Help with Water Pump

[alec_t]

What I meant is, only the filter pump 12.6V system was hooked up. The alarm module is the only 12V part that gets connected to the 12.6V filter pump system.

That's right. But if the SigGnds of the filter system and alarm module were linked the alarm LEDs for the filter channels should have lit.

 

[salty joe]

If I have this right, you are telling me it's OK to connect the ground from the 12.6V system with the ground from the 12V system. Is that correct?

 

[alec_t]

At one point (the mains earth point) the respective star grounds (see my power/gnd pictures) of the tidal system, wave system and filter system all get connected together, effectively forming a giant star ground. So at the mains earth point the 12.6 (filter pump) system ground will indeed connect with the grounds of the other (12V) systems. Mains earth is the ultimate reference point. If the different system grounds are kept separate up to that point then currents in one system can't adversely affect the other systems. That is the purpose of star grounding.
The alarm module is a special case since it receives signals from the tidal, wave and filter systems. It's +ve supply (which goes only to the buzzer) is presently 12V but, for reasons I mentioned in my PM, would perhaps be better taken from the 12.6V rail instead. (You could then think of the alarm module as part of the filter pump system.)

Edit: Now that you've got the filter pump system up and running you might like to consider the add-on in the attached.
Although the battery charger has both current-limiting (for the bulk charge) and voltage-limiting (for the top-up charge), further research indicates a refinement is to knock back the charger voltage from the 13.8V limit to 13.6V once the battery is fully charged if it's to be left on standby continuously. The add-on will do this by sensing when the charge current has dropped to ~70mA. It uses an LM324 which MUST be separate from any other since it runs from ~20V. The pic shows the 4 connection points to the FPPB-Mk2.

 

[salty joe]

Thank you Alec. I'll get that mod worked into the system. Many thanks.

 

[alec_t]

It's only a few extra components, with parts/values you may already have, and can be built on its own for addition at a later date or incorporated on the FPPB board. Should prolong battery life a bit since it terminates what would otherwise be a continuous trickle charge. Pity it can't use one of the spare LM324 opamps in the filter system FSM.

 

[salty joe]

I do have all those parts, and got started but have a question.

Should a 0.1uf cap be installed between pins 4 & 11 and should pin 11 be connected to signal ground and pin 4 to 12.6V? I'm kind of assuming you know I'll just do that, on the other hand I'm not sure, it looks like LM324 gets enegized from Vext.
Thanks.

 

[alec_t]

Oops, there's me making too many assumptions again and you're right to raise the questions .

Should a 0.1uf cap be installed between pins 4 & 11

Yes. You're getting the hang of things!

should pin 11 be connected to signal ground

It connects to PwrGnd actually (the only ground in the FPPB).

pin 4 to 12.6V?

No.

it looks like LM324 gets energized from Vext.

Spot on. I used that label to distinguish from the other + supply voltages. In other words it gets the same voltage as the input of the charger.

 

[salty joe]

Thanks-I got burned a couple times on this project when I thought "this must be how it goes". We are sooo close, caution is the word.

 

[alec_t]

Yes indeedy.
BTW, if you fancy an indication that charging is taking place you could connect one end of a 1k8 resistor to the output pin of the U2a opamp, connect the other end of that resistor to the anode of a LED (green?), and connect the LED cathode to PowerGnd.
Incidentally, when you were setting the 317 output pin voltage to 13.8 did you have the battery disconnected?

 

[salty joe]

I do like the idea of a charge indicator. Just want to make sure I've got it right-the 1K8 would go between D1 and the LM324. In other words, we are using the same three LM324 pins as the mod. Is that right? I just finished the mod, I'm sure I can sqeeze a few more parts in.

I don't remember if I had the battery connected or not when I set the 13.8V. It sounds like I should disconnect the battery and re check.

Would it be OK to connect the unused inputs from this LM324 to the power ground that is connected to pin 11?

 

[alec_t]

the 1K8 would go between D1 and the LM324. In other words, we are using the same three LM324 pins as the mod. Is that right?

