Help with Water Pump

[salty joe]

KISS, IC number is 10610-under that it has SDC 7500. I couldn't find a data sheet on it.
D15 has 3 pins and I got the same values in reverse when the probes were reversed. Pins 1-2, 664. Pins 1-3, 001. Pins 2-3 100. All resistors showed resistance and seemed consistent.

Q1 & Q2 were consistent. Negative probe on pins 1 & 2. 1-2, 1. 1-3, 1428. 2-3, 494.
Positive probe on pins 1 & 2. 1-2, 545. 1-3, 576. 2-3, 1.

Alec, I don't want to expand this any more if I don’t absolutely have to, so I’ll pass on another LM317.
Is it possible to find a little fan that would hook right up with no additional parts? If not, I’ll put some extra fins on the heatsink. I don’t think it’s getting too hot as is, but not so warm is better than real warm.
Thanks for the ‘additional battery in use’ red LED. A warning light in the fishroom will be a very good thing.
Thanks guys.

 

[KeepItSimpleStupid]

Datasheet SDC 7500: https://www.google.com/url?sa=t&rct...tJfmPafFrCex9Fw&bvm=bv.51156542,d.eWU&cad=rja

 

[alec_t]

I don't want to expand this any more

Understood. It's sure grown from humble beginnings .

Is it possible to find a little fan that would hook right up with no additional parts?

I just googled 'brushless fan 24V' and got lots of hits. One of those could run directly from the '+Vext' point.

 

[salty joe]

I worded the fan question poorly-sorry about that. What I meant is, I now realize the fan from the limp PS draws too much current but do you think there might be a little bitty fan that could be connected to the green LED 'battery charge' line? If you think that possibility exists, what specs should the fan have?
It would be neat to have a fan come on when the battery is being charged, but only if it can be done without adding much more circuitry.

 

[KeepItSimpleStupid]

This project is reminding me about what was said about "ISDN" which apparently got the acronym "I'ts still not done". Not sure if ISDN is even used much anymore, but supposedly you needed an ISDN line on one side of a 56K modm in order to get those speeds. ISDN: https://en.wikipedia.org/wiki/Isdn

OK, maybe I got the citations wrong. Wikipedia says: It Still Does Nothing, Innovations Subscribers Don't Need, and I Still Don't kNow.[9][10]

 

[alec_t]

do you think there might be a little bitty fan that could be connected to the green LED 'battery charge' line?

Problem is such a fan (if it existed, bearing in mind the LM324 could source/sink only a few mA) would move too little air to be effective. When I mentioned a second '317 previously, for some reason I was thinking '12V fan'. Duhh! The existing fan probably is 24V so usable as is, supplied from the +Vext point and switched, in resonse to the green LED output, via a 2N3904 or a non-heatsinked FET (depending on its current requirement). Thus few extra components.
Does the fan have a marked voltage/current rating (often on a circular label on the frame centre)?
If not, can you SAFELY confirm what voltage is across the fan terminals when running? You may need to tack on some short lengths of wire temporarily to the terminal points to attach the DMM probes.
What dimensions are the fan (40mm x 40mm is one standard size)? That will give a clue as to it's current draw.

This project is reminding me about what was said about "ISDN"

LOL, KISS. Yes, it's still evolving; but we're almost there (I think) .

 

[salty joe]

ISDN….I hear ya KISS…but we really are getting there. Bringing a red LED ‘on backup’ warning into the fishroom is worthwhile. If one of the PS for the filter pumps fail, the battery will get completely discharged and I might not have a clue. I could easily go a week without entering the control room once everything is humming along.

The mod for the second ‘on backup’ red LED is done, thank you Alec for that. I did not get a chance to hook everything back up to test.

The V where the fan in the limp PS plugs in is 12.9. The fan is 60mm square. Thing is, the PS is only supposed to run the fan when the temp reaches a certain point but the fan runs as soon as the PS is plugged in. IDK that the 12.9V number is trustworthy given all the problems with that PS. Plus the fact that there is no label on that fan makes me want to get a new fan with the right specs. The board is pretty cramped, but we have room for a little transistor and a few other parts….If there is a way to make a fan turn on with the charging function that would be sweet.
BTW, that was a good try on fixing the limp PS, I appreciate the effort. I enjoyed it and picked up a couple things.

 

[alec_t]

IDK that the 12.9V number is trustworthy

I don't think it is either, in view of the odd fan behaviour. Maybe the control IC has gone bananas and is pulsing the fan on/off rapidly, so what you measure is a sort of average between 0V and 24V. The fans I've seen listed all seem to have standard voltages, e.g. 12V, 24V,.....
If you really are ditching that PS you've little to lose by rescuing the fan and running it at 24V from your other PS. If it stays cool the chances are it's a 24V model. Have the fire extinguisher handy, though

The fan is 60mm square.

I'll check for typical current draw. We may get away with a 2N3904 for driving that. Do you have a spare FET? That would certainly handle the fan and need only a freewheel diode added. There's probably a FET in the flakey PS for rescuing.

