Alarm Pager (delay time)?

**abbbe** · 06-11-2008, 07:30 PM

Im thinking of wiring up an old mobile phone to my car alarms siren so when the alarm is triggered it uses the speed dial feature of the phone and phones me.

There was someone on the net that says he will mod any mobile phone to do this but he wanted about £100 + plus a phone.

I've managed to get it going using a 5 pin relay the only problem im having now is that I tried wiring it up to the siren so that when the siren goes of it activates the relay and calls me the only problem with that is that every time you turn on/off the alarm the siren chirps and the thing phones me up...lol

im starting to think ill need to make a time delay circuit so it doesn't kick in until the alarm has been running for a couple of seconds.

I've read that its possible to wire a resistor to a capacitor and then wiring that to the relay so that it takes a few seconds for the for the cap to charge before triggering the relay but there wasn't any mention of what resistor or cap that is needed :-(

Any help would be greatly appreciated ;-)

**abbbe** · 06-12-2008, 06:19 PM

Anyone

**tigergibb** · 06-12-2008, 06:36 PM

555 timer.. google it

**abbbe** · 06-12-2008, 07:42 PM

Thanks for the reply

I was going to do a 555 circuit but when I went to buy them there was three different types a NE555N a NE555D and a LM555 and I wasn't sure what to buy. Also I couldn't find a diagram for the pins let alone wad caps and resistors I would need, then I come across an old site where someone said that they managed to get a delay using only the caps and resistors but again they didn't say what ones where needed

**DroStar** · 06-15-2008, 12:13 AM

Originally Posted by abbbe

I was going to do a 555 circuit but when I went to buy them there was three different types a NE555N a NE555D and a LM555 and I wasn't sure what to buy.

The extra letters identify minor details like manufacturer, package type, temperature range, etc. It would be best to get one as a DIP package as they are easiest to prototype with. It would also be a good idea get one with a wide temperature range. So the NE555N or SA555 or LM555CN would work.

**abbbe** · 06-17-2008, 07:37 PM

Thanks for the info

I've ordered some 555 timers but I cant find a diagram on how to wire it up

All I need is a delay of about 10 seconds (can be a bit more or less) from a 12v source to the relay.

There's loads of diagrams on the net but none of them are for the simple circuit I need

Can anyone please point me in the right direction

**Maheriano** · 06-17-2008, 10:38 PM

Wouldn't it be easier just to use the web to send yourself a text? A phone call will be pointless, you're just going to look at the number and hang up anyway right? Plus with the SMS, you don't need to use another phone.

**colin** · 06-17-2008, 10:51 PM

Ahhh finally the electronics comes in handy.

You can make a very unstable timer using a simple resistor and cap circuit. The cap charges and then discharges through the resistor, which takes a determined amount of time. Problem with this is heat variation... changes everything. Your timing isnt too specific though so this should work just fine for what you want.

555 is overkill for this situation because of the extras required.

http://www.elxevilgenius.net/08Prjects/processr/RCI.htm
http://robots.open.ac.uk/ibotz/RCcircuits/
http://hop.concord.org/amu/amu.mess.act3.html

**DroStar** · 06-17-2008, 11:21 PM

Delay On circuit using 555 timer: http://clarkson-uk.com/555-timer/operation/frames3.html

**abbbe** · 06-18-2008, 05:38 AM

Thanks for ALL the replies

Ill stick with the 555 for now seeing as I already bought them.

This diagram seems to be the best one ive seen: http://clarkson-uk.com/555-timer/operation/frames3.html but there are a few things im not sure about like what does T1, RA and C mean?

Also there are a few things on the diagram I don't understand so ive edited it slightly and attached it below.

Thanks again everyone