Correct. Like this (the LED cathode ground being PowerGnd):

I don't remember if I had the battery connected or not when I set the 13.8V. It sounds like I should disconnect the battery and re check.

Good idea. The voltage setting is critical to correct charging. It's the voltage at the '317 output pin you need to measure; not at the '12.6V' output. I take it you've got the '317 heatsinked? It will get hot when putting ~ 0.5A into the battery.

Would it be OK to connect the unused inputs from this LM324 to the power ground that is connected to pin 11?

Yes. I was going to mention that but you beat me to it

 

[alec_t]

I'm keeping my fingers crossed that the added LM324 will work in practice as it does in simulation. Its signal inputs are above the specified "supply voltage - 1.5V" limit, so we're pushing our luck. Two different simulation models think its ok, but in the event that it's not then a couple of extra resistors and a 2k trimmer will do the trick (hopefully there's room to squeeze them in if necessary).

 

[salty joe]

The '317 is on a heatsink, thanks for making sure. Heck yes, if we need to add a few parts they'll fit somewhere. Thanks.

 

[alec_t]

.....and another minor tweak (groan ). The perceived wisdom is that for a battery left on float charge there needs to be some reduction of the charging voltage as temperature increases. This could be done by replacing R9 in the post #2091 pic with a 68k NTC (= Negative Temperature Coefficient) thermistor. Only a few cents, next time you're ordering components. Ideally the thermistor would be in thermal contact with the battery and connected back to the pcb via a screened pair of insulated wires, or at least a twisted pair.

 

[KeepItSimpleStupid]

While cruising the net saw this https://code.google.com/p/marelab-solar/

 

[salty joe]

Hi guys- just returned and will need a day or so to lose the jet lag. I’m anxious to fire up the soldering iron, but that would be a very bad idea today.
BTW, it was no problem bringing a nice rock home! I did get a couple funny looks, though. It will be the main focal point.

.....and another minor tweak .

Thanks for getting ahead of so many potential trouble spots.

Ideally the thermistor would be in thermal contact with the battery.

IDK for sure, but the shell of the battery appears to made of polypropylene. If that’s the case, no pun intended, I don’t think there’s glue that will stick. Maybe time to break out the Gorilla Tape.
I’ll start with twisted wire and if that’s not good enough, I’ll shield the wire.

While cruising the net saw this https://code.google.com/p/marelab-solar/

I guess that’s what ()blivion advocated from the getgo. It does look very cool.

 

[KeepItSimpleStupid]

Joe:

That cool Kapton tape I sent you would work fine and it's easily removeable. I've seen some designs that use the battery terminal as te place to mount the thermister.
For a 10K PTC, I'm seeing surfact mount and resistro like available. They tend to pot the sensing device on the battery terminal Fast-On or whatever.

 

[alec_t]

A blob of Blu-tak (or whatever the equivalent is in the US) would also do for keeping the thermistor in place. Its thermal conductivity should be more than adequate but in any event is non-critical since temperature change will be gradual.

 

[salty joe]

I got the output of the LM317 adjusted to 13.83Vwith the battery disconnected. I’m glad that won’t need any more adjustments-the tiniest turn on that pot changes the V a lot.

The signal ground from the 12V alarm module is now connected to the ground from the 12.6V filter pumps and the alarm LED now works for the filter pumps.

The green LED to indicate the battery is being charged stays on no matter what, when there is power. If the pumps are unplugged and running off the battery, the green LED is on. I’ll go over it tomorrow with a fine toothed comb.

Also, the alarm LED does not light up when the filter pumps are unplugged. I’ll have to double check the FSM. I wondered if maybe because the pumps had power from the battery, the FSM did not make the alarm LED light up?

Every other detail on the filter pump/battery backup looks good. After these pesky little bugs get worked out, we’ll be ready for a full system test run.
Thanks very much.

 

[alec_t]

I expect the green LED issue is because the LM324 in reality isn't working as per the simulation, as I mentioned in post #2092. I'll look into a fix.

I wondered if maybe because the pumps had power from the battery, the FSM did not make the alarm LED light up?

That's correct. The FSM detects when the pumps are commanded to run but for some reason are not drawing current.