Help with Water Pump

[alec_t]

Here's the proposed add-on Fault Sensor Module (FSM) for detecting the situation that Vt is high (i.e pump nominally on) but there is no pump current. (With hindsight a variation of it it could also have been used to detect a locked rotor but with pump drawing current.....but we won't go there )
View attachment 68771
Operation
U1 is a quad op-amp so can handle 4 pumps. Each amp is used as a comparator, comparing the individual voltage Isense with a common 140mV reference derived by R1/R2. Consider the first section. Providing pump 1 current (pulsed or continuous) exceeds ~0.5A (Isense1 > 140mV) the amp output is low, discharging C3. If current fails then C3 charges (providing Vt1 is high) and signal Fault1 rises above 7V (the upper Schmitt threshold of gate U1d in the PDM) in ~ 1.2s and operates the alarm.
If this module is used with paired pumps then one Vt control signal (from U3c of the timer) should be fed to two of Vt1-Vt4 and the other Vt signal (from U3d of the timer) should be fed to the other two. Each PDM will need its own Fault input signal.

Re the alarm set-up, I think you've presently got multiple sounders, Joe?
Way back when, I did post a "Tidal-timer, Power, Alarm and Speed-set Module (TPASM)" which combined various alarm inputs to drive a common sounder, but lit individual alarm LEDs.

 

[KeepItSimpleStupid]

But... Wouldn't you think that locked-rotor might be more common? As the friction increases and or the pump gets dirty, the pump could stop? Only Joe has seen these pumps mechanically up close and personal.

 

[ronv]

Here's the proposed add-on Fault Sensor Module (FSM) for detecting the situation that Vt is high (i.e pump nominally on) but there is no pump current. (With hindsight a variation of it it could also have been used to detect a locked rotor but with pump drawing current.....but we won't go there )

I was just thinking that if the driver ic turns itself off after a second with no rotation the same thing would replace all the latch stuff. Oh well.

On a side note- There is quite a bit of circuitry in the test circuit compared to what is being tested. Are you convinced we haven't just raised the failure rate? I've had this type of problem in the past with harware diagnostics so I'm a little sensitive.

 

[alec_t]

But... Wouldn't you think that locked-rotor might be more common?

Yes I would. The add-on is entirely optional. Just trying to cover all bases (or at least as many as reasonably practical).

I was just thinking that if the driver ic turns itself off after a second with no rotation the same thing would replace all the latch stuff.

The problem is we just can't be sure what the IC is or does. Hence the back-up.

There is quite a bit of circuitry in the test circuit compared to what is being tested. Are you convinced we haven't just raised the failure rate?

I think it's unlikely but I see where you're coming from. If the add-on fails we just get no alarm from a pump going open-circuit (e.g. if a lead is damaged or a plug is inadvertently pulled out), so we're surely no worse off? The OEM system provides no alarm anyway. Do you have any suggestion, Ronv, for a simpler 'Vt is high but no current' check?

 

[ronv]

No, No better ideas, but it is easy to find out if the hall IC provides locked rotor protection. If it does the single circuit would provide an alarm for both open and shorted pump eliminating quite a few components. But as you say that probably is a solution past its time. Now its just curiousity.

 

[salty joe]

Re the alarm set-up, I think you've presently got multiple sounders, Joe?
Way back when, I did post a "Tidal-timer, Power, Alarm and Speed-set Module (TPASM)" which combined various alarm inputs to drive a common sounder, but lit individual alarm LEDs.

Yes, I've been adding a little piezo on each PDM. Could the + side of all eight alarms (eight PDMs) be tied together and fed to a piezo like this? https://www.ebay.com/itm/Extremely-...742?pt=LH_DefaultDomain_0&hash=item4aba2e426e Even though there will be two seperate power supplies? It would be super to use a single loud alarm and then look to see which LED is off for the problem pump. If it's not that simple , I'll go back and find TPASM. Thanks very much-thanks all.

 

[KeepItSimpleStupid]

Joe:

An LED off (or at least the one going to the motor) doesn't mean the pump is in alarm AND the piezo on doesn't mean the unit is in alarm.

