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Thread: Pauls HP UHU drive project

  1. #61
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    Quote Originally Posted by contactirfu View Post
    ok Kreutz, I want to buy one of your BOB with spindle control when are u planning to get it to us, with all that you discussed above.

    RGDS
    Irfan
    I am still on the design/prototyping stage, will send the gerbers to the fab early January. Will keep you posted.

    Thank you,

    Kreutz.



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    duplicated....

    Last edited by kreutz; 12-18-2008 at 12:41 PM.


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    Default Paul's miil project - soft start options available no w

    Hey All.
    it's beginning to look like I'll be restricted from very much shop time when I leave the hospital to go home. this should mean I can spend reasonable amounts of time at my electronic assembly area............... If this pans out I think I'll build at least two new drives that haven't been repaired/aultered etc.
    I keep thinking of soft starts, where & what to apply to test the theory in my application......... quite awhile back I purchased some thermistors, at least two sizes knowing me. I'd like to try thermistors to slow the on rush on start up. where & what size, grade, ? becomes the question. I'm currently unable to check what I have so I guess we'll have to look at this on a theoretical level. I'm guessing that I would put one thermistor in each leg of the incoming voltage to the 134vdc power supply. I'm posing this as a question to you whom know more about this ?
    with luck I'm going home tonight & could list the actual thermistors I have to see if they'd work...............
    Thanks
    Paul



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    Quote Originally Posted by tenmetalman View Post
    ........I keep thinking of soft starts, where & what to apply to test the theory in my application......... quite awhile back I purchased some thermistors, at least two sizes knowing me. I'd like to try thermistors to slow the on rush on start up. where & what size, grade, ? becomes the question. I'm currently unable to check what I have so I guess we'll have to look at this on a theoretical level. I'm guessing that I would put one thermistor in each leg of the incoming voltage to the 134vdc power supply. I'm posing this as a question to you whom know more about this ?
    with luck I'm going home tonight & could list the actual thermistors I have to see if they'd work...............
    Thanks
    Paul
    NTC resistors (resistors with negative temperature coefficient) are successfully employed as soft start (and charging current controllers) for small power supplies, they work "hot" (the hotter they get the less resistance), but they are not a solution at the power level of the HP_UHU drives.

    Get Well and best regards,

    Kreutz.



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    Default Paul's miil project - soft start options available no w

    Quote Originally Posted by kreutz View Post
    NTC resistors (resistors with negative temperature coefficient) are successfully employed as soft start (and charging current controllers) for small power supplies, they work "hot" (the hotter they get the less resistance), but they are not a solution at the power level of the HP_UHU drives.

    Get Well and best regards,

    Kreutz.
    Well fart ! ! ! !
    What's next ? I have a stash of Large oil Electrolyte & start capacitors, some transformers, wire wound resistors & so on that came out of a backup power supply. (Don't ask I couldn't get the batteries..) I know Kreutz is real busy trying to make ends meet. I'm in the market for suggestions that don't involve additions relays............
    Paul



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    OK, this is a bit long, I'm not trying to drive the thread of course, I'll appologize in advance.

    Just a note on SSRs, they tend to be pricey in a stand alone form, but schematically they are rather simple to add to the board itself. In their simplest form, they can be a pair of SCRs in parallel or better yet, a triac. All that is required is a small gate drive circuit consisting of a few components. Buy a $12 lighting dimmer at a store, it will have all the required components. Add a medium heatsink and the 600W capacity will easily double. A simple swap of the triac for a 40A model and adding a little more gate drive current and you can switch anythng your circuit breaker will provide.

    Working in the lighing control industry, I have been thinking about using just such a device to help with the soft start. Dimmers work by removing a portion of the AC sine wave to the load by simply turning the lights on and off at 120 HZ(2x the 60HZ of standard US power) by waiting to turn on the device for a few milliseconds after the AC voltage crosses 0V, you cut out a small amount of power to the load. Varrying the point at which you turn on the load affacts the RMS voltage and power delivered.

