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555 timer thread for skybird9

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kchriste

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Since I can't add attachments to a PM:
skybird9 said:
You helped a guy with a Vellman MK111 problem a couple of years ago. He wanted to turn on an LED for 8 seconds and not have it come back on. I have the opposite problem. I want to push a button, wait 20 seconds and then close the relay for 1 second and stop until I push the button again. Basically, I want to blow a (12v DC) horn (1 second blast) 20 seconds after I start the timer. I haven't bought anything yet. If there is something better that you could recommend, I would appreciate your advice. Thanks!

The MK111 would be the wrong kit for that. You need something with two timers or a dual (LM556) timer. Something like this might work for you:
**broken link removed**
You'll have to change the leftmost 22uf cap to a 470uF one to get apx 25 seconds. If you replace the leftmost 47K resistor with a 50K pot, you can fine tune it to 20 seconds. Like this:
555delay-gif.22049
 

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