# Self charging keyboard - Is it possible or just funny?

Last night I had a drink with my friend and short after he started talking about self charging keyboard. It is a wireless keyboard and it "could" be charged when you are typing ( mechanical to electrical ) or by cleaning it ( whipping off the keyboard with something and then electrons "would" be stored somewhere).

I think this is fairly funny but that can be good brain teaser... So what do you guys think? I know that this was caused by "few" drinks but still... I would love it if someone could debunk this.

If by self charging you mean wireless charging, then yes it is a possibility. Much like the wireless charging pad Samsung has come up with.

billy_joule
Last night I had a drink with my friend and short after he started talking about self charging keyboard. It is a wireless keyboard and it "could" be charged when you are typing ( mechanical to electrical )
Piezos are possibly the best option:
https://en.wikipedia.org/wiki/Energy_harvesting#Piezoelectric
Maybe under each foot, or under every key? my wireless KB states 50mA requirements (max), I'm not sure if that's a reasonable ask from piezos in this application. It may mean uncomfortably hard key action.

or by cleaning it ( whipping off the keyboard with something and then electrons "would" be stored somewhere).
What energy conversion is happening here?

Maybe a way of taking in and using or storing natural body heat while the user uses the keyboard. Not sure how practical this is, but I'm sure there could be a way. Possibly using the keys or a wrist rest to take in the heat and convert it.

DaveC426913
Gold Member
What energy conversion is happening here?
I think he's thinking of static cling via wiping.

billy_joule
billy_joule
Maybe a way of taking in and using or storing natural body heat while the user uses the keyboard. Not sure how practical this is, but I'm sure there could be a way. Possibly using the keys or a wrist rest to take in the heat and convert it.
On that scale, Seebeck generators are probably most appropriate:
https://en.wikipedia.org/wiki/Thermoelectric_generator

So, yes, it is possible but probably not worth it. These sorts of micro power harvesting methods exist but I think you are applying a solution to a problem that doesn't exist - If you have a computer you clearly have access to power, even if only battery power from your laptop/tablet etc. Building a self powered KB is a waste of time and money (IMO) unless you go all out and power your entire device which would require something like this:
http://www.cnet.com/news/pedal-power-pedal-your-desk-to-power-your-laptop/
or a huge array of Seebeck generators and a roaring fire.

russ_watters
Mentor
Last night I had a drink with my friend and short after he started talking about self charging keyboard. It is a wireless keyboard and it "could" be charged when you are typing ( mechanical to electrical )...

I think this is fairly funny but that can be good brain teaser... So what do you guys think? I know that this was caused by "few" drinks but still... I would love it if someone could debunk this.
It is certainly possible in principle, so what is needed now is to figure out if it would be practical. See if you can find a wireless keyboard with listed battery specs from which you can calculate the power drain. Then try to calculate the power you could generate by typing based on the key stroke distance and force.

CWatters
CWatters
Homework Helper
Gold Member
The AAA batteries in my keyboard lasts quite a few weeks

Last night I had a drink with my friend and short after he started talking about self charging keyboard. It is a wireless keyboard and it "could" be charged when you are typing ( mechanical to electrical ) or by cleaning it ( whipping off the keyboard with something and then electrons "would" be stored somewhere).

I think this is fairly funny but that can be good brain teaser... So what do you guys think? I know that this was caused by "few" drinks but still... I would love it if someone could debunk this.
I've got a calculator that runs off of light. There's a little strip that absorbs the stuff. It's about 40 years old.

DaveC426913
Gold Member
I've got a calculator that runs off of light. There's a little strip that absorbs the stuff. It's about 40 years old.
Yeah but pocket calcs don't have to broadcast signals.

CWatters
Homework Helper
Gold Member
I tried to run some numbers but the tricky part for me was estimating how many key presses I average a day.

the tricky part for me was estimating how many key presses I average a day
You could use a keylogger to keep track. Maybe track over the course of a week or two and then find the average.

how many key presses I average a day.
I create around 4000 words per day and 5 letters aprox for one word.

billy_joule
My wireless KB has no power switch. This suggests it only transmits when used, or at least power drain when unused is negligible. So I don't thing key strokes/day is the important metric, the real question is if energy generation of a stroke > energy consumption of a stroke transmission.

@ billy_joule
energy generation of a stroke > energy consumption of a stroke transmission - Valid
The minimum we can get out from all of this is to extend battery life ... still need to calculate how much energy we can get from typing.

CWatters
Homework Helper
Gold Member
My wireless KB has no power switch. This suggests it only transmits when used, or at least power drain when unused is negligible. So I don't thing key strokes/day is the important metric, the real question is if energy generation of a stroke > energy consumption of a stroke transmission.
Unless you store the energy then average figures can be used to estimate feasibility.

CWatters
Homework Helper
Gold Member
Seems nobody else wants to do the sums so...

Lets assume that a pair of 1000mAH (1AH) AAA batteries power a keyboard for 4 weeks and the user types 4000 five letter words a day. So that many keystrokes would have to provide the same energy as the battery.

The number of keystrokes is 4 * 7 * 4000 * 5 = 560,000
The energy in the battery is 1.5 * 1* 3600 = 5400J

So each keystroke must provide 5400/560000 = 0.01J

Work = force * displacement
so
force = work/displacement

Lets say the useful key travel is 2mm or 0.002m..

Force = 0.01/0.002 = 5N

I think that's about an order of magnitude too high?

According to this..
..typical keyboard forces are around 40-60 grams or 0.5N

3301 and gennarakis
Only 10%? Thats barely 3 more days of usage :)

russ_watters
Mentor
Seems nobody else wants to do the sums so...
I did, and got a similar answer (mine was all in terms of energy though), but wasn't going to share it with the OP...

CWatters
Homework Helper
Gold Member
Only 10%? Thats barely 3 more days of usage :)
???

russ_watters
Mentor
???
Think of it like regenerative braking: it would run for a month on the original charge, them 3 more days from what it harvested.

CWatters