I'm disappointed that it isn't powered by the kinetic energy of the pressing: I heard some Philips Zigbee control devices work that way (but Wifi might be too power hungry for that).
And I was expecting them to use the ESP8266 for this: Does anybody know if (at scale) that would have been cheaper?
It doesn't look like the ESP8266 has the necessary I/O to do the audio provisioning trick that the Dash is doing with that hybrid module.
Provisioning these things can be a hassle sometimes. The TI CC3xxx has a really wacky one. A custom provisioning app transmits the SSID and password of the target network by sending encrypted packets to nobody: the CC3xxx sniffs the length of the encypted packets and picks up the necessary information from the string of those length bytes.
The audio thing is a lot more elegant, but needs some filtering and processing to make it happen.
The CC3XXX "SmartConfig" was complete garbage the last time I was evaluating it on a CC3200. It didn't work on 802.11n networks, only b/g. And that was when it worked. I got it only once trying on both an iPhone and Nexus 5, I would hate to have to answer any customers' support questions about using something so flaky.
The audio thing does require an app though to do provisioning, which I suppose isn't a problem for the kinds of people ordering this thing.
My preferred provisioning method is to let the little Dash-like device broadcast some setup or config access point. You connect to it, get an HTML UI to input target AP credentials into, and submit the form. It works from just about any device.
Totally agree about the SmartConfig. Interesting idea, very convoluted method.
Thankfully most devices I've been working on have a touchscreen to provision the SSID/PW, or we just ask the user to put it in a text file and inject it via a thumb drive. It really doesn't have to be this hard.
Agreed, but touchscreens and SD or USB means connectors, which are often a significant part of BOM cost and take up space. If you can do it all from the one-chip/module you have in there it's a big benefit when it comes to making something small and cheap.
Like I said, I've been fortunate to have alternate provisioning means.
I think the audio trick is a pretty elegant hack. Device agnostic and doesn't need a lot of handholding. But it also has an impact on the BOM. You need to add that Cortex M3 + microphone to sniff it out. Otherwise the whole thing could have been run off one chip like the ESP or GainSpan GS2100.
Doing the access point-to-client switcharoo is a good one too but needs a bit more instruction on the customer side, plus a way to whack the device back into setup mode when you need it.
The ESP8266 has peak draws of almost a watt when transmitting, unless Amazon releases a crank-to-order device that doesn't seem particularly plausible. I'm slightly surprised that they didn't use the Espresso solution here to keep their part count down, but it is possible this model is just to gauge market interest.
As I mentioned in the other thread, the ESP8266 is a Wifi chip that you can buy for $5/each on an order of 1, and can run custom code, so you'd only need one of those plus a case, battery and button. You could probably build a button for less than $10, without even ordering large quantities.
It says it uses wifi.
There are $5 wifi modules, which I guess would have enough processing to remember your wifi, and do 1 HTTP request, and (in volume) should be feasible for $10. A spark core (which has a bit more functions), costs $20 retail.
What would be the advantage of these LiPo batteries over traditional lead-based batteries? In car's, I understand weight (and volume) are really important, but for stationary usage these seem way more expensive / Wh stored?
If you are going to count hydrogen emission as a problem for a lead-acid battery then you should be honest and point out that lithium batteries of all varieties have a habit of failing in spectacularly combustible ways.
Cars need tremendously high drain for brief periods to start the engine, especially under adverse conditions like winter when oil starts out being cold and less viscous. They also generally don't deep drain the battery. The ability to be optimized for those constraints plus their simplicity and low cost is why they still own that market. This is not my field, but I'm not aware of any battery chemistry that could conceivably compete with them, and because of their lead we'd like an alternative if there was one.
I'm also curious about their lifetime. My laptop batteries are pretty weak after three or four years. It's much easier to justify $thousands as a one-time purchase than $thousands/year. For many of its applications, this is going to have to beat a generator. Which, come to think of it, probably means that if they're pitching this as a way off the grid it is precisely because it won't be even remotely competitive with a generator.
For a given generation of lithium battery cell and management technology, there is the option of trading off between capacity and durability.
Field-replaceable laptop batteries are engineered as a consumable, and runtime, weight and charging speed are given priority over long life. Laptops with integrated batteries make a somewhat different tradeoff, but still assume that battery replacement will be a maintenance expense for some users. In both cases, the expected average lifetime of the laptop itself is also a factor, which I'd guess would be about 5 years, max.
Packs for laptops make different tradeoffs vs packs for a car, or home power storage. From memory, based on some back of envelope calculations, tesla trades 15-20% of nominial capacity of the cells in their auto packs for >=4x or greater durability. Packs for home energy storage would probably make similar tradeoffs, and might get more life with less aggressive charging rates.
You charge your laptop everyday. So it depends on how often you recharge them, which means it will depend on how big of a battery you'll buy. If you buy a 100 KWh battery (probably around $10,000-$15,000), I think that should last most Americans at least several nights to a week? So it might approach 10 years before it starts degrading, and then probably a few more years of charging it every day. I assume's Tesla's batteries will be relatively high-quality as well.
Isn't the idea that you keep it topped of and use it when grid power is expensive or missing? That usage pattern would involve multiple charge cycles, perhaps even 365 in a year. I guess it would actually follow the Tesla charging patterns fairly close as well. What is the estimated lifetime of a Tesla's battery?
If the battery has sufficient excess capacity, you can split it into multiple banks of smaller batteries, and cycle which ones you charge and which ones you use. Add a small computer and you can use whatever logic gives you optimal charging/discharge patterns to optimise for lifetime.
If the angle changes, the details of the building's facade changes as well. You can see in the code that he isolates the building's details from the first frame. Then compares later images to it to do the "tracking".
GSM networks ping all devices on regular intervals (besides the handoffs between cells when traveling and when there is data to transmit). This interval is a setting of your network, from minutes to hours.