Help with Water Pump

[salty joe]

Pigtail is what I did KISS. And yeah I used plastic boxes so the grounds are just wired together. Gotta love the redundancy.
No master GFI Alec, so that's cool.
Thanks all.

 

[salty joe]

I decided to get the last pair of PDMs (7th and 8th) working before starting the emergency backup. I found a signal ground that I missed about halfway into checking every connection. Now both PDMs toggle pumps, but the alarm LEDs for both PDMs stay on-even while the pumps are toggling along. As soon as the pumps stop, the alarm LED goes off. In other words, the alarm LEDs are sychronized with the pump LEDs.

I wondered if anyone had a "check this first idea" before I start back on checking every single connection.

 

[alec_t]

Check all pin connections of the PDM ICs first.

 

[KeepItSimpleStupid]

Joe:

Look at the base of Q2 to ground before and after pressing Trip Test. It should change.

 

[salty joe]

As I was checking the pin connections out I realized that that fault (pin 12 on the IC) was not grounded. So now we have 4 pairs of good PDMs. Thanks guys.
Tomorrow I'll start emergency backup for the two filter pumps.

Should the two filter pumps not be powered by two independant GFIs? I was wondering, what would happen with emergency backup if the filter pumps were connected to individual independant GFIs and only one GFI tripped?

 

[KeepItSimpleStupid]

@Joe

I believe your 24 VDC supply provides an isolated 24 VDC. 24 VDC under 100 W is considered Class II and as long as it's protected by a fuse or a PTC thermister it does not require conduit or any other protections. 24 VAC or VDC is considered a "Safe" voltage.

The GFCI would really only be protecting the AC side of the system, not the DC side.

---

Without control power, the pumps should be off and without pump power, the pumps should be off.

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Thinking ahead for the battery side of things, if you can limit the current to 7 Amps or so (<100 W) and fuse at the battery, conduit would not be required.
Just thinking ahead.

 

[alec_t]

I was wondering, what would happen with emergency backup if the filter pumps were connected to individual independant GFIs and only one GFI tripped?

Only one pump should switch off.
I think GFI regulations your side of the pond must be different from here. Here, a single GFI would normally be used to protect all outlets served by a single ring mains circuit.

 

[salty joe]

OK, thanks. I was concerned about electronic "confusion" if one GFI tripped and emergency backup was called for, while the other filter pump was still connected to a live GFI.

Around here, several receptacles are usually run in series behind a GFI, but I did not want a problem with one component shutting down half of the reef tank.

On to emergency backup.

 

[salty joe]

For backed up power;

I have three 7.5A Schottkey diodes; can one be used for D2? This is the only Schottkey I have that accepts a heat sink.

I have a 1 ohm 5W resistor. That's OK for R1, isn't it?

Here are my other Schottkeys. Will one of them work for D1?

https://www.ebay.com/itm/20-x-1N582...ultDomain_0&hash=item3a71fbaaa2#ht_1387wt_803

https://www.ebay.com/itm/20-x-1N581...ultDomain_0&hash=item3cbb268d88#ht_1424wt_803

A snubber was mentioned awhile ago-should I add one?
Thanks.

 

[alec_t]

I have three 7.5A Schottkey diodes; can one be used for D2?

That's OTT if you mean the D2 shown across the '317 (not the D2 in the PDM). A 1A diode (as per second link) would suffice.

I have a 1 ohm 5W resistor. That's OK for R1, isn't it?

Yes, but OTT.

Here are my other Schottkeys. Will one of them work for D1?

Use the 3A diode (as per first link).

A snubber was mentioned awhile ago-should I add one?

I would.

 

[salty joe]

Thank you.
Am I correct to assume two snubbers will be used, and they will be connected between pump positive 1 and power ground and pump positive 2 and power ground?

 

[4pyros]

You can use parallel diodes also.
Smaller, cheaper, and less voltage drop.

 

[salty joe]

Will you guys please tell me if I have the trimmer in backup power hooked up correctly?
I connected the junction of LM317 ADJ/Q2 collector and R4 to one leg of the 2K trimmer. I connected the other two legs of the 2K trimmer to power ground along with –legs of C1 & C2, Q2 emitter and the connection for the negative battery terminal.
Also, to the right of LM317 OUT is +12. Does this +12 get connected to a 12V terminal point on the controller?

