Some good readings about hardware startups and starting a hardware business: How To Build A Hardware Startup, Created by Marc Barros (local copy of paper) "It's a simple question: Why are you starting a company? It's hard to answer. Either because you don't know or you are embarrassed about how simple the reason is. The good news is you can get away without have a clear why for a very long time. Most people will never ask you, instead they will focus on what you have built. The bad news is down the road then the deck is stacked against you, when you are exhausted from the journey, and when you are wavering between a crappy and a really crappy decision, not having a clear why make you a leader without a compass."
Some years ago a have started building Clone PI AVR. Made a PCB, soldered all the components and ... and never found time to finish it until today. Well I haven't finished it yet but at lest gave it a first test run. For the screen and buttons i have re-purposed some front panel of some old router. Now i see that i will have to put it in to another box for better mounting on the metal detector itself but this time it was good enough for test run. For Atmega programming I used Mini Pro TL866 programmer I have bought while ago - works like a charm. You can see some photos and video on work in progress. https://www.youtube.com/watch?v=VZVZoRKr3T8 Circuit of Clopne PI AVR: HEX file for burning Atmega 8 and PCB Sprint layout.
I was annoyed with Eachines H8 Mine constant beeping in headless mode so decided to make it silent once and for all. This mod is easy - just open the transmitter, remove beeper by desoldering it and solder similar LED instead of it ( check the polarity - positive is marked on the PCB ). Then drill a hole of LED diameter in front side of controller case and it is done.