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Help needed: AA 1.5v Low battery detection circute

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Have you managed to find out if either input terminal of your TriggerLinc connects to battery plus or minus?
 
Have you managed to find out if either input terminal of your TriggerLinc connects to battery plus or minus?

Not yet. I'm still out of town. I'm returning back home next Monday. I'll test the TriggerLinc and start building the circuit as soon as I get back home.
 
Smoke detectors go on top. Leak detectors go on the bottom. Would not one at the low point be enough?

No. Dishwasher is in the kitchen, Washer and dryer are in laundry room.

hi Mark,
In your previous posts you have only referred to one device a 'dish washer', not the full house.

A security system is to prevent burglaries, a leak detector 'battery failure detector' will not prevent leaks, so I think your comparison is unfair.

Have you already had water leakage problems.??

I'm not talking about leak prevention. I'm talking about leak detection to notify me about leaking.

We had slowly leaking dishwasher that damaged our kitchens wall and floor. The leak was small (dripping) and water went towards the wall and eventually started to penetrate into the wooden underlying floor.
We did not see the leak, and discovered it only because of a smell from that area. We fixed the dishwasher and after that I decided to install TriggerLinc sensors to monitor for leakage not only under dishwasher,
but also under cloths washing and drying machines and in the bathrooms under the sink (inside cabinet).
 
No. Dishwasher is in the kitchen, Washer and dryer are in laundry room.



I'm not talking about leak prevention. I'm talking about leak detection to notify me about leaking.

We had slowly leaking dishwasher that damaged our kitchens wall and floor. The leak was small (dripping) and water went towards the wall and eventually started to penetrate into the wooden underlying floor.
We did not see the leak, and discovered it only because of a smell from that area. We fixed the dishwasher and after that I decided to install TriggerLinc sensors to monitor for leakage not only under dishwasher,
but also under cloths washing and drying machines and in the bathrooms under the sink (inside cabinet).

In that case I dont think I would have gone with a battery powered sensor setup. What if the battery decides to give out will you are gone?
Are your smoke detectors battery powered as well?
In a commercial system these would be powered buy a battery backed up power supply.
 
In that case I dont think I would have gone with a battery powered sensor setup. What if the battery decides to give out will you are gone?
Are your smoke detectors battery powered as well?
In a commercial system these would be powered buy a battery backed up power supply.

I'm looking for a 'low battery' solution for a few reasons :
1. It is very interesting project for me.
2. I don't want to run additional wires to power the detector from external power supply.
3. It can help others with the same problem if it works out fine.
 
Thats all good and I hope you have fun doing it.
As long as you realize it's not foolproof.
How long does the battery last?
Maybe you would want to consiter a bigger external battery like a "c" cell.
 
Thats all good and I hope you have fun doing it.
As long as you realize it's not foolproof.
How long does the battery last?
Maybe you would want to consiter a bigger external battery like a "c" cell.

Thanks! Of course I understand that it will not be foolproof. But it will be much better than nothing.
I have TriggerLinc for 1 month and I don't know yet how long the battery lasts. I'll install Lithium AA battery. It suppose to last much longer then Alkaline battery.
 
fmark # 27 . . . FWIW:-
In the UK, inexpensive (but Approved!), smoke alarms use a 9v layer-type battery. These will last about 2-years and when low the wretched thing gives short "beeps" - for a week or so you ignore it, thinking it's something on the Telly, or Outside, etc. Then you remember you've forgotten to replace the SA Battery and you check the SA, by pressing the TEST-button - no response! - so you buy another battery the next day....

So, provided OP can rely on a self-checking battery-test circuit, therere is no reason safety-wise why he can't use a battery. However, the SA has had a lot of design effort by professionals.

My issue is that this thing needs to be wet/damp-proof to prevent corrosion of terminals, etc. etc. AND I'm none too keen on the use of single-cell as originally suggested.

Those Lithium AA batteries will be 3v surely . . .
 
1) Not easy to calculate because of variations in transistor Vbe. Trip point depends on R1 and R3. Simulation shows that, with the values given, Q2 begins to turn on when battery voltage drops to 1V. Increasing R1 (or reducing R3) increases the turn-on trip voltage.
2) I don't know, because the internal circuit of the TriggerLinc (TL) is unknown. My circuit will only work if one of the TL sensor terminals is connected internally to TL battery negative (-). It needs three connections :- (i) from Bat to the TL battery positive (+), (ii) from Ground to - , and (iii) from Out to the TL sensor terminal which is NOT connected directly to + or -.
Using a multimeter, can you detect if either of the TL sensor terminals is directly connected to TL battery + or - (I would expect it to be connected to one or the other. If it's connected to + then we can modify the circuit to cope.)?

I verified with the multimeter that one of the TL terminals is connected to battery negative (-). So I'm going with the version A of your circuit.
 
Good luck. Keep us posted. Just hope the TriggerLinc can actually send a signal when its battery is down to 1V :)
 
Good luck. Keep us posted. Just hope the TriggerLinc can actually send a signal when its battery is down to 1V :)

Sure. Tomorrow I'm going to buy components. The only problematic thing is that I don't know how to test the circuit. :)
I have home-made power supply with variable voltage (on LM317T) that gives voltage from 1.2 - 15.0 volts. May be I need to 'kill' a few AA batteries for tests...
 
May be I need to 'kill' a few AA batteries for tests...
I'm sure a friend or neighbour would oblige with a dead battery :)
 
You can use diodes to drop the voltage, .7 volts or .3 volts per diode.
 
Generally that's ok, but not sure if using a diode would give similar results to a real dying battery in this particular application. A 'good' 1.5V cell + Si diode would give a 'good' 0.8V source capable of driving considerable current, whereas a dying cell may go increasingly high resistance and be unable to drive much current. For that reason my suggested circuit may not work with the TriggerLinc as the OP hopes :(.
We'll soon know.
 
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It works !

Generally that's ok, but not sure if using a diode would give similar results to a real dying battery in this particular application. A 'good' 1.5V cell + Si diode would give a 'good' 0.8V source capable of driving considerable current, whereas a dying cell may go increasingly high resistance and be unable to drive much current. For that reason my suggested circuit may not work with the TriggerLinc as the OP hopes :(.
We'll soon know.

O.K. ! Today I finally built and tested the circuit. And it works ! :)
Thank you alec_t for the circuit and your help !
I played with the 500k pot and set it to approximately middle position. It trips at ~1.2 volts. This should be good enough for battery to still operate and send me notification.
Now I need to solder it all together and install inside TriggerLinc.

My only concern is amount of current that this circuit draws when in idle. Unfortunately my multimeter does not allow me to measure amperage, but I guess it is negligible amount of current and should not drain the battery.

Thank you again !
 
Glad it works!
My only concern is amount of current that this circuit draws when in idle.
It's tiny; about 8 microamps in the idle state according to the simulation in LTSpice. Once tripped it draws about 80 microamps.
 
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