asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

DIY PI-TOP, rise against hoarding manufacturers !

Sat Nov 26, 2016 10:56 am

Last week, after a mishap concerning my laptop and a glass of wine, i found myself at the local IT-store as if in china with my car broken down. A lengthy back and forth turned a malfunctioning keyboard into a malfunctioning whole and all i got was shrug - R.I.P. Never again !

ergo: pi powered laptop

I picked a composition of suitable parts and i hope to pick your brains concerning their compability. Gratitude for helping a fellow pi-ous soul : )

___________________________________
my PITOP

Main processing unit:
Raspberry Pi 3 B

10.1" Touchscreen:
http://www.waveshare.com/product/10.1in ... h-case.htm

20000 mAh Battery:
https://www.amazon.fr/gp/aw/d/B01L90C9H ... F0KM&psc=1

Peripherals:
Thin usb keyboard, usb speakers

The whole crammed into a makeshift aluminium casing, Presto! At least that is what i thought before waking up - in cold sweat between fluctuating mAh, minimum voltage and maximum amperage.


Thanks to all willing to shed some light -
By pi, i could sure use some.

steveb4pi
Posts: 62
Joined: Sun Aug 11, 2013 6:12 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 9:02 am

Unlike (say) China, the UK is a 'high wage' economy .. anything that involves 'some-one' doing 'some-thing' will cost an arm and a leg.

When you break your laptop's screen/keyboard etc. I suggest you go onto eBay and buy the cheapest working 'same' brand / similar 'model' second hand unit you can find .. then swap your hard drive (and RAM) into the 'new' one and it's "job done" ..

Take it to the 'Computer Shop' and it will be £50 an hour plus 'parts' that will cost you more than buying a brand new laptop .. plus there's a good chance they will reformat your entire hard drive...

You CAN plug your laptop hard drive into a USB enclosure and use it with a Raspberry Pi ... however whilst you will be able to rescue your JPG's and wav/mp3's you are in for a whole load of DRM pain when you try to play your movies ...

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 10:10 am

Well no can do with an outdated obscure thinkpad series i obtained in some lenovo outlet - The parts, keyboard included, were outright rare and unaffordable.

What i actually wanted to know was if the composition i posted above would work together as a standalone unit or if there are any compatibility issues.

fruitoftheloom
Posts: 24544
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 11:08 am

asderad wrote:Last week, after a mishap concerning my laptop and a glass of wine, i found myself at the local IT-store as if in china with my car broken down. A lengthy back and forth turned a malfunctioning keyboard into a malfunctioning whole and all i got was shrug - R.I.P. Never again !

ergo: pi powered laptop

I picked a composition of suitable parts and i hope to pick your brains concerning their compability. Gratitude for helping a fellow pi-ous soul : )

___________________________________
my PITOP

Main processing unit:
Raspberry Pi 3 B

10.1" Touchscreen:
http://www.waveshare.com/product/10.1in ... h-case.htm

20000 mAh Battery:
https://www.amazon.fr/gp/aw/d/B01L90C9H ... F0KM&psc=1

Peripherals:
Thin usb keyboard, usb speakers

The whole crammed into a makeshift aluminium casing, Presto! At least that is what i thought before waking up - in cold sweat between fluctuating mAh, minimum voltage and maximum amperage.


Thanks to all willing to shed some light -
By pi, i could sure use some.
https://www.pi-top.com
Thinking outside the box is better than burying your head in the sand...

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 1:28 pm

wow didn't know that site existed, odd - thanks for the link but could you answer my question ?

steveb4pi
Posts: 62
Joined: Sun Aug 11, 2013 6:12 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 2:56 pm

Display looks fine, seller even claims it's Pi compatble.

Can't say anything about the PowerBank battery .. the link delivered me to a French site :-)

Things to watch out for :-
1) Many PowerBanks can't/won't charge at the same time as delivering power to the USB outputs & those that do may 'glitch' if you plug in an external power block at the same time as running the load (i.e. the Pi)
2) Real capacity can be hard to discover (lots of sellers, especially eBay quote the battery voltage mAH not the 5v mAh) thus (for example) a single cell is quoted as '2200mAh' when you will be lucky to get 1200mAh out of it (and a 5 cell '10,000' when it's actually 5,800)
3) LiPO batteries have a recharge 'half-life' .. some are down to 50% capacity after only 200 to 300 recharges ...

fruitoftheloom
Posts: 24544
Joined: Tue Mar 25, 2014 12:40 pm
Location: Delightful Dorset

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 3:10 pm

Thinking outside the box is better than burying your head in the sand...

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 7:00 pm

Thanks to fruit for the very very instructive link and my bad steve, didn't cross my mind that you can't speak french ; )

In a nutshell: "20000" mAh, input: 5V, 2A / output: 5V, 3A max. + Automatic charge detection and some security features like protection against over-, undercharging, shortcircuits etc. So with an 500-800mA for the pi and, what?, 1-1.5A for the screen i should be golden right ?


