We consideredĀ battery packĀ options;Ā lithium ionĀ was considered for its weight and energyĀ densityĀ butĀ this was discountedĀ due to risks around battery damageĀ and high temperature charging.Ā Ā So,Ā we chose a battery solution which resolvedĀ bothĀ the safety concernsĀ andĀ theĀ risk of damage to the product.Ā
NextĀ we considered switches and force sensors looking at a wide variety of solutions. Initially we found the desired force sensorĀ contributedĀ aroundĀ 80% of the cost of the product. So,Ā we set about investigating ways of achieving the same thing without the cost.Ā As we developed the design it became clear that the force sensor didnātĀ require aĀ high degree ofĀ accuracy.Ā It just needed to be enough to recognise a touch.Ā
We began prototyping the sensor using various materials and PCB patterns. The solution weĀ developedĀ was 1/10thĀ of the cost of the original force sensorsĀ with a cost of $0.2 vs force sensor cost of $22 ā a significant saving indeed.Ā
With the prototype sensor produced the rest of the product wasĀ architected into several individual PCBs connected byĀ off shelfĀ flat flexĀ PCBs. We evaluated the options of flexi- andĀ rigid-flexĀ pcbsĀ here.Ā At the initial launch volumes these add cost without bringing much benefit.Ā ThisĀ can be revisited as sales volumes increase.Ā
The PCB designs wereĀ completed, firmwareĀ written, prototype bring up completed and tested and samples shipped for testing and feedback.Ā