Micro USB as its the "Mobile device standard"

what about Solar panel on the back + accu?
does the display need that much to "refresh" ?

Didn't think about a solar panel.
Maybe a very narrow one on the front, if it's useful.
I have to check how much power the display needs to refresh (didn't receive it yet).

I know that you can get surface mount Solar Panel ICS from sparkfun electronics.. or you were last i checked. I think they were in a.. SO-8 package format?

Right, didn't know about those ! Unfortunately, you can just pull 50uA max from them :/

What about using them to trickle charge a capacitor.. and then use that pent up charge to suppliment the power usage?

The simulation told me that part is asking to crack, will see if there are other affordable materials for the front plate :)

Thread the lanyard around the screw posts.

CR2032s can be a total bastard to replace and I think with the kind of activity one of these things sees at a con it might be a better idea to use a simple AAA battery or something. The bulk increase wouldn't be too bad, really, and the ability to replace the battery quickly with things you can find everywhere is important.

A watch battery would be quite appropriate for this, because you can get 3 volts out of it. An AAA would probably have to be stepped up, losing efficiency. This thing will need ridiculously low power when it's running, even in slideshow mode. The e-ink display won't need power when it's waiting for the next picture and the controller can put itself to sleep until next time interrupt, drawing only micro or even nanoamps. The refresh would need couple milliamps every few seconds, but that would still give you hundred+ thousand image flips (and couple weeks of continuous slideshow) from a 200 mAh CR-battery. (Of course, this is speculation from typical specs, but that's what I would expect.)

You say that but I can't imagine my Kindle Touch is all that different from this and it still runs dry even when being left alone, so I find the utility of one of those little button cells to be questionable.
Again, these are meant for use at cons and there's an intention to make them display a bunch of images so that you can have all your refs with you in it or whatever, so the screen's going to be refreshed pretty often. AAAs might not be the solution, but CR2032s definitely aren't. Super flat LiPo battery will probably be the best way to go about this of the options presented here, and that's gonna drive up the cost.

That's everything else in the Kindle eating the power. You've got an 800 MHz Arm Cortex A5 in it, it's listening to WiFi, 3G, it's got a Linux derived OS that does background tasks. Also, when it's switching pages it has to lay out the text, and the user facing software in Touch is implemented in javascript, so it's running in a JITted virtual machine; not even native code.

In this application you can use a really low power dedicated MCU. This would spend most of its time shut down, waiting on physical interrupt. It does absolutely no processing at all in between. A5 in the lowest idle states uses microwatts per megahertz. An MCU like this that does nothing but bang a few bits over the bus can run at super low frequencies and uses one or two microwatts, or even just dozen nanowatts (I've looked at specs and seen some practical applications with these sort of power ranges). And that's not per megahertz, it's all together. (You don't even need to run it at megahertz speeds, kilohertzes (if you select one that can step that way down) would be fine for this when it's on battery and not talking to USB (in which case it's got external power anyway). Done right, five nines of the power is spent on the e-ink refresh and that's few milliampseconds.

But again, this is speculation based on what I'd do.

maybe try a cell phone battery

If you go with built-in rechargable battery, then definitely micro-USB, because then you can connect it to any tablet or smartphone charger. Otherwise, I'd go with mini-USB, as that's still more common in other devices. (I have dozen cables like that).

More flash the merrier, it doesn't tend to be very expensive these days.

If you need menu based interface, 3 or 4 buttons. Up, down, enter, (back/cancel). 1 button interface can't configure it on the fly, which would be a bit of a bummer; but is there anything else to configure than slideshow delay? (2 buttons? One to change static/slideshow, one to adjust slideshow delay, 1-2-5-10-20-60 seconds; You can flash the current setting on the screen when it's changed.) If you want to be able to enable/disable pictures from the slideshow rotation, then you need to implement the 3/4 button menu interface really.

I'm linking the rechargable battery idea honestly. A couple of Li-Poly batteries.. and a usb charge controller. For testing purposes.. adafruit has said items for sale/in stock so he could see if they'd work for his purposes.

It seems a bit.. overdesigned?

Why go with e-Ink? you'd be looking at black and white only.. sure battery life would be insanely high, but does a con-goer really need more than 5 or 6 hours of screen life?

If I was going about making something like this, I'd take apart something like a Motorola MF601 Digital Photo Frame ( http://www.amazon.com/Motorola-MF60...../dp/B00DFCZF8W ), and used that as a starting point. 6 or 7 inch LCD, an SD card slot, an Arduino to handle the display, a 1500mAh Battery, you could probably get 8 hours of screen life from that with the right low-power LCD, and all you'd need to do is plug it in to charge overnight. you could probably make these for $50 in parts once you've got the RnD worked out.

The most important thing about the E-Ink display is that it reads like paper. Using an LCD with an Arduino a 1500mAh battery is excessive. It's heavier, doesn't have the best readability, and also anyone interested in that solution will already have a tablet or something that they can use to show refs. More is not always better...

why would you want to show refs/conbadges on a monochrome screen?

At least bump it up to a color e-Ink screen (they exist!).

I don't know if you saw the mockup but it looked VERY stylish.. Also, using the LCD would be pointless because someone could just buy one of those photo frames for a pittance and hot glue a lanyard clip to it.

I'd take it apart and 3D print a proper lanyard conbadgey housing for it, but yes, that's about the best idea for a hack.

Still. Could there be a color E-Ink option that's more expensive, maybe?

I think that'd bring it out of the levels where enough people would be willing to buy it. Color E-Ink screens are way more expensive(the only devices that have them on the market are over $500).

I don't know why you'd need three buttons on the back. Two would be fine, one to navigate forward in the list of pictures and one to navigate back.
Offering the largest storage size probably wouldn't increase the price TOO much, right? It'd be the most desirable for sure.

All nice so far. I'd go with the CR2032,the same as with Mainboards. I'd go for two buttons, one being a reset button, the other raising an interrupt. Micro USB. Even though there is flash, I'd still look forward to put a micro SD slot anywhere and use the serial communication with it.

Pour l'alim j'irai avec quoi que ce soit de rechargeable, de toute manière c'est pas comme si ça consomme énormément.

Micro USB vu que c'est le standard pour les gadgets aujourd'hui

Pour les boutons, je dirai deux, un pour allers à travers les images, et un on/off si cela fait du sens

Et finalement 2MB, histoire d'avoir de la place (et pourquoi pas faire une rotation entre les images si c'est pas trop complexe et consomme pas trop

off c'est l'état normal quand ça ne change pas d'image :3

pour info, un ecran e-ink quand ça raffraichis ça se passe comme ça si tu veux une image sans trop de traces de l'image précédente dedans : http://youtu.be/_uqT7RVwC_w

donc je crois pas qu'un effet de transition soit prévu.

Rechargable battery, Mini-USB (I think that's the more common one), 3 buttons (on/off, cycle to next image, toggle autocycle through images) and 2MB. Not sure if I'm too late to have any input, but I may as well try.

How would it handle images that aren't the same size as the screen?

Je suis fortement partant :D Ça m'intéresse beaucoup!