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> Hardware layout: battery, main screen hardware
NormMonkey
post Nov 28 2019, 12:11 PM
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Hi all,

I thought the battery on the Cosmo was under the keyboard. I even remember reading how the hardware team added a super-capacitor to ease power transfer to the other side. However, when I'm charging, it feels like the top (right under the cover display) is warm, while the other side is cold. Where is the battery located?

I'm also curious what's the little oval on the right side of the main screen? I thought it was a light sensor. However, when I turn on Adaptive Brightness, the display adapts to light levels on the Cover Display side of the device rather than the main screen side.
I can confirm using a Sensors app that the light sensor reacts to something located betwixt the cover camera and the cover display. Same for proximity sensor (which does make sense).
Maybe it is a second light sensor that is currently disabled or otherwise unavailable?
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Daniel W
post Nov 28 2019, 02:25 PM
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While I haven't yet received my Cosmo, its battery also sits under the keyboard. Planet Computers has stated they're reusing the same size and type of battery for the Cosmo, and there's nowhere else it would fit. They also need to put as much of the weight in the bottom as possible. Further, when I charge my Gemini, the top, but, thus far, not the bottom, tends to get a bit warm, even though the Gemini battery clearly is below the keyboard.

As the Gemini and, I suspect, the Cosmo, uses Pump Express + (aka 1.0), a rather primitive fast charging solution, even by 2016 standards, it can only ask the charger for 5, 7, 9 or 12 volts, and I've never seen my Gemini ask for anything but 5 or 9. Feeding 9V to a single Li-Ion cell would cause fireworks, so a DC/DC converter, making clever use of tiny capacitors to "transform" direct current, converts the voltage into what the battery needs at the moment, which changes a bit, as the battery charges. That conversion is a bit lossy, so that chip, apparently in the lid, may get noticeably warm.

For reference, Pump Express 3.0 and 4.0 can set the wall wart voltage in about 0.02V increments and can even measure the cable used, so it can ask for exactly the correct voltage at any time. That requires a more costly voltage converter in the charger (and you still need one in the phone, for 5V only chargers), but when fast charging such a device, voltage conversion losses should mostly happen in the wall wart end, not in the device being charged.

Using the app AndroSensor (just what I had on my Gemini) the small oval, with two tiny lenses, acts as a combined light and proximity sensor. Shining a bright LED onto it registers high lux readings, while covering, even when reading 0 lux, causes the proximity value to drop from 1 to 0 (the only values it knows). My readings are a bit finicky, but that might depend on the age of the app. It says both sensors are from MTK, which should mean MediaTek, so it's likely a standard sensor in their reference designs. Whether the Cosmo actually uses it, is unknown to me. I do know that the auto brightness on my Gemini is too hit and miss to be useful for me. I might sit in a dark place, but the sensor may stare right into a small overhead LED light, and think full brightness is called for. Or, if the rear of my Gemini is facing the sun, but I have a dark corridor behind me, it may drop the brightness to nothing.
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NormMonkey
post Nov 29 2019, 07:17 AM
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QUOTE(Daniel W @ Nov 28 2019, 05:25 PM) *
As the Gemini and, I suspect, the Cosmo, uses Pump Express + (aka 1.0), a rather primitive fast charging solution, even by 2016 standards, it can only ask the charger for 5, 7, 9 or 12 volts, and I've never seen my Gemini ask for anything but 5 or 9. Feeding 9V to a single Li-Ion cell would cause fireworks, so a DC/DC converter, making clever use of tiny capacitors to "transform" direct current, converts the voltage into what the battery needs at the moment, which changes a bit, as the battery charges. That conversion is a bit lossy, so that chip, apparently in the lid, may get noticeably warm.

Thanks @Daniel, that is a great explanation.

It doesn't make sense to me to have the power come in at the USB-C on the bottom, route to the top for conversion and then route to the bottom again for the power cell. Especially on the way back down, it would be a lower voltage and higher current, which I can't imagine is all that awesome across the little flex cable.


But it doesn't have to make sense to be true. Good to know that's how it is for the Gemini too. I'm a Planet newbie, this Cosmo is my first Planet device. This hardware is fantastic and I wait with 'bated breath for a Linux partition.


QUOTE(Daniel W @ Nov 28 2019, 05:25 PM) *
Using the app AndroSensor (just what I had on my Gemini) the small oval, with two tiny lenses, acts as a combined light and proximity sensor. Shining a bright LED onto it registers high lux readings, while covering, even when reading 0 lux, causes the proximity value to drop from 1 to 0 (the only values it knows). My readings are a bit finicky, but that might depend on the age of the app. It says both sensors are from MTK, which should mean MediaTek, so it's likely a standard sensor in their reference designs. Whether the Cosmo actually uses it, is unknown to me. I do know that the auto brightness on my Gemini is too hit and miss to be useful for me. I might sit in a dark place, but the sensor may stare right into a small overhead LED light, and think full brightness is called for. Or, if the rear of my Gemini is facing the sun, but I have a dark corridor behind me, it may drop the brightness to nothing.


Huh. When I shine a bright LED on the one to the right of the main screen on my Cosmo, I cannot see the two tiny lenses. However, I see exactly that when I look at the spot between the camera and the cover display. I get the same results you describe from AndroSensor when I test light level and proximity on the cover sensor, but I get no response when I try on the one to the right of the main screen.

My guess is that they're using the exact same screen /assembly as for the Gemini so the cut-out is there, but the PCB doesn't include the sensors. I suspect it's a combo sensor with both brightness and proximity in one component, and the proximity sensor needs to be on the front so that's where they put it.


I tried Adaptive Brightness but I quickly turned it off. It reacts to light changes in front of me instead of behind me. If I'm standing under a bright light and holding it main screen up, the brightness should increase so I can see despite the bright light above, but it doesn't because the ground is dark. Likewise if I'm sitting in a reclining chair and holding the thing with the front facing forward, the brightness changes depending how I sit, even though the conditions behind me are pretty constant.
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