1. The charge/discharge issue won't be because i'll get two - charge one, use the other, repeat.

2. Wait the "battery" voltage ? like of the individual units inside the bank ? I just supposed it to be 5V for the advertised capacity. Is there actually a way to find that out short of finding an in depth review ? (or breaking it open : )

3. I never saw any amazon article with an whopping 4.8 out of 450 reviews, accounting for hecklers and fakers that's still a pretty safe bet quality wise i guess. (+ black friday, it's off a lot)



Another thing: scanning the forum i read about the general unsuitability of power banks for the fluctuating drainage of a processing unit since they were conceived for stable and steady flow, with many a user reporting the low voltage indicator on screen and it's resulting instability. Plus there is the hungry screen. Should i opt for an voltage converter board + any big li-on battery ?

aBUGSworstnightmare
Posts: 2315
Joined: Tue Jun 30, 2015 1:35 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Sun Nov 27, 2016 7:12 pm

Why not use a 5V BEC and a high capacity 2S LiPo?

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 9:40 am

is 5V the absolute max the pi and screen would ever need ?

how does this fare concerning amperage and it's fluctuation - should i get one of those "smart" all in one power boards ?
https://shop.pimoroni.com/products/mopi-mobile-pi-power


would it charge and discharge simultaneously ?

JimmyN
Posts: 1109
Joined: Wed Mar 18, 2015 7:05 pm
Location: Virginia, USA

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 1:14 pm

asderad wrote: 2. Wait the "battery" voltage ? like of the individual units inside the bank ? I just supposed it to be 5V for the advertised capacity. Is there actually a way to find that out short of finding an in depth review ? (or breaking it open : )
The capacity rating is for the cells, which are 3.6V nominal. So a 20000mAh (20Ah) would be 20 x 3.6 = 72 watt hours for the pack. But for the 5V output (the voltage must be stepped up from 3.6), then you'd have 72Wh / 5V = 14.4Ah or 14400mAh, minus the losses in stepping the voltage up to 5V. Power out always has to equal power in, minus any losses.

So the 20000mAh battery pack will only provide 14400mAh at 5V, less about 10~20% for losses, which results in an actual capacity of only about 12960 to 11520mAh at 5V output. No need to tear one apart, they always use the cell capacity value since it's much larger than what you'll actually get at the 5V output, it's a marketing thing. If you were manufacturing 20000mAh packs would you advertise them at that cell capacity to fall in line and compete with the other manufacturers, or would you advertise the true capacity of maybe 12000mAh at 5V and probably sell very few since yours are going to be about the same price, as they are using the same cells.

And probably 99% of consumers don't know there is a difference, and that they are not getting the advertised capacity.

If you go with series cells (7.2V) then it works the other way. A 20000mAh pack at 7.2V would be 20 x 7.2 = 144Wh. 144Wh / 5V = 28800mAh. So the 20000mAh 7.2V pack will provide 28800mAh at 5V, minus losses. But with series connected li-ion cells you need a balancing charger to monitor each cell while charging and is the reason why the battery banks all use paralleled cells at 3.6V, much simpler and safer to charge.

aBUGSworstnightmare
Posts: 2315
Joined: Tue Jun 30, 2015 1:35 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 3:41 pm

asderad wrote:is 5V the absolute max the pi and screen would ever need ?

how does this fare concerning amperage and it's fluctuation - should i get one of those "smart" all in one power boards ?
https://shop.pimoroni.com/products/mopi-mobile-pi-power


would it charge and discharge simultaneously ?
Well, that depends on your display!
I.e. I'm using a display from a Google Nexus 7 tablet where the backlight supply voltage is even below 5V (running it at 4.2V actually), others need (typ.) 12V (they are fine with 3S supply most of the time i.e.), the bar-type one needs 19.xV and another one needs 24V (using step-up for the backlight supply voltage on both of them).

What do you want to use the board for? Swapping batteries? If this is the answer to all your questions depends again on your screen selection! This board has no step-up!

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 5:03 pm

JimmyN wrote:
asderad wrote: 2. Wait the "battery" voltage ? like of the individual units inside the bank ? I just supposed it to be 5V for the advertised capacity. Is there actually a way to find that out short of finding an in depth review ? (or breaking it open : )
The capacity rating is for the cells, which are 3.6V nominal. So a 20000mAh (20Ah) would be 20 x 3.6 = 72 watt hours for the pack. But for the 5V output (the voltage must be stepped up from 3.6), then you'd have 72Wh / 5V = 14.4Ah or 14400mAh, minus the losses in stepping the voltage up to 5V. Power out always has to equal power in, minus any losses.

