Light Dependent Resistor

radiohead

Joined May 28, 2009
514
You should test your photocell with a multimeter to see what it reads in both darkness and light. Some will have high resistance in the light and others will have high resistance in the dark, depending on the type you get.... similar to a positive and negative temperature coefficient of thermistors. If the type you have is corrct for the application, you might want to lower the value of the 1M pot to 500K or even 100K. Play with the values to see what works best.
 

Thread Starter

aussiemike

Joined Jul 19, 2011
13
I have taken the advice of Metallica Boy to switch the circuit using the transistors. I have now linked the switch to another 555 timer circuit and it is working well. www.dianibeach.com/alarm.jpg
However when I shine a torch on the LDR circuit the switch on the timer circuit stays on and does not go off till I have turned the light off.
Can anyone help me with a small change of this circuit to make the timer go on only for the 5 seconds I require regardless of whether the light stays bright or not.
Regards
Mike
 

PeeSeeBee

Joined Jun 17, 2011
56
How long does the backlight on the phone stay on for when the call is disconnected? I was just wondering if you really needed a seperate timer.

Is the phone, electronics, & siren all at the top of the tree, or just the siren? I was womdering how you keep the phone charged up.
 

Thread Starter

aussiemike

Joined Jul 19, 2011
13
Unfortunately the light stays on for about 15 seconds which is too long to have a siren sounding. I only need it for 5 seconds maximum.
I can keep the phone on a permanent charger.
Only the siren is up top. The rest is in a building.
 

Thread Starter

aussiemike

Joined Jul 19, 2011
13
Unfortunately the light stays on for about 15 seconds which is too long to have a siren sounding. I only need it for 5 seconds maximum.
I can keep the phone on a permanent charger.
Only the siren is up top. The rest is in a building.
 
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