How to monitor a sensor that cycles between open and closed during alarm

[rhughes]

I nabbed myself a breadboard to set up some test circuits. I had to put a 1k ohm resistor inline with the anode on the optoisolator, or all of the current flowed through that and the LED on the water softener wouldn't light. I then put a 470uF cap in parallel with the anode/cathode on the opto and it keeps the opto in a closed state *almost* until the LED blinks back on. I think I need a larger cap, but that was the largest one I had.

I should have it working after spending a bit more time on it with a couple of beers.

Hi,

Please keep us updated. I'm planning to do the same thing with my water softener.

Thanks.
Randy

 

[signal15]

The power supply to LED that is in the water softener does not have enough current to close the optoisolator that I have enough. If I run 6 volts through the optoisolator, it's not enough to trigger an alarm. But if I run 9 volts through it, it works great.

I'm guessing I need to get a more sensitive optoisolator. Because I was in a hurry, and it was only $3, I just grabbed one off the shelf. The specs on the package were covered with a sticker that tore off the text when I tried to read them.

So, I need to find one, and radio shack sucks and doesn't have them.

 

[pipeman]

Are you trying the Resistor/Capacitor on the water softener side of the optoisolator?
I was thinking of that circuit on the ELK side.
If the water softener circuitry can drive the isolator to close, you would have plenty of power on the ELK side.

 

[signal15]

Are you trying the Resistor/Capacitor on the water softener side of the optoisolator?
I was thinking of that circuit on the ELK side.
If the water softener circuitry can drive the isolator to close, you would have plenty of power on the ELK side.

Yes, on the water softener side. The ELK side of the isolator I had planned on just looking for open or closed. I don't understand what putting the cap on the ELK side would get me...

 

[rhughes]

Are you trying the Resistor/Capacitor on the water softener side of the optoisolator?
I was thinking of that circuit on the ELK side.
If the water softener circuitry can drive the isolator to close, you would have plenty of power on the ELK side.

Yes, on the water softener side. The ELK side of the isolator I had planned on just looking for open or closed. I don't understand what putting the cap on the ELK side would get me...

Hi,

I spoke with an Electrical Engineer friend about this last night and he said that this problem would likely occur. There wouldn't be enough voltage on the input side of the optoisolator to drive everything needed to accomplish latching on that side. He suggested using a latching relay on the output side of the optoisolator. In that scenario, when the low salt LED starts blinking, it triggers the latching relay on the output side of the optoisolator to latch closed (or open, as the case may be). Using a 2-Coil latching relay (a quick search found some for under $5), you would then need another current to trigger it to reset. In my case, I'm using something other than ELK (Barionet) and have another relay available that I can cause to pulse periodically from my ISY to reset the latching relay. I would reset it probably twice per day so the "low salt" announcement would periodically be triggered over the whole house PA. In the case that the low salt LED was still blinking when a reset is done, it would immediately latch the relay again and prompt the announcement. This would occur until I refilled the salt and the low salt LED went off. I haven't tried this yet.

Randy

 

[pipeman]

The zone inputs are internally connected to a 2.2k ohm pull-up resistor and capable of supplying a small current.
I have two zones driving modified doorbell buttons with an internal LED.
Those are 3v LED's , so the current supplied is about 4 ma. with the button open and current trough the LED and pull-up resistor.
When the button is pushed, the LED is shunted and the input zone has about 5.5 ma through the pull-up.


If you connect a capacitor from the zone input to ground, as the capacitor charges the zone should see initially 0 volts, increasing to 12 volts.
If you use your optoisolator as a switch to ground (through a low value resistor), that discharges the cap towards ground for 1/2 second, then the internal pull-up resistor will charge back towards 12 volts during the second 1/2 second cycle.
If the values are fine tuned the zone should see an open condition when your salt is OK, then a rapidly fluctuating voltage between, say, 4 and 8 volts when the LED is blinking.

 

[pipeman]

Don't know if this is resolved, but you might skip the whole electronic thing by using a phantom output as a timer.

I found and copied this from the ELK site.

"Re: Custom settings & Counters
Posted by kphillips on 08/13/2004 06:39 PM
The quickest way is to use a phantom Output as a timed flag. Try this: WHENEVER Zone 1 BECOMES NOT SECURE AND Output 50 STATE IS OFF (substitute any output) THEN ANNOUNCE Miscellaneous 4 (vm242) (sub any voice phrase) THEN TURN Output 50 ON FOR 6 SECS (modify time to suit) The voice will speak 1 time when the zone is initially tripped. The output will turn on for 6 secs. If the zone trips again while the output is still ON (this is the debounce time) the rule will be exited. The voice will only speak if the zone trips while the output is Off.

Edited by kphillips on 08/13/2004 06:45 PM"