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Help with Water Pump

Discussion in 'General Electronics Chat' started by salty joe, Dec 30, 2011.

  1. salty joe

    salty joe Active Member

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    I put off replacing the LM324 and adding trimmers to the wave pumps' FSM until my 25 turn trimmers arrive.
    If it's possible, I think only half of that LM324 got fried. The pair of pumps on the 'good side' trip the alarm down to just under a 2 sec. cycle on an unplugged pump. Given that R3-6 is 300K and the FSM has the mod from post 2279, do you think a 2K2 resistor in line with a 250K trimmer is a good place to start? I have a variety of fine tune trimmers coming.

    All four new PDMs for the four extra tide pumps seem to work. Yahoo! I only got a chance to run the newly arrived new pumps for a few minutes, but they seemed to happily toggle and flick right along. The only glitch was one of the alarm LEDs is lit and the alarm goes off nonstop. (This FSM is dedicated to the four additional tide pumps) I am going to look at it in the morning-any idea what to check out first? Thanks.
     
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Quite possibly.
    Sounds good.
    Good too that the new pumps and PDMs are ok. Could be the one alarm channel that's playing up has a wrong connection somewhere. I'd start by checking the Fault signal path; check too if the Alarm output of the relevant PDM is stuck high even with its associated pump turned off.
     
  3. salty joe

    salty joe Active Member

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    That seems to be the case. If there's power to that PDM, there's 11.87V coming out of leg three of Q3 no matter what else. I double checked the part number for both Q3 & Q2. The transistors seems to be correctly hooked up. Bad transistor?
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    What is the voltage at the R9/D10 junction?
     
  6. salty joe

    salty joe Active Member

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    I probably jumped the gun and pulled the board. At least I didn't start replacing parts. I was so ready to go after that transistor...:)
    Anyway, we're getting ready for a roadtrip for Thanksgiving so I'll have a look at it when we return on Saturday.
    Thanks.
     
  7. salty joe

    salty joe Active Member

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    The voltage at the D9/R10 junction is 4.45V when the pump is toggled off and 4.99V when the pump is toggled on. When the alarm LED and pizo come on, the pump stops but the pump LED stays on and the V at D9/R10 remains at 4.99 until it toggles off. (That typically happens twice during the 30 sec. run time.) Oddly the alarm does not stay on nonstop as it did before I removed & replaced the PDMs??? Adjusting the 50K trimmer seems to have no effect.

    I ran a piece of 18g or 16g wire connecting a row of terminal points for the star ground. The spliced ground wire from eight new power supplies, eight PDM power grounds and the four PDM signal grounds as well as the timer and alarm signal grounds are all connected here. All was well.
    When I added the four additional PDMs, I ran a piece of 16g wire from that star ground to another row of terminal points for a continuation of the star ground about 10-12 inches away. I directly soldered the signal ground from the new FSM and new alarm module to the wire connecting the terminal points. The spliced ground wire from the four additional new power supplies, four PDM power grounds and the two PDM signal grounds are connected here. Is the ground OK?
     
  8. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Try connecting 33k (or slightly more, depending what you have available) from the R9/D10 junction to the 12V rail. Then operate the trip test.
    The added grounding sounds ok.
     
  9. Little Ghostman

    Little Ghostman Well-Known Member Most Helpful Member

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    i have read this from the start and followed it all the way through! gripping stuff and i have learnt a huge amount from it! thanks all its got to be the all time best thread ever!
     
  10. salty joe

    salty joe Active Member

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    Hey Little Ghostman, glad you're here. If you read this start to finish, you are hardcore! I'd expect someone like you to go places.

    Alec, thanks for checking out the ground.

    I connected a 33K between R9/D10 and 12V. The alarm tripped faster than I could push the trip test. The pump and the pump LED both turned off and the alarm LED and pizo both turned on.

    Before connecting the 33K I pushed the trip test and it seemed to work as planned-alarm LED and pizo turns on, pump and pump LED turns off for about 30 sec.

    Thanks.
     
  11. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Welcome aboard LG. You must have stamina to get right through the thread! Glad you've found it useful.
    Then something seems fishy with Q3. That should have ensured Q3 was switched fully off. Yet without the 33k Q3 seemed to be doing its thing ok. Strange. Check its connections/polarity. Can you swap out Q3 if necessary?
     
  12. salty joe

    salty joe Active Member

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    Q3 is hooked up just like all the other PDMs. I also double checked the part number.

    I'll pull that board again and triple check Q3 and that vicinity. If everthing checks out, I'll replace Q3 with a new transistor.
    BTW, by polarity you mean leg 3 of Q3 goes to alarm etc., is that right?

    I had the other pair of PDMs running and when I turned off the breakers at the main breaker box, the problem pump LED stayed dimly lit for over 5 minutes. It ever so slowly got dimmer and dimmer. I also unplugged the new controllers from that PDM.

