Show HN: PedalPC – Generate electricity and get exercise while you work

Hi HN,

The PedalPC is a computer desk with a built-in, pedal-powered generator. It helps keep you fit by making useful, moderate physical activity an integral part of your workday. It also provides you with a clean, reliable, and dependable off-grid source of electricity that you can set up anywhere.

I built it because I wanted some way to get exercise while I worked, but didn't want the energy I expended go to waste. I didn't see anything on the market, so I built my own. I've redesigned and rebuilt it several times over the years to arrive at what's shown here.

I've been working on this as a side project since 2010. I'd appreciate some feedback on it before developing it further.

The amount of electricity you can generate depends on your age, physical health, and how much you pedal each day. I'm 58 and produce around 220-240 Whr a day pedaling 3-4 hours per day. The PedalPC's maximum designed power output is 100 W. I typically generate about 60 W.

That may not sound like much, but it's enough to power my computer, monitor, printer, desk lamp, and a cooling fan. It also recharges our phones and battery-powered LED lights we use around our home for nighttime illumination. It also powers our router and fiber network terminator to give us 24/7 broadband internet and wifi.

The desk uses an e-bike direct-drive mini hub motor as the generator. It's driven by a toothed belt to minimize noise. The generator charges a 12 V LiFePO4 battery to smooth out the generator's variable output and store any excess energy generated for use when you're not pedaling.

The desk has four 12 V DC power sockets and four pairs of USB power sockets. You can view the power consumption of each power socket and turn each one on or off from a dashboard in your web browser. Each 12 V socket also has PWM control, for varying things like cooling fan speed or beverage cup heater wattage.

The dashboard is served from a small web server built into the desk. You can use it to host any other content you want, like a blog, wiki, small Fediverse instance, etc. (I use mine to host this project's web site.) You can also use it for a DNS server (e.g. pihole instance), file backup server, etc. Of course, you'll need to pedal enough each day to keep the server running! My dream would be to develop a network of desks like this, with each user hosting and powering their own content.

I have built similar machines for two software developers in our town. One was mostly identical to the one shown here, with a built-in desktop. He uses it with his laptop. The other was built without a desktop, so he could use it with his existing standing desk. He uses his to charge batteries, power banks, and phones while he works. Both seem quite happy with them.

Future plans are for a version made specifically for standing desks, better documentation, and an API to make it easier to integrate with things like Home Assistant, NextCloud, fitness loggers, or your own personal dashboard.

Would you like a desk like this? (If so, please sign up for the newsletter in the footer on my site :) ). If not, what would you like to see instead? Any advice you may have is welcome. Thanks.

That's a good question.

The simplest solution would be to plug your equipment into USB and AC power strips, then switch the power strip cords whenever you want to change setups.

The problem with doing this is:

1) You lose the ability to individually monitor the power consumption of each device, and

2) You'd have to use an AC inverter to power your non-USB-powered (e.g. your laptop or monitor). Using an inverter wastes a lot of energy, because you're converting from DC to AC back to DC. The more energy you waste, the less you have available to power your equipment.

This is fantastic! The first thing I thought of was this old Woody Allen film:

https://youtu.be/Zhl-AHUS-f4

The second thing was this graph by Doug Malewicki:

https://www.oocities.org/mdetting/sports/hupgraph.gif

Good job, hats off to you! I had the same idea some years back, and again during covid when I would o longer bike to work. As an old time bike mechanic and electronics engineer, I did some concept sketches but never ended up building it. You did and it looks good. Both the sturdy frame, the adjustments ability for seat and "handlebars", and the motor drive and electronics also look practical.

For me personally I would miss the desk space - I really like to have ample space to put keyboard, paper notes, electronics etc on. How would one use this with a regular desk? Have you tried it?

Frankly, I've grown to miss it too--especially when I'm doing breadboard development and need more space. I'm currently building one to be used with a standing desk (a regular desk is too low--your knees will hit the underside).