Yes, a good idea but why are you using a normal constant current charging chip and not a solar power charging IC? With an additional JST connector it would be much more useful than now!
All this Power Board (LiPo / AAA) are a good idea but it would be better to have a really low power main board. 500 uA deep sleep current is too much. Why it is not possible to have a board with 20 uA or less? It is possible. The Pycom WiPy needs 16 uA in deep sleep, the DFRobot Firebeetle around 50 uA. So you are much more flexible than handling an additional ATTiny on the power “shields”.
Daisy chain the boards with the flexible “cable” is a nice way but in case I will chain them not one after the other but side by side? Would it be possible to have as much pins as possible as castellated pins on the edge of the main board? So it would be perfect to connect it with a custom PCB!
Is a LoRa / TTN main poard pland beside the ESP32? And how about LTE connection?
For a special use case (this is not sooo serious but greetins to Nathan and all beekeeper!) I would love to have a realy low power LiPo / solar powerd smol board with HX711 or better NAU7802, LoRa support and I2C ports for BMEx.
A solar power board (with super-capacitor charging circuit)
A low-power processor board (probably based on one of the STM32 ultra-low-power devices)
Long FPCs - so you can stack the boards end to end
Z FPCs - so you can stack boards side by side
An RF (probably LoRa) peripheral board
A LTE + GNSS board as soon as chips are available
An environmental board with VOC sensor
We had not thought about a load sensor board but we’ll add that to the “under consideration” list too - thanks!
We may make a castellated Header board, but adding castellated pins to a smôl processor board would take up a lot of board area. I will need to think more about that. But thank you for the suggestion.
I am happy to have discovered the smôl ARTIC R2 board and would like to power it with solar cells along with the ESP32 processor board and the GNSS board. Is there any indication when the smôl solar board will be available?
Or do you have a recommendation, which chip or even better, which small format board from another product series would be suitable alternatively until the release of the smôl solar board?
Unfortunately we have not yet started designing the smôl solar power board. We have been busy with many other SparkX projects and products… Sorry!
For now, my suggestion is to use the LiPo Power Board and to assemble a “solar panel + 5V regulator” which provides power to the ESP32 Board over the USB connector. The LiPo battery will be recharged from the solar 5V through the ESP32 board and the LiPo power board.
Thank you for your suggestion. Is there also a way to use supercaps instead of LiPos to achieve more charge cycles? Would it make sense to connect them to the LiPo power board in place of the LiPo or would I need to replace the whole board?
That is an interesting question: “Can a LiPo charger IC be used to charge a super capacitor instead?”
I do not know the answer. Perhaps? Probably not? It would take a lot of testing…
I suspect that the charge profiles of LiPo batteries and super capacitors are too different. For super capacitors, I always use a dedicated IC like the LTC3225.
Could I also use this one https://www.sparkfun.com/products/9946 as solar charger to power the smol esp32 board in some way? The current draw of the esp32 board at 5 V would be much higher than at 3,3 V (and I also cannot find a suitable board with the LTS3225 that you suggested).
I would like to use the smol ESP32 together with the smol GNSS board, a compass (and a small solenoid like this one for example https://www.sparkfun.com/products/11015 - although possibly with 3,3V as well)
Or is there maybe a native smol solar board on the horizon?
Apologies. We are still working on many other projects and we have not yet had time to look at the smôl solar power board… It will be weeks, probably months before that could happen…
The energy-harvester board is a nice solution but I do not think it would work well for the smôl ESP32 + ARTIC R2. Combined, those two boards will draw much more than the 100mA the harvester board can provide, particularly when the ARTIC transmits.
Also, electromagnets take a lot of current. The one you mentioned draws 1.1A at 5V. Less at 3.3V, but still approximately 700mA.
I will keep thinking about this but, right now, I do not have a good solution for you. Sorry!
