!blog - corey menscher

HelioHopper is a small helicopter whose short “hopping” style of flight is powered by solar energy.  It was developed with Oscar Torres, Theresa Ling, Drew Burrows, and myself.

HelioHopper’s goal is to educate an audience of the abundance of ambient solar energy in our environment. Multiple HelioHoppers, made of flexible solar panels, small batteries, and counter-rotating blades, are scattered in a field. As sunlight falls upon their solar panels they gather enough energy to take a short flight, emulating grasshoppers. The frequency of hops is directly proportional to the amount of sunlight available to the HelioHoppers…providing a physical representation of available ambient energy. Seeing multiple HelioHoppers jumping randomly as their energy requirement is met will hopefully inspire viewers to consider the availability of solar energy, as well as the futility of creating energy-harvesting objects that serve no other purpose.

Once the energy is depleted, the HelioHopper’s solar panels begin to harvest ambient solar energy to allow further flight. We wanted to demonstrate the abundance of energy available, as well as the concept of “The Paradox of Efficiency”. This paradox states that as we increase our energy efficiency…in this case harnessing the available solar energy…we find more uses for the energy, which negates any savings. HelioHoppers were created by the mere fact that we CAN harness the solar energy andimplement existing parts (batteries, plastic, motors) in a way not previously executed.

The frequency of hops can also be related to the amount of solar energy available. Similar to cricket chirp frequency being related to the temperature outdoors (http://www.loc.gov/rr/scitech/mysteries/cricket.html), the HelioHoppers will take flight as sunlight intensifies.

We used a small remote-controlled indoor toy helicopter as a platform for developing HelioHopper.

We created our own circuit for harvesting solar energy and storing it in a small lithium-polymer battery, with the intention of releasing enough energy to propel the HelioHopper into the air so it can fly a short distance. The solar energy is collected by 4 5.5V flexible solar panels, which are quite light. To release the energy, our original intention was to base the circuit on a 1381 Miller Solar Engine based (using 1381N 3.7V voltage trigger), but there were a number of unforseen problems.

The biggest problem with using this circuit was that we used a small 3.7V 20mAh (20C) LiPoly battery. Due to the nature of lithium polymer batteries, they can not (or rather should not) be discharged more than 1v or so. This meant that we needed the circuit to come on at 3.7V, but turn off again around 2.7V. The circuit we attempted to use, however, wanted to drain the battery completely because it was designed for capacitor energy storage. We attempted to circumvent this problem by using an additional 1381L 3.4V voltage trigger, but we later found out that the 1381 voltage triggers actually flip on when ANY voltage above their threshold is provided. We thought the trigger would only work within its 3.0V to 3.3V range, but we were wrong. This led to us moving to a 555N timer IC. The 1381N was used to trigger the 555 timer, which was configured to turn on a transistor for a 10 second period, giving us a 10 second flight. This is theoretically better for the battery as well, as the 10 second duration kept battery discharge well within it’s 1V range.

Unfortunately, the 3906 transistor we used to turn on the motors was not capable of driving them with enough current. It tops out at around 200ma and we needed more like 600ma for sustained flight. This was solved by using a TIP120 transistor, which can pull over 1A. The TIP120, however, is a very large component with a metal heatsink. Having to use it immediately killed the possibility that our prototype would fly with the circuit onboard.

On Aspen Mountain, there area a number of “shrines” dedicated to fallen musicians…Elvis Presley, Jerry Garcia, John Denver, and even Liberachi. (view a panorama here.) The shrines are not well known or clearly marked. Usually a local has to show you the location, unless you sumble upon one while skiing through the trees. The shrines consist of memorabilia to the musician as well as a quiet place to sit and contemplate the musician’s life. The Jerry Garcia shrine is one of my favorite places to take a break on the mountain, and I always wanted to leave something behind. Instead of leaving a photo, ticket stub, or some other type of physical object, I decided that I would leave the actual MUSIC. Thus, the jerryPlayer was born!

jerryPlayer is a crank-powered audio amplifier. The original intention was to include a 1.5V mp3 player as well to create a self-sustained solution, but I had many problems hacking an existing MP3 player to work, which I’ll discussin a moment. The player is powered by a hand-cranked dynamo that can generate a max 12V at 500mA (short circuit current). The energy is stored in a 1F 11V capacitor. Here’s the energy data:

Measured Open Circuit Voltage (V): 12V
Measured Short Circuit Current (mA): 500mA
Target Capacitor Capacitance: 1F
Target Capacitor Charged Voltage (V): 11V
Target Capacitor Total Energy (Joules): 72J
Time to Charge (seconds): 63 seconds
Observed Power (Watts): 1.142W

The dynamo was taken from a LED bicycle light and hacked for my purposes. The unit came with a small power conditioning board that included a bridge rectifier chip (to allow the crank to be turned in either direction) as well as a capacitor to smooth the current. This was then connected to an LM386 amplifier, which needs a minimum of 6V. This amplifier is a simple one, but provides a good amount of power for the few feet of space I want to fill. The output will eventually be connected to a waterproof speaker to sit outside the housing, but for now it’s conneced to a 3″ speaker. When fully charged, the amplifier provides a decent audio signal for about three and a half minutes until it cuts out. This is actually better than I expected, and will provide a nice “snippet” of music for the shrine…encouraging people to hear a small portion and then move on. (I don’t want people to necessarily hang out for an extended period…although they could keep the player going with a few turns of the crank every few seconds.)

The amplifier’s input was connected to an iPod Shuffle to provide audio for the presentation, but I intend to use the the capacitor to power a 1.5V or 3.3V mp3 player in the final version. This will presumably reduce the amount of playback time, but from my tests it should only reduce it by a minute or so. I rendered four Coby 128mb mp3 players I bought at a Super Value store inoperable in my tests. They worked for a short while, but eventually died. I think this may be due to excessive current, although they are extremely low quality players and could just be very touchy about the condition of the power they are given. (I was using an LM317 variable voltage regulator, which supposedly provides relatively “dirty” current.) They would not have been a good solution anyway because their interaction requires that a user hold down a play button to power the device, and then hit the play button again to start playing. This could have been achieved though an external momentary switch, but I would prefer the player to begin playing when it is powered, so I will probably be using the Sakura DIY mp3 player for the final product.

Yesterday I presented on the topic of Abiogenic Petroleum Origin in my Sustainable Energy class. One of our textbooks is titled “The Bottomless Well”, and while it has nothing to do with abiotic oil, it reminded me of the topic.

The generally accepted model of “fossil fuels” states that oil comes from the fossilized remains of organic matter (plants and animals) sitting within sedimentary layers of rock that have been subjected to geologic forces over millions of years. But the theory of Abiogenic Oil Generation postulates that the creation of petroleum deposits dates back to the formation of the earth itself. The hydrocarbons already existed within the solar system, and instead of vaporizing into space, were subsumed into the earth’s mantle. It’s kind of a “crackpot” theory in most circles, but there is some traction. Much of the science is valid. But it will be a very long time until we can determine its true viability, as the depths at which the abiotic oil deposits are supposed to exist are over 150km deep. The deepest we can currently drill (and only for isolated projects) is about 6km!!