With sw1 removed pin2 is 0.05V. Removing the sw had no effect on voltage. Opening and closing sw has no effect either. Yes I tested the sw, it's good.

 

With sw1 removed pin2 is 0.05V. Removing the sw had no effect on voltage. Opening and closing sw has no effect either.

Good Lord here we go again.
Does the circuit work with the switch installed.
SG

 

No.

 

You must have a short on pin2. check the wiring and the cap C2.
SG

 

Removed the cap and same 0.05V on pin2. sw closed it shorts to gnd and 0.0V pin2 and q1 base.

 

Removed the cap and same 0.05V on pin2. sw closed it shorts to gnd and 0.0V pin2 and q1 base.

Remove the transistor and check again.
SG

 

w/o xstor it is 5V on pin2. I also pulled the led and plugged MM on pin3. With pin2 LO there is 4.5V on pin3.

 

w/o xstor it is 5V on pin2.

Then the xistor is bad or the wrong type or installed incorrectly.
SG

 

xstor in sw open=0.04V pin2, 4.44V pin3
xstor in sw closed= 0.00V pin2, 4.44V pin3
xstor out sw open=4.94V pin2, 0.00V pin3
xstor out sw closed=0.00V pin2,4.44V pin3

 

Or if it is open on power up you have x time to close it before alarm is triggered.

Hi

Here is the correct wiring for your description.
The graph below show the LED on power up for 5 seconds, when the switch is closed, when the switch is open for 3 seconds, and when the switch is open.

Also,
I didn't show it but connect a 0.1uf bypass cap between pins 1 and 8.

eT

 

Here is the correct wiring for your description.

Thanks, will build this tomorrow and check it out. Impressed with what I'm seeing of Spice. Downloaded it today and played with it a bit, but it's going to be a steep learning curve to get on top of it. I like CircuitLab better for drawing, but it has a limited symbol library and treats the chip symbol I use as a black box and can't analyze it. Thanks again.

Sam

 

Thanks, will build this tomorrow and check it out. Impressed with what I'm seeing of Spice. Downloaded it today and played with it a bit, but it's going to be a steep learning curve to get on top of it. I like CircuitLab better for drawing, but it has a limited symbol library and treats the chip symbol I use as a black box and can't analyze it. Thanks again.

Sam

I use LTSpice but it does have a steep learning curve.
It's not the best "drawing" tool but it's an awesome simulator.

eT

 

I built eetech00's circuit. I substituted a 68uF cap for C1 to slow the charge rate down. C1 now charges and it works. Thanks E. I notice the R3 was moved out from between V+ and pin2 and pin2 tied to pin6 so Mim's had it wrong. Not the 1st time I've had problems with one of his schematics. Looking at it in retrospect pin2 was tied HI by the 47k resistor acting as a pullup and the timer could never switch. So problem solved. I got a bit sidetracked testing the timer and even built a transistor tester. Lesson to be learned "don't always believe what you read in books". Just for grins and giggles I turned the power supply down. Worked fine at 5V and even at 2V although the LED was pretty dim at 2V. I expected the 555 to quit at less than it's rated 4.5V min. So kudos to eetech00!

 

Hi

Good observations

Glad it worked..

eT