Although, with the current PDM, you can add 2 diodes and 1 resistor to each PDM to OR the alarm signal to a specific alarm LED and the single piezo.

I can't remember if the "alarm module" has more smarts.

With two power supplies (actually 3, if you count +12), you will have to connect the grounds together.

 

[alec_t]

To save you digging out the TPASM schematic, here's the relevant alarm section:
View attachment 68804
You can extend it easily to 8 PDMs and drive a loud sounder as is. If you want mega-sound you could replace the transistor with one of your FETs

 

[KeepItSimpleStupid]

@alec

I like that circuit. Kinda clever.

 

[salty joe]

@alec

I like that circuit. Kinda clever.

+1. When the alarm sounds, the LED for the problem pump would be lit. Is that right?
Thank you Alec for finding that, thanks very much for writing it in the first place. I will use it for sure.

With the FSM hooked up, will it use the same alarm as the PDMs use?

 

[ronv]

Are the regular diodes needed?

 

[()blivion]

When the alarm sounds, the LED for the problem pump would be lit. Is that right?

Yes, each LED should indicate which pump tripped the alarm at the time.

Are the regular diodes needed?

I wondered that myself when he first posted the circuit. The LED's themselves are diodes after all.

Also, when I simulated it, there were some problems if more than one pump managed to trip at the same time. I can't remember what they were exactly as it was an unlikely and minor problem. Something like exceeding Ibe of Q1 or the LED's dimming a significant amount. IDK, but it was nothing serious so I didn't mention it.

 

[KeepItSimpleStupid]

Also, when I simulated it, there were some problems if more than one pump managed to trip at the same time.

I saw that too by inspection.

 

[alec_t]

When the alarm sounds, the LED for the problem pump would be lit. Is that right?

Yes.

With the FSM hooked up, will it use the same alarm as the PDMs use?

Yes. LEDs for the FSM would be optional. For example, the Fault1 output of the FSM could couple via a 1N4148 diode to the left end of R1 in the alarm module. Or you could swap the positions of D1 and D5 then connect the Fault1 signal via a 1N4148 to the anode of D1, so that Alarm1 or Fault1 would light D1 if there was a problem with Pump1.

Edit: Ignore the last 3 sentences, I was forgetting the hook added to PDM-Mk15.

Are the regular diodes needed?

Yes: otherwise the reverse voltage rating of an LED would be exceeded.

Also, when I simulated it, there were some problems if more than one pump managed to trip at the same time.

I think the only 'problem' is that two LEDs on simultaneously result in them drawing roughly (depending on their individual characteristics) half the 8mA current they would draw if energised individually. So choose high-brightness types .

 

[ronv]

Yes: otherwise the reverse voltage rating of an LED would be exceeded.

But the alarm signals are open collector not ground so I don't see a reverse voltage path.

 

[alec_t]

Good point.
When I drew up the circuit originally I hadn't decided what all the alarm sources would be. Ok, scrub D5-8, D11, D12 from the alarm module.

 

[alec_t]

I've just edited post #1354 re the FSM connection. Must have been asleep when I posted . The addition of alarm inputs as described in post #1354 would not work with the FSM because its Fault outputs need to drive into a high impedance, but could work with other types of fault monitoring system.

With the FSM hooked up, will it use the same alarm as the PDMs use?

Yes, if you use the Mk15 version of the PDM. Connect the Fault output signals from the FSM to respective Fault input terminals of the PDMs. Each PDM has diodes D10/D11 which 'OR' the over-current or lack-of-current alarm states of the relevant pump.
The FSM can be extended to handle more than 4 pumps, by replicating the components shown between the vertical dotted lines.
Joe, would it help if I drew a block diagram showing the interconnections of the various modules in the system as I envisage it?

 

[salty joe]

Yes, Alec that would without a doubt be helpful. Thanks very much.
I hope to start soldering PDMs this weekend.
Thanks all for all the fine tuning and tweaking. Thanks for kicking this around.

 

[salty joe]

Alec, I forgot to mention that the speed module will only be hooked up to a single pair of pumps. Sorry.

 

[alec_t]

Ok. Here's how I see it.
View attachment 68843