help reading a schematic

[leonrayo]

Hello, i'm new on this forum and i would apreciate a little help reading this schematic. i need to explain it for school project.
Thank you all

 

[davidbball13]

do you have the key

 

[Torben]

Hi Leon,

For us to help you, we need to know what you are having trouble with. What exactly about the circuit do you need to know and what don't you know?

If it's just what the various symbols mean, you can Google "schematic symbols" for plenty of help with that. One good site is

Do you know what the circuit is supposed to do? What do you mean when you say "explain the circuit"? Are you supposed to figure out what it does, or *how* it does it? In how much detail do you need to explain it?

Please don't take this the wrong way, but people on this site usually will not do homework for other people. We're totally happy to give you a hand working it out though.

Anyway, if you can answer the above questions it will be easier to help you out.


Torben

 

[JimB]

That is a very unusual circuit, where did you find it?

JimB

 

[leonrayo]

Sorry about that, torben. I didn't meant to give my homework for others to do.
I will trye to ansuer those questions. That circuit is suposed to detect the presense of a person and then produce a sound in the speaker that is the alarm. Now i realise that the ldr detects the presence, but how? because much light or less light? other question, wich transistor acts like a switch that activates the circuit, is it TR1 or TR2? I think its TR2 but i have doubts. Now when the circuit is activated, IC1 wil receive a tension and generate the sound of the alarm, this is an IC M581A and i didn't found much information about this component. Then this sound is amplificated by TR5 and reproduced by the speaker. This is how i see this circuit, but i'm not sure. One last doubt, how does VR2 affect this circuit, what is his influence on it?

Once again, sorry about my english, hope this time i'm more specific!
Thank you

 

[pfofit]

have you seen this http://www.datasheetcatalog.com/datasheets_pdf/M/5/8/1/M581A.shtml

Although the T092-3 cases shown have no input pin???

cheers