electronics question

[MmmBoost]

ok electronics gurus out there, heres my dillemma

ive added a shock sensor to my car in the spare tire well. it is the type that completes a ground connection whenever motion or shock is detected. keep in mind that it is usually for less than half a second that the sensor completes the ground for each bump of the sensor.

ive wired the sensor's ground into the normal trigger for the rear hatch to set off the factory alarm.

my problem is that the factory alarm has a small delay, slightly less than 1 second.

what type of circuit could i make to make it report ground to the alarm trigger for say, 2 seconds, any time that even a little blip is reported from the shock sensor?

 

[Enraged]

you could use something like a monostable 555 timer circuit. theres lots of info on the net on how to build the circuit.

 

[MmmBoost]

wow man, thats what i was looking for... i thought the 555 could only be used for certain things... didnt realize it was so versatile

ill update tomorrow to let y'all know if it worked or not.

 

[Enraged]

http://www.electronics.50g.com/555t.htm

that example might help. its been awhile since I used a 555, but they are pretty simple.

 

[isnms]

You're planning on setting off the factory alarm when slightly bumped?
Do you have a sensitivity adjustment for your sensor?

I know, here, the wind can get up pretty good and set off the warning on my alarm. It just chirps a warning on a two stage alarm. More violent shock will set off full alarm.

 

[CRE]

Sensativity isn't his issue, it's the pulse length from the sensor to the factory alarm that's the problem.

There are a few ways to do it, a cmos 555 is easy and reliable.

 

[isnms]

My point is; With the slightest vibration his plan is going to set off full blown alarm, not a warring chirp.
Factory alarm does not have two stages.

 

[CRE]

Gotcha... Hopefully he had enough foresight to get an adjustable shock sensor and plans to adjust the sensativity to prevent that. (If not he probably does now.) :biglaugh:

If inclined, he could add a second stage to the alarm sys. with a second 555 and a counter. :naughty:

 

[jetjock]

556

 

[MmmBoost]

yeah, the shock sensor is adjustable, and im gonna set it so that a moderate bump or motion will set it off, i dont care if someone accidentally coughs on it lol...

im finishing up the circuit i built with a 555, thanks enraged for the tip!!!