machine running at full speed reliably. I really like RV1S, just hoping that one day I can find an RV4S for an upgrade

Fingers crossed as I should be receiving a lab power supply today so should be able to check really quickly whether it's actually PSU problem. Will keep you updated.

[arvydas]

Just hooked up the machine to a lab power supply. To be honest, it's the first time I heard it running so smoothly!

[Mike]

Anyway, found a few power supplies that should be suitable. They are rated at 9A nominal output current and have way more advanced features. The ones that originally came in your machine seem to have a feature for "Applicable to peak output wattage 200%" which sounds dodgy... There is also a limitation of 10s duration at peak current. I think that's why they are sort of suitable for the machine as all steppers do not run at 100% all the time and you just get power spikes when the arm moves around.

Well sounds dodgy grammatically - Chinglish? Don't think I'd ever buy a PSU from a company that can't write proper specs... I usually use TDK-Lambda, and never anything cheaper than Meanwell.
There are some very good PSUs ( e.g. PULS) specifically designed to handle short peaks ( and with intelligence to enforce it by shutting down if exceeded for too long) - obviously this is for thermal reasons, but it indicates that the magnetics are working comfortably inside spec.
For this type of application I'd go for a PSU that is rated significantly over the required load to ensure that there's plenty of margin.  Something with active PFC is probably also a good idea as this ought to be able to deal with surges better.

For dual PSUs it would seem to make teh most sense to have aone hogh and one low load on each, to spread it evenly.

If I stick power supplies with nominal current way above required by the machine I think I should be on the safe side. Plus I'll be putting 3 PSUs instead of just two.

One, honking big PSU may be a cheaper and more effective approach. You're rarely going to get a peak draw on all loads at the same time.

[arvydas]

Mike, I was considering TDK-Lambda, but decided to try out Meanwell. Considering that TDK-Lambda are priced £200+ for the specs needed I ordered four RSP-320-36 for £44.50 + VAT each. They have PFC and with 8.9A max rating each they should be more than enough for the requirements of the machine. Here's the link to the product page with specs:

http://www.ecopacpower.co.uk/mean-well-power-supply-rsp-320-series-150w-320w-3-3v-48v-8693.html

They have higher spec alternative twice the price, however there is a 2-3 week lead time which I can't wait. I decided to go with multiple PSUs in order to distribute the load as I think it will be healthier for the motors to be on separate power supplies instead of just one. Motors are rated at 1.5A so it may seem like an overkill, but I want to upgrade the machine once and forget about it!

I really can't wait to see my machine working properly probably for the first time since I got it!

[arvydas]

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

 

Mains power in the nineties must have been very stable when they were designing this machine...