17' tablet (OPi normal)

gaara · Published in 2015-3-14 22:33:34

Edited by gaara at 2015-3-14 16:29

Another question, about the resistors...
I think I need to start at 0.5 Ohm, 1 Ohm, 1.5 Ohm, up to.. 5 Ohm maybe, for 12V output. (?)
If it's true, how should be the value of power max ? 22W, like you said ? These resistors are not cheap, like 3.4€ each (x10) !!

Thnks for your help

Edit: I have found a battery, 42000 mAh

RaveenBouy · Published in 2015-3-14 23:35:59

A simple equation for you. (since i dunno how many amps you're using.)

V = IR

Voltage(v) = Current(A) x Resistance (R) to find R,

R=V/I

KingNyx · Published in 2015-3-14 23:40:20

Yah resisters are a pain in the ass.

http://www.digikey.ca/en/resourc ... ion-calculator-ohms

Use the voltage times ohms calculator to get the amperage you want.
That screen is about 14 ohms and honestly up till this point I forgot how large it was.
To get to the resistance we want, we would need like 15 ohms. The question will be how much juice is lost inside the resister and if it is worth while.
It should indeed max out at 22w lower is better though. But im afraid I cant think of a way of limiting the amps hitting that LCD without using power to do it.

It may perhaps be better to just get everything working and do that last.

gaara · Published in 2015-3-15 00:27:19

Edited by gaara at 2015-3-14 17:28

Yes, the equation gives me, for the screen alone: (but you're right, I should measure it at the end, when all will be active)
R1= 0.88x12 = 13.63 
If I want to try first 0.90 A:
R2 = 0.9x12 = 13.33 

So, the resistance I should add = R1-R2 = 13.63-13.33 = 0.3
Is my reasoning good ?
For the power (W), maybe I can use cheaper resistances for my tries (they can heat a little, don't matter), and when I have found the good one, I buy the good W value ? what do you think ? (sorry for all this questions!)

KingNyx · Published in 2015-3-15 00:41:25

Its fine haha. Sharing information is important.

Trying 0.90 wont do much tbh. Your screen was already running 12v 0.85. So if your amperage stays higher, you wont be doing anything, you need to drop the amperage lower. (assuming im correct lol)

RaveenBouy · Published in 2015-3-15 00:58:28

Errrrrm :C current is indirectly proportional to Resistance. If you increase the current, resistance falls and vise versa. so imo, you need to increase the resistance

KingNyx · Published in 2015-3-15 01:00:58

Yes thats what I mean XD Which is why I said a 14-15 ohm resister to keep his amperage below 8.5

RaveenBouy · Published in 2015-3-15 01:09:52

KingNyx replied at 2015-3-15 01:00
Yes thats what I mean XD Which is why I said a 14-15 ohm resister to keep his amperage below 8.5

Soz :C didn't read dat and yah i'd suggest a resister which is above 14.2 and lesser than 15

KingNyx · Published in 2015-3-15 01:14:31

Its all good XD

gaara · Published in 2015-3-15 01:24:16

Edited by gaara at 2015-3-14 18:30

Trying 0.90 wont do much tbh

Yes, I know this, it's a little step, but it was an example

I would to be precise, to increase the resistance little and little !!
But I think I have understood now. Steps about 1  will be good, maybe 0.5 to affine. (15 maxi)
Thanks a lot for all the tips, now I'm waiting for the SSD and the Battery. (a little expensive but with it I'm pretty sure my project will works at least 2h, just for a movie, and that's exactly what I want!)