Stepping problems aren't a power supply regulation issue. Most times its a motor resonance issue, 2nd is improper conditioning of the computer interface. It is a well known that switching supplies sometimes don't have the dynamic response to handle multiple motors. Switchers have the enrgy storage is in a small inductor and small cap, where an unregulated linear regulator has a large cap to handle those dynamic current loads. I've had users that have had to discard their switching supply to goto an unregulated linear supply to fix their problem. Industrial use uses unregulated supplies for both steppers and servo's, and servo's have an even larger peak current demand.[/quote]
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I have luckily been able to help several CNC hobbyists over the last 18 months with stepping problems in this area, (as well as fixing PS problems for a variety of equipment over many years before!) so I guess its also a question of the size of power supply in comparison to the current requirements. For example, if yoo need a max peak of 25 amps and your unregulated power supply can supply 100 amps, I am sure everything will work fine, probably up to a requirement of 75 amps or so.
But if as a DIYer you need say a max of 8 amps and your supply is designed for a max of 8 amps (hobbyists are not always clever with electronics! I have even helped Hobbyists that had peak requirements far greater than their PS could supply. Sold to them by CNC companies/ebay with the words "That will work just fine!"), then you are on the "edge of functioning" so to say, very occasional (but expensive!) loss of positioning on some jobs only.........I had one system that kept "estopping" for no reason, that was also a supply with a lot of noise when running.....
Looking at such setups with an oscilloscope can often quickly demonstrate where problems are happening.....and which CNC Hobbyist has a 'scope, only a few I guess......I am lucky enough to have bought two over the last 30 years and both still work....I would go as far as to say that building a DIY CNC without one can of course work, but fault finding is far easier with one.....or conversely, you could say that proving that each component during building is also easier!! I actually saved a friend from buying a new PS, because it was actually working fine, but a grub screw was not working on a UJ and was slipping occasionally!!!! The threaded hole had not been fully cut and the screw was "bedding out" at the bottom of the hole.....found with a scope!!
Most unregulated supplies often run hot, often need therefore extra ventilation and of course can add some zeros to the electricity bill if they are used over very long and extended periods as they use power whether needed or not, where as correctly designed SMPSs basically only take as much power as they need (the one mentioned is around 86% efficient)......this can also be a considerable saving both in temperature, noise produced and total power usage...
SMPSs handle sudden loads up to their max output in a far cleaner way in my experience, ( the PS depicted was originally designed for a top end HiFi System with VERY suddenly changing power needs when music is played, that have to be supplied as good as instantly as the system was being used with frequencies far above 25Khz.....not unlike a hobby CNC!!)
in a worst case situation where there are occasional peaks that go above the max allowed, this can often be covered by some extra capacitance on the output, though I have personally in CNC not needed to do that yet with the supply in question, but in other areas where spikes of heavy demand were needed to be supplied......and the original design engineer had not done a good job!! (I was in the computer industry for over 30 years. Big line and laser printers from the 70s, 80s and early 90s are notorious for producing spikes and other loud harmonics, CNC machines are a doddle in comparison, believe me!!)
Every single person that I have ever met in CNC that also had something against such SMP supplies, HAD ACTUALLY NEVER USED THEM HIMSELF!!! He was ALWAYS speaking third hand!!! Thats how "old wive's Tales" stay alive......they are simply not true in this case....
The reason is that many small CNC companies/private users (I am told by people like yourself) use unregulated supplies are that they are cheaper to buy (even when rated at 200% of the max expected load) and far easier to to fix by semi or untrained personel, as their knowledge often does not run to fixing SMPSs supplies........which are probably usually at least a factor of 10x more complicated!!! As well as being dangerous to work in without expensive equipment and good training.
Larger industrial worldwise CNC companies like Bosch Rexroth for example, which is a company with a turnover of over €90M per year in the CNC world, use
ONLY SMP Supplies! Why, because nowadays they are smaller, lighter, more reliable and electrically clean.....
Goto:-
http://www.boschrexroth.com/dcc/Vornavigation/VorNavi.cfm?Language=DE&PageID=g97568for more details....
Particularly this page for power supply details, although in German, page down and you can see that the "Schaltfrequenz = Switching frequency) lies between 400 and 1600 Hz.....
http://www.boschrexroth.com/dcc/Vornavigation/Vornavi.cfm?Language=DE&VHist=g97568,g96067,g98367&PageID=p179794You can also (as in my example) go for the "half way house" type of a SMPS that is not really a "true" SMPS ( its a Step Down Switching Regulator) as it uses a conventional Toroidal Transformer to reduce the voltage first (this makes it FAR safer and almost as simple as an unregulated suppy to make/fix for people with less than perfect "electronics & mains voltages knowledge" to build and set up). A slight loss in efficiency of probably around 5-6% is the only effect though in comparison to a trully SMPS version....
Otherwise the method internally used is often relatively similar. But all the complicated electronics though are safely inside the chip and therefore very stable and have no need of adjustment!! Adjustments for output voltage (in this case) for a double chip set up are limited to a single potentiometer, once the 4 resistors are calculated for the basic voltage setup. Actually, I could even replace that Pot with a fixed value once it had been adjusted.....it must only be adjusted once.
As I say always, each to his own favourites, each to what he is happy with, but I personally reserve my comments for things I truly understand and use myself and have used for many years. I have been building electronic projects since 1955, and building power supplies since the 1960's....I also learnt electronics in the RN and have since worked in the electronics/computer (hardware side) industryfrom 1973 till 2006..... finding and fixing all and every problem on major computer systems was my job, from the 80s on, I was a specialist.
Years ago we would replace the offending part, repair it and return it later to service. Officially this was not done anymore after the '90s, but when you have no spare handy, we still repaired, or at least worked down to the component, but if it was not available, then you are stuck!!!
I can honestly say that simple unregulated supplies are a true "cheap" answer for some things, but otherwise they have no other "good" points that are better than either "Step Down" or true Switched Mode Power Supplies.....its only price and sheer simplicity where they score.....which of course keeps them attractive for many still.....
Have a great day.
1074fd.pdf