    Simply hooking up a dimmer to a rectifying power supply will actually do nothing unitll you get below 50% RMS output (note that light output is perceived as a power function, 50% on a dimmer slide or knob is usually less than 50% power, the control is nonlinear to correct for the eyes nonlinear response to lighting intensity). This is because the dimmer just cuts out the first portion of each sine wave, the peak voltage thru the device is still 1.41*VRMS and your rectifying circuit will still receive peak voltage, you just limit the current capacity a bit. Once you start dimming below 50%, you reduce peak voltage and thus the output voltage of your transformer and rectifier is reduced proportional to peak voltage ie 75% dimming is 50% voltage on your power supply.

    The trick to using this as a soft start is to slowly fade the load on just as you would lights. this will gradually increase the peak voltage the transformer and capacitor sees limiting the inrush current due to a high differential voltage. A little math can easily tell what fade times you need, but a few seconds should be sufficient. A basic dimmer contains less than 8 passive electrical components. The front knob or slider is a nonlinear pot (`200kohm max) that controls the time constant on an integrating circuit. Once a very small cap has charged up past a set voltage, a diac trips and a simple gate drive circuit provided a small pulse of current to the gate of the triac. As long as current flows thru the triac, it stays latched and conducts the main voltage. Once the sine wave crosses 0V relative to neutral, it turns back of. This resets the timer and and the process resets. The simple dimmers use a mechanical switch to turn power on and off and the pot simply adjusts light level, there is no built in fade (with few exceptions this is true for products you appear to dim to off, there is a mechanical switch behind the scenes for code compliance reasons). A simple dual timer circuit that effectively decreases the time constant of the gate drive circuit will give a pre-programmed fade on rate. The circuit has to controll delay from 8.3 milliseconds(1/120th of a sec) to 4milliseconds over a few seconds. After 4ms, the device can go to full on all the time because the transformer has already reached full voltage. For $30, you can purchase a "digital" fade dimmer, it has a small micro and LED feedback, but its perk is once turned on, it fades lights on. Several products contain an advanced (advanced is relative to a light switch, it isn't really advanced) programming function that allows fade on and off times to be programmed, this would allow an off the shelf module to do the work for you, but you will need to do a bit of work to increase current capacity of the device (beef up power traces with heavy wire, add larger triac, replace choke with wire, it is for AM radio RFI supression, but the massive transformer you are connected to provides enough inductance to keep switching times relatively slow)

    Ok now drawbacks of triacs
    -They have a ~.7V drop across them and are ~98-99% efficient. At 2KW of power, that is 30-40W of heat generation (multiple triacs can be put in paralle to spread out the heat, but the circuit gets complicated to balance, besides comercial products do 2KW with a single triac and a passive heatsink the size of two light switches)

    -Off the shelf dimmers have a specified minimum load (usually 40W light bulb but this is verry conservative) that provides enough current to keep the triac latched at low light settings. This is a minor problem charging small power supplies with a slow fade on, but bigger supplies that draw >.2A while being dimmed up are ok (remenber, there is no real load at startup) With a roll your own solution, this is easily avoided by giving the gate a constant drive current untill the main voltage drops back to 0 (simple dimmers only give a starting pulse because they sit in line with the load, they are not connected to neutral and thus do not have access to a power supply and have no way to provide this current)

    -Triacs hate short circits and will be instantly destroyed. I have blown up hundreds of these things (part of safety testing) and the results are usually not pretty - think black char and smoke completely covering the PCB, often with molten coper and lead splatter. Fortunately they are dirt cheap and easily replaced.

    -A few NTC Thyristors would be a heck of a lot easier to implement and would usually have less steady state Voltage drop, but the 20sec to 1 min cool down period may be an inconvenience. Then agian, they don't solve the whole turn on and off thing.

    -You need to balance both sides of the AC half wave thru the transformer otherwiase you will have a DC current thru it and will saturate the core. Dimmers specifically rated for MLV (Magnetic Low Voltage) lighting do this via careful component selection, but in reality a regular dimmer will work just fine. If you make your own circuit, just make sure there is less than 2VDC preferably 1VDC across the transformer. While fading on, there will naturally be an imbalance, but as long as fade is <3-5s, the dynamic event can be handled by the transformer. This is also a good reason to use a triac instead of a pair of SCRs as a triac is essentially two SCRs back to back in one package (low quality dimmers may use SCRs, but all decent ones use triacs). SCRs may have different internal voltage drops due to manufacturing but triacs tend to be very consistent due to shared silicon and the fact that it is processed all at once

    -As it turns our, triacs are used in industry for just such soft start devices. NTC thyristors win out in most designs for cost and complexity reasons, but many specialty supplies do use them

    Like I said, sorry for the long winded post about a soft start ideas, Its just something I've been thinking about for a while and this seemed like a place where someone could make use of it.

