Having gained some direction after Phase I of the project, 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.
- The design must include an induction coil for hassle-free charging.
- The design must include a magnet which allows the product to be secured to metals parts on a car.
- The design must include a source of power.
- The design must include a source of light output.
- 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.
- [MAYBE] The design should include an on/off button OR always be on except when charging.
- [MAYBE] The design should include a mechanism that allows the user to see when the light is charged.
- [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.
In Component Packaging: Part II, I will be discussing points 3-5. Later posts will discuss general design elements, material and process selection, product usage analysis and more, so be sure to check back.