How can I create a 12V delay timer to keep a motorcycle satnav unit powered while the engine cranks? Must be small, robust, waterproof and idiot-proof
My motorcycle has a switched 12V feed to a satnav cradle. When I crank the engine the feed is temporarily cut, and my cheap Android Auto satnav reboots instantly, forcing it to reconnect to my phone - which causes a delay.
The satnav unit probably needs no more than a couple of amps for up to 5 seconds.
Edit: Satnav apparently needs up to 1A at 12V, and let's say for up to 2 seconds.
Dome light delay timers are available - e.g. https://www.ebay.co.uk/itm/280645125423 - but these are bulky and designed for switched earth circuits. I have reasonable soldering skills but don't understand electronics, so if someone could please point me towards a wiring diagram that provides clarity about which capacitor(s), diode(s) and resistor(s) would achieve what I want I'd be really interested to have a go making my own.
I'd then appreciate some advice about how to seal these components in some sort of waterproof material (resin? silicone?) to protect them please. If this could all be achieved within a black device no bigger than my little finger that would be ideal.
Thanks in advance!
(Apologies if this has been asked and answered a million times - I've Googled a lot and haven't found anything.)