Help with Water Pump

[alec_t]

I'm losing track of how many pumps do what . If you use the controller as in the link just posted (except that the 24V input to our controller will be via the diodes for back-up), then each PDM will need a separate Vt signal derived from a respective gate output of U1. So yes, minor surgery. Good luck with that.

 

[salty joe]

I put the circuit together to run two pairs of pumps in the wave mode. That is an amazing circuit. Wow, only 5 additional parts. It works perfectly, thank you! I am thoroughly impressed. Again.
"I'm losing track of how many pumps do what "
The tank will have two pairs of pumps in the wave mode and two pairs of pumps in the tide mode. (8 pumps) Tomorrow, I’ll add two pairs of pumps in the tide mode to the bench/bucket test and hope it goes as well as today. Those are all new pumps. They move some serious water. I anticipate having to tune them down. A very good problem to have.
The PS backup is doing its thing. Thanks very much for that. I’m lucky I ran into the diode problem when I did.
A pair of the old pumps will be used to move water through the filter. They will be driven by an old PS and a pair of PDMs with no controller.

 

[alec_t]

Glad to hear it's all systems go now! Does your wife still think you're building her a luxury jacuzzi?
Will your filter pumps (which I gather are the most crucial ones) have a backup supply?

 

[salty joe]

My wife thinks I'm a little bit crazy-as long as I help around the house she's mostly OK with my tank project. She's excited to get water in it too!

Yes, backup for the filter pumps would be great. I have the circuit mostly built for that, I was hoping we could get after it when the bench test is done. Thanks for asking.

 

[salty joe]

Quite a gob of wires for 8 pumps, isn't it? I promise to make things a little neater when everything is done.

Everything works as planned except we have 24V coming the wrong way through at least one PS backup diode and into the PDM again. I replaced 3 diodes yesterday and checked them before and after installation. This diode is not one of those 3, but I checked all diodes and they all looked good yesterday. Any ideas?

 

[alec_t]

Wow. Are you sure that's not a telephone exhange you've got there?. I can see now why KISS was advocating a DIN rail system of interconnected modules.
As for the spurious 24V, logically it seems either a diode is faulty (despite your checking) or your telephone exchange has a crossed line. I can only suggest re-checking.

 

[salty joe]

As crazy as that bird's nest looks, I was methodical about hookups. I am confident there. The two pairs of pumps on tide (flick too!) and two pairs of pumps on wave seem happy to do their thing.

The 8 PS backup diodes are lined up in a straight row accompanied by 9 terminal connections. A bare wire is soldered to the cathodes and connected to the 9th terminal. After disconnecting all diodes and starting with diode #1, here are the values I just took from my DMM on diode setting; 1, 1, 1, 003, 641, 621, 626, 621. With the DMM probes reversed-1, 046, 1, 003, 1, 1, 1, 1.
Two days ago, before hooking up pumps, I got values from all 8 diodes that looked like the current values of diodes 5-8. Since then, I ran the pumps for 5-10 minutes.
Last night I happened to notice an LED was lit up on a PDM that had no PS plugged into it. Sure enough, that pump was running and there was 24V coming out of that anode.

 

[alec_t]

here are the values I just took from my DMM on diode setting; 1, 1, 1, 003, 641, 621, 626, 621.

The first four are clearly quite different from the last four. They should all be roughly the same I don't like the look of the first four. '1' is the reading you should get when a diode is reverse-biased; ~600-800 when forward-biased. I wonder if some of the diodes have beeen wrongly marked as to which is the anode/cathode? Cathode should have a colored band. If a diode was connected in reverse from what it should have been then it and at least one other would fry because they would pass pump current (amps), i.e. much more than the rated 200mA. I'd suggest test all your stock of diodes to ensure the polarity is as indicated by the colored band.

 

[salty joe]

I put the negative terminal of my DMM on the cathode (which is marked by a band) on 10 of the new 1N4148 diodes and got values around 625 on all of them. The diodes that are getting fried are from this batch.
The thing is, a couple days ago after I replaced diodes 1, 2 and 5, I checked all 8 diodes and got values of around 625-646 on every single one. This is after they were installed. I put the negative probe on a cathode, since they are connected, and moved the positive probe to each individual anode. After running the pumps for 5-10 minutes, four diodes are goners.
Could it be that a whole lot more than 200ma is going through the diodes on the way to the controller? Can that be checked with my low budget DMM? Grasping at straws here. Thanks for kicking this around.

