Connect with us

How to control 700 solenoids?

Discussion in 'General Electronics Discussion' started by Deuce, Apr 14, 2015.

Scroll to continue with content
  1. hevans1944

    hevans1944 Hop - AC8NS

    4,626
    2,159
    Jun 21, 2012
    True in principle, but probably not so much for this application. The solenoid valves have short duty cycles, on to make a raindrop then off to allow space between drops. Speed is on the order of ten milliseconds between valve cycles. Variable coil current would probably needlessly complicate the design.

    The OP still hasn't specified a particular solenoid valve. My son works for a company that makes fast-acting valves used mainly for precise dispensing of glues and pastes. Google pico-valves and visit the Nordson website.
     
  2. mofy

    mofy

    46
    14
    Dec 19, 2014
    Thanks, probably right, but don't car injectors, which are very fast cycling, use the high current pulse/hold current solution?
     
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,626
    2,159
    Jun 21, 2012
    I wouldn't know about that, not having worked on cars since carburetors went away. I suppose it is possible, since modern cars use an ECU to control everything.

    Conceptually, all you need is a capacitor from the MOSFET drain to common to store charge, and a resistor in series with the power supply and the MOSFET drain to limit the current after the capacitor discharges through the MOSFET into the solenoid. If it is necessary to limit the peak current, a small resistor in series with the drain will do that. The RC time constant required for a particular operating frequency (cycle rate) will depend on that frequency. There needs to be enough time between successive solenoid actuation and de-actuaction cycles to re-charge the "boost" capacitor. Other solutions, not frequency dependent, are possible. For example, two MOSFETs can be used, the first to switch the high-current pulse on, and then the second MOSFET with a current-limiting resistor to take over conduction during the low-current holding part of the pulse. In actual implementation, both MOSFETs would be turned on simultaneously and then the high-current MOSFET would be turned off, followed a short time later by the turn-off of the second MOSFET to de-actuate the solenoid.

    IMO, such complexity is only warranted for high current, high duty-cycle solenoids that remain actuated long enough to experience a significant temperature rise. I would ask the solenoid valve manufacturer for their recommendations after selecting a particular valve and describing its intended use. They might even have life-cycle data for different drive methods they recommend.
     
  4. mofy

    mofy

    46
    14
    Dec 19, 2014
    "IMO, such complexity is only warranted for high current, high duty-cycle solenoids that remain actuated long enough to experience a significant temperature rise. I would ask the solenoid valve manufacturer for their recommendations after selecting a particular valve and describing its intended use. They might even have life-cycle data for different drive methods they recommend."

    I agree, the other caveat would be response time: an initial high current pulse will pull the solenoid in quicker.
     
  5. Viktory2k1

    Viktory2k1

    41
    3
    Apr 14, 2015
    Those boards I posted have no speed spec but can transfer all PWM for leds so they gotta be pretty fast. Don't want to hijack but can you tell me how to build those boards? I thought those were tip120 transistors but I guess not. $55 is $50 too much for me, maybe a few part #'s and a quick schematic?
    Thanks
     
  6. brevor

    brevor

    87
    16
    Apr 9, 2013
    Sorry, i can't find the link to those boards.
     
  7. brevor

    brevor

    87
    16
    Apr 9, 2013
    It's hard to say how to build your own clone of those boards, they don't give much information on the website. They do say it uses mosfets so they are not TIP120 transistors. If you really need to know you may have to buy a board and reverse engineer it.
     
  8. Viktory2k1

    Viktory2k1

    41
    3
    Apr 14, 2015
    I am so naive in this catagory of electronics, it's unbelievable. Heres what I got so far. I do have a LEDWIZ and a PACLED64 for controller boards totalling 96 outputs all PWM. I am having some motor contron difficulty at this time so may be typos along the way.
    I will need 1 curcuit per output for this but if I get money, I will just buy 4 of the darn things but I do want to learn this. First, I need the board and am hung on that. I am thinking of this http://www.ebay.com/itm/131351781898?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT
    Don't know how many curcuits I can get from 1 but....
    My parts list contains the following:
    1 220 ohm reststor
    1 PC817
    2 470 ohm resistors
    1 BUK 9575-55A MOSFETs
    X 96.
    Or just wait until I get some money and buy those boards.
    I could probably get all parts except the PCB for $50 from mouser or ebay from China. I could have easily avoided this if I knew about my condition in advance. I do see a pain mgt specialist Monday but a day late and a dollar short.
    Everything would be run from a 360w 12v PSU with extra large resistors for the RGB LED 3w 5v flashers(X10).
    I know all solenoid or coils will need a IN4007 diode so I don't have an issue with feedback of high voltage. I think those things on the boards are the pc817 but multichannel optos. I can't do that because I don't have the printed boards and not going to solder a million wires to it. 80% of this is just to control 5050 rgb led 5m strip cut to pieces to mimic the effect of ws2812 addressable strips. Someone was developing a board for those but he stopped but gave me the proto-type schematic. Here is a demo of what I am trying to mimic but I do not see this happening as I can barely type this message. Screw it, I will attach my FILES too:
    If I wasn't lied to 17 years ago, this would be not happening. I was diagnosed with a "thoracic strain" in 1998 and finally, after suffering all this time, found out the truth.(no viruses)
     

    Attached Files:

  9. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    If you are going to power this with a 360W power supply, I hope your solenoids use less than 1/2 W each.

    Bob
     
  10. Viktory2k1

    Viktory2k1

    41
    3
    Apr 14, 2015
    If I am not mistaken, you would need 700 blocking diodes also. Just want to get a grasp at all this. The boards I mentioned should be fast as they can control RGB LEDs also which need precise timing. Are those really rated at 50A? How could the tracers handle that kind of current?
     
  11. brevor

    brevor

    87
    16
    Apr 9, 2013
    The mosfets are supposedly rated for 50 Amps, but in the real world you would not want to run them that hard.
    You may want to check out the following thread where they discuss the current limitations of mosfets.


    http://forum.allaboutcircuits.com/t...burn-when-they-are-protected-by-fuses.110439/
     
    Last edited: May 12, 2015
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-