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  • OT: Solid state winch control

    I am interested in building a solid state control for my Warn 8274 self recovery winch. The current control scheme uses 4 constant duty 200 amp solenoids. 2 switched in parallel to connect the field 1 terminal on the motor to the armature for power in, and the other two in parallel to connect field 2 to the armature for power out. The solenoids are quite expensive, and during prolonged use, will occasionally weld themselves closed, and require replacement. Recently several winch manufacturers have began offering solid state m.o.s.f.e.t. switching controls to run the winch, instead of solenoids. This looks to me to be the perfect solution, with no moving parts to get screwed up by the harsh conditions.

    The catch is, the winch will draw upwards of 500 amps at full load. Designing a power supply to handle this kind of current is beyond my abilities. What I am wondering, is if any of you know how I would go about doing this, or if there are any online sites that may have similar project instructions that would get me heading in the right direction?

    Bellow is the wiring diagram for the solenoid control:



    Any thoughts or information is of course appreciated.

    Thanks,
    Jason

  • #2
    Designing a power control circuit for that sort of amperage isn't for the casual pretend engineer, like myself. It could become very expensive very quickly as the devices blow up for no apparent reason. I doubt that you will find plans for such a controller.
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    • #3
      Ah, but where is the fun in life if something doesn't blow up at least occasionaly

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      • #4
        Ah, but where is the fun in life if something doesn't blow up at least occasionaly
        Agreed, but I prefer it to be intentional.
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        • #5
          So, Evan, what do you think I am going to end up blowing up, the control circuitry, or do you think I will do damage to the winch itself.

          I think what I need to design is a standard H-Bridge drive, with appropriately sized mosfets. I found some power mosfets on digikey, rated for 160A @ 30 VDC that might work out nicely. They still are a bit small for what I need, can mosfets be wired in parallel for more current capacity?

          I am not so much worried about my controls going out in a spectacular puff of smoke. The components themselves are not going to amount to that much money. A replacement winch motor is, however, quite costly. I just dont see how the control circuit could fubar the motor.

          If any of you can help me along, I am not going to hold anyone responsible if I burn it to the ground. I just need to know if I am heading in the right direction. Do you think the H-bridge will work if I can source the components appropriately? Here is a link to the power mosfet I found on digikey: digikey link

          If you all definitely think this should not me a amateur project, for whatever reason, are their any commercial controllers that you can think of that I should investigate. The control pack from Warn goes for about $500, which seems mildly excessive for maybe $100 worth of electronics. Gotta pay for that R&D though I suppose.

          Thanks,
          Jason

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          • #6
            My cheap winch, draws 450 amps.

            Under full load, most winch loads are only minor tension wheeling in and out cable.

            my thoughts would be to find a electric golf cart or hyster control..
            Excuse me, I farted.

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            • #7
              I don't know about that, my 9000hs routinely has (had) over 5k fully dangling from it, taking my buggy up vertical walls from 15-30+ feet, with the tires just barely against the wall only because of the geometry of the cable going over the lip. And I have also taken my buggy to the top, anchored mine at the top, and pulled several other rigs over, one after another. I would love to have solid state, but it would have to be able to sustain the high amp loads for 5+ minutes continuous at a minumum.
              Russ
              Master Floor Sweeper

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              • #8
                I'm with you baddog, my winch routinely sees hard pulls.
                That is why my solenoids fail. They weld shut due to carrying high current for too long. I typically get 1 year out of the constant duty solenoids. Obviously they are mechanical devices, and subjected to some pretty severe environments, but the root cause of failure is, I believe, prolonged high current use.

                The more I am looking into this, the more I think it is doable. It is going to require a few power mosfets in parallel for each portion of the h-bridge. If overheating is still a problem, even with a good heat sink, I can always build an enclosure in the passenger compartment of my buggy, and fan cool them. If I figure something out, I will be sure to detail my project on here.

                Hopefully someone will chime in and tell me if I am on the right track so far.

                Later,
                Jason

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                • #9
                  The winch I assume is always "on" unless it is "off", in other words it is not speed adjusted in any way.

                  Then, your major specs are only a few.

                  1) the max current rating at upper temp limit.

                  2) the "Rds(on)", which is the effective resistance when fully "enhanced" (turned on) at max temp. The high temp Rds(on) may be 2.5 times the 25C rating, sometimes more.

                  3) the gate-source voltage to fully turn on the device at maximum current and worst case temp etc.

                  4) the thermal resistance from junction to case.

                  the application of (1) is obvious

                  (2) affects the power dissipation, and hence the heating

                  (3) affects your drive circuit. You have two "high-side" switches, which may be a problem to keep turned on. You may need a boost power supply to run them.

                  (4) affects the heating and limits the amount you can skimp on your heatsink.

                  There are lots of very high current Mosfets around for 100V and below. I have used 45 amp units at higher voltage, larger currents are available for lower voltages. For the low voltages, you are better off with Mosfets.

                  You will need to handle the currents without trouble, but the dissipation can be 'cheated" depending on duty cycle.

                  I don't know how long the winch is to be "on" at a time, nor the percent "on" time overall. With a short "on" time, and low "duty percentage" the heatsink need only handle the "average" dissipation, and have enough mass to absorb the higher dissipation for the shorter "on" time.

                  A suitable anti-turn-off-spike diode is already in most Mosfets. Just be sure it has sufficient current rating. Some are NOT rated for as much as the Mosfet. That may or may not be an issue, the time of conduction is dependent on the stored energy in the rotor mass and inductance.

                  Also, a resistor-capacitor damper may reduce spiking. The power supply must have a local bypass to allow the Mosfet internal diodes to conduct spikes without a large voltage rise.

