Help with Water Pump

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I'm happy to try to amalgamate the various suggestions to date to improve the design of the tidal simulator system, but I'd like to make sure we're all singing from the same hymn sheet.
Here's a list of features as I see it. Feel free to add/subtract/modify.

1) Reliability is key, but so is cost, so compromise may be necessary.
2) System is modular, consisting of:
...(a) Power supply,
...(b) 4 x pump driver modules,
...(c) Timer (programmer) module,
...(d) (optional) Speed controller.
3) Power supply
...(a) Set at ~ 20VDC,
...(b) Protected by reverse-biased 3A Schottky in each pump module.
4) Pump driver module
...(a) One per pump,
...(b) Controlled by 12V logic,
...(c) Separate signal and power ground connections,
...(d) Limits peak current instantaneously to ~5A (as per OEM controller),
...(d) Latches power off, until manually reset, if current exceeds ~1.5A for > ~ 1 sec,
...(e) Slow(ish) start/stop (probably not necessary if current is limited),
...(f) Has Schottky to protect power supply.
...(g) Main control element is n-MOSFET, unless Joe prefers the protected low-side switch suggested by KISS.
5) Timer module
...(a) Incorporates the 12V regulator,
...(b) Excludes the (unnecessary?) soft-start circuitry (part of the pump module?),
...(c) Provides 12V logic outputs to the pump driver modules.
6) Speed controller
...(a) A switched-mode buck converter with adjustable output (~ 10V?)
 
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@ronv
Close: 16 VDC max. Nice find
@Joe
Here is a link to products that I have used for a "construction" technique for control systems. This is one of the better limnks to illustrate how it works. **broken link removed**

This page doesn't use the Snaptrak systm, but shows typical "modules" that can be snapped intto DIN Rail. Snaptrak is just cuttable length of plastic that a certain sized PC board snaps into. Separately available clips allow the track to be snapped onto a piece of DIN RAIL.

DIN RAIL can come slotted and there are varius types. TS32 is probably the easiest to work with. It's 32 mm wide and looks like a U with ears. The ears sit about 1/8" from the surface.

In a typical industrial setting, DIN RAIL and WIRING DUCT and a enclosure with a back panel and terminal blocks comprise the basic system that acts as an Erector set for controls. Power supplies, relays, AC outlets, even Ethernet switches can be purchased for the rail.

To get an idea of what else is availbable, although not necessarily for this project, www.mouser.com has these DIN enclosures available: https://www.electro-tech-online.com/custompdfs/2012/06/hb4774.pdf They are not conducive to breadboarding.

I did some custom instrumentation using the Snaptrack/DIN rail construction inside of a rack case that turned out really nice.

It's a thought.
 
Pump Circuit

Here is a thought for a control circuit based on a 317 regulator.
I didn't have a 1.5 amp version in spice so the current limit resistor would need to be rescaled.
It would have slow start and over current shut down based on Alec's proposed circuit.
The voltage would only go down to 1.7 volts or so but that should be okay for a stalled pump. The 317 has all the bells and whistles to protect itself, so that should be OK. Give it a look. Maybe someone has a 1.5 amp version of the 317 to make it right.
 
@Alec_t on Post#603

Very nice feature summery. I have almost no complaints, and what I do have is minor to be sure.

When you say it should be "modular", is this for ease of construction by making a step by step assembly more understandable? Or is it so Joe can expand later on down the road? And does it have to be all THAT modular? Can we not combine the functions of speed control into the timer? Or less favorably, into the pump drivers? Also, where do all the modules insert into the circuit? Maybe a block diagram is in order...

From what you have said so far, I see it more or less like this...

View attachment 64934

But it could easily be any number of ways mind you.



4) Pump driver module
...(c) Separate signal and power ground connections.

Although it *IS* most certainly best practice and highly advisable, For this project separate grounds prolly have limited usefulness because.

(1) 12V logic is highly immune to noise, do to the logic level gap. (Which would require HUGE current spikes to traverse.)
(2) With respect to (1), the currents are fairly low, and most of the time they are also changing slowly so spikes are less likely.
(3) It's easy enough to make the logic IC's decoupling capacitors large enough to withstand noise without changing the schematic.
(4) We can make use of the fact that our enclosures thus far are tin boxes and implement a solid large area ground plane with ease.
(5) It's all going to eventually be connected somewhere anyway, though separate until the PSU is certainly preferred.
(6) Keeping modular construction on the table limits how much we can separate the two grounds, unless we run more wires.

If all we want to do is remove potential ground loops and lower the chances of a current spike from draining logic IC juice, then a fat ground and power conductor combined with fat decoupling capacitors should be sufficient IMO. Mind you I would be singing a different tune if we were talking 5 volt or lower logic combined with analog and power circuitry. Also as I said, this is a small thing.

Just my two cents.
 
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()blivion said:
@Alec_t on Post#603

Very nice feature summery. .
Click to expand...

+1. And thanks ()blivion for sharing your thoughts.



Thank you. I'm dying to fire up the soldering iron.

alec_t said:
1) Reliability is key, but so is cost, so compromise may be necessary..
Click to expand...


