Coin Cell Hacks That Won The Coin Cell Challenge

It’s amazing what creative projects show up if you give one simple constraint. In this case, we asked what cool things can be done if powered by one coin cell battery and we had about one hundred answers come back. Today we’re happy to announce the winners of the Coin Cell Challenge.

Supernova Award: Coin Cell Powered Railgun

A railgun powered by an LIR2032 cell wins the Supernova Award with a cash prize of $500.

This project by [consciousflesh] dumps about 500-750 Joules of energy into a set of electromagnets to launch a graphite projectile. It makes quite a flash because the projectile is torn apart in the process.

The Supernova Award sought the project that burnt through the coin cell the quickest. This one’s a thinker, since the internal resistance of the coin cell is so large that you can’t get a lot of power out of it quickly. The solution is to transfer that power to another storage medium first. In this case, [consciousflesh] built a clever multi-stage DC-DC converter to get the most out of a single LIR2032 — the rechargeable cousin of the CR2032 which has lower internal resistance and yielded much better results.

Heavy Lifting Award: Coin Cell Powered Screwdriver

Driving screws into a 2×4 using power from a CR2477 wins the Heavy Lifting Award with a cash prize of $500.

This project is by [Ted Yapo], and is a fascinating way to get a lot of torque out of a tiny power source. Like the railgun above, [Ted] uses an intermediary medium to store the energy. He started with four NiCad batteries which had been stored with shorting bar across them (no juice to provide a head start). He discharges the CR2477 through a boost converter which he altered to produce a constant current output to maximize the power transferred.

The demo video is a bit comical as the familiar poor performance of NiCad cells means he took breaks between attempts to drive the screws further. He ended up with 19 screws started but only 3 fully driven. What we really liked seeing is that he continued his tests. After fully charging the batteries from wall power he was able to drive 27 screws. This equates to a total charge of only 11% from the coin cell battery.

Lifetime Award: Light Level Geolocator

A light level geolocator powered by a CR2032 is the winner of the Lifetime Award with a cash prize of $500.

[Jaromir Sukuba] took a really interesting concept, figured out how it worked, implemented it with super low power, and then proceeded to test across different parts of the world. His creation receives the Lifetime award because it is calculated to operate for 10 year with the LCD on, or 30 years with it off.

It’s a logging device that deduces its location in a very interesting way: by recording the ratio of light and dark in a 24-hour cycle. It’s a reverse calculation of sunrise and sunset (where you would need to know your coordinates). This takes date, sunrise time, and sunset time to calculate location. [Jaromi Sukuba] found some friends on in different parts of Europe to help test, sending each a prototype. The results are quite good. They can be off by a few dozens of kilometers but for extremely low-power, long-lifetime datalogging of wildlife movements this works with similar accuracy to the hardware that inspired his design adventure.

21 Winners of $100 Tindie Credit

In addition to the top prizes, 20 entries have been awarded $100 credits to for their excellent work. Check out the list of winners here, browse through all of the entries, and make sure to join us below for a few honorable mentions.

Honorable Mentions

We had many favorite entries that didn’t make it into this list of 21 winners and you will see a few more articles that feature those in the coming days. But we wanted to mention a few that were strong contenders for the top prizes.

Can you jump start a car with a coin cell battery? Sadly, no, but it’s not for lack of trying. [Ted Yapo] gave it his best and was a contender for the Supernova Award.

Looks like it might be possible to blink an LED for 20-40 years using [Robert Mateja’s] modern update on the concept of the LM3909. That’s an end-of-life chip whose purpose was to blink an LED. When we featured a story about that part, [Robert] grabbed his low-power magic wand and came up with this design which placed highly in the Lifetime category.

And finally, the ability to run a trainset around the Christmas Tree using a coin cell is extremely impressive. We previously featured this project built by [Mike Rigsby] which was hopelessly tied for the Heavy Lifting award but a winner had to be picked. This is excellent work [Mike] and we’re glad to have debated it in depth during judging. Well done!

22 thoughts on “Coin Cell Hacks That Won The Coin Cell Challenge

    1. I really like the way he uses a raw LCD for that project. I have a few of those lying around. I set an Arduino to pulse 2 outputs in opposite phase, and connected the LCD pins between them, with voltage dividing resistors. But I couldn’t get any visible results.

      Of course I don’t know the pinouts of my LCDs, but just by messing about, something should have worked eventually. I tried different time intervals. A bit of basic research seems to indicate it might be a bit complicated, and require driving more than just 2 pins with a simple AC signal. Like, there’s waveforms involved or something.

      So, I don’t suppose Jaromir wants to write a primer for how to drive raw LCDs from a microcontroller? Can’t be much harder than 7-segment LEDs, right?

      Or if not Jaromir, maybe somebody else did?

      1. It is indeed a bit harder than LED display.
        Driving LCD from two pins with opposite phases is completely OK way to drive an LCD, provided it has only one backplane and the voltage swing is OK for the particular LCD.
        Once it has more than one backplane, it’s getting more complicated and it’s advisable to use dedicated driver or MCU with driver to generate appropriate waveforms. Also, builtin driver provides better consumption than bitbanged solution. See AN1428, AN658 from Microchip, for example.

        I can write primer for driving LCDs, though I can’t guarantee anything.

        1. I haven’t got an LCD controller chip, and I’m not building anything with the LCDs. They’re just scrap ones. Maplin in the UK sell them in packs, you get a few LCDs (and a VFD) for a few quid, but with no docs. There’s 2 types of pack, each one contains the same selection of displays. The point, I suppose, is for people to tinker with, so that’s what I’m doing. No information on the Internet as far as I know. I thought I’d try figure it out then put the information up somewhere.

          The purpose is I just want to play with LCDs and see if I can control the raw dumb modules without controllers. The one in your project looks really neat, you don’t often see raw modules used in amateur projects.

          I don’t even know the pinout, but I figured sending 2-phase signals to random pins should make something appear, so far no luck. So it’s probably multiple backplanes. Whatever that means!

          I selected 3 volts, cos it seemed about right, lots of LCD stuff runs off 3V watch batteries or a couple of AAAs.

          I hear LCDs will work on DC, but over long enough it breaks down the liquid crystals, but 3V AC isn’t hard to come up with. I’ve no idea what sort of time period for the polarity change. I guessed around 10 – 100ms but it’s probably the backplane thing that’s messing up.

    1. We knew the internal resistance was going to be a problem for anyone trying for the Supernova, and Heavy Lifting is just a silly idea. But if we always color inside the lines we’ll never see what happens when ideas that aren’t supposed to be there get into the mix.

  1. I wouldn’t trust *any* of the projects here to last more than 10 years on a coin cell. Experience from PC hardware shows that the CR2032 CMOS battery typically fails after 5-10 years. However, assuming a battery capacity of 240mAh (typical value for CR2032) and a current consumption of 500nA of the RTC/NVRAM chip (typical value for the good old DS1307, some modern RTC chips even go down to 200nA), the theoretical battery lifetime should be 54.8 years. The reason for this huge discrepancy between theoretical and real battery lifetime is aging/limited shelf life of the battery itself. Energizer specifies 8 years for their CR2032 batteries and other vendors are probably not much better either. The same problem will also affect the projects listed here.

  2. Dataloggers running on a coin cell are pretty common here on Hackaday, but many projects start with custom PCB’s, needing reflow, custom bootloaders, and other things beyond the reach of beginners. Our latest student logger gets the job done with six jumper wires between two off-the-self modules. Assembly can take as little as 20 minutes, and it still sleeps at a couple of μA; so will run for years on the Cr2032 backing up the RTC.

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