Build a coin counter from particleboard and a Pi Pico
Feed the Meter
© Lead Image © Andrey Burmakin, 123RF.com
Parking meters and vending machines detect and count the coins you insert, but how do they work? We'll show you how to mimic the functionality with some particleboard, a Raspberry Pi Pico, a few extra chips, and some Python code.
Counting coins is a problem that was solved decades ago, but I was wondering whether I could come up with a solution of my own. While I may not have the same set of sophisticated tools that a parking meter manufacturer has, it should certainly be possible to create an electronic coin counter using just a Raspberry Pi Pico and some common components. Writing software that can count is trivial, but how do you detect what type of coin was inserted? If you assume that only legal US coins will be used, the easiest way to recognize them is by measuring their diameter. Table 1 lists the diameters of US coins, both in millimeters and in inches [1].
I decided to sort the coins using different sized slots. The coins roll down a small ramp and pass several cut-out slots. If the coin is the correct size, it falls through the slot. The required width of the slot depends on how fast the coin is rolling past whereas the height of the slot needs to be slightly larger than the actual coin while still being smaller than the next largest coin. In my case, the slots were approximately twice the width of the coin (see Figure 1).
It is not difficult to draw a small rectangle, but it is tricky to try and cut it out with straight edges that accurately follow the rectangle. Making a cardboard prototype was no problem, but it took some more effort to cut the slots out of particleboard.
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
US / Canada
UK / Australia
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
OpenMandriva Lx 6.0 Available for Installation
The latest release of OpenMandriva has arrived with a new kernel, an updated Plasma desktop, and a server edition.
-
TrueNAS 25.04 Arrives with Thousands of Changes
One of the most popular Linux-based NAS solutions has rolled out the latest edition, based on Ubuntu 25.04.
-
Fedora 42 Available with Two New Spins
The latest release from the Fedora Project includes the usual updates, a new kernel, an official KDE Plasma spin, and a new System76 spin.
-
So Long, ArcoLinux
The ArcoLinux distribution is the latest Linux distribution to shut down.
-
What Open Source Pros Look for in a Job Role
Learn what professionals in technical and non-technical roles say is most important when seeking a new position.
-
Asahi Linux Runs into Issues with M4 Support
Due to Apple Silicon changes, the Asahi Linux project is at odds with adding support for the M4 chips.
-
Plasma 6.3.4 Now Available
Although not a major release, Plasma 6.3.4 does fix some bugs and offer a subtle change for the Plasma sidebar.
-
Linux Kernel 6.15 First Release Candidate Now Available
Linux Torvalds has announced that the release candidate for the final release of the Linux 6.15 series is now available.
-
Akamai Will Host kernel.org
The organization dedicated to cloud-based solutions has agreed to host kernel.org to deliver long-term stability for the development team.
-
Linux Kernel 6.14 Released
The latest Linux kernel has arrived with extra Rust support and more.