Sounds good to me.

alec_t said:
...(d) Latches power off, until manually reset, if current exceeds ~1.5A for > ~ 1 sec,.
Click to expand...


Would that shut down all four pumps or only the problem pump? Sounds like a fuse type thing. Great idea. I still can't get over the 10A fuse not going when 15A were being run through it.
alec_t;1065492 6) [U said:
Speed controller[/U]
...(a) A switched-mode buck converter with adjustable output (~ 10V?)
Click to expand...

Adjustable speed would be nice but not critical. So if it's a pain to write or is very complicated to build, no biggie.
The first tide circuit did EVERYTHING perfectly when running light bulbs. That's an amazing circuit you wrote, Alec. Plus you keep an open mind.
Thanks one and all for all the ideas and knowledge. This has been fun and I've learned a lot. Of course what I know about electronics would fit in any one of your little fingernails with room to spare. Thanks a million everbody!
 
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+1. And thanks ()blivion for sharing your thoughts.
Click to expand...

NP, and thanks for the +1. I'll try to keep watching this thread and inputting my thoughts as much as I think it will help.

That's an amazing circuit you wrote, Alec. Plus you keep an open mind.
Click to expand...

I agree. He has been instrumental in this whole project. From the first suggested timer circuit way back some moons ago, I knew he was on the ball. And he has consistently proven to be very capable and able to roll with the punches as they are thrown at him. If you two lived in my neighborhood, I would take you out and buy us some drinks. Many cheers to you Alec_t for work well done and to you Salty for a project that has proven vastly popular with this community.
 
@()blivion
Thanks for all the comments.
Your block diagram (nice graphics) is exactly as I envisaged the set-up; but I had forgotten the cup-holder . The modular approach (thank KISS) should both ease construction (we hope!), so that the project isn't overwhelming and the design can be tweaked in stages, and allow for future expansion/modification.
@Joe
Would that shut down all four pumps or only the problem pump?
Click to expand...
Only the problem one.
Sounds like a fuse type thing
Click to expand...
I'm in the process of trying to simulate the action of a resettable fuse such as the type Ronv linked to. Using that combined with a transistor-based shut-off I think we can get reasonable protection for both pump and controller.
This has been fun and I've learned a lot.
Click to expand...
I don't suppose the melt-down was fun . I've certainly had fun on the design side and I think we've all learned a lot more about BLDC motors.
 
One thing about 15A flowing through a 10A fuse. Well, the current wasn't measured. The wiring could have been such that it limited the current say to 8 amps, just by being resistive. If the wiring isn't rated to higher than the fuse, the circuit doesn't blow at a controlled place. Wire resistance is defined by R = pL/A where A is the cross-sectional area, L is the length and p or Rho is a material property called resistivity. Usually it's the resistivity of copper.

Wire tables will generally have ohms/1000 feet of wire.

Bad connections and/or solder joints also act as resistors and they could be limiting the current.

The most annoying fuse issue that happened to me TWICE. The second time is it wasn't a surprise anymore.

I was about 18 YO and working on a Decwriter II (a High speed 300 bps teletype device), No power. I removed the fuse, checked it with an ohmmeter and the fuse checked good. Still no power. I checked the voltage across the fuse and got 120 VAC. The fuse was open in circuit under load, but was closed when no current was flowing. The case of the "intermittent fuse"

alec said:
I don't suppose the melt-down was fun . I've certainly had fun on the design side and I think we've all learned a lot more about BLDC motors.
Click to expand...

You always learn stuff after a failure. One perplexing one that I was involved in investigating was an explosion of Hydrogen (2000 lb burst) without a fire. Oddly, enough the ventilation monitors and my shutdown design shut the system down. The Hydrogen alarm was in a box. Management working at peak efficiency.
 
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At last.... a draft of a beefed-up pump driver module ("PDM-Mk2" for ease of reference).
Operation:-
Supply volts = 24. Pump-motor coil resistance = 2.14Ω, inductance = 3.4mH (confirmed by KISS).
Pump ok, rotor not locked
0-max rpm in 0.4 sec (confirmed by Joe).
Pump peak current = 24/(2.14 + 0.33+ 0.04+ 0.02) = 9.5A (where .04 and .02 are the assumed resistances of the resettable fuse and the turned-on FET).
As the motor spins up its back-emf rises so the current draw ramps down to a steady-state ~1.1A after ~ 0.4 sec.
The voltage developed across current-sense resistor R8 is tapped off by the trimpot, set so that 9.5A is not quite enough to cause current to flow through zener D6 to turn on Q2.
During the current ramp the resettable fuse heats up, but 0.4 sec is too short for it to reach its trip point (assuming the right fuse is selected!).
Pump ok, rotor locked
Pump current remains at 9.5A instead of ramping down, so the fuse trips, hopefully after no more than ~1 sec. This raises the voltage on the trimpot to a value causing the zener to conduct, so Q2 turns on. Its collector current pulls down Q1 base so Q1 turns on and provides more base current for Q2. Q1 and Q2 are thus latched on until a momentary-action switch is pressed to reset the latch. Q2 switches off the FET (hence the pump) via D4 and Q1 collector going high provides an alarm output.
Pump short-circuited
Current is ~ 10.5A. Voltage on the trimpot is enough to cause zener current to flow immediately and the latch is set, switching off the FET in ~70mS. The fuse doesn't have time to trip.

