Help with Water Pump

[alec_t]

the sticker on the back of new pumps say 40W.

So full-speed run current is ~1.8A; nearly twice that of the old pumps. Useful info. Presumably the PDM trimmers are set somewhere near their max to prevent the trip operating?

 

[KeepItSimpleStupid]

Let's have Joe measure the voltage across the low om resistor. There should be test points there, anyway.

 

[salty joe]

I have the PDM trimmers all set about in the middle. The only time the alarm has sounded is when the tide pumps are in reefcrest or one of the other variable flow modes, in which case it does not seem to matter where the PDM trimmer is set.

Is the low ohm resistor Rsense? Everything is real easy to get to.


I replaced R1 in the wave timer with a 10K. Very nice fix-thank you Alec. Unfortunately, I was already close to the sweet spot so the little wave did not get much bigger. But that's something I needed to know. Still playing around with it.

It's looking like a little more horsepower is needed. Is it possible to feed the Vt, 12V, 24V, signal ground, power ground and expand the FSM from the tide system for two additional PDMs and two new pumps on each side? The tide controller would run 4 pumps per side instead of the existing 2 pumps per side.

 

[KeepItSimpleStupid]

Is the low ohm resistor Rsense?

Yes.

 

[alec_t]

The only time the alarm has sounded is when the tide pumps are in reefcrest or one of the other variable flow modes, in which case it does not seem to matter where the PDM trimmer is set.

That tells us the over-current sensing in the PDMs isn't triggering the alarm; rather, it's the under/zero-current sensing in the FSM which is doing it.
1) Roughly how long does the alarm sound for?
2) Did you try the tidal FSM R2 mod I suggested in post #2279?
3) I'll look into the expansion of the tidal system to see what further mods might be needed. Do you have room on the Tidal controller board (TTAM) to accommodate another CD4093 IC?

I'm glad I'm not footing your electricity bill

Edit: The current waveform in your new pumps may be quite different from that in the old ones, so the FSM (designed for the old ones) may respond differently. To give us a clue on current profile, can you determine how the voltage across the Rsense resistor in the PDM varies while the new pump is doing its reefcrest thing? Also, with the pump off, can you feel how many 'notches' there are when you rotate the impeller by hand?

 

[salty joe]

Across Rsense in reefcrest mode I get 0.28V for several seconds which drops to 0.16V for several seconds, causing a quick beep. Back up to 0.28V then down to 0.06V causing the alarm to sound until it goes back up to 0.28V. Then down to 0.08V, but that does not make a peep. Seems weird.

(The new controllers have a dial to adjust how fast the pump runs through the reefcrest cycle)

I have not done the FSM R2 mod.

I don't have any room on the existing boards but if we can pull off adding on to the tide, I was going to have a board dedicated to all the extra stuff and mount it beside the two additional pairs of PDMs.

When I rotate the impeller by hand the magnet stops it every 1/4 turn. (The old pumps impeller stop every 1/2 turn)

Thanks guys!

 

[alec_t]

I fed those Rsense measurements into a sim of the FSM and got the alarm to trip at the 0.06V and 0.08V points as expected but not at the 0.16V point. Not quite as you experienced, but your measurements are each some sort of average of what is probably a rather spikey waveform, so not surprising that simulation and reality didn't quite match up. As you say, weird that you didn't get a peep at the 0.08V point though. Also, with the pump rotor being a 4-pole type the current waveform during a rotation might be quite unlike that in the old pump so the sim may not model it well.
Be that as it may, by doing the FSM R2 mod you should (according to the sim) get no alarm trips at all for the whole of that reefcrest duration.

Simulation also shows you should be able to drive 4 further PDMs ok with the existing Tide module. U3c can provide a Vt signal to 4 PDMs without sweat and U3d can do likewise for the other 4 PDMs.
The Alarm section can be extended easily adding a respective 'LED + diode' string for each new PDM.

 

[salty joe]

Outstanding, thanks a whole bunch for checking that out. I'll get some parts ordered.

 

[salty joe]

The Alarm section can be extended easily adding a respective 'LED + diode' string for each new PDM.

It would be hard to extend the existing alarm module because the board the alarm module is on is a royal pain to remove to work on.
Would it be OK to make a seperate alarm module, dedicated to the additional four pumps?

