Electrically Assisted Zipper

In this instructables, I will explain how I made an electrically assisted zipper for coats. I realize that it might seem to be a system designed for extremely lazy person as it extremely easy to zip up a coat zipper… If you have 2 hands available! If you have only one hand available, it can become a nightmare to zip-up your coat.

The system described in this instructable is the result of numerous iterations and is still improvable, feel free to use this instructable just as a little bit of inspiration and make your own -better- system!

The global idea is to place a flexible track (made from GT2 belt) parallel to the zipper, place a motor unto to slider and move it thanks to the motor rolling on the flexible track. This, of course, means that the motor must be quite small and yet have decent torque (see material list to see the motor I went for)

• Super glue

• Mini motor such as this one

• GT2 belt (at least as long as the zipper track)

• GT2 pulley

• Momentary switch x2

• 9V battery

• L293D

• 3D printer (I am using a elegoo neptune 2)

• Tailor's pins

The first -
and one of the most important - step is to choose the zipper on which you are going to work to add the system.

There are two things to keep in mind when choosing the zipper:

· The ”slider” part has to be big enough to glue the system to

· The slider should slide easily on the tracks, otherwise, the system will not work as the small motors we are using in this project have really limited torque.

There are a
lot of mini motors out there that you can find on numerous website: Aliexpress, Amazon, Ebay, etc.

There are a few parameters that you must check when choosing the motor for this project:

· Output shaft speed: this speed is described in RPM. The motor I am using is a geared motor which means that the motor speed is decreased through a few gears (the torque is proportionally increased).

· Biasing voltage: We are running the system on a 9V battery, we have to make sure that the motor will run (if possible) at the voltage of the battery so we do not have to manipulate the voltage trough modules that would complexify the system.

One quick precision about the motor speed. You must decide at the design stage how long you want the motor to take to fully close the coat. I chose that I wanted the coat fully closed within 2s, I have around 70cm of travel, the speed I need is 70cm/2s. The pulley diameter is 12mm (or 1.2cm). To know how fast your motor should spin, you can do.

RPM*π*1.2cm/60s=70cm/2s

Hence the result: RPM=560RPM

Keep in mind that this speed is in case you run the motor at rated voltage, and you do not count slipping. I can choose a motor with a speed close to 560RPM, and I should get the aimed speed.

On the motor is mounted a GT2 pulley, when the pulley starts spinning, it engages with the belt and moves the slider up and down. On my motor, the output shaft was smaller than the inside diameter of the pulley, I have printed an adapter out of PLA

I personnaly use Autodesk inventor, but of course, you can use whatever modeling software you prefer.

Take the measurement of the slider so that you can create a custom footprint adapter. On the photo, you can see the adapter for my slider and although the general shape of yours will probably closely resemble mine, every slider is different!

My work process here is to observe the shape of the slider that can seem complicated at first glance and then decompose it in simple shapes (lines and circles). Although this step can be done with a simple ruler, a caliper can really come in handy.

The track simply consists is a GT2 belt glued onto a piece of fabric (the fabric is in blue on the picture). The fabric is then sewed on the inside of the coat. Be careful, alignment is quite important here, to minimize unnecessary friction, the belt should be always aligned with the path of the pulley mounted on the motor. Before sewing the fabric on the coat, you can just put temporary tailors’ pins to test the system.

You can make a simple custom PCB, but because my project still needs some improvement, I am assembling all the electronics onto a breadboard.

The electronics consists in an H-bridge controlling the motor in either direction upon pressing of either push buttons. You can wire the motor as shown on the picture.

You can see on this video the slider moving, the torque was too low to actually close the zipper but this gives you an idea of what it looks like. To be able to actually close the zipper, I had to operate the motor at a voltage of 12V (I switched the 9V battery to a 12V drone battery). Closing the coat eventually worked (I do not have a video of that 😐), but it took almost 5 seconds (instead of the 2s aim). For the next version, I will try a motor just a little bit more powerful and I will choose a coat with a better slider.

This instructable did not present a completely finished product, but rather where I am at in the
development of an electrically assisted zipper. I have went through quite a few design (see picture above) and I still have a way to go in making the system working perfectly, if you want to try to make something similar, please please do not get discouraged when something does not work on the first try 😊