Brilliant auto-off feature for a bike light

auto-off-bike-light-switch

If you’re going to use your bicycle as transportation at night you really must have a head and tail light in hopes that the crazy drivers don’t hit you. For good reason, these lights don’t turn themselves off. But [Miceuz] kept forgetting to shut it down upon arrival and always ended up with dead batteries. His quest for an auto-off feature that actually worked ended in a brilliant and simple add-on circuit.

He first thought about using an accelerometer, but couldn’t find one that fit the bill without also adding a microcontroller. He came up with an even simpler circuit, which can be seen at the base of the black plastic housing. It’s a bit of copper clad board with a small spring attached. The spring completes an RC timer circuit which drives a MOSFET. When that circuit is charged, the MOSFET connects power to the bike light. When the cap runs out the MOSFET threshold cuts power and everything turns off. Since the spring jiggles while he rides it provides the momentary connection necessary to charge the capacitor. Stay stationary for about 30 seconds and the auto-off kicks in.

Robot performing a tightrope act

This robot is able walk the tightrope (translated). Well, it’s more of a shuffle than a walk, but still a lot better than we could do.

In the video after the break you can see the bot starting on the platform to the right. As it steps out onto the wire (which rides in a groove on the bottom of its foot) the robot spreads its arms to help maintain balance. When the other foot leaves the platform that is the last stride we will see until it reaches the other side. The rest of the act consists of sliding the feet a little bit at a time until it gets all the way across.

[Dr. Guero] has been working on at least one other balancer as well. Also embedded after the break is a robot riding a bicycle. It actually puts a foot down when stopped, and gives a stuttering push-off to get going again. This guy would be right at home riding past you in the hallways of the Death Star.

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Turn signals on your head

Several weeks ago, I was in Culver City L.A., and happened to find a hackerspace nearby. It was a pleasant coincidence that the night I chose to randomly show up, was their public meeting which focused more on projects people were doing. The place was packed, I was barely able to squeeze in the door and actually stood outside for part of the meeting, just listening to people talk about what they’re making.

One of the projects I did get to see was this bike helmet built by [Naim]. At first I was amused at the idea, but the idea of putting lights and an accelerometer on a helmet wasn’t that groundbreaking. But as [Naim] kept talking, he caught my attention. For one thing, the one he was showing at the hackerspace seemed to have some built in correction for natural head movement. In this video he does look around a bit without false positives. At the hackerspace he explained the way he monitors the motion to avoid natural movements causing the lights to initialize.

The part I was really interested in was his power. He spent tons of time reducing the power consumption on the base arduino. I believe the number he used was 10 years of standby without causing the battery to vent or die. If you pick up the helmet at any point during that time period, it automatically turns itself on based on the accelerometer’s motion. While the bike helmet itself was a fairly cute idea, I was really trying to get him to send me the information on how he’s saving power. I believe he had to cut the traces to the arduino’s native power management. Hopefully we’ll still hear from him on the details.

Washing machines that do it without electricity

Those of us living in the first world take clean clothes for granted. Throw them in the washing machine, transfer to the dryer after 45 minutes, and you won’t smell for another two weeks or so. But for people living in areas without electricity, clean clothes are a huge amount of work. Hand washing a family’s clothes is estimated at 6 hours per day, three to five days per week. Here’s a post that looks at some of the different human-powered washing machines out there.

We’ve built our own human-powered machine before using a five-gallon bucket with a hole in the lit to receive the handle of a toilet plunger which acts as an agitator. But that pales in comparison to some of the machines seen here. The concept we like the most is shown above. It’s an MIT project being used at an orphanage in Peru. The bicycle lets you easily power the spinning basket inside of the drum. The rear derailleur has been mounted on the axle so that the rider has a wider range of gears when spinning heavy loads. Take a look at the post linked above to see all of the offering, but we’ve also embedded video of two of them after the break.

If you were looking for a washing-machine powered bike instead of a bike-powered washing machine you’ll want to head on over to this post.

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DIY GLOBARS for nighttime bike visibility

Inspired by a non-existant yet still cool illuminated bicycle handlebar project, [Becky] over at Adafruit came up with her own version of light up  handlebars. Not only is her project actually real, they’re also a pretty cool build that brings a little lightcycle ambiance to twilight bicycling.

[Becky]’s light up handlebars are inspired by the GLOBARS concept design that made the blog rounds earlier this year. Instead of custom machined aluminum tubing, [Becky] used an Adafruit LED strip neatly assembled with heat shrink tubing and waterproof tape, along with an 8 AA-cell battery holder in a fabric and velcro pouch suspended from the top tube on her bike.

After wrapping the LEDs around the handlebars, [Becky] wrapped them in clear handlebar tape she sourced from Amazon. From the video after the break, the 2 meter LED strip on [Becky]’s handlebars verge on lightcycle territory, but sourcing a 6 AA-cell battery holder over an 8-cell will bring the brightness down to a reasonable but still safe level.

You can check out [Becky]’s build video after the break.

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Hackaday Links: July 13, 2012

Testing LEDs

Over at the Albuquerque, NM hackerspace Quelab, [Alfred] needed to test a bunch of surface mount LEDs. He ended up building a pair of 3D printed tweezers with a pair of needles attached to the end and a space for a coin cell battery. It works and Quelab got a new tool.

Woo Raspberry Pi

[tech2077] added an FTDI chip to his Raspberry Pi to do a little single cable development. We’ve seen a few similar builds, but surprisingly nothing related to the on board display serial interface. This wiki page suggests it’s possible to connect an iPhone 3G or iPhone 4 display directly to the Raspi. Does anyone want to try that out?  Nevermind, but it would be cool to get a picture from a display plugged into that display port on the Raspi.

I like to ride my bicycle, I like to ride my bike

Over at the 23b hackerspace a few people were having trouble finding a good bike cargo rack that wasn’t overpriced. They built their own with $30 in materials and a salvaged milk crate. It looks great and is most likely a lot more durable than the Walmart model.

If that cargo rack fell off, it would look like this

Apparently you can get ‘spark cartridges’ to attach to the underside of a skateboard. [Jim] saw these would look really cool attached to his bike so he did the next best thing. He attached them to his sandals. It does look cool…

Less heat, less noise

[YO2LDK] picked up a TV tuner dongle for software radio and found it overheated and stopped working after about 15 minutes (Romanian, Google Translate). He hacked up a heat sink from an old video card to solve this problem. Bonus: the noise was reduced by a few tenths of a dB.

Electric bike (earplugs not included)

It’s obvious this bike has some extra parts. But look closely and you’ll see the chainring has no chain connecting to it. Pedaling will get you nowhere since [PJ Allen] rerouted the chain in order to drive this bicycle using an electric motor.

He’s got beefy motor which pulls 350 Watts at 24 Volts. For speed control he opted to use an Arduino, pumping out PWM signals to some MOSFETs. This results in an incredibly noisy setup, as you can hear in the bench test video after the break. But once this is installed on the bike it doesn’t quiet down at all. You can hear the thing a block away.

The original road test fried the first set of 7A MOSFETs when trying to start the motor from a standstill. It sounds like the 40A replacements he chose did the trick through. We didn’t see any information on the battery life, but if he runs out of juice on the other side of town we bet he’ll be wishing he had left the chain connected to the crankset.

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