Making Electric Door Locks

Planning to park the van in remote places and being away all day, the risk of a break-in will be high. So, a security system with AI sensing, glitter bombs and instant de-cryogenisation of a mean rottweiler might happen in this van's future.
 
But for now it should at least be protected against the most used fast break-in methods that target the Ford Transit's factory system. Those can open a door in a matter of seconds. Examples:
And spoofing key fobs is pretty easy on some cars (dunno on the Transit).
 
So the goal is to complement each factory door lock with another lock, independent from the factory system. If the latter gets compromised, the doors will still be locked.
 
Adding key locks to each door would do, but it would be a pain to use. It's got to be as easy as pushing a button before exiting the van... 😅
Here is the plan:
  • Electrically operated interior bolts for 3 doors (passenger, sliding, rear)
  • Hidden control switch near the driver seat
  • Additional exterior keylock on the driver door
In high risk areas the driver will simply actuate the complementary electric locks with the switch, lock all the doors with the Ford key fob, and lock the exterior keylock on the driver door:
 
A few aftermarket electric locks are available. They are typically designed to be installed in the doors and connected to the existing door lock wires. Like the Cargo Van Locks Inc model from US Upfitters ($460 a pair, $860 complete Ford Transit kit):
 
The Thunderbolt lock also optionally comes with its own key fobs ($280):
However, 3 sets of the cheapest model would be more than $700, and would have to be adapted for non-door mounting. They are also pretty big, which could be cumbersome since they'll be installed in the living space.
 
Note that some house door locks can also be repurposed for van use. I opened up this one, hoping to connect it to the 12V system and control its bolt's motion. But hacking its motion mechanism was not simple. However, it is somewhat solidly build, and will work wirelessly as is with batteries. At $70 it is a bargain compared to the $240+ locks above:

Anyway, water under the bridge, can't take my mind off the idea of building my own impenetrable DIY door locks now...
Wait... wrong one ! 😂
 
Now, that's better:
What a cute itty bitty thing ! Very low profile, at 6.5" x 2.1" x 1" (16.5x5x2.5cm). It is extremely robust, and yet weighs a very reasonable 0.9lbs (400g). That's a home run !
 
Maybe I should do a whole production run ?
 
It was built for less than $50, using the following parts:
3/8" OD 0.028" thick tube
1/4" ID 5/16" OD tube
7" x 7/8" x 5/8" aluminum bar
M8 eyebolt (mounted on the actuator)
(not shown) M6 35mm bolt
M4 25mm flat head bolt
Mini linear actuator's specs: 12V 1.2" stroke 14lbs 0.6inch/s (30mm 64N 15mm/s)

The hacked sliding bolt plate comes from an 'Everbilt 6-1/2 in. Zinc-Plated Heavy Duty Spring Bolt' lock from Home Depot:
First, a ~38mm long and ~10mm large slot was drilled and dremel'd on the side of the barrel:
The stock steel lock bar was ditched, too heavy. Instead, an aluminum bar was cut out of a 3/4" thick plate and shaped to freely slide inside the lock's barrel. A threaded hole was tapped into it to receive the M6 bolt that the actuator will connect to.

The rest of the build is pretty self explanatory:

Lastly, some thought needs to be given to the possible failure modes. If motion is impeded (door not fully closed, foreign object in the strike plate, etc) the commercial electric locks will apparently just not close, as they are seemingly based on an pulsed motion, like the factory door locks.
 
However, an actuator will keep pushing until its limit switch is reached. If motion is impeded, it might end up breaking or frying up.
 
This can be avoided with a springy or compliant connection to the sliding bolt. But that would have made the build more complicated. So instead I will likely protect each actuator with a fast acting resettable Polyfuse like the MINIASMDC030F-2, connect the switch to a ~3" timer, and add a buzzer to alert the user in case of a failed closure.


  Updated   Version 2.0

Actually, instead of adding failure protection via electronics, to make things simpler the bolt was modified with a spring, and the eyebolt was replaced with a bumper:
 
This way, the actuator can now fully retract without self-destroying when deploying the bolt out, even if the bolt's motion is impeded.

The rod end of the actuator is held in place thanks to some 3/4" square tubing, so the rod remains aligned with the bolt pin throughout its motion.
 
There is no failure protection when the bolt retracts as it does so by just sliding back in its barrel. But since that motion is not dependent on external elements (like a floor catch hole when deploying out), it is unlikely to get impeded.


All that's left is to make 2 more, and install the locks on the B pillar for the passenger and the sliding doors, and on the floor for the rear cargo doors.
[insert pic once installed in the van]
 
But that's for later. For now, abracadabra, we got Fort Knox on a shoestring budget ! 😂
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