                  One other issue is the voltage drop thru the Mosfets. This must allow the motor sufficient voltage remaining. The solenoids presumably are essentially short circuits when closed. The Mosfet drive may also have a re-designed motor, capable of operating on slightly lower voltage.
                  Last edited by J Tiers; 07-15-2007, 12:19 AM.
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #10
                    One other concern is that normally, transient snubber
                    diodes across the coils assume power is applied in the
                    same direction, but the winch reverses polarity to reverse
                    direction, so the circuit would have to somehow flip the
                    polarity of the snubber diodes across the coils, electrically
                    by preference. Your suggested STM 160A FET has a
                    nominal R(ds) of about 3 milliohms, so device drop would
                    approach 0.5V, probably not a problem for the power supply
                    or motor. Four of these 160A FETs in parallel at $5 or so
                    each for each leg begins to add up... Some sort of debounce
                    and optical isolation would
                    be a good idea to separate power ckt from the control ckt.
                    Steve

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                    • #11
                      upon looking at my own wiring diagram some more, it appears that an H-bridge will not work. The motor in question has 3 wiring connections, field 1, field 2, and armature. The motor is grounded via it's case and the winches case to ground. I was mistaken in my initial description of the solenoid control scheme. It actually uses one solenoid to connect 12vdc to F1, and the opposing solenoid to connect F2 to the armature for one direction, and in the opposite direction, the solenoids connect 12vdc to F2 and F1 to the armature.

                      It looks like I need two separate unidirectional high side drivers, but, the problem I see with this is that current will be applied backwards to one of the drivers, while the other is running. Perhaps I can isolate them with diodes, I don't know. I will continue to research.

                      The other option, would be to hard wire the motor so it is unidirectional, and then proceed with a H-bridge design. There is a plethora of schematics and information for them online since it seems to be the driver of choice for the robot builders. The biggest problem with rewiring the motor, is that it will have to be electrically isolated from the case of the winch itself. Maybe I can disassemble the motor and remove the ground from the motors case and put in a fourth lug for ground. I will have to think about it more.

                      Keep the info coming though, I appreciate all of the help. I found some 490amp mosfets, about $18 each, however, it say that the case style is limited to 160 amps. It is in the same package/case style as the link I posted above. I also found some 120 amp darlingtons, which may be an option, and they were a bit cheaper.

                      Whatever I do, I will be trying to find used/surplus components if it is looking to get very expensive.

                      As for the question on how long the winch will have to run at any given time, I would say, worst case scenario is 10 minutes. My battery reserve will not go much longer than that at full current draw, and if I haven't rescued myself in 10 minutes, it is time to rethink what I am trying to do, and go at it from a different direction.

                      Later,
                      Jason

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                      • #12
                        When I was still repairing electronic stuff, I'd get car stereo amps in with blown mosfets. It became obvious to me that in many cases the problems were due to dragging down the power supply voltage (12 to 14 volts in vehicles) to the point where there wasn't enough voltage to fully enhance, or turn on, the mosfets. Under this condition, the rds rises, which means that more power is dissipated within the mos devices themselves. At the same time, less power is delivered to the amp circuit, and it then asks for more from the power supply, and current draw tries to go up.

                        If you're driving a motor through a controller, it's much the same. As less voltage becomes available to it, it slows down, develops less back emf, and behaves more like a short. I'm talking about a loaded down condition here, and a winch certainly is a heavy load.

                        My feeling is that if you're going to be loading the battery to the point where its voltage is dropping to 12 v or less (which is easy to do), then you should have a separately regulated voltage supply for the control circuitry. This voltage can be derived from the vehicles battery, but it would deliver a constant voltage of not less than maybe 14 volts, even if the battery voltage drops to 9 or 10 volts. Your high current mosfet arrays will live longer.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          Years ago, I had a winch with a chainsaw motor on the side of it.
                          It'd snake a log up a mountain. No pictures sorry. I had large drum one laying in the shop with a hydraulic motor on it. I don't know where it has gotten to now thou. The new Ramsey I bought? it is chinese made, no doubt, it looks exactly the same as the ones HF sells. Plastic planetary gears in one end. I got to take one like it apart recently. After seeing that I hope I never really need it.

                          I got a old hand winch with a hitch-ball hole in a mount plate, it has dragged more cars out of bad places, I almost had to slam my buddy Doc to get it back from him after loaning it to him for a year or so.
                          Everytime I use it I seem to bleed. The cable is all fish-hooked up and with the mount the way it is it seems to pinch blood out every use. Them winch cable fish hooks are mean, kinda like a barb on a real hook, once they get into the flesh, you tear them out. It is laying on the porch right now after moving the big truck out of the shop.
                          Excuse me, I farted.

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                          • #14
                            Have a look at
                            http://www.siliconchip.com.au/cms/A_105741/article.html
                            Hope this is some help
                            Lin
                            Just got my head together
                            now my body's falling apart

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                            • #15
                              Lin, thanks for the link. Those have been commercially available for a while too, I really have no need for a remote control though. I have my winch's controls hardwired into the cab of the buggy, as well as the plug in remote still. It is an idea I have toyed with though, buying a cheap RC car and using the bits to run relays to run the winch, but it is just something I have thought about. No real need for it IMO.

                              Anyhow, I have one last question for the night. I am now looking at this HEXfet as my number one choice: IRF13245-7PPBF-ND link. It is rated for 24VDC, 429 Amps, costs $5, and capable of operating at temps of up to 175* C. Anyhow, my question is this. The data sheet says that the packaging limitation for current handeling is 160 Amps. Does this mean, that this is the maximum current that it can handle while relying on the FET alone to dissipate the heat, i.e. if I have a robust heat sink, and can keep it within normal operating temperatures, can I use it to switch the full 429 amps which it is rated for?

                              Thanks again guys.

                              Jason

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