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arbalet-project / arbadoc

Documentation, diagrams and wiki for the Arbalet LED table
GNU General Public License v3.0
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Wrong power supply dimension #5

Open Adesin-fr opened 7 years ago

Adesin-fr commented 7 years ago

Hi,

I've made a small calculation : Each WS2812B module contains 3 LED, and each led can consume up to 20 mA. This leads to 60mA per LED. So, for a table containing 150 LED, if each led is set at full power white, we need 150 x 0.06A = 9 A !

I think that asking for a 5V / 5A power supply could cause to strange behavior ;)

It should be more reasonable to ask for a 10 A PSU.

PS : Boujou de normandie !

AurelienC commented 7 years ago

Hello,

Good remark.

I don't have find much documentation, but I find 50mA at 5V for the full brightness of R, G and B LEDs. This is about 7.5 A for 150 LEDs.

Indeed, a very powerful PSU must be a good thing, but not necessary with a "normal" use of the table. A good 5A power supply can provide most power in a short period of time and each LED has a tank capacitor.

Adesin-fr commented 7 years ago

Yes, that's right, for normal use, and if we don't use as a giant torch, 5A is certainly enough :) Perhaps we should warn in the doc that 5A is sufficient for normal use, but at full power it will not be enough...

Also, what about a french documentation ?

ymollard commented 7 years ago

It probably depends on the LED strips. I've made some measurements on my strips from different manufacturers, powered with a lab power supply, I actually never needed more than 3.5A even at full brightness. I have the feeling that the theoretical 50mA per LED is a bit overkill especially when multiplied by 150. Strong power supplies are bigger, this is maybe not something you want close to your coffee table.

Also, what about a french documentation ?

I do accept pull requests on that repository :)

Adesin-fr commented 7 years ago

I can't remember where I did saw those 20mA per LED, but nothing in the datasheet about IF current !!

It might be a general rule about led : when I did my high school, we did always took 20mA for a LED current... nevermind....

If I had some free time, I would translate the pages... perhaps someday ;)

Adesin-fr commented 7 years ago

How should I proceed to translate the docs ? Should I suffix each file with "_fr". i.e. : assembly_guidelines_arbalet_lava_fr.odt ? Or should I create a different subtree ?

ymollard commented 7 years ago

If you follow the advice given by LED strips manufacturers they also suggest 7.5 amps or so.

Adding _fr is fine. You'll need the Oxygen font.

Adesin-fr commented 7 years ago

Great, I'll start translating the docs ! I'm not very used to Github. Should I first fork the projects to be able to pull request after ?

(PS : So silly to discuss in english since we are both french !!)

ymollard commented 7 years ago

Great! Yes, fork the project, then clone your own copy on your local disk (on Linux git clone https://github.com/LemarinelNet/arbadoc.git), then create the new file, then git add the_new_file.odt, then git commit, type a description of your work and save the result, you can do several commits and at the end git push to save your work online. The pull request is made afterwards from github.

Adesin-fr commented 7 years ago

Ok ! I'll work on it as soon I'll have some free time :)