I've been waiting for something like this-- with the right implementation it could be a huge success-- but there's lots of room to get it not-quite-right.
Basically, the biggest technical and design challenge was the battery life.
We wanted to make the lock in a way that the user does not have to charge the lock/battery nor has to worry about replacing the battery at least for a couple of years.
To accomplish that, we had to look across all of the components that consume power. On the radio side, bluetooth LE solved that problem for us. Since we are sending data in bursts and the amount of data transferred is so little, the radio power consumption is almost negligible. We also use an ultra low power micro-controller with intelligent power management to low power consumption when the lock is not in use. The biggest power sucker was the mechanical actuation system. So that became more of a mechanical design and engineering problem. Using a solenoid was our of equation. There are extremely inefficient. We design the lock so that the actuator movement is minimal and is driven by a very low power motor. However there was one last issue. Most of the off-the-shelf batteries leak energy and deplete even if you are not using them after a 1-2 years. We are now using an advance lithium battery technology that has a very high energy density as well as very low leakage rate (This technology is commonly used to power sensors in remote sensing and telemetry application)
Eventually when the battery level drops low after a few years, you can notification on your phone and you can then replace the battery.
Since the lock will probably be in motion when not not in use, couldn't you just use some kind of kinetic charging mechanism to charge the battery? Is kinetic charging not enough powerful? Or is the circuitry too complex?
As a cyclist and mobile phone user, i find this idea entirely unattractive. I'm therefore interested to hear that you feel differently. Could you perhaps explain what it is you like about this? What problems does it solve for you?
Comments
I've been waiting for something like this-- with the right implementation it could be a huge success-- but there's lots of room to get it not-quite-right.
We have been working on this for about a year.
Basically, the biggest technical and design challenge was the battery life.
We wanted to make the lock in a way that the user does not have to charge the lock/battery nor has to worry about replacing the battery at least for a couple of years.
To accomplish that, we had to look across all of the components that consume power. On the radio side, bluetooth LE solved that problem for us. Since we are sending data in bursts and the amount of data transferred is so little, the radio power consumption is almost negligible. We also use an ultra low power micro-controller with intelligent power management to low power consumption when the lock is not in use. The biggest power sucker was the mechanical actuation system. So that became more of a mechanical design and engineering problem. Using a solenoid was our of equation. There are extremely inefficient. We design the lock so that the actuator movement is minimal and is driven by a very low power motor. However there was one last issue. Most of the off-the-shelf batteries leak energy and deplete even if you are not using them after a 1-2 years. We are now using an advance lithium battery technology that has a very high energy density as well as very low leakage rate (This technology is commonly used to power sensors in remote sensing and telemetry application)
Eventually when the battery level drops low after a few years, you can notification on your phone and you can then replace the battery.
Since the lock will probably be in motion when not not in use, couldn't you just use some kind of kinetic charging mechanism to charge the battery? Is kinetic charging not enough powerful? Or is the circuitry too complex?
Maybe store some mechanical energy in a spring to help reduce the amount of "stuff" that needs to be moved just by the battery?
that will complicate everything! and also increase the cost. besides you can't harvest much energy from that kind of mechanical movement...
cheaper and simpler to have a replaceable battery.
If mechanical motion is minimal, how do you protect against banging/tapping/jostling the lock while pressing the "open" button?
That sounds really useful.
As a cyclist and mobile phone user, i find this idea entirely unattractive. I'm therefore interested to hear that you feel differently. Could you perhaps explain what it is you like about this? What problems does it solve for you?