simple Light dependent buzzer

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madmikejt12

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hi, i have done a circuit with a 9v battery, a buzzer, an LDR and 2 transistors, when there is no light i want the buzzer to sound, i am using a lazer on one wall and an LDR on another and when the beam is broken, i want the buzzer to sound can you see anything wrong with this circuit?
Thanks, Mike
 

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Here is how to turn-on a transistor or darlington-connected pair. Match R1 to the value of your LDR. The little 9V battery won't last very long if the LDR and R1 are low resistance or if the LED or buzzer are continuously activated.
 

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The R1 determins the sensetivety of it.

If its low resiatance then the bzer will start even in dim light if its high then the buzer will need to be im a darker place to start.
 
worked a carm, set it up, leftt my room untidy, went out and my mum opened the door slightly BZZZZZZZZZZZZZZZZZZZZZZZZZZ she shut it and wouldnt go in again!!!!! :lol:
 
mine only work on breadboard, when i solder them, they never seem to work, i check all the tracks and nothing is touching things they shouldnt be, so i give up on them!!!

but, i have got ONE project to work, an adjustable LED flasher using a 555
 
madmikejt12 said:
mine only work on breadboard, when i solder them, they never seem to work, i check all the tracks and nothing is touching things they shouldnt be, so i give up on them!!!
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Don't give up.
1) Look at whether the emitter and collector of the transistors are reversed. A good pic of the pins of a transistor is shown in its datasheet.
2) Maybe your soldering iron is too hot or too dirty. My temperature-controlled soldering iron tip is cleaned by a quick wipe on a damp sponge then makes a perfect solder joint in 1 second.
3) Use rosin-cored solder. :lol:
 
i mean soldering circuits with no transistors, just diodes (which i checked and are the right way round), resistors, switches, a 555 etc
 
i have just baught a new bit for my iron aswell as a battery powered one (incase the electricity goes ) lol
I use lead-free solder, can't find it at the moment..

i seem to have a problem with soldering the component and it isn't stuck to the copper track properly so i try to melt it again and it goes onto the next track............
I burned a copper track once, soldering, unsoldering, soldering..... that was on the "light flasher to music" project (havnt got it working yet)
 
With my old temperature-controlled soldering iron I can solder and unsolder things over and over without damage. Yours is too hot.
 
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