BTW, the gob of wires is not as bad as it looks. The picture includes the 8 full length coils of wire that will be used when these pumps are in the tank. I wanted the bench test to be realistic. Plus the new controllers won't be near the PDMs and our controllers.

BTW, BTW, the little light sensor https://www.electro-tech-online.com/attachments/tank-011-jpg.73813/ is a variable resistor of sorts-the resistance changes with light intensity. What a neat little thing! A 2K2 resistor in place of the light sensor nicely defeats the night mode.

 

[alec_t]

Could it be that a whole lot more than 200ma is going through the diodes on the way to the controller?

That's a posssibility, though in theory it shouldn't happen. It may be that there's a voltage spike when all the power supplies start up which is killing the diodes. So, as you suggested earlier, it would be worth trying beefier diodes such as 1N4007 (which are rated at 1kV, 1A). Personally I think using eight PS for back-up is a bit OTT; I would use only two (or at most 3). You might be able to salvage some 1N4007's from the mains input side of some junk electronics kit (old TV, video etc).

A 2K2 resistor in place of the light sensor nicely defeats the night mode.

That's a convenient solution.

 

[salty joe]

Thanks Alec, 1N4007 are on the way. I can see where it seems OTT to back up all 8 PS, but it makes the hookup a little easier since every PS 24V gets the same treatment. It's such an easy circuit to build and besides it makes me feel good.

In the meantime, is there any chance we could work on battery backup for the two filter pumps?

I tried to insert a smile on this post, but this site does not like my computer.

 

[alec_t]

OK, I see your reason for 8 PS.
I drew up a schematic some while ago for the battery backup/filter pumps but not sure if I posted it? Anyway, I'll dig it out and revise it. Will you be using just the old pumps and an old power supply for those?

Edit: Here's a couple of spare smilies for you

 

[salty joe]

Hey, thanks for the smiles, I can always a smile.

Yes, I planned on two old pumps, two PDMs and an old PS for the filter pumps.

Here is the schematic I have started. https://www.electro-tech-online.com/attachments/backedupsupplymk3-gif.72192/

You mentioned awhile ago that it might be good to insert a fuse somewhere, I can't remembeer where.
Would it be very doable to set up a switch like we used on the PDM alarm test to stop the filter pumps for a set time, say 10- 15 minutes? Thanks for everything.

 

[alec_t]

Here is the schematic I have

That's the one. So I did post it. However, it assumed you would be using two new power supplies. I'll revise it and re-post.
If you have a spare CD40106 left we can use that to add a 15 min timer. I'll work on it.
BTW, re the 8-diode power back-up, with power off double check that there is no connection from their commoned cathodes to anything except the 7812 voltage regulator input and its associated input capacitors/Schottky diode; in particular no low-resistance connection to any PDM.

 

[salty joe]

I do have a CD40106, that's super-Thanks!

I'll go over the 24V input on our controller with a fine toothed comb.

I do have two old PS, would it complicate things to use both PS? Maybe each pump with a dedicated PS for redundancy?

 

[alec_t]

I do have two old PS, would it complicate things to use both PS? Maybe each pump with a dedicated PS for redundancy?

Not complicated, but the battery is already providing power back-up to these pumps so do we really need the redundancy? Your call.

 

[salty joe]

Yeah, since I have two old PS and if it won't complicate things we might as well have a dedicated PS for each pump. Then each PS could be plugged into different GFI receptacles. I hate the idea of a single GFI trip shutting down all filtration.

 

[salty joe]

BTW, re the 8-diode power back-up, with power off double check that there is no connection from their commoned cathodes to anything except the 7812 voltage regulator input and its associated input capacitors/Schottky diode; in particular no low-resistance connection to any PDM.

The 24V feeding our controller is connected to the first leg of the 7812, the + legs of a 100uf and a 0.1uf cap and a 2K2 resistor that is connected to this LED. https://www.ebay.com/itm/15-x-LED-3...ultDomain_0&hash=item3a6966a45d#ht_1323wt_806

This is the only unauthorized addition to all this electronic work. I hope it's not the problem because I'd be a little embarrassed, on the other hand I hope it is the problem because it’d be problem solved.

 

[alec_t]

No, that LED won't be the problem. If there's nothing else connected at the 24V feed point then it looks as though diode breakdown occurred for whatever reason.
Do you also have a spare CD4020 IC?

 

[salty joe]

Yes, I do have a few CD4020.