Anyone have a good plan for a battery powered status indicator that could show a bar graph or similar?
I’ve built a sensor that estimates the amount of hot water available fairly well as a % and I’d like to have some kind of simple indicator that updates ~5 min intervals in the bathroom for how much hot water is left.
I doubt you will find anything like that being battery powered.
That type of thing is usually wifi based and wifi is fairly power hungry. Not to mention the display/light bar that you would use is going to use up a battery pretty quick…well…unless you have a really big battery or change it pretty often.
I have a wifi based temperature sensor from my smoker that uses an ESP module and with it just running to measure the temp and send it to HA (not driving a display or light bar) a 10,000 ma battery runs about 4 days (not that I ever run my smoker for that long but I tested it when I first built-it).
so add an always on display then cut that time at least in half?
But if you eliminate the battery requirement then the rest should be fairly easily available, especially if you want DIY with an ESP.
Yeah but I don’t know of any good way to have it mains powered and be over where its visible for a long soak or shower when I’d want to know how the hot water level is.
I’m wondering if there could be some way to add a PIR sensor or something since of course it would only need to display while someone is there to see it…and reduce power drain to just like every 5 minutes for the 30-60 minutes a day that it might be used…but was hoping someone already figured out before I do a major DIY
motion sensing might be a good option. A low powered PIR that wakes the processor.
This display also came to mind - it will show the last updates even after a power off. So you could put everything to sleep in between updates and still see the last value at all times. https://www.adafruit.com/product/4778
esp32 deep sleep, wake every 5 minutes, refresh eink display and go to deep sleep again sounds about right. Check wich esp32 boards have the lower power consumption in deep sleep mode.
But that doesn’t solve the problem of the power consumption of the display itself.
eink or epaper display only draws power when changing the display, you can disconnect the power and the image will still be on the screen.
Reading forums, reddit, etc, it seems that with a power pack of two 18650 you can achieve 6 months - 1 year or more, It depends on the number of times the information is refreshed (wake up, connect to wifi, read stats, show on screen, deep sleep… maybe… 10-15 sec powered on?)
You can skip updates at night to save battery. for example from 00:00 to 07:00. I am not an expert on the subject, but there are many tutorials about it.
interesting, I didn’t know that.
Hadn’t thought about eink but that would eliminate a lot of complications.
You can make something like this, but smaller:
Very nice with the picture frame, also you can put some other usefull information on the screen. Can’t wait to see your project!