Any ideas for temporarily silencing a piezo sounder?

[bigal_scorpio]

Hi to all,

My son has just got his first home and seen as nowadays burglaries are regular in most areas he immediately bought and fitted an alarm system.

The type he went for was a wireless one to avoid any routing of wires and the problems and associated damage etc. It has good PIRs and door sensors, in fact it is very capable as alarms go but it has one small problem in that when arming or disarming it chirps the siren to give a bit of assurance that all is as it should be. Usually this confirmation is heard only on the inside from the main panel but on his alarm it goes to the main bellbox outside and is very loud.

I need some solution that stops the external chirps but will still allow the alarm to function when it should. I was certain when he told me of the problem that there would be a setting or jumper that would stop the external sounder chirping but sadly there is nothing like that.

The only thing I can say for sure about the circuit is that I can find the wires to the piezo. Since this box is up high on his house a ladder is needed to access it and that brings another problem! Its the end of summer here in the UK and it never stops raining at the moment so any solution would be better if it was sure fire for a first time fix, as its not nice (or safe) on a ladder in the wind and rain.

Any ideas guys?

Thanks for reading this and hopefully some advice, Al

 

[tunedwolf]

A good start might be to let us all know what manufacturer/ model number or, at the very least, where the alarm was purchased, so that we have a starting point. The chirp is generated using the exact same circuitry as the alarm siren, just much shorter duration obviously. You won't be able to disable one without the other unless the manufacturer has allowed for it in the design.

 

[Ian Rogers]

Its normally the small internal buzzer that chirps.... Is there a configuration sequence where you can set these things
I have a wireless alarm and I can set all manner of things.... It seems really strange that the outdoor siren is used in this manner..

 

[bigal_scorpio]

Hi Guys,

Sorry but No make, No model, No numbers, not anywhere!

Manual says nothing of the problem and the seller does not know, we asked.

All I can do is give this link to an identical one on ebay. **broken link removed**

Any suggestions gladly tried. Al

 

[Wade Hassler]

The ebay link shows two exterior-sounder options: one wired, the other -less.
The wired sounder is trivial, but the wireless one means you're on the ladder, unless you can re-do the firmware in the alarm.

 

[flat5]

How about a monostable and a relay or something to disconnect the sounder for a short time when receiving a signal.
If the signal stays longer than the short bleep it allows the receiver to function normally.

 

[bigal_scorpio]

The ebay link shows two exterior-sounder options: one wired, the other -less.
The wired sounder is trivial, but the wireless one means you're on the ladder, unless you can re-do the firmware in the alarm.

Hi Wade,

The wired sounder is just a second one to be used inside the house to alert to possible danger eg fire, or so it says in the leaflet. So stuck with wired

Al

 

[bigal_scorpio]

How about a monostable and a relay or something to disconnect the sounder for a short time when receiving a signal.
If the signal stays longer than the short bleep it allows the receiver to function normally.

Hi flat5, I was thinking along those lines but I am having a problem with the how to bit. I assume that the only signal I would get at the sounder would be a short ac or frequency modded blip and wondered how to get that to drive a transistor or whatever?

At first I was wondering about just using a large cap so that the first few seconds of any alert or blips would be absorbed in charging it? I have a good range of caps including non-polarised electrolytics, but didn't know the effect of it on the rest of the circuit?

Al

 

[tunedwolf]

The early wireless alarms from B&Q had the same awful feature you describe set as default, a chirp and strobe flash on the external box as I remember, however it was selectable in the configuration. If your setup definitely does not have this as a config option, then as the others have suggested, introducing a delay of sorts may overcome the chirp. Something simple like a resistor in series and a cap across the bell trigger line. You'll be aiming for an RC time just larger than the chirp. To do it though would mean taking down the bell box and delving into the siren trigger circuit, finding the trigger line going from the transceiver to the siren, breaking it and inserting said resistor

 

[flat5]

I'm just a hobbyist and not a very good one
I suggest you open the box and take good pictures of what is inside.
Post them here. We need info.
The sounder might be device with the oscillator inside. It may just need a dc voltage to set it off.
You can use that voltage.

Another screwy idea is to adapt a cheap wireless doorbell sender & receiver to interrupt the sounder.
When you set the alarm you also 'ring' the doorbell which will trigger a relay to momentarily disconnect the sounder.