Door alarm

Thread Starter

roll cast

Joined Apr 3, 2011
11
I'm making a door alarm
heres the circuit I've made

I have had to sub some parts as my sim doesn't have them, the spdt will be key operated and the push to break will be a normally open reed switch
Will this work
 

SgtWookie

Joined Jul 17, 2007
22,201
Your circuit has far too much "white space" in it, and as a result the components are tiny.

You must have used .jpg format, as it is impossible for me to read the part numbers or what the pins are.

You should try to make the schematic more compact by moving the components closer together. Also, use the .PNG format - as it is not "lossy" like .jpg is, or huge like .BMP's are.
 

SgtWookie

Joined Jul 17, 2007
22,201
1) Battery voltage is too high. Most 555's specify 16v for max, some 18v but that's pushing it. If you're thinking of running from two "transistor" PP3 9v batteries, they won't last long at all.

2) You have 750 Ohm resistors from the voltage supply to pins 4 and 8, and another 750 Ohm resistor from pin 1 to ground. Not good.

3) What kind of repeat rate did you expect?

4) You have LEDs in series-parallel, but only 1 current limiting resistor. Each series string needs its' own current limiting resistor.

5) You are using an NPN transistor as an emitter follower, on the output of a 555 which is already an emitter follower arrangement; so you will lose at least 2v from the supply voltage.

6) I presume the SPDT switch is a test LED / Operate switch?

7) The pushbutton switch above it is the N.O. reed switch? They're closed when a magnet is near, you know that right?

8) What's the thing above the transistor that looks like a table lamp with two cords?
 

Thread Starter

roll cast

Joined Apr 3, 2011
11
3. i HAVE TESTED THE ARRANGE OF 9K,10K, AND 10μf AND ITS RIGHT

6. YES YOU'RE RIGHT
7. iF YOU PUT A NON MOVING MAGNET BEHIND IT IT WON'T COME ON WHEN THE MAGNET COMES NEAR IT AS THE FIELD BALANCE EACHOTHER
8. iTS BUZZER JUST ROTATED STRANGELY
 
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