Tuesday, June 23, 2015

Add delay to window alarm

Can I do it with analog electronics, e.g. with a capacitor? How do I discharge the capacitor? Does it discharge "slowly" by itself or do I need a resistor/LED? I probably will need a transistor too. Capacitor will be used to control the current flow via the transistor. When capacitor is fully charged, it will let current flow through the transistor which in turn activates the alarm circuit.

If I want a 10 second delay, I can achieve it with a resistance of 100K and capacitor of 100uF [see RC time constant]: tau = 100e3 * 100e-6 = 10 seconds.

https://www.youtube.com/watch?v=GeveeSTyvGs
  • Capacitor: 470mF, 100mF
  • Resistance: 47K, 22K
  • Diode: 1N4001, 
  • Transistor: 2N???
https://www.youtube.com/watch?v=LQji9_O9-aI

http://www.the12volt.com/installbay/forum_posts.asp?tid=91691

https://answers.yahoo.com/question/index?qid=20100910203520AAoZUtq

https://en.wikipedia.org/wiki/RC_circuit

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