Firebeetle with solar panel

I’m testing FireBeetle ESP32e with 18650 battery and it runs quite well without major issues so far. I’ve connected several sensors to the fireBeetle and deep sleep at 30 second interval right after MQTT upload. Once all setup, I’m planning to run the unit at 10 minute interval.
Now the questions:

  1. FireBeetle already has TP4056 on board. If I want to charge the 18650 battery from 6v solar panel, can I directly connect the panel +/- to the VIN/GND pad behind the usb C port? Or is there any other way to do it?
  2. I notice the “Low-power Solder Jumper Pad” on the board. Can I cut this?
  3. For another project, I’m looking for an ePaper display. Which one you recommend for FireBeetle?



Hi Jerry, welcome to the forum!

The maximum voltage input for the TP4056 from the datasheet is 8V, so as long as the open circuit voltage of your panel doesn’t exceed this, then you’re golden.

Another alternative would be to use a panel with an in-built 5V regulator, and USB port. That way you avoid any fiddly soldering, though you’d lose a little efficiency.

According to DFRobot this means the RGB LED will only work when the device has an external 5V. I couldn’t find it on the schematic so I’ll have to take their word on that one.

Looks like DFRobot themselves make one for the ESP32, so I’d go with that:

Broadly speaking though, any display should work if you can find a library for your dev environment (Arduino, Micropython, plain C, whatever)

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Thanks James
Can’t wait till weekend when I can test it under the sunlight
(by the time I get home from work it’s dark already)
I’ll post the result once I get something!

I finally completed the test setup so I’m going to put the whole thing in my backyard tomorrow and see what happens. Fingers crossed!
If everything goes alright, I’ll 3d print a nice enclosure and waterproof it.
One weird thing. I cut the “Low-power Solder Jumper Pad” and now the red light is on. That LED has never turned on so far either USB powered or battery. What a weird (or stupid) thing it is!

Unfortunately it’s a failure. The firebeetle works great over the night but once the sun rises, it can’t wake up from the deep sleep. I suspect the charging voltage is a little too high. The solar panel is rated 6v and I think it’s actually over 5v during a normal sunny day. Do you think it’s worth purchasing another 5v panel and give it a go again? I’m a little disappointed and kinda lost interest… :disappointed_relieved:

Hi Jerry,

Sorry to hear it’s giving you trouble! Do you have a multimeter handy to check the open circuit voltage of the panel? Those sporadic data points are weird!

Hi Jerry
Don’t know a great deal about exactly what you are trying to do but I find it highly suspicious that all of the sensor results seem to pretty faithfully follow the battery voltage variations.

What is the actual battery voltage.
What do the numbers on the left Y axis represent.
At present the only numbers that actually mean anything are the right Y axis ; temperature. But even this follows the battery curve. Suspicious what!!!
Cheers Bob

Just got back from work.
The panel produces over 7V when it faces a direct sunlight even in the morning and I think that’s what makes everything goes wrong.

Even with more than half covered by masking tape, it still could produce 7V!
(the panel is listed 6v on eBay)
It’s my fault I should have checked the output voltage first before throw everything under the sun.
(I’m busy doing my day job so it’s actually difficult)
I think I need to put some sort of regulator between the panel and fireBeetle.

Anyway, don’t get confused by the voltage readings. It’s not perfectly smooth but clearly shows the trend if you just ignore the failure between 8:00am to 11:00am yesterday.

Note the three top lines aren’t doing anything (soil moisture sensors attached to 3 analog pins). Mid red dots are temperature readings from bme280 and the bottom line is the analog reading from A2 pin where the fireBeetle’s built in voltage divider is connected. I don’t know much about the electronics but people says you can get approximate voltage values if you multiply the readings by 2.

Actually I don’t know exactly what I’m doing… and that’s the problem haha!
Have a look at the Grafana screenshot I attached to James’ comment. It’s not perfect but rather makes sense to me in terms of battery level reduction and temperature etc over last 2 days. Don’t worry about the 3 soil moisture sensors on top. They aren’t doing anything.
I put the whole thing in my backyard on Saturday night (1/4/23) and everything went alright until sun hit the panel at around 8:00am 2/4/23. The panel produced too much voltage (or current) and I think fireBeetle shut down due to this. I brought everything back to my workshop and after that all the lines look pretty stabilsed.
FYI, My fireBeetle’s built in voltage divider schematics are as follows:
Screenshot 2023-04-03 192249

Hi Jerry
The temperature still spiked very sharply at just after 8AM which would be unusual unless you can explain it like the sensor suddenly getting into direct sunlight.
Even though you claim the others are doing nothing they still show a sharp increase at the same time.
This suggests to me that the marriage between power source and electronics is not all that it could be. In other words it is not right.

I would suggest you get your power supply and /or connections etc in good order before you go chasing fairies. One thing to remember, if your power source is not doing the right thing you can’t expect anything else to work properly. Believe me it won’t.
Cheers Bob
PS. Those numbers on the left Y axis still don’t seem to relate to what the battery value actually is. They are only displaying a relative level and only indicate that the voltage goes up by some arbitrary amount when the sun shines. Not by how much.