 

[alec_t]

Am I correct to assume two snubbers will be used

I was forgetting we're talking new controllers/pumps. Unless you can fit snubbers directly across the pump terminals forget them.

One end leg of the trimmer goes to R4, the other end leg goes to PowerGnd, the wiper can go to either end leg.

Does this +12 get connected to a 12V terminal point on the controller?

No. That output is redundant (a hangover from when we considered backup for the old pumps).

 

[salty joe]

Did you find this post helpful?
I certainly did!
I only have enough 7.5A Schottkeys on hand for one try. After hooking up the trimmer, I was unsure so I stopped. I think we're in good shape-thanks.

All PDMs have a snubber across the pump leads, will that do the trick?

It's noted on the backed up power schematic not to connect +24SupplyNew to the +Supply input of the PDMs. But +24SupplyNew is shown going into the anode of D2 from the existing PDM.

 

[alec_t]

All PDMs have a snubber across the pump leads, will that do the trick?

No, because the pump leads (Pump+, Pump-) will now go to the OEM controller input rather than the pump.

It's noted on the backed up power schematic not to connect +24SupplyNew to the +Supply input of the PDMs. But +24SupplyNew is shown going into the anode of D2 from the existing PDM.

Ignore that note. Also, the +12V output from the back-up system is not redundant, it's needed for the PDMs. Apologies.

 

[salty joe]

Thanks Alec.
The new pumps come with a nice little controller, but it doesn't offer speed control for the different modes- just high, low and four other wave/pulse modes. I found a 10K resistor in that controller that has 2.75V across it in high and 0 across it in low. The 5V line that I'm pretty sure controls pump speed has 5V at high and 2.43V at low.

Given that there seems to be a 10K resistor involved in speed control, do you think installing a 10K pot on the 5V line might give speed control to all modes?

 

[alec_t]

I don't think the 10k resistor directly affects speed, even if its voltage varies in sympathy with the '5V' line. Tracing back from the 5V line (yellow wire), it connects via R11 (looks like 1k) to pin 11 of the IC, which is presumably putting out a PWM signal. An electrolytic cap (C8?) from the wire to ground smoothes the PWM signal. If R11 is indeed 1k then a 25k pot could perhaps be connected between the '5V' line and ground, and a speed control voltage could be taken from the pot wiper. This might or might not work, depending on the control input characteristics of the pump. It might be necessary to reduce the pot value, at the expense of a reduction in the max speed of the pump. (A 10k pot would give ~10% max speed reduction).

 

[KeepItSimpleStupid]

@alec
I have to hand it to you on the way you handled your recent mistake. Absolutely ingenious. You put it there on purpose.

@alec
GFI's on this side of the pond.
We don't generally have a GFCI on the entire building and for the most part GFCI's are required only in certain locations such as near water, the kitchen and outside. I'm not exactly sure what the new code is, but ARC FAULT is becoming more of an issue all around. I think they are required for almost any living area now. Where I live, we still have fuses. Some insurance companies will not insure you unless you have breakers. You are grandfathered until you do major remodeling. The porch and an outside receptacle has a GFCI at home. That's it. I use a hair dryer with a built-in GFCI and a carpet sweeper with a built-in GFCI. It would probably be a good idea to get a small cord with a GFCI in the middle of it. I just felt it was very important to have a GFCI outside.

Things like two 20 Amp GFCI circuits for the kitchen and a 20 A GFCI separate feed to the bathroom won't cut it until the service gets upgraded. That's like a $1000 to $2000 USD expense. In our case the feed has to be moved and a disconnect placed on the outside of the building.

 

[salty joe]

If R11 is indeed 1k then a 25k pot could perhaps be connected between the '5V' line and ground, and a speed control voltage could be taken from the pot wiper. This might or might not work, depending on the control input characteristics of the pump.

R11 is 1K. I do want to give it try. To hook the pot or trimmer up, one leg to the 5V line, one leg to ground and the wiper can be connected to either leg. Is that right? I could put a trimmer on the side of the controller pretty easily, I think. If 25K doesn’t do it, I’ll throw in the towel. It’s not worth sacrificing top speed for.
I have to tell you, I am amazed what you can ascertain from a picture!