We appreciate your patience and would like to provide an update on progress on TOUCH TIME since our last update late November.
Over the last few weeks we built a handful of samples of our pilot production boards with an added 5 volt charge pump that directly drives both the high resolution LCD display and LED backlight separately from other componentry to insure they maintain the higher voltage they need all the time for operation. This means even with high current drain actions (many repeated finger swipes) and resulting voltage drops the display maintains its 2.7 voltage it needs and prevents the MCU resets we saw on previous samples.
Although the charge pump did solve one issue it raised one final issue with regard to overall battery life.
One specification that is not very widely discussed or even provided from most coin cell battery manufacturers is the variance of internal resistance over the life of the coin cell battery. In fact most manufacturers don't publish this data since it could arguably show a "derating" of up to 50% of stated battery lifetime. Through significant testing and research we discovered that although a new battery starts at below 20 Ohms, when having high pulse drains due to LED and touch swipes we reach a 45 Ohm internal resistance at significantly below the full 240mAh capacity of the CR2032 battery. We discovered that with the new charge pump added to circuitry at internal resistances of 45 Ohms we get to a point where the CR2032 can’t drive circuit, thereby causing MCU resets. This means that although the battery capacity at this level is an estimated 40-60% of total capacity, we may get resets, which in our minds is the effective end of life and shorter than our one year target battery life.
The main selling feature of TOUCH TIME is a significant long battery life. Therefore, we have to move to a larger capacity coin cell battery as well as one that can handle higher mA loads. Fortunately we are able to move to the CR2450 higher capacity battery that is more than 2X of the current CR2032 we had planned on using. Using this larger capacity battery won’t grow thickness of watch due to extra space we had available and only slight increase in case length. However, this change will cause a delay in our production schedule.
Attached are some pictures of our current pilot production components and we are still proceeding to build a few additional pilot production units with current battery/hardware solution. In the coming month we still plan to pass some of these samples to Kickstarter Reviewers we have already selected so they can test the watches provide feedback to our supporters regarding the TOUCH TIME watch.
We are also working to quickly modify the components to support the change to the larger capacity battery and in coming weeks can formalize the target final pilot production build and final production and shipment schedule. Stefan and myself are also scheduled to be in China week of Jan.21st before Chinese New Year and can provide additional updates at that time.
We appreciate your patience and we are working hard to finalize and perfect the TOUCH TIME watch for you here in early 2013. It goes without saying that we value all of your support immeasurably and we regret this delay. We are hugely proud of our product and we will continue to update you on our progress as we perfect the first, and only non-rechargeable battery powered capacitive touch digital watch.
Thanks for your support!