So the 20000mAh battery pack will only provide 14400mAh at 5V, less about 10~20% for losses, which results in an actual capacity of only about 12960 to 11520mAh at 5V output. No need to tear one apart, they always use the cell capacity value since it's much larger than what you'll actually get at the 5V output, it's a marketing thing. If you were manufacturing 20000mAh packs would you advertise them at that cell capacity to fall in line and compete with the other manufacturers, or would you advertise the true capacity of maybe 12000mAh at 5V and probably sell very few since yours are going to be about the same price, as they are using the same cells.

And probably 99% of consumers don't know there is a difference, and that they are not getting the advertised capacity.

If you go with series cells (7.2V) then it works the other way. A 20000mAh pack at 7.2V would be 20 x 7.2 = 144Wh. 144Wh / 5V = 28800mAh. So the 20000mAh 7.2V pack will provide 28800mAh at 5V, minus losses. But with series connected li-ion cells you need a balancing charger to monitor each cell while charging and is the reason why the battery banks all use paralleled cells at 3.6V, much simpler and safer to charge.

Wait, are all the cell values normed ? I figured you could manufacture them at any desired voltage.

Wait, we are talking about difference in voltage through different "wiring" ( paralell / serial ) and not different cells right ?


Anyhow thanks for that serious piece of insight. Never would i have imagined advertised capacity not to correspond to advertised output. That's borderline misleading no ?

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 5:17 pm

aBUGSworstnightmare wrote:
asderad wrote:is 5V the absolute max the pi and screen would ever need ?

how does this fare concerning amperage and it's fluctuation - should i get one of those "smart" all in one power boards ?
https://shop.pimoroni.com/products/mopi-mobile-pi-power


would it charge and discharge simultaneously ?
Well, that depends on your display!
I.e. I'm using a display from a Google Nexus 7 tablet where the backlight supply voltage is even below 5V (running it at 4.2V actually), others need (typ.) 12V (they are fine with 3S supply most of the time i.e.), the bar-type one needs 19.xV and another one needs 24V (using step-up for the backlight supply voltage on both of them).

What do you want to use the board for? Swapping batteries? If this is the answer to all your questions depends again on your screen selection! This board has no step-up!

I considered purchasing this
http://www.waveshare.com/wiki/10.1inch_ ... with_case)
screen, which seems to run with a 5V, 2.5A power adaptor.

I actually wasn't sure if the advertised voltage requirement is the absolute max a given screen could ever need. Like if limiting my output to eg.: 5V would cause complications a "smart" board could avoid.

I guess i'd need a step down converter with two outputs ? Or one for each appliance ? (screen, pi)

User avatar
bensimmo
Posts: 4988
Joined: Sun Dec 28, 2014 3:02 pm
Location: East Yorkshire

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 6:15 pm

In a battery there are cells, a cell has a fixed voltage design. It's part of the chemicals and materials it uses.
That doesn't alter, only capacity and the way it drains (there is a voltage drop as it uses up its power).
I would suggest possibly reading Wikipedia on batteries and cells.

Electronics (with respect to Pi and Display mentioned) are designed to work at a fixed voltage, never more and never less than it's design. It does not alter.
Its current (A) does changes and that is how much energy it needs to use up. You specify a power supply that will cope with the absolute maximum demand.
So 5V 2.5A will be it maximum current draw for the display. The spec sheet would show more detail, like typical current draw.
(I suggest Wikipedia and voltage/current/power)

A power bank (USB type) will supply 5V until it runs out.

asderad
Posts: 8
Joined: Fri Nov 25, 2016 1:16 pm

Re: DIY PI-TOP, rise against hoarding manufacturers !

Mon Nov 28, 2016 7:32 pm

bensimmo wrote:In a battery there are cells, a cell has a fixed voltage design. It's part of the chemicals and materials it uses.
That doesn't alter, only capacity and the way it drains (there is a voltage drop as it uses up its power).
I would suggest possibly reading Wikipedia on batteries and cells.

Electronics (with respect to Pi and Display mentioned) are designed to work at a fixed voltage, never more and never less than it's design. It does not alter.
Its current (A) does changes and that is how much energy it needs to use up. You specify a power supply that will cope with the absolute maximum demand.
So 5V 2.5A will be it maximum current draw for the display. The spec sheet would show more detail, like typical current draw.
(I suggest Wikipedia and voltage/current/power)

A power bank (USB type) will supply 5V until it runs out.
No need for wikipedia i think you just refreshed my old base schooldays electricity remnants. Voltage is the base "tension" a piece of electronic hardware needs for all the components to function, fixed by design - Amperage is the "speed" of the current, the drainage rate of the cell/s that fluctuates in function of it's workload right ? (if not i'll just wiki it)

So, cope with the sum max possible draw of all components > smooth sailing right ?

What if the voltage would differ ? e.g.: 5V and 12V ? I'd have to step down and/or up in function of my battery right ?


right ?

: )

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