Circuit doesn't behave as it should

[Stanislav]

I have the following schematics

Here is the original one(the second one):
http://www.zen22142.zen.co.uk/ronj/24h.html

The checked parts in the image above are not mandatory and that's why i don't use them. I have connected the common terminal of the relay to the positive side and the normally opened to the negative side of the circuit. Not sure if that's the correct way. Anyway, i have connected the range wire to pin 7 of the IC and when i apply power(12V) to the circuit the relay turns on immediately and therefore the LED is turned on. And that's it, it just stays like that without switching again. I wait about 1 minute(far more than the expected interval). The potentiometer is set to it's minimum resistance, so the expected interval is about 30 seconds. I have checked all connections and everything seems to be alright. Note that the relay that i'm using is not the one from the original circuit, the coil resistance of my relay is 230 Ohms. I'm a beginner in electronics and really have no idea what to do. Can someone help me with that?

 

[davenn]

hi there
welcome to the forums

you had better show us pics of your construction to see if you have made any wiring errors ... sharp and well lit, so we can read values
Did you use vero-board like they did ? if so show both sides of the board

you should have a 1 k resistor in series between the relay contact and the LED else it mite have a short lifespan

Dave

 

[(*steve*)]

The diode IS necessary.

The reset part of the circuit is almost certainly necessary

There are a few connections shown in a way that you might have missed.

 

[davenn]

from the www site description...
In single-shot mode - the output pin does a second job. It uses D1 to disable the oscillator - so the count stops with the output pin high.

If you want to use the timer in repeating mode - simply leave out D1. The count will carry on indefinitely. And the output pin will continue to switch the transistor on and off - at the same regular time intervals.