Choosing the fuse will be important: too low a holding-current value may cause spurious trips during normal start-up of a good pump, whereas too high a value won't offer much protection and the pump coils or internal FETs may cook if the rotor locks. To get the speed of response needed I think the SMD package of fuse will be necessary. I have no practical experience of resettable fuses so will start another thread to seek advice.
 
Thanks for the link, KISS. Even using that to narrow down the choice leaves us a bit short on info though.
 
alec_t said:
At last.... a draft of a beefed-up pump driver module ("PDM-Mk2" for ease of reference).
.
Click to expand...

That was pretty darn quick-thanks, I appreciate that a lot.

Can MBRS340 still be repaced with 1N5822?
https://www.futurlec.com/Diodes/1N5822.shtml

An alarm, I love it! Would this work? Do I need four alarms?
**broken link removed**

Is this still a good choice for the MOSFET?
https://www.futurlec.com/Transistors/IRF3205.shtml

Can you give the critical specs (for this project) for the Zener diode BZX79C2V7

Please tell me if I have this right. Their will be four beefed up PDMs. If so, I can't see how to hook up with IC4093.
Does R1 (33K) in PDM-Mk2 replace R4 & R5 (10K) from post 367?

We talked about heavy duty jacks, but the pump plug does not appear very heavy duty at all. It melted along with the jack on that dark day. I'm thinking since the plug failed too, heavy duty jacks are of no benefit. Does that make sense?

Thanks, thanks, thanks.
 
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Can MBRS340 still be repaced with 1N5822?
Click to expand...
Sure. Almost any 3A Schottky diode.
Would this work? Do I need four alarms?
Click to expand...
Well I haven't drawn out an alarm module yet but, yes, that would do nicely. I see you get 2 for the money, but I was thinking all 4 DPMs could use a single buzzer.
Is this still a good choice for the MOSFET?
Click to expand...
Yes. I was assuming you'd salvage bits from your present build; or will you be starting from scratch? If you compare PDM-Mk2 with your present build you will notice many parts in common. Since there will be extra components I guess you'll need a different board layout, but instead, IMO, it would be preferable to build each PDM on its own little board. I like KISS's idea of going modular (though not necessarily with the full DIN kit he mentioned, unless you've got a rich Uncle!).
Can you give the critical specs (for this project) for the Zener diode BZX79C2V7
Click to expand...
Any 2.7V zener diode.
how to hook up with IC4093.
Click to expand...
I'll draw up a revised timer module schematic for that. Initially I'd be inclined to try one PDM.
Does R1 (33K) in PDM-Mk2 replace R4 & R5 (10K) from post 367?
Click to expand...
R1 replaces R5/R6/D3 in my version of the dwg (though I'm not sure if my version has the same component numbering as the one I posted). All will be clear (famous last words) from the revised timer module.
I'm thinking since the plug failed too, heavy duty jacks are of no benefit. Does that make sense?
Click to expand...
It only makes sense if the pumps are still under warranty. They'd be better fitted with heavier duty plugs and corresponding sockets for reliability. Just for testing you can probably get away with the present connectors. Just watch out for smoke signals

Edit: If going modular, connectors such as
https://www.futurlec.com/ConnTerm.shtml
are useful for wire terminations.
 
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The 1812L150/24 https://www.electro-tech-online.com/custompdfs/2012/06/Littelfuse_PTC_1812L-1.pdf , I think, seems reasonable. 0.3 s at 8 Amp to trip. 24V 1.5 A nominal. I found them at www.newark.com. I used the selection guide there.

@alec
The Screw terminal/header/sockets are definably the way to go especially for motor and power. A few different sizes can prevent inadvertent insertion. If using a perf-board, you have to watch the spacing. The drawback to most of the other wire to board connectors is the expensive crimp tool. Usually $50+ USD.
 
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@KISS
Yes, those disc-form PTCs in post #617are too slow; hence the need for SMD parts.
The 1812L150-24 spec say it trips at 1.5 sec (the 1812L150 is 0.3s and the 1812L150-12 is 0.5s). So perhaps one of those 3? Those are max trip times. I can't get info on tolerance so what might the min times be I wonder?

@Joe
Here's the new timer module. It also incorporates the 12V supply and the alarm circuitry (not worthwhile to have a separate module just for the few alarm components), so let's call it the "TAM".
N.b I have removed what was diode D1 in the PDM-Mk2 and put it instead as D11 in this TAM, thus avoiding an extra Schottky diode in each PDM.
Operation:-
The timer part functions as before. Gates U3c and U3d of the 4093 each drive two PDMs.
Any incoming hi alarm signal turns on a respective LED and also Q1, thus sounding the buzzer.
The ground leg of the 12V regulator is probably the best point for linking the heavier conductor PowerGnd wire to the lighter conductor SignalGnd wire.
 
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