geekhack
geekhack Projects => Making Stuff Together! => Topic started by: MOZ on Sun, 13 March 2016, 12:10:29
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As part of my TS65 (https://geekhack.org/index.php?topic=79161.0) project, I'm looking to add wireless functionality to the board.
This thread is more general, to find out what features users would like to see in a Bluetooth wireless keyboard. Since my project is open-source, once I have the firmware support and electronic design completed, the wireless features should be easily made into an adapter board that can be used with existing keyboards.
I need to get answers to some simple questions and you are more than welcome to add more.
First, some background:
1. USB can supply 5V at 500mA once enumerated as a keyboard device, truly it can supply 2.5W.
2. Most barebone keyboards use around 40-50mA at 5V, which is 200mW - 250mW.
3. Bluetooth Low Energy (BLE - BT 4.0) uses around 25mA at 3.3V, which is 100mW (Taking into consideration of 5V to 3.3V stepdown efficiency)
4. Rest of the 2.15W (~430mA @ 5V) is available for the other bells and whistles as well as charging a battery if required.
5. Rechargeable AA batteries are about 1900mAh @ 1.2V (Typical) - Using two in series which is quite common for such applications, we can draw about 4.5W. Using a barebones keyboard with BLE and no backlighting/RGB we can get about 12 hours considering the efficiency of step-up conversion.
6. Li-ion/Li-Po batteries suitable for a portable keyboard would be about 2100mAh @ 3.7V - 7.77W, which should give around 21 hours of battery time on the the barebones BLE keyboard.
NOTE: I'm a bit lost as to how existing wireless boards last so long on battery. I would really appreciate an answer on this.
Questions:
1. What kind of battery would you like to see in a keyboard?
-- AA
-- Li-Ion/Li-Po
-- Doesn't matter
-- Other, please specify
2. Would you like to have the board the ability to charge over USB?
-- Yes
-- No
-- Doesn't matter
3. What would be the max acceptable charge time?
-- 1 hour
-- 2 hour
-- 4 hours
-- Over night charge (Around 8 )
-- Other, please specify
4. Due to limitations of USB a max of only 400mA can be used for charging a battery, this would mean a charge time of around 4 hours. Would you like the ability to charge via a dedicated charger (Such as one supplied with your phone)?
-- Yes
-- No
-- Doesn't matter
5. If your answer to 4 is yes, what would be your preferred method for charging using a dedicated charger?
-- Same connector used to connect to computer
-- Dedicated secondary USB port (micro or mini)
-- Barrel-style wall wort connector
-- Qi, wireless charging
-- Doesn't matter
-- Other, please specify
6. What is the minimum acceptable battery time?
-- 12 hours
-- 24 hours
-- 1 week
-- 2 weeks
-- 1 month
-- Other, please specify
TIA
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For the sake of comparison, I'll mention my custom bluetooth keyboard; I recently added bluetooth to my Atreus by chopping up a Handheld Scientific adapter. My main complaints would probably be cost, inconvenience of desoldering parts, size, and having to design my own brackets etc. for the pcb and battery. It charges a Li-Ion battery via USB but does not pass the connection through (so, bluetooth only). In terms of the end result, I'm quite happy with it, it charges in a few hours, and lasts 10-ish hours of active use. As it can charge while being used, it's not exceptionally inconvenient to run out of power.
Regarding what I'd like to see from an adapter/board to embed in future projects:
> What kind of battery
Li-Ion/LiPo
>Charge over USB?
Absolutely yes.
>Max acceptable charge time?
Overnight
>Dedicated charger
No way, don't want more cables and adapters to keep track of.
>Wireless charging?
Qi/wireless charging would be kinda cool, I'd consider it.
Overall, I'd be interested in either a bluetooth/charging module to add to a keyboard with some other controller, or a single module integrating an atmega32u4 with the bluetooth and charging stuff.
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The trick to having good battery life is just using power optimized components. For example the nRF51822 (bt4.0) chip can run on 200 ľA average current at around 6 key presses per second. The 200 ľA figure is from Raytac. With 2 x AAA batteries it amounts to some silly number like 260 days of continuous typing, not taking battery degradation into account.
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1. Li-Ion/LiPo
2. Yes
3. 4h would be nice
4. No, no more cabels for a wireless build pls :D
5. Wireless charging, with charge pad as removable case :D
6. 24h, incase I have to go to a party afterwork and get hangover :D
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I've thought about modding my keyboard to be wireless and I was considering the Adafruit Bluetooth LE board which sells for about $30. It includes bluetooth, can be powered with usb or a lipo battery, and includes a charging circuit.
1. What kind of battery would you like to see in a keyboard?
-- Doesn't matter
2. Would you like to have the board the ability to charge over USB?
-- Yes [Qi charging is fine too]
3. What would be the max acceptable charge time?
-- Over night charge (Around 8 ) [prefer 8 hour battery life if its this long]
4. Due to limitations of USB a max of only 400mA can be used for charging a battery, this would mean a charge time of around 4 hours. Would you like the ability to charge via a dedicated charger (Such as one supplied with your phone)?
-- Doesn't matter
5. If your answer to 4 is yes, what would be your preferred method for charging using a dedicated charger?
-- Qi, wireless charging
6. What is the minimum acceptable battery time?
-- 12 hours