I am trying to make a weather station that has a BME280, a RF Receiver (to connect to the exterior module), a 3.95" TFT LCD, and POSSIBLY a couple other sensors, which I haven't decided exactly what they are yet.
I want the weather station to be powered by a battery, but I don't want to take the batteries out to recharge it...
Am I able to follow this: https://www.jaycar.com.au/lbc with two 26650 batteries?
Or does that tutorial only work with the batteries that Jaycar makes it with? I wish to follow the exact thing that Jaycar does, only with 26650 batteries.
Is that possible?
Please post links to datasheets of the items You have in mind.
Clicking on links is not desirable.
The 14500 is just another 3.7v lithium battery - a small one
The 26650 is just another 3.7v lithium battery - a larger one
Essentially the only things that count in that box are the charger module and the DC converter module. None of this is unusual stuff but:
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There may be better choices for charging the larger battery, but that may not be important.
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Assuming your need for the larger batterie(s) is real, you should check that the DC>5v converter is up to supplying the power you need. This stuff could be a long way from a Jaycar Uno clock project.
and, further to 2:
- You may find you are better off with a single battery with similar output to 2x26650.
The Lithium Charger Module Datasheet:
https://www.jaycar.com.au/medias/sys_master/images/images/9677424885790/XC4502-dataSheetMain.pdf
The battery originally used in the project:
5v Boost Module Datasheet:
https://www.jaycar.com.au/medias/sys_master/images/images/9677429604382/XC4512-dataSheetMain.pdf
Resistor Datasheet:
https://www.jaycar.com.au/medias/sys_master/images/images/9661651550238/RR0600-dataSheetMain.pdf
The battery I want to use:
My aim is to have the weather station running for 48 hrs without recharging. I don't THINK the mega2560 will draw more than 200ma, so according to https://www.digikey.com.au/en/resources/conversion-calculators/conversion-calculator-battery-life , the project should run for 50 hrs between recharging. I was just wondering if this sounds accurate and if anyone knows if this will work or not.
I was also wondering if this would work:
https://www.jaycar.com.au/power-pack-for-raspberry-pi-with-li-ion-battery/p/XC9060
I rather think this whole saga is half-arsed. You say
So what is the actual charging supply, and what do you intend to do while the battery is being charged? On the crudest estimate with your figures, you need to be planning on standing around waiting for up to 9.6 hours while the battery gets charged. It is starting to sound very much like you should consider powering the whole thing off the charger supply, whatever that is, and dispensing with the batteries altogether or, at best have them float across the supply for use in the event of power failure, but there is no clear intention there.
There would have to be a bazillion and one battery powered weather stations around here, and I don't think you have seriously looked at any of them. For starters, you should look into sleep-mode, power saving, and the black arts around them. Also, I understand that a Mega is a poor choice for battery operations. A 3.3v Pro Mini may well be quite satisfactory and is a lot more frugal.
I want the battery to be a power backup, basically.
at best have them float across the supply for use in the event of power failure
I do not want to miss any readings if the power goes out.
I cannot run a 3.95" TFT LCD off of a 3.3v Pro Mini, obviously. Plus I don't think a Pro Mini has as many digital pins as I need for this project. I don't care if the weather station is plugged in all the time. In fact, that is what I am planning on. If you looked at the project OR the datasheets you would see that the charging supply is a usb cord (plugged into a PC, wall outlet, phone charger, etc.
I have looked at a few weather stations out there, only none are what I'm looking for as they are too simple or don't run on batteries
This is one:
https://create.arduino.cc/projecthub/antiElectron/enviro-7-touch-panel-weather-station-with-remote-sensor-7cce54?ref=search&ref_id=weather&offset=66
It is basically what I want, only it doesn't use a Mega. If I do follow that project, is there going to be any point using that battery? The author doesn't say anything about that.
You can’t use lithium batteries connected as a float supply . Have a look at lead acid , also have a look at power saving techniques - use a “ minimal uno”, sleep, only powering sensors when you take a reading etc . This could get your power demand very low .My Maplin device runs for a couple of years on two AA battery !
How long would it last if the TFT LCD is on all the time?
No idea , do the sums . Why does it need to be on all the time
- realistic output from solar panel - can it supply enough power ?
-what happens at night
-capacity of battery
-time to charge flat battery - current consumption and minimising it
How are the sums calculated??
Not sure what happened there .. looks like I’ve added to my previous post , above ^
Measure the total project current draw in mA and multiply that by hours of battery operation required, to get absolute minimum mAh battery capacity required.
Buy a battery with twice that capacity.
Buy a solar panel that can provide those mAh during hours of expected sunshine.
It looks like I'll need a 30000 mah battery.
I was thinking of using this:
Do you think that'll work?
If that number is not make a mistake, you have an extremely inefficient circuit.
Most weather station builds use sleep modes, which drastically cuts power consumption.
I do not know how many mA my circuit is drawing - I'm guessing 300mA????
Times that by 48 hours = 14400 mAh
Double that = 28800 mAh
Round up to nearest AVAILABLE battery = 30000 mAh
How do sleep modes work? Can you sleep mode it while still displaying data on a screen & logging it to sd card?
I don't mind if the screen is off at night, but it HAS to keep logging data throughout the night.
I've got about eight sensors and a screen on my Mega2560, I don't know how many mAh that will draw.
Measure it.
Always-on TFT screens and battery power are a terrible combination, but with a big enough solar panel and battery bank, who cares?
Excellent tutorial on sleep modes: Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors
This is probably a REALLY stupid question, but how do I measure it??
Use your multimeter. If you don't have one and intend to continue in this hobby, it is an essential tool.
The data sheets from the components should give you a reasonable estimate of the current draw for each, so look all of those up and add them.
The 7 inch TFT screen in the project you linked draws 500 mA, so that project is a totally unrealistic model for an always-on display.
Yes, I have a few of those, but where do I measure it?
At this point I'm using a usb from my pc.