Large-format e-paper: why you salvage instead of buy
A 20-inch touchscreen e-paper panel is not a part you can buy. Both answers on Hacker News said the same thing: gut a finished product. Here is why, and what that costs in Sri Lanka.
If you want a large-format e-paper touchscreen, meaning anything past 20 inches with touch that actually works, the honest answer is that the part is not sold to you. Someone asked exactly this on Hacker News in Ask HN: Good large format (>20 inches) touchscreen E-Paper display options?, for a low-power calendar project.
Two people answered. Neither named a panel. Both said: buy a finished product and take it apart. That is the whole story, and it is worth unpacking.
🔍 Two replies, one answer
The suggestions in the thread were short and both pointed the same direction:
"It won't be cheap for sure. If you just want 1 for personal project, better to buy of the shell eink monitor (i remember dasung has one) and gut it." — mrheosuper
"Sony DPT-RP1? Some are jailbreak-able." — xiaoyu2006
One says buy an e-ink monitor and strip it. The other says buy a document reader and jailbreak it. Nobody offered a module, a breakout board, or a driver kit. When a hardware question gets zero part numbers and two salvage suggestions, that is the market telling you something: at this size, the component channel does not exist for individuals.
🧮 Why the module market stops at small sizes
Small e-paper modules are everywhere in hobbyist electronics because the panels are cheap to make, easy to drive, and sell in volume for shelf labels and badges. The economics fall apart as the diagonal grows, and the touch layer makes it worse. Roughly, your options tier out like this:
| Approach | Touch included? | Where it comes from | Main risk |
|---|---|---|---|
| Hobbyist e-paper module | Rarely | Electronics distributors, online marketplaces | Sizes stay small; big ones are the exception |
| Salvaged e-reader / document reader | Yes, built in | A used consumer device | Locked firmware; you inherit someone's OS |
| Gutted e-ink monitor | Usually not | A finished monitor product | You pay full retail, then void the warranty |
| Signage-grade panel | No | Commercial suppliers | Sold B2B, minimum orders, not a one-off purchase |
The pattern: touch and large size only arrive together inside a finished product, because that is where the integration cost was already paid by someone else. Buying the panel alone means recreating a controller, a timing chain, and a touch digitiser that a manufacturer already solved.
Key takeaway: For big e-paper, the cheapest engineering path is almost never the cheapest bill of materials. Buying a whole product and repurposing it is not a hack, it is the sensible route.
💰 What "it won't be cheap" means from Sri Lanka
That comment about cost lands harder here than in the US or Europe. A hobbyist in California pays roughly what the listing says. From Colombo, the sticker price is the start of the calculation, not the end. Three costs stack:
- The device itself, which is a premium-priced niche product before anything else happens.
- International shipping, on an item that is fragile, flat, and awkward to pack.
- Import duty and taxes at landing, which vary by what the item is classified as.
That third one catches people out, because classification matters more than intuition. An e-ink monitor may land as a monitor; a reader tablet may land as something else entirely. Work the landed cost out properly rather than guessing:
- Sri Lanka monitor import tax calculator for display-class hardware.
- Sri Lanka parcel import duty calculator for a general courier shipment.
I am not going to quote rates in a blog post that will be stale in a month. Run your actual figures. The point is that the "just gut a monitor" advice assumes a retail environment where the item costs what the page says it costs, and that is not our environment.
⚡ "Low power" is doing a lot of work in that sentence
The original poster wants low power for a calendar. That instinct is right, and slightly misdirected.
E-paper's real property is that it holds an image with no power at all once the refresh finishes. A wall calendar is close to the perfect use case, because it changes a handful of times a day. But the panel is rarely what drains your power budget:
- The panel draws power only during a refresh.
- The driver board or single-board computer driving it is usually running continuously.
- The network radio waking to sync a calendar feed costs more than most people expect.
So if your calendar runs on a full SBC that never sleeps, you have built a low-power display attached to an always-on computer. The fix is in software: deep sleep between refreshes, wake on a timer, sync, redraw, sleep again.
If it will hang on a wall permanently, measure the draw with a plug meter. Our appliance electricity cost calculator will convert watts into a monthly rupee figure at current CEB tariffs, which is the number that decides whether this is a fun project or a small ongoing bill.
🛠️ What I would build instead
For a wall calendar specifically, I would question the requirement before buying anything:
- Do you need touch? A calendar you look at is not a calendar you poke. Dropping touch removes the hardest constraint in the whole build and opens up panels that are merely expensive rather than unobtainable.
- Do you need 20 inches? Two or three smaller e-paper panels in a frame, each rendering a different pane, is uglier in a photo and far easier to source.
- Do you need e-paper? A recycled Android tablet with the backlight dimmed, screen-off between refreshes, and a greyscale theme gets you most of the visual calm at a fraction of the cost, using hardware many households already have in a drawer.
- If it must be e-paper at size, then follow the thread's advice: buy the finished device, and treat the firmware as the project. The jailbreak suggestion means the software effort moves to the front, so budget your time there.
Nobody in that thread said "this exists, here is the link." Two experienced people said "take something apart." Trust that signal before you spend a month searching for a part that would have shown up in ten minutes if it were purchasable.
💡 What this means for you
If you are building hardware from Sri Lanka, this small thread is a useful lesson in reading a market. The absence of an answer is an answer. When a well-populated technical forum produces zero part recommendations for a category, stop searching and start redesigning the requirement.
The specific takeaways:
- Large touch e-paper is a product-level capability, not a component-level one.
- Salvage and repurposing is the mainstream path, not a compromise.
- Landed cost, not sticker price, is your budget. Calculate it before you order.
- Power on an always-on build is dominated by compute, not the display.
The calendar on the wall is a good goal. Just solve the sourcing problem the way the market is actually shaped, not the way you wish it were.