Edit: Current for that size fan is ~ 40mA-100mA RMS depending on make/model.

 

[salty joe]

The second 'on backup' LED works like a charm. The trimmer adjusted the LED very nicely. It'll be good to have the 'on backup' warning in the fishroom. Thanks.
I ran the fan on 24V for 5-10 minutes and it did not get the least bit warm. It moves a fair amount of air.
I have a new IRF3205, would that do the trick?
My new 'old' PS arrived. Filter pumps, battery backup, charging system, all indicator LEDs, everything seems fine.

 

[alec_t]

everything seems fine

That's what we want to hear!
I'll sketch up the small mod to drive the fan using the IRF3205.

Edit: Revisiting the 'on backup' LED driving arrangement I realise now it will only operate when mains fails, i.e. both PS's are off. If mains is on and one PS fails then the LEDs won't light, although one pump would be running on backup. There are two ways to overcome this and give each pump its own mains/backup indication:-
(a) duplicate the R5/R6/D10/D12/trimmer combo,
(b) turn the logic on its head and use a respective pair of LEDs (preferably green) to indicate 'on mains power' instead.

Option 'a' uses 2 x 5 = 10 components (including the present 5), whereas option 'b' avoids the need for trimmers and uses only 6 components, 2 of which would be off-board anyway (the fishroom LEDs) and 2 of which would be 470 Ohm resistors. Do you have that value in your spares box?

 

[salty joe]

Thanks Alec for another good catch.
I'm afraid I might not notice a green LED that is off. (I'm assuming option B would have a green LED lit up when the PSs have power and the green LED would be off when the pumps are on the battery.)

A red LED says trouble like nothing else to me. I think option A could be squeezed onto the board. But I don't really need another LED on the board, I only need the warning light in the fishroom. Is it possible to add another red LED to the fishroom as shown in FPPB-Mk2 mod for option C?

 

[alec_t]

I'm assuming option B would have a green LED lit up when the PSs have power and the green LED would be off when the pumps are on the battery

Correct. Ok, we'll go for option C.

 

[alec_t]

Here's the add-on for driving the fan:-

Version 'a' occupies least space and uses a 2N3904 which gets its base current via the green LED (the '3904 is rated at 200mA continuous current so should cope ok; try it and see if it gets too warm). If you want to go beefier (at the expense of greater board space) then use version 'b' (note the different resistor values). With either version the +ve supply for the fan is taken from +Vext if you're feeling bold and assume the fan is rated 24V; or is taken from the battery +ve ('out' from the '317) if you play safe and assume the fan is rated 12V. From your fan test my money would be on it being 24V; a test at 12V direct from the battery would indicate if that's enough to get a decent air-flow.
Here's the modded 'on backup' part of the circuit:-

Note that neither trimmer now connects to +Vext. Each trimmer connects instead to its respective 'Supply+' point (adjacent the supply fuse). Any queries, shout.

Edit: The 'on backup' LED brightness and contrast can be improved by replacing the 1k resistors R5a/R5b (not R6a/R6b) with 330 Ohm.

 

[salty joe]

Thank you Alec. Those mods will both be used for sure. I doubt I can get them both on the board I want them to be on though. Now that we know what's going to be on that board, I might re-do it to get everything to fit.

Anyway, I won’t be able to do any soldering until Monday.
Thanks a million!

 

[alec_t]

I might re-do it to get everything to fit.

Why not just mount the add-ons/mods on another strip of board, piggy-backed on to the main board?

 

[salty joe]

You're right. I worry too much about trying to make everything just so.

 

[salty joe]

The fan driver uses pin 14 from U2a, but pin 14 is in use. The other three corner pins 1, 7, and 8 are open. Will one of them work?

 

[KeepItSimpleStupid]

There better be a connection to U2/14. It's the tie point.

 

[alec_t]

pin 14 is in use

Yes, but it can drive the fan circuit too. You could use one of the other opamps in the IC, but then you'd have to wire up its input suitably....unnecessary work.
Re the suggestion in post #2173 to run the fan from the battery connection, I've just realised that means the '317 will have a load current of at least the fan current so the charger won't shut off at the intended 50mA point. We could make it shut off at fan current + 50mA, but that's an unknown as yet and might need a different resistor in series with the 2k trimmer for the '50mV' adjustment. That little problem wouldn't exist if the fan is run from the +Vext point (~20V), but running it at 20V would justify a prolonged soak test to make sure the fan is happy.

 

[salty joe]

OK, thanks guys, I thought maybe something was amiss. Double duty for pin 14 it is.

Thanks for the heads up about the fan connection. I was going to go with 12V just to be safe. Another really good catch. I'll run the fan at 24V for an hour and if it heats up, I'll get a brand new 24V fan. BTW, since I'm using a little piggyback board and space is no longer an issue, the fan circuit will be the beefy version B.