Light Cycle and Light Stick Design

Hyderabad, India

Prepared by David Moon, CSI volunteer, September, 2013

Background:

Community Solutions Initiative is an IEEE PES group with a goal of bringing low-cost, safe, and clean

energy alternatives to developing countries around the world. One of the products developed by CSI is

the Light Cycle, a pedal-powered generator, which uses a bicycle and an automotive air conditioning

blower motor to charge 12v batteries. The 12v batteries are then used to charge Light Sticks

(rechargeable LED flashlights built by CSI), charge cell phones, or power a variety of other equipment

capable of running on 12v direct current. The ultimate goal is to create a profitable business for a local

community member by generating an income through charging electronic devices for others by pedaling

the Light Cycle, and also offer a safe, low-cost alternative to things like kerosene or fuel oil.

I have been living in Hyderabad, India for approximately 8 months working to build, demonstrate, and

place Light Cycle units in government schools throughout Andhra Pradesh to promote entrepreneurial

interest in low-cost, clean energy-generating devices. I have teamed up with a local community partner,

Ikya Global, to aid me in locating schools that can best benefit from the products that Community

Solutions Initiative can offer.

I am currently working with Ikya Global to place 5 Light Cycle units, along with 100 Light Sticks at

identified schools before I return to the United States in October, 2013. Due to the cost and availability

of parts needed to build the Light Cycle, Light Stick, and charging components I have made several

modifications to their original design.

Objective:

This report is meant to serve as a supplement to the current Light Cycle and Light Stick build

instructions. Several modifications have been made to take advantage of readily available and more

cost-effective parts in Hyderabad, India. These modifications may, or may not, be advantageous in

other parts of the world. I hope that these ideas will aid others in future design and development

endeavors for the Light Cycle and the Light Stick.

Light Cycle & Light Cycle Frame:

The previous Light Cycle frame is made from manufactured lumber, mostly 2”x4”’s and 2”x6”’s. This is

very hard to find in India, and it is extremely expensive in comparison to the cost of lumber in the United

States; however, plywood is readily available in India and far cheaper. Another excellent resource

specific to India is a common model of bicycle with a fold down kick-stand that fully elevates the rear

tire off of the ground. This is similar to the kick-stands seen on some motorized scooters and small

motorcycles. I took advantage of these two abundant parts and designed a new frame and motor

mount for the Light Cycle.

With this new design no modifications to the bicycle are necessary, namely the axle extensions required

in the previous model. Although there is a lock on the kickstand, I did use some nylon rope to secure the

kickstand in place so it is unable to wiggle at all during use of the Light Cycle. There is one piece of pre-

cut lumber used in this build; however, this piece can also be replaced by 2 or 3 small pieces of plywood

stacked on top of one another. This Light Cycle frame design produces a reduction in cost from Rs. 1003

($15.67 USD) to Rs. 174 ($2.72 USD), a savings of around 87%. An added benefit to this design is that

the entire unit is now mobile. The frame, motor, battery, and charging components could easily be

packed into a small box and transported on the rack over the rear wheel of the bicycle.

Octopus Hub & Charge Controllers:

The previous model of the octopus hub uses several AML connectors, which are relatively expensive in

India, and it can be difficult to find consistency in size, shape, and model. I replaced these with small

sections of circuit breadboard and silicone sealant. Electrically speaking these charge controllers are

identical to the previous models. Most of the voltage regulator is left exposed to allow for heat

dissipation, and I have yet to see any problems with the charge controllers during charging. I also

replaced the electrical end-cap on the octopus hub with an electrical bus connector. This doesn’t

produce a reduction in cost, but I feel that it creates a more durable product with no added cost.

By eliminating the need for AML connectors, and sourcing some slightly cheaper parts, this design

reduces the cost of the octopus hub from Rs. 550 ($8.59 USD) to Rs. 407 ($6.36 USD), a savings of

around 26%.

Light Stick:

I made several changes to the Light Stick to both reduce the cost and increase the functionality of the

light. By far the most common complaint I’ve heard when demonstrating the Light Stick is that people

want more light. Unfortunately adding lumens comes with sacrificing total operating time between

charges. The solution that I have come up with is simply to allow the user to decide if they want

brighter light for a reduced amount of time, or if they would prefer a dimmer light for a longer period of

time. I achieved this by adding two more LED lights, using (3) 1.2v 1100mAh nickel metal hydride cells,

and replacing the existing on/off switch (a penny) with a 3-stage circuit board switch that allows a low

setting that passes through the original 12 ohm, ½ watt resistor (using approximately 0.2 watts of

power), and also allows a high setting that bypasses the resistor (using approximately 0.9 watts of

power). The low setting can provide adequate light for around 16-20 hours, and the high setting is

capable of providing light for around 4-5 hours. The new switch also negates the need for the following

components: (1) screw, (2) nuts, (1) small spring, (1) washer, and (1) penny. Here is a front and back

picture of the switch I created.

Once placed on the Light Stick, all but the switch itself is sealed with silicone sealant to protect the

electrical components.

Another modification I made is that I replaced the copper tape (which is unavailable in India), or strips of

sheet copper (which is expensive in India), with solid single strand copper wire, the same wire that is

pictured above in the switch. I used standard insulated electrical wire for the bottom portion of the

Light Stick, and attached it to the bottom screw between two washers. This made the copper end cap

unnecessary.

As a more durable alternative to using clear packing tape to cover the backside of the lights, I used a

clear epoxy coating which creates a completely waterproof coating over the electrical components.

I replaced the long spring and plastic spacer inside the battery compartment with a small graduated

spring and washer. I used a rubber adhesive to attach the spring to the washer, and I used a small

length of solid copper wire to help the transfer of current through the spring. The size of the washer

and spring together fit snugly inside the PVC pipe, which doesn’t allow it to come out or rotate once

placed inside the battery compartment of the Light Stick.

I was able to purchase several other parts at a much discounted price when buying in bulk and, together

with the modifications, was able to reduce the cost per Light Stick (including cells) from Rs. 113 ($1.77

USD) to Rs. 95 ($1.48 USD), a savings of around 16%.

Conclusion:

With all of the modifications made to the Light Cycle, Light Stick, and accessory components, an entire

unit consisting of the Light Cycle, (1) 12v 7Ah battery, (1) amp meter, (3) charging sticks, (1) octopus

hub, and (30) Light Sticks can be produced at a cost of around Rs. 7164 ($112 USD). This is a reduction in

cost from approximately Rs. 9101 ($142 USD), yielding a savings of around 21% from the previous

models built in India.

*At the time of writing this report the exchange rate was extremely volatile and was ~Rs. 64 to $1 USD.