Make your own 12V 10s off Relay

Here is a simple scheme for 12V approx 10s OFF Relay. It’s very easy to build. Scheme and part list are shown below.

  • R1 – 6.8 Ω
  • R2=R3 – 100 kΩ
  • D1=D2 – 1N4007
  • T1 – 2SD892 (Darlington NPN transistor)
  • C1 – 100μF/25V

alternative (if you cannot find 2SD892 transistor you can use one below)

  • T1 – BC517 (this one has higher hfe than 2SD892, so you also have to change capacitor)
  • C1 – 33μF/25V
  1. BROWN – ignition (+12V)
  2. GREEN – to relay (No.85)
  3. RED – constant power supply (+12V)
  4. BLACK – ground (-12V)

If you want to change delay-off time, you can change the capacitor. For longer delay use higher value capacitor, for shorter time, use lower value capacitor. Change only capacitance, not voltage.

Buy one 4-pin car relay (NO-normally open)

Bring constant power to relay pins No.86 and No.30.

Relay pin No.87 will give power (+12V) to DC-DC converter when ignition is ON and 10s after ignition is off.

And here are the images how I have coupled it along with DC-DC converter.


Thanks to rjc_147 who pointed out for D2 diode & Credit to Razor AMD for the content.

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