REFINEMENT


Having gained some direction in the ideation phase, our first task was to resolve the design of the light itself. There is intended to be tight integration between the lights and the charging station, so it is vital to always keep the user experience of the product forefront in our minds. While designing the packaging for the light, there were several key points to keep in mind.

  1. The design must include an induction coil for hassle-free charging.
  2. The design must include a magnet which allows the product to be secured to metals parts on a car.
  3. The design must include a source of power.
  4. The design must include a source of light output.
  5. The design must include a mechanism that allows the product to bend near 90°'s in one direction.

Several other points were also being considered.

  1. [MAYBE] The design should include an on/off button OR always be on except when charging.
  2. [MAYBE] The design should include a mechanism that allows the user to see when the light is charged.
  3. [MAYBE] The design should include mounting points to allow it to work with other accessories.

This post will focus on points 1 & 2.

Induction Coils

Specifically we are focusing on those used in inductive charging. The two main types of coils being considered are the flat coil and solenoid coil.






The solenoid coil is commonly found in electric tooth brushes, while the flat coil is found in many new products (Especially smart phones) utilizing the Qi standard of inductive charging. In terms of performance they are relatively similar. The size and shape will be the deciding factor as to which is used in the design.

Magnets

Magnets come in a huge range of shapes, sizes and strengths. Ideally the magnet should have slightly more strength than is needed to hold the product onto a steel bolt (generally the smallest ferromagnetic object on a car). The magnet used will therefore reflect on the shape, size and weight of the product.



Coercivity

All magnets lose some of their strength over time. Coercivity measures how resistant the magnet is to becoming demagnetized. Over time, magnets need to be re-magnetized by being introduced to a stronger magnetic field (In industrial applications, a DC current is run through a nearby coil). Luckily,  modern magnets such as Samarium-cobalt and Neodymium have high coercivity values (as little as 1% loss over 10 years), hopefully negating the need for re-magnetization.

Induction Coils & Magnets

Unfortunately, magnets disrupt the flow of energy to an induction coil. We had to know exactly what implications this would have in our design, so we tested just how much of an effect a magnet would have by utilizing a setup borrowed from an electric toothbrush. We placed a moderate strength bar magnet at locations within, above and nearby the coil, and then charged the unit for 1 minute. We then documented the run time after each charge.


Luckily, the only placement that had a significant effect was when the magnet was inside the coil. Although the results look reasonably promising for allowed flexible placement of both the magnet and the coil, we must remember that the effects of all placements would be worsened if using a more powerful magnet.


Battery (Power) & Light


The run-time of the product from fully charged was proposed to be within the 3-4 hour range as a minimum. This time would allow for the majority of mechanic tasks to be performed without having to cycle out the unit/s during work. A standard rechargeable AA battery was intended to be used. 

From having sampled existing torches, a light with an output of 20 lumens was seen as the minimum light output (Also keeping in mind there would be a point where there was simply too much light).

Simple tests were conducted with varying battery and LED varieties.





Some aspects of the test were extremely positive: The light output from a single LED was sufficient to light an area under or within the car, and the battery provided enough power to sustain the light for over 48 hours - more than 12x the minimum specified.






Other aspects were not so great. At this stage it became apparent that rechargeable AA  batteries did not supply the voltage required to run an LED. However, rechargeable CR123A and CR2 batteries could be found with the required voltage (3v+). The capacity on these batteries was usually only 1/2 to 1/3 of that as a AA (800-1200mAh compared to 2500mAh). This would still guarantee a run time of 20+ hours, and the physical size of these batteries were also much smaller.

Flexibility

Initially, the ability to bend near to 90°'s was seen as a key innovation within the product. With all of the components required in the product, the ability for it to bend was initially seen as somewhat of a hard obstacle to overcome. How and where do you put the mechanism? What components are easier to hold in individual sections of the unit? These were the questions we were asking ourselves.

It wasn't until the creation of several form studies that it clicked.





We were directly inspired by a common ball joint found within Lego. Its ability to separate on a whim, while still being solid enough to support the required weight had 3 key advantages to our previous ideas.

  1. The ball joint provided sufficient strength to hold the object in place at all angles, and allowed for free axis movement.
  2. It promoted the separation of all electrical components from the non-electrical. No power had to run through the ball joint.
  3. The ball joint attachment could be removed and replaced with various accessories.
Although this system did not allow a full 90°'s of rotation, our product testing concluded that the bending was more than adequate.