I recently got my hands on the xEM access controller. It seems to be a RFID based car ignition immobilizer that was repurposed. I’m gonna try and reverse engineer the box, but it’d probably be a much more efficient idea to build a system from the ground up. I feel like theres a decent potential in the Arduino family of chips.
Using the safety detent spring hole isn’t a bad idea. The issue I see there is figuring out how to keep the safety from flopping loose when the pin is withdrawn. The detent pin is the only thing keeping the safety from falling out of the lower.
Also, using the M-16 selector is a no-go per the ATF. You’re not legally allowed to use any of the full auto FCG pieces in a civilian rifle. Dumb, and you’ll probably never actually get called on it, but there it is.
For the proto I’d definitely just buy one of the cheap automotive immobilizers off of eBay. I’ve had a similar one in my car for 13 years now with no issues. A cool feature that mine has is that it hooks into the driver door switch and only turns on the unit when the door is opened. It then looks for a tag for 30 seconds before going back to sleep. Hooking the door wire into a grip switch would keep the unit asleep and not drain the batteries when it sat in a corner for months at a time.
@I0TA When I say “MIL-SPEC” I’m referring to most semi auto FCG’s on modern AR models. (Basicly, using existing assemblies instead of redesigning the entire trigger package.)
You’re right when you say that that’s pretty much all it has to keep the selector from falling out. What about some sort of internal snap ring or “collar”?
Or you could just install an ambidextrous safety selector… That solves that problem right there now that I think of it…
Either way, I think it would require some custom manufacturing or at least modification to current selectors.
The only reason that the selector “holds” in the safe or fire position is that detent spring and pin. Perhaps making the hole in the selector for the “safe” position a little deeper so the pin can actually “lock” in place would work.
Or, I should say, instead of having just a straight pin going up into the safety decent, it could be positioned behind a small spring to give it a little “play” but still have tension on the pin.
When the unit “unlocks” it just retracts the pin or pushes it back.
Here are my $0.02 on the matter…
use the existing safety as a power switch to the RFID lock. That way, the system is not constantly draining batteries sitting idle. When the user wants to use the weapon, they flip the safety to fire position. That powers the RFID reader, which instantly reads the chip and “unlocks” or “enables” (depending on which way you want to go design wise), and then you can fire.
allow the user to select “fail secure” or “fail safe”. In door lock terminology, fail secure means if the system fails (batteries, malfunction, etc.) the door stays locked, but fail safe means the locks open and every door is passable (safe for people who might otherwise be trapped). With weapons, “fail secure” would mean you can operate the weapon, while “fail safe” means the weapon is disabled in the event of a system failure.
discussing all this on a public forum will invalidate any patent rights you may want to explore… unless you filed within 11 months of the first mention of a patentable claim… which isn’t likely to happen… so be aware and maybe move this discussion to a private message thread if you want to retain those rights. This forum allows multiple users in a PM thread.
The issue with solenoids is they are likely to be susceptible to the magnet attack previously discussed. Look for a micro-servo.