While a lot can be done with a microcontroller and some code sometimes a project can get by just by using some electronics that serves the same or a similar purpose as what you're trying to build.
This concept is what we will be looking at in the project, is it possible to make a functioning door lock with recycled electronics? (spoiler: it is). We are going to take a look at how we would go about doing this and some upsides and downsides.
Let's get started!
So if you've seen any of my other tutorials you'll know that I've made a wireless door lock already (check it out here), however, the previous one used an Arduino and some custom code, the purpose of this project is to make it as easy as possible to make a wireless door lock.
While we go about building a wireless door lock with no code we will, however, learn basics about circuits and how to repurpose old electronics which has proven to be a very useful skill.
So there are a few things we have to keep in mind while trying to find electronics that can be repurposed into a door lock, for one it needs some sort of wireless communication, whether that's Bluetooth, RF or even WiFi and secondly we have to make sure our donor piece of electronics has at least one moving part that can be used to slide to door lock.
It just so happens that an RC Car fits perfectly into this category, its got wireless communication with a controller and moving parts for us to tap into.
So the final parts list is as follows:
- An RC car
- 5 volt power supply
- Slide lock
The tools we need are:
- Soldering iron
- Hot glue gun
So first things first we want to get an idea of what we are working with, we need to take the car apart. This can be done pretty easily just by unscrewing all the visible screws. We should then see the main circuit board and two motors, the back motor is used as the drive for the car and the front motor is used in conjunction with a gearbox to turn the front wheels.
If you take a closer look at the front motor you'll notice that there's a little notch that sticks out that connects to the steering assembly, this will most likely be the way we move our slide lock, so we can set this motor aside for now.
Let's take a second to see what parts have come out of the car so we can get an idea of what's useful and what's not:
- The front motor is definitely something we are going to use.
- The main control board of the car is also a must.
- The rear motor has no gear system on it so finding a way for it to move a slide lock would be quite challenging compared to the front motor, so we can get rid of this.
- The Battery compartment on the car is also not too useful as in a later step we will be powering the car from a wall supply.
These, for the most part, are what you would find in a typical cheap RC Car, some car may have more. The important thing to note is that we only need the front motor and main control board
At this point, we need to test if the front motor is actually capable of moving the slide lock backward and forward. To do this we need to make a slight mod to our slide lock, we need to pull out the little metal handle. This is normally held in place by friction or glue so getting it out is pretty easy.
Once that's out place the nob of the steering motor into the hole and hold it in place. Now supply 5 volts to the motor and if everything goes well you should see the slide lock shoot forward (if this isn't clear enough check out the images).
We've found our parts, we've tested and now we are ready to put it together. We can now glue to the motor onto the slide lock with the notch in the hole we made by removing that metal handle. Then we need to find a place for the main control board of the car. I ended up just gluing mine in place on top of the motor.
So when it comes to powering this we could just use the original 3 AA batteries but after a couple of hours they would be dead so I decided to try hooking it up to a 5-volt power supply. Now keep in mind that AA batteries are 1.5 volts so the three of them add up to 4.5 volts which is a little less than 5 volts but as I suspected it worked just fine.
As fun as this project may be, we also have to keep some of the downsides in mind. For one, you shouldn't put this on an actual door. Most of these cheap RC cars operate on the same frequencies which means if your neighbor suddenly drives their car they might end up locking you out. Also, these circuit boards aren't reliable at all so after a few weeks of constant use you might just find your door permanently locked.
Please keep in mind that this project is just a demo and is definitely not meant to be used on any active doors.
So at this point, the wireless door lock should be finished. I mounted mine in place just to give it a test but ended up taking it down the same day as I don't want to risk my door being locked while I'm out of the room. Thanks so much for reading if you have any questions id love to answer them in the comments!