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  • Delay Relay, Active time = 1.1RC = e.g 47UF * 500K = 1.1 * 500,000 * 0.000047 = 25.85

in which

Capacitor  47UF connect to Threshold
Resistor 500K connect to Trigger

Flashing Blue Red LED Alarm

  • Module combines of NE555 and CD4017, when the 1st, 3rd, 5th pulse comming, blue LED flashing, and when 2nd, 4th, 6th pulse comming, red LED flashing. When 11st, 13st, 15th pulse comming, blue LED flashing, again and again. Then it looks like alarm light.
  • Change trim pot can change frequency.

Delay Relay

Calculation T=1.1*500000*0.000047=25.85 seconds maximium

1.1 constant value
500 000 = 500K = trim pot maximium resistance value
0.000 047 = 47UF = fixed on board capacitor


  • Re-count (top) = re-count time of delay
  • Reset = reset relay status