Need help with power drops

Discussion in 'General Electronics Chat' started by Radioflyer, Aug 25, 2013.

  1. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
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    I have a variable voltage linear DC power supply that can provide up to 18v @ 2 amps; the load that is being powered only requires 5-9 volts and about .5 amps to run properly. The machines that are being powered through the power supply are the only instruments used that are sensitive enough to show an affect of this drop (lights in the room don't dim or flicker, other devices on the mains circuit seem to be running perfectly)

    The voltage and amperage readouts remain stable (+/- .1 volts), yet the load eventually bogs down and wont get the force needed to run properly or at all even.

    I have powered several devices, with 2 separate power supplies, and running the power supplies off 2 completely different mains to help determine the cause, experiencing the same loss of power to the device. The odd thing that i cant figure and am quite confused by, is the inconsistency of the said problem... One day everything will run great through the power supply, other days the power will start to drop after 20-30 minutes of load, and other days the loss isn't noticeable for a few hours of operation.

    I have replaced the devices, bought a new power supply, new power cords, pretty much new EVERYTHING running from the load to the wall outlet. A few things that i have considered the possible culprit, but haven't had a chance to troubleshoot would be dirty power, input and output frequency, supplied power to the mains, other loads on separate circuits, and faulty wiring of the mains (which i wouldn't be doing myself).

    Any ideas to what exactly is even dropping (if the volts and amps are remaining consistent), and/or what could cause such a drop, would be much appreciated!

    Thank you and feel free to ask any other questions
     
  2. crutschow

    Expert

    Mar 14, 2008
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    If the volts and amps are constant, then there's nothing else to drop. :confused:
     
  3. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
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    That's where I'm lost as well...

    whenever I notice this "drop", i can turn up the supplied voltage and MAKE the machine run, but not at all smooth enough to use properly

    ...also, i have only measured the power supply output levels of the amps, and I have tested the mains voltage, which is consistent @ about 123 v
     
  4. #12

    Expert

    Nov 30, 2010
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    This is so contradictory that I can't begin to guess the answer.
    and, ps, a DC power supply doesn't have an output frequency, unless you count, "0". (Probably just a misplaced thought.)
     
  5. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
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    I've exhausted what basic knowledge I have concerning electronics. I've even consulted a couple engineers specific to the tools and instruments of my industry as well as power supply & device techs... all of whom have a similar bafflement at how this problem is even possible
     
  6. #12

    Expert

    Nov 30, 2010
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    So, why don't you measure the power supply output volts? If the volts and amps remain steady, the "load" is stalling.
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Did you try adding a large electrolytic (min. 100μf) across the circuit supply to carry it through any sudden 'brown-outs' in the supply.
    And are there suitable .1μf decoupling caps across strategic points, if home built circuit?
    Max.
     
  8. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
    17
    1
    Sorry, I meant that I have only checked output levels of the power supply, both volts and amps... i just havent tested amps on the mains.
     
  9. #12

    Expert

    Nov 30, 2010
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    If the output of the power supply is stable in both volts and amps, that covers everything except the "load". What is this "load" that stalls while using the same amount of power it started with?
     
  10. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
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    The power supply and devices are all commercially built...

    I haven't cracked open this power supply to see what caps are present (dont want to risk voiding any warranty), but similar (different brand) power supplies that I have used over the years have all contained at least 1, usually 2 large caps (400μf) as well as .1, 1, and 10μf caps placed throughout the circuit.

    As well, the machine itself that is being powered always has an electrolytic cap placed in the circuit, typically ranging from 22-47μf and 30-50v.
     
  11. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
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    The load is a coil-type tattoo machine (almost identical to an old coil-type doorbell)... powered by the use of 2 electromagnetic coils to pull an armature bar in a downward motion, which is connected to a set of springs that return the armature bar to its starting point. The circuit is broken once the armature bar is pulled down to the coil and away from the contact point, thus causing the cycle to start over and repeat... this cycle typically runs at 80-120hz (repeatedly switching on and off).

    The load was the first variable that I had replaced with new machines (4 brand new machines, 2 completely rebuilt machines, and a "control" machine which has been used daily by the machine builder on his own works without any sort of problems). The builder of these particular machines is very well revered in the industry, so I cant imagine there being a problem with the design or assembly of ALL the new equipment, as well as the "control" machine the builder lent to me specifically for troubleshooting purposes.
     
  12. #12

    Expert

    Nov 30, 2010
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    This is where I vouch for post #7. That kind of machine is horribly noisy and could confuse most power supplies with its rapid fire electromagnetic radiation. However, I am guessing more like 1000 uf and a .1 uf in parallel to absorb that amount of noise.

    Still, you said you could turn the voltage up a bit and get the machine to run, so why don't you just do that?
     
  13. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
    17
    1
    The magnetic field created by the tattoo machine definitely crossed my mind, but unfortunately that goes beyond my knowledge of electronics. So the small field created by the load could indeed affect the supply? In what sort of manner?