    I guess I better go over that PDM with a fine toothed comb. Besides Q3, anything I should check first?
     
    Last edited: Dec 1, 2013
  13. alec_t

    alec_t Well-Known Member Most Helpful Member

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    I assume that doesn't happen with the other breakers/pumps/LEDs ?
    If leg 3 is the collector then yes.
     
  14. salty joe

    salty joe Active Member

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    That's right. It's the first time I've seen it. Tomorrow I'll remove that board and give it a going over.
     
  15. salty joe

    salty joe Active Member

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    I took the problem PDM 12 and its mate from the array and bench tested both. They behaved like model citizens. I figured the problem must be in the FSM or alarm module and took that board loose. I did find a component lead that I failed to trim. It could have caused a short in the alarm module, but was on a channel that was not causing trouble. I put everything back together and channel 12 is still sounding the alarm every 10 sec or so, turning the pump and pump LED off. Then I noticed a yellow flash from behind PDM 12 at the moment the alarm sounds! Right about then, I am most certainly appreciating the safety factors built into this system. PDMs 11 & 12 go back on the bench. No burn marks or anything. Wiring looks good. At C4, power ground was close to supply+ so I gave it a little more clearance. I could not find any conductivity between the two. Put everything back together again and now channel 12 is back to where it was a few days ago-if PDM 12 has power, the piezo and alarm LED are activated no matter what else, meanwhile pump 12 and its LED toggle right along with its mate. The trip test does work and when it is activated the alarm LED becomes a little brighter and of course the pump and pump LED turn off for 30 sec. I plugged the pump in and out looking for the dreaded yellow flash but it seems to be gone. Good riddance to it.
    I went over the FSM and could not find anything hooked up wrong.
    Just wanted to let you guys know I’m working on this. I guess tomorrow I’ll put the four new PDMs and the FSM and alarm module on the bench. Ug.
     
  16. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Wouldn't you know it. On their best behaviour until your back's turned ;).
    Yellow flashes certainly are bad news. Could be due to a stray wire touching where it shouldn't, or to voltage spikes when the pump turns off, if a Schottky diode or capacitor isn't doing its job. Glad they're gone; but a voltage spike could have upset something in the PDM.
    Temporarily disconnect one end of D11 in the Ch12 PDM and see if the problem persists. If the problem goes away, the FSM/Alarm module has the fault. If not, the fault must be in the Ch12 PDM or in the Ch 12 new controller or its power supply. If that's the case then run the Ch 12 pump with its controller and supply but without the Ch12 PDM. That should help pin the fault down.
     
    Last edited: Dec 4, 2013
  17. salty joe

    salty joe Active Member

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    I disconnected D11 and the alarm for channel 12 still sounds nonstop, even though channels/pumps 13 & 14 were toggling at the time. I swapped the new controller and PS from pump 12 with another that 's never been a problem. Channel 12's alarm still going.
    I guess I better pull PDM 12. Thanks for that diagnostic.

    I hooked D11 back up and fired up PDMs 11 & 12 on the bench. I think I was mistaken when I called PDM 12 a model citizen. There is always 11.99V at the alarm except when the trip test is pushed, it goes to 12.00V for 30 sec. I should have checked V at the alarm from the getgo. Sorry about that. I took a good look at the bottom of the board and saw no arcing or anything.
     
    Last edited: Dec 4, 2013
  18. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Ah. 'Alarm' should be close to zero before the trip test. So the PDM seems to be the culprit.
    Simulation shows that Rsense is critical. If either end has a dry joint (due to oxidation, contamination or too low a soldering temperature) its effective resistance is raised. Even a few extra tens of milliohms is enough to guarantee the alarm tripping despite the pump current being near normal. So while you have the PDM on the bench it's worth re-soldering Rsense. A dry joint (not always discernable by eye) could also cause local arcing intermittently, hence the flashes you saw previously.
    What voltages do you get from the PDM (a) at R8 and (b) at the D4/D10 junction?
     
  19. salty joe

    salty joe Active Member

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    I re-flowed both sides of Rsense, no help there.
    At R8 I got 0.00-0.01V and at D4/D10, 11.58V.
    Thanks.
     
  20. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If the alarm still trips with those readings and the pump running then the problem lies in the Q3/R9 area of the PDM, or in the alarm module itself.
    With power off, check the resistance (with DMM probes both ways round) between the collector and emitter of Q3.
    With the PDM 'Alarm' output temporarily disconnected from the alarm module but instead connected via a ~10k-33k dummy load to ground, power up and with pump running check the voltages at Q3 base, collector and emitter.
     
    Last edited: Dec 6, 2013
  21. salty joe

    salty joe Active Member

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    I couldn't find any conductivity between the collector and emitter of Q3.

    With a grounded 22K connected to the PDM's alarm output, I got 1.65V at the emittor, 11.41V base and 12.04V collector of Q3.

    Much appreciated.
     

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