Recycled Wireless Door Lock (No Coding)




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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!

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Step 1: Project History

So if you've seen any of my other Instructables 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.

Step 2: Parts List

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
  • Batteries
  • 5 volt Power supply
  • Slide Lock

The tools we need are:

  • Soldering Iron
  • Drill
  • Hot Glue Gun

Step 3: Opening the Car

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

Step 4: Testing

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).

Step 5: Putting It Together

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.

Step 6: Why You Shouldn't Do This

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.

Step 7: Fin

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!

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    11 Discussions


    1 year ago on Step 7

    Congratulation on an excellent instructable. You have accomplished an excellent little bit of re3pouposed engineering which i love to do myself.

    I buy these little "dumb" RC toys all the time- sometimes six at a time because they change so often. When I find a deal on them, I snatch them up. Basically, they are all the same under the plastic. I have had an RC doorlock on my mind for a long time. If you couple your doorlock 'electronics' to a few extra bits, like transistors, you could actually have a specific switch code, like left-left-right-right as a sort of 'combination" to open your lock. The rear wheel motor is not particularly useless since it usually has forward/reverse and can thus be coupled to a 'toy' gearbox, which could provide some powerful torque to drive a threaded lead screw (say a 1/4-20 all thread rod and nut) to move a slide lock back and forth. I agree this is a bit more engineering, but worth it for added security. I doubt some kid playing with his outdoor toy car will 1: be in range (these toys have an exceptionally low power transmitter) and 2: pull off the exact pre-determined "combination" in a limited time- which could be set by a simple R-C circuit. (again, more engineering, huh?) As for the idea that these toy circuits are not reliable, there is some merit to that. But, electronics is a set of exact physics that works or it does not. So long as you do not over-stress the output and do not abuse the set, it will function indefinitely- or until the capacitors deteriorate over decades or the environment goes bad on it- like excess moisture, corrosion, mold or heat, etc. That could be solved by simply encasing the rig in silicone or epoxy, isolation box(?). Essentially, with some thought, the reliability factor can be greatly enhanced.

    Regardless of my ideas, you are the guy who made an excellent instructable, so, my challenge is to try one myself. The time and effort these take to make a really good one, such as yours, is what intimidates me.

    Anyway- Your project is inspiring. thanks for doing it. Keep on thinking you are going to be a great developer of such things in your future.JB

    4 replies

    These are all great ideas and id love to see them in action. While I agree that an RC car can defiantly be made into a reliable and useful door lock I feel like the amount of effort youd be putting in wouldnt match the outcome. For example if an Arduino is used instead of the RC Car and most of the issues would be solved Using an RC Car with all these hacks might be over engineering it when there are easier options. Either way thank you for the great feedback!

    Yes, I completely agree- I just enjoy the "bash" of it all. Taking junk and making stuff. It's all too much fun.


    Reply 1 year ago

    I had the same thought on the combination. Well done on the job of documenting the hack, even though the door lock isn't practical.


    Reply 1 year ago

    Perhaps a new contest would be appropriate- Toy Hacking.

    Chris W.J

    1 year ago on Step 7

    I love this idea. These are the kind of projects I enjoy, especially with a bunch of old mini drones and old rc cars lying around it's a great way to reuse them for something fun. When I was younger I made something similar to launch flying model rockets that came in kits. Excellent job. Great, easy to understand tutorial.

    1 reply

    Thank you! I also have way too much old tech lying around, this is a nice way to give it near life and learn something along the way.


    1 year ago

    I like this idea. But as you said, toy RC electronics may not be suited for a security objective. is it possible that some kid around the block playing with his drone or RC car, will be opening and closing the latch continuously?

    1 reply

    Yeah, like i mentioned that is one of the biggest issues with this project and why it should not be used as an actual door lock


    1 year ago

    If you wanted to make something more serious of this, it shouldn't be too hard to incorporate some sort of encryption, such as used in remote opening of car doors. You could use a microcontroller, or it might be possible with the radio control. I fly RC planes, and the Tx/Rx uses all sorts of encryption and channel hopping so as not to interfere with another person's plane - and there can be lots of them in the air at once. I also have a cheap Motorola walkie-talkie that has 128 channels using encryption so that what you say can't be understood by somebody on another channel. That person can hear that you're talking, and he can't use his channel at the same time - but he can't understand what you're saying.

    I once worked on a hotel door locking system, and the mechanism was better than simply driving a bolt. If a door sags a small amount on its hinges, the bolt doesn't align any more, and it takes more force that you'd get from a servo. In the hotel mechanism, the servo moved an interposer in the lock, and the lock was opened by manual force. If the interposer wasn't in place, then turning the handle didn't do anything. If it was in place, then turning the handle pushed the interposer, which pushed the latch.


    1 year ago

    Ok if you want a lock you can use, try a hidden magnetic latch & pull it back with a neodymium magnet. As long as no one knows it's a magnetic lock, you're perfectly safe.