    To answer your question of why not just turn up the power a bit, is because the machine wont run smoothly due to the increase of voltage being supplied. There are indeed situations where an increase in voltage is all that's needed to get the desired affect. Unfortunately this isn't one of them. Only adjusting the electrical properties of the machine without adjusting certain physical elements, such as the distance of the contact gap, spring tension and thickness, armature bar weight, relative geometry, etc., can disorient the harmony between the physical and electrical properties. This much-needed harmony is the product of a well-built, well-tuned machine; which without, can have some pretty serious, adverse affects on the quality of the tattoo, and more importantly, the amount of trauma to the client's body.

    Imagine pushing somebody on a swing and with each push maintaining a constant, fluid motion so as to exert the minimal force necessary, while also experiencing as minimal fatigue as possible... Opposed to pushing too soon or too late and having to work much harder to achieve the same desired goal.

    I have never personally experienced anything like this throughout my entire career... Im mentally exhausted at this point, to say the least.

    It's also a relatively new facility that I'm working in. And these inconsistencies were never prevalent until shortly after working at this facility. Could both my new and former power supply been damaged from the mains or ?? The new power supply ran flawlessly for about a week before the drops started happening again. The former power supply was replaced after 4 or 5 years of use, but only a couple months after moving to my new facility, when i noticed the drops for the first time.
     
  14. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Through out all your attempts to troubleshoot this problem, you have discovered that 'the problem' continues.

    The only thing it could be. The thing which has remained unchanged in all the efforts to 'fix' it, has been the machine, the tattoo gun.

    Seems it is the tattoo gun which has a problem.
     
  15. wayneh

    Expert

    Sep 9, 2010
    12,100
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    +1 I don't know anything about these guns but it sounds to me like it's mechanically gummed up. Use it on a known good power supply and see what happens.
     
  16. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
    17
    1
    The machines, or guns, were the first variables addressed throughout this whole thing... 4 brand new machines were purchased as well as having 3 of my old machines completely rebuilt (coils, springs, a-bar, capacitor, contact pin, every shim, wire, and gromet, everything). The machine builder even lent me one of his personal machines which he uses daily and has never had problem. Every machine I plug in and run, eventually experiences this "drop", sometimes after 20 minutes, other times not until after 3-4 hours... and other times everything will run great.

    I've tried to log any sort of outside cause that could even come close to affecting this circuit, and honestly i've notice little, if any, consistencies in behavior

    I also replaced my footswitch and clipcord before moving on to replacing the power supply.

    At this point, everything on this side of the wall outlet has been replaced...
    This has been quite the spendy glitch
     
  17. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
    17
    1
    The machines seem to run perfectly when taken to the builder and ran from his facility or if they're just hanging by the clipcord and left to run in attempts to record a drop at some point. Its sounds silly, but the most consistent part of the drop, is me. Once i hold the machines and start actually tattooing, the power seems to dropout and until eventually needing to be re-tuned, and then its stable for a matter of minutes before it starts dropping again.

    And when i refer to this "drop" i cant determine whats dropping out... volts and amps read consistent and steady. The force needed to push the needle properly is the first thing that i will notice, then soon after there is a noticeable change in the sound... as if you were gradually turning down the volts.
     
  18. wayneh

    Expert

    Sep 9, 2010
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    I think you're on to something. Again, I don't know anything about these tools but is there any way that the heat and/or compression of being grasped in your hand is somehow causing an internal binding of some kind? Or, maybe it's not you but just the fact that you're using the tool - putting it under a load, causing it to heat up - as you work with it.

    I think this is going to lead to a forehead slapping moment, once the culprit is identified.
     
  19. Radioflyer

    Thread Starter New Member

    Jul 25, 2013
    17
    1
    Well Wayne, it was indeed a forehead slapping moment the other day...

    in a state of boredom and mental exhaustion, i decided to have some fun fabricating a lighter armature bar. As I grabbed 2 spare a-bars from my spares bin (which is metal and also kept in my tool box text to the machines) and compared them side by side for size and what not, I noticed they had the most faint, hardly even noticeable, magnetic charge toward one another. Years ago, I had heard of this happening to tattoo machines and asked others in the industry about the possibility. Everybody i talked to kept telling me that it was a "myth"... I've been tattooing for over a decade and never seen this personally but i also thought it was ridiculous to write off the ability for these machines to remain magnetized when they're not running... it seems like common sense to me that a chunk of iron purposely used to create a magnetic field could indeed become magnetized. Hence why I'm now having this discussion on an electronics forum with folks who actually know what they're talking about concerning such things.

    So anyway, i checked every other screw and spare part in the tool box and sure enough they too were all magnetized.

    I demagnetized the machines, and low and behold they run fantastic. BUT, they still eventually become magnetized during use, sometimes only after 15 min, and other times i'll use a machine for hours without any change whatsoever. I have still yet to find what exactly is causing this to happen and why is it all of the sudden happening after 12 or so years of use without any prior issues...

    Well, thank you guys for all the input thus far. As always, AAC has been super helpful.

    Cheers, I'm off to hopefully locate the cause.
     
  20. wayneh

    Expert

    Sep 9, 2010
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    Interesting. C'mon back and let us know. Sure glad you didn't start rebuilding your power supply!
     
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