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  1. #21
    Quote Originally Posted by Hemsworthlad View Post
    I,ll second this my, 3 ps arrived today and i,m well chuffed they just look and feel quality.
    Thanks Irving and Kip.:clap:

    Edit: ended up costing me 17.38 each inc delivery that was for 6 supplies.
    Quote Originally Posted by Hemsworthlad View Post
    I,ve just been quoted 16.00 Del for 3 of these to yorkshire from the seller and they are on there way as we speak.
    Could you clarify (so I can put on my best haggling hat ) - excluding delivery...what did he charge per PSU?

  2. #22
    Thanks (& sorry for labouring the point! )

    For anyone wanting to order a few of these - the seller will allow collection via your own courier.....& Parcel2Go will deliver upto 25kg to your door for about 7.50 in total (the ad says they weigh 2.5KG each, so factoring in some 'headroom', you could therefore get 9 PSUs into the one Parcel2Go delivery - can't imagine you'll be popular with the driver though!)
    Last edited by HankMcSpank; 25-07-2009 at 10:47 PM.

  3. #23
    So after the sage of parcel farce, parcels 2 go etc was it possible to get to around the 40 volt mark ?

    .
    John S -

  4. Quote Originally Posted by John S View Post
    So after the sage of parcel farce, parcels 2 go etc was it possible to get to around the 40 volt mark ?

    .
    Still working on it John, looking promising but haven't had much time this week...
    Last edited by Lee Roberts; 26-07-2009 at 03:44 PM.

  5. #25
    Quote Originally Posted by irving2008 View Post
    Still working on it John, looking promising but haven't had much time this week...
    Old thread - what was the outcome? (did anyone manage to tame the voltage?) The seller is still knocking these out at 12.99 per PSU (his wife must be a tad miffed at them laying around the house by now!) ....


    http://cgi.ebay.co.uk/NEW-UNUSED-50V...item587e03d24d knockout price.

  6. #26
    Hank

    i bought two of these a while a go before seeing this original thread and still not got round to powering them up let alone start to tweak them. i would be very interested in anything further found out about them on the voltage drop front. My drivers can do the full 50v volts but would be happier at a few volts lower to save the possible crispy bacon burn factor. By the way i picked mine up direct from the old fellow (i live in Swindon)
    If the nagging gets really bad......Get a bigger shed:naughty:

  7. #27
    ecat's Avatar
    Location unknown. Last Activity: 08-02-2014 Has been a member for 6-7 years. Has a total post count of 157. Received thanks 5 times, giving thanks to others 8 times.
    Adding up the costs of a diy cnc machine continues to make my eyes water so finding these makes for a refreshing change :)

    In theory the output from the opto isolator should be wired to a feedback pin on the main PWM controller chip. If memory serves me correctly and the chip follows convention then the function of this feedback pin is very simple:

    if the voltage on this pin is above a certain threshold value (around 2.5v perhaps) the PWM controller switches off and if the voltage on this pin is below said threshold the PWM controller switches on - this is how the output voltage is regulated.

    As the PSU already has some way of varying the output voltage there may be some additional complications but all that should be needed to decrease the output voltage is a change to a single resistor such that the voltage on the feedback pin is increased by about 20% for a 40v to 47v output range (ish).

    Disclaimer: I know enough to hurt myself and nothing more :)

  8. #28
    I'd have thought the way they do this is to modify the duty cycle of a PWM stream. I'm tempted to order one - it appeals to the lazy mountaineer side of me ("I want to climb it because it's there" or transposed to this particular situation "I can't be arsed to climb a mountain, so I want to get the voltage down on this 50V PSU because erhm it's not 45V")

  9. Quote Originally Posted by HankMcSpank View Post
    Old thread - what was the outcome? (did anyone manage to tame the voltage?) The seller is still knocking these out at 12.99 per PSU (his wife must be a tad miffed at them laying around the house by now!) ....


    http://cgi.ebay.co.uk/NEW-UNUSED-50V...item587e03d24d knockout price.
    I managed to blow one up and to fry the input of my PicoScope.... (cost me 300 to replace it :sad: ) due to selecting a reference point that wasn't the ground potential I thought it was!

    The problem is that the design doesnt directly match the reference application schematic for the controller chip, and has a third-party board full of SMT parts that appears to do the opto-isolated feedback with at least one custom chip on it... Also there appears to be three power supplies in there, the main 50v job from a 400vDC rectification and two others, one of which is a -ve rail.

    As we know there is a input pin who's voltage controls the output. This goes into the SMT board and I believe this voltage drives a current source (as per the reference model) that controls the feedback circuit, however I was unable to identify that part on the board and suspect its inside the custom chip. Also there is obviously some sort of comparator on it to drive the 'in regulation output and control the current limit' but again suspect this is inside the custom chip too.

    The result of all of this is I was unable to find an easy way to change the control range. I believe the necessary resistor(s) to change are on the SMT board but I cannot yet identify them. And then other pressures overtook the time I had available...

  10. #30
    Tom's Avatar
    Location unknown. Last Activity: 30-11-2016 Has been a member for 7-8 years. Has a total post count of 172. Referred 1 members to the community.
    I bought one ages ago (as a result of this thread) and just plugged it in. It's been running the machine ever since.

    Open circuit my supply measures 42.7V (the data sheet spec is 42.8V +/- 0.5V, so no worries).
    The data sheet calls this voltage "out of regulation" (ie. there's less than 5.5V or more than 13.5V on Ucr). I haven't checked what happens when I put voltage on Ucr, because the "out of regulation" voltage is the one I want, and it seems to cope with load OK at 42.7V. The 4.3 signal diagram on the datasheet (attached) is the useful one.


    On my machine Ucr (pin 28) is just floating, but I should probably tie it to ground to avoid surprises. I haven't bothered because, well, it just works.

    Happy days.
    Attached Thumbnails Attached Thumbnails 500W Power Supply Datasheet ep002g1spec.pdf  

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