I’m interested in using electronic shelf labels (ESLs), the (mostly) radio-controlled, mostly eInk-based labels you can find in shops and supermarkets. I’ve been able to find a few brands and label vendors (e.g. on A**express), but failed to find any option to buy “just” a single ESL gateway (used for updating the labels).
My use case, e.g: have a large label on the inside of my door that tells me, in red, stuff like “You can’t leave yet, the following windows are still open: …” etc. Since battery life times are stated to be up to 5 years, ESLs look promising for this. However, what is sold is “solutions” for stores, including a lot of stuff I do not need for my purposes.
Has anybody ventured into this, based on openhab or similar platforms? Are there ESL gateway standards that I should be aware of, or is everything vendor-specific?
I love this idea!
I have no experience with ESLs (now I know what they’re called, though) but if I were to do this, I would roll my own using an ESP32 + eInk display. It could stay in deep sleep mode most of the time, and wake up, connect to wifi, pull the state, update the screen and sleep again once every few minutes. You should be able to achieve several months battery life this way, maybe beyond a year if it doesn’t have to wake up too often.
There are even ESP32 modules that include the e-ink display! Check out this youtube video.
The 7.5" one is expensive indeed ($48), so I only bought one.
Let’s not forget that this is the size of a kindle, though.
There’s also 9.7 inch version for $137 which is way beyond an impulse buy for me.
The pricetag-sized versions are much less expensive though, 2.13" is $10.
I didn’t see that actually!
Being a 433 MHz system, it could be possible to hack it so that you could feed a display data from an arduino with a 433 MHz transmitter rather than needing their proprietary gateways. But, hacking that could take a very long time, plus I’m already using 433 MHz remotes for several things, and having intermittent prolonged bursts of e-ink data would definitely interfere with the remotes, so I’ll have to pass on this and stick with WiFi which lets everything coexist.
I’ve used a 2.9 "waveshare display for displaying weather data (Wemos D1 mini, GxEPD library) Unfortunately, the displays are only suitable for use cases where the display is not updated as often. I have measured the data every 10 minutes and transfered them to openHAB via MQTT and refresh the display every 60 minutes. It has lasted a little over a year then the display was broken.
Apart from that, the displays work quite well and together with the deep-sleep mode of the Wemos D1 this should also work battery-powered.
Looks like an easy-to-use setup, indeed! I need to think about how to wire something like this to a proper power supply (WIFI means it’s not really battery-friendly) while it is hanging on my door. Let us know how your little project goes, please!
True, WiFi is inherently battery unfriendly, but depending on how often you need it to update, it could work. It uses no power when it’s not connected :-).
You could also possibly do a hybrid approach of waking the microcontroller with a 433 MHz signal, at which point you could connect WiFi to request the latest update.
But, at this point, it may indeed be easier to just mount it on the wall next to the door rather than on the door itself, so that you can supply it with wired power.
In my case, I have double doors, so this would actually not work that well – the wall is too far away.
Edit: There’s one more way! I haven’t used this myself yet but I remember looking into it a while back. Search for ESP-NOW. It’s a proprietary power-efficient 2.4 GHz connectionless communication protocol supported by both ESP8266 and ESP32. This would let your device wake up quite often to see if there’s an update.
It means you will have to built your own WiFi to ESP-NOW gateway using two ESP32’s with serial communication between them (i think) but that’s totally doable. Maybe someone has already done it?