    John

    Last edited by sigma relief; 12-20-2008 at 12:12 AM. Reason: long post had a typo, there are still many more left


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    Hi all, where I can found UHU HP PCB, and schematic to build one to test or buy an PCB !

    Thanks in advanced,
    Alejandro



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    Hi,
    Just contact Paul (tenmetalman), the "owner" of this thread. I think he has PCB's and/or complete kits available. The scematics and PCB-layout files are burried in a thread here on the 'zone and I can't seem to find it at the moment. I'm sure someone lese will point you to it. Otherwise PM me your E-mail adress and I'll send it to you. Or I'm sure Paul will provide you with the correct shematic and part-list when you get the PCB from him. Also make sure the UHU-Wiki

    /Henrik.



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    ping.

    attempting to wake up the sleeper thread. Any news on topic, Paul, Kreutz, Henrik? BTW wonderful post, John (sigma relief), full of nice ideas.



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    Default MOSFET REPLACE?

    I have been waiting for my heat sink for the HP UHU Controller and now that it's here I find that I am short one IRFP264N FET. I had used the forth one on a power dump circuit I built. When I went to buy some more the only ones I could find were on Ebay. I've ordered some but I was hoping to build three more HP UHU Controllers after I got the first one to work. Is there any effort at finding a replacement? The STW52NK25Z comes up on digikey's site. Is it a drop in replacement?



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    Default replacement MOSFET

    Bob,
    If your still waiting for a mosfet email me, we'll work something out. as fas as purchasing more drive kits I can accommodate that too. let me know via email what you need now.
    Paul



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    Thank you,

    I have the IRFP264N's I need coming from Hong Kong. I just wanted to know I can still get more controllers after I prove out this one.
    I am working with several friends to replace the electronics on a Wells Index 833 mill. I've built the embedded UHU controller and it's working fine under Mach 3. My friends wanted to see the HP UHU working before they buy the next three kits.

    Anyone thinking of adding H.O's mod to the existing HP board?

    Bob



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    Default R46

    I have been trying to trouble shoot my HP-UHU board and found that R46 was shorted. When I looked at UHU MODIFIED_Dated1.4.08_R1.0b the schematic page 5 did not match the board page 6. Page 6 shows a trace from U12 pin 3 directly connected to U13 pin 6. This appears to make R46 redundant.

    I have checked to see if this was referenced on any of the threads but was unsuccessful. Was this a known fault that I failed to read about?

    Bob



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    Quote Originally Posted by BobVanDyke View Post
    When I looked at UHU MODIFIED_Dated1.4.08_R1.0b the schematic page 5 did not match the board page 6. Page 6 shows a trace from U12 pin 3 directly connected to U13 pin 6. This appears to make R46 redundant.Bob
    Hi Bob,

    Good point. I see the same connection on the layout drawing and on my board. What it appears to do is pull Pin 3 of U12 low as if an ESTOP happened.

    I too must be missing something because no one has complained as yet. But then I haven't powered mine up yet. I'm only about 3 years behind.

    John

    Last edited by jcdammeyer; 08-25-2011 at 01:42 AM. Reason: Mistake.


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    Default R46

    I don't believe this is a problem. I wouldn't have even noticed it except R46 appeared shorted and I thought I made a soldering error. The board obviously works the way it is. I notified Tenmetalman, the owner of this thread, by E-mail and got a Help Ticket response from CNCzone. I just wanted to document this in case others thought they had a problem.

    The kit itself was easy to assemble and looks great. I'm not electrical so I'm having a tech look at mine. The problem I'm having is the motor turns as if shorted to the high voltage power. Nothing to do with the Emergency Stop.

    I was surprised that U12 and U13 have the legs numbered 1,3,4 & 6. That's the first time I've seen that.

    Bob



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    Quote Originally Posted by BobVanDyke View Post
    [B]
    I was surprised that U12 and U13 have the legs numbered 1,3,4 & 6. That's the first time I've seen that.

    Bob
    The package is a standard size and uses a standard footprint. Normally such a package has 6 pins. Hence the numbering.

    John



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Pauls HP UHU drive project

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