Nigel
Well-Known Member
- Joined
- Jul 7, 2014
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- 16,687
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- Location
- Wales
- Country
- United Kingdom
- Dash Cam
- Gitup F1+G3ꞈꞈꞈꞈꞈ Viofo A229ꞈꞈꞈꞈꞈ Blueskysea B4K
Might be better to use a dual pole relay, then you know that both will switch at the same time.There are 2 relays. The 12v from the car battery (power magic pro) triggers both relays. On the top relay, it redirects power to the dashcam from the car battery to the 5v -> 12v step up adapter when it doesn't detect 12v from the power magic pro.
Once the 12v power source from the car battery shuts off, the lower relay completes the circuit for the usb male cable to the 5v -> 12v step up. This tricks the USB battery into thinking that it was just plugged in and turns the USB battery on. Since the relay completes the circuit, the 5v to 12v step up is enabled and powers the dashcam plug at 12v.
Also, since the relay coils are driven by a transistor in the PMP, might be a good idea to use a relay with a flyback diode, or add one to the design.