How do I create a circuit that closes when activated

[gra1234]

driving relay with pir

My 9 year old son is very interested in science and is working on a project that involves hooking up a motion sensor (PIR) to a clock alarm. The challenge is to get the PIR to de-activate a sounding alarm. We thought if we could create a circuit that closed when the PIR was activated, it just might do the trick. We have the PIR and the clock as a start - All thoughts are greatly appreciated!

 

[FvM]

motion activated pir light switch circuit

Assuming, you have a standard analog output PIR device, this PE/Heimann application note may help
It gives a typical circuit as it may be used in a PIR operated light switch or intrusion alarm. Other manufacturers may have additional application notes or reference circuits.

 

[vandelay]

Use a normal open relay that closes when the coil is powered, or the other way around; a normally closed relay that opens when coil is powered - with a logic inverter circuit driving the coil. Relays come in all sorts of types, if you are looking for components online, my preferred sources are usually Digikey, Mouser, or Newark.

 

[melc]

I'm not sure I've understood your question, but I guess the problem is more than opening or closing a circuit with a normal closed or normal opened relay.

A standard PIR detector have already a normal opened relay. It also had an amplifier like the one described in an earlier post and a window comparator which is driving the relay. Some PIR detectors have already some capacitors before the window comparator keeping a long closing relay time after the PIR is sensing.

As long the PIR is sensing only a movement variation, based on a fresnell lense which is focusing the radiation on detector (and as long the fresnell have multiple focus points), a person which is moving and is emitting heat with a wavelenght of say 4-15um, will be sensed as many time as the fresnell will focuse the radiation on the sensor.

But after the person goes away from the PIR range area or stay still, the PIR sensor will turn automatically OFF.

Now, ask again what do you want to do, based on the explanation above.

 

[mister_rf]

So you have a motion sensor PIR module.
Also a clock alarm.

In order to activate or deactivate the alarm by the motion sensor you need to add a relay and of course a power supply for the PIR module.
All the wiring details are related to the PIR datasheet. We need to know some details about the PIR module. Not all the PIR modules have a relay included.
See for example:
http://www.panasonic-electric-works.cz/pewcz/en/downloads/ds_61802_0002_en_napion.pdf
http://www.passandseymour.com/pdf/U106-U109.pdf

There’s possible to control the relay directly or to add an external transistor between the PIR module and the relay.
The relay must operate at same voltage as the PIR module.

 

[t1000x]

there a switching IC in the market, but i forgot the part number. it acts like a relay; it loses when a certain pin received a high inputs and open when the pin is at 0 state.

 

[KMoffett]

This is a photomosfet relay:

http://pewa.panasonic.com/pcsd/product/pmos/pdf_cat/aqw61_eh.pdf

Available from Digikey.

It containes two mosfets and two LEDs. When the LEDs are off, one mosfet conducts(NC) and the other mosfet is off(NO). When the LEDs are lit the conducting mosfet is turmed off and the off mosfet conducts. They can be used independently or as an SPDT switch. Anyway the NC mosfet conducts when no power is supplied to its LED.

Ken

 

[gabin]

simply an assut high switch will do your job.

 

[vivek_bahire]

Light activated scr

 

[teqno]

simple you can find a invetor or NOT gate then the trick is you going to design an construct circuit you will need a breadboard......................

 

[KMoffett]

teqno,

After a year and a half gra1234, with only one post, will probably see your suggestion.

Ken