 

[alec_t]

Would it be OK to make a seperate alarm module

Sure. Same principles as the existing one. Give us a shout if you need help on that.
Presumably you'll also be making another FSM? Did you get round to trying the mod to the present tidal FSM, to cure the phantom beep in the reefcrest mode?

 

[salty joe]

I just finished another 4 pump FSM and a seperate alarm module for those four pumps. The FSM mod is installed and I hope to find a little time tomorror after work to give it a bucket test. (I drained the tank-all the electronics were rock solid for that week or so-super nice job you guys!) Thanks!

 

[KeepItSimpleStupid]

joe

Did you test the pump back-up time, or don't you have a decent battery yet?

AND... It looks like one of my earlier suggestions of trying to use connectors or depluggable terminal strips came back to haunt you but your dealing with it OK. i,e It's a pain to remove. Pullling a a module, swapping a module is a real PITA.

The DIN rail movable modules was a hard sell, I'll admit, but it again could have helped here. It didn't look like your case is big enough for another module or two?

The third suggestion you did take - MAKE IT MODULAR. Aren't you glad you did.

And a Reminder, when everything is running again, record the initial voltages across Rsense at some consistent speed that you can reproduce. I'm hoping you can use this data to predict a failure. e.g. Look at initial, 3 month, 6 months etc., then decide on an interval like once a year or so.

You did a fine job!

 

[salty joe]

There was so much new stuff coming my way that I felt that going with what was already familiar was the only way I could get it done. Please don't think I did not appreciate your suggestions. And how, I am glad the PDMs are modular. Especially with 4 more to make.

I'll put the pumps on hi and record the V across Rsense for all pumps. Great idea-thanks.

 

[salty joe]

Adding another resistor paralell to R2 in the FSM cured the false alarm. Very nice fix-thank you!

What stinks is now I have a ground problem on the board I pulled. I found it by wiggling a terminal point. It's causing trouble with the filter pumps. I'll pull the board back off tomorrow. Ugg. Oh well. Shoulda listened to you, KISS!

 

[alec_t]

Glad the false alarm is cured. That fix will (says he confidently) still allow the FSM to operate with a genuine 'no-current' fault.
Shame about the ground point. Murphy playing his usual tricks

 

[salty joe]

A simple re-flow fixed the ground problem and the tide pumps in reefcrest mode no longer have false alarms.
But every five miutes or so, the wave pumps, running on hi, give me a little chirp. That would be less than 1/100 cycles for a false alarm. The V at Rsense is 0.02 for a split second before jumping up to 0.28 every time the pumps turn on. So it looks like the board needs to be pulled one more time to add the FSM mod for the wave pumps too. Am I on the mark here?

 

[alec_t]

Good to hear you solved the ground problem.

But every five miutes or so .....

There's always a "but" .

Am I on the mark here?

Spot on. Useful info re the Rsense voltage. If that mod doesn't do the trick another option, admittedly more involved, would be to increase the value of each of R3 to R6 in the FSM.

 

[salty joe]

There's always a "but" ..

Aint that the truth!
Thanks. I'll get that last FSM mod done in the morning. Meanwhile, the PDMs are getting done with empty spots for the FET, IC and terminal points until the parts arrive.

 

[salty joe]

It looks like the FSM board needs to be pulled again. I still get a chirp every few minutes from one of the four wave pumps. It's funny how that mod worked for the alarm sounding on the tide pumps on reefcrest mode, but not on the little chirp from the wave pumps on high.

What do you reccomend for R3-R6?

I have to say, the ability to look at the alarm module to see which pump has a problem is superb design. Thank you.

 

[alec_t]

It's funny how that mod worked for the alarm sounding on the tide pumps on reefcrest mode, but not on the little chirp from the wave pumps on high.

Presumably the new controller does something different when the pumps are on high. Perhaps a soft start? Odd, though, that it's just for one wave pump and not the others. That could be due to a slight difference in the pump itself, or in the grounding path, or in the Rsense resistance in the PDM, or component tolerances in the FSM.
I'd suggest somewhere in the 220k-330k range for R3-R6. That will increase the delay between low/no pump current detection and the fault signal being generated.