You mentioned the LTC3225 earlier in this thread. But even this one only has an output current of only 150 mA, right? Do you know of any IC (or even a board) that would be suitable to power the smol Artic R2, ESP32, and GNSS board, and leave some extra power for an additional GPS board and maybe something like at least 50 mA for a tiny actuator? Or to make it simpler: Which IC would you choose to design a smol solar board? Actually, I couldn’t find any IC other than the Maxim MAX20361 that provides more output current than the LTC3225. But then it only works with solar panels with a maximum voltage of 3 V. Is the market for solar harvesting ICs really so limited?
My idea was to use the LTC3225 to charge one or two super-capacitors. Probably to 5.2V. Probably at a current of 50mA to 100mA - the current that a small solar panel can provide. The capacitor(s) would hold enough charge to power the ESP32 plus GNSS then ARTIC R2 while they perform a wake_get-position-_transmit_sleep cycle for tracking applications. The system would be on for perhaps one minute then asleep for perhaps 59 minutes during daylight for example. At that duty cycle, solar plus super-capacitors would be a good solution. The capacitors can easily deliver enough current for the ESP32 and ARTIC during transmit.
It is a technique we used successfully on the Artemis Global Tracker. The two 1F capacitors hold enough charge to power the Iridium modem while it transmits. The peak current draw is 1.3A - but only for a few 10’s of milliseconds.
Interesting - thank you very much! So the high current of 1.3 A does not run through the LTC3225 at all, but directly from the supercaps? Is that the reason why these ICs usually have so “regular” little output current? Unfortunately I don’t understand how the circuit would have to look like to use the supercaps as a “parallel” current source to the LTC3225 during current peaks. Do you (or anyone?) know of a small board that allows this?
I had looked at the boards before but thought they were not compatible with the smol esp 32 board, since they are made for their own Mikroe platform, not for Arduino. Now, following your suggestion, I have been researching again over the last few days to see if I can come up with a solution. To work with the smol esp32 board, wouldn’t it need corresponding libraries? There are at least a few Arduino libraries for Mikroe boards, but as far as I have overlooked not for these two. Or would I have to read and address them completely manually?
It looks like those MIKROE boards have a suitable supercapacitor charging and power circuit. The smôl power boards also have an ATtiny processor on board which can be used to monitor and switch the power with a programmable wake-up. It may be possible to use the MIKROE boards as a stepping-stone to get your project started? With the ESP32 in deep sleep, the current draw will be low - hopefully low enough to not drain the capacitors between transmits.
Do you suggest to use the smøl powerboard together with the Mikroe UPS Click Board? Doesn’t the smøl board expect an always available power source (the LiPo)? However, the Mikroe would only provide power when it has sufficiently charged the supercaps, right?
Or did you mean I need to use a separate attiny that puts the ESP32 board into deep sleep mode? Wouldn’t that be possible (and more economical) via a signal that the Mikroe UPS board could send itself? Or does it need a complex command to do that?
I have now managed to put together the setup I need except for the solar power supply. I am using the smol ESP32, the GNSS board and the Artig R2 board. Through the header board there is also an IMU board connected via I2C. And since I also want to operate a motor, I have designated the CS2 pin for this as output. But now I realize that I need another free pin on the header board to check the voltage and the charge level of the supercaps. Otherwise the ESP32 might start an energy-consuming transmission with the Artic R2 in the worst case and take away the last energy reserves of the whole system. Is it possible to “double use” one of the pins on the header board to check the charge level? The Mikroe UPS solarcharger board (https://www.mikroe.com/ups-click) sets the PGOOD pin LOW and HIGH depending on the charge level. The ESP32 should be able to read this pin to make it work.
I would be very happy if there was a way to still save my smol project. Otherwise I would really have to change to another platform. Thanks a lot for any hints!
Could make any sense to have the LiPo Board between the ESP32 board and the Mikroe UPS solar charger board for example?
Apologies for the slow reply - I have been away on vacation.
I am sorry. I really do not know what to suggest. You could use a I2C-GPIO “port expander” to provide more pins - but there is already one on the ARTIC R2 board. It is a PCA9536 and has a fixed address of 0x41 - meaning that you can not put two of them on the same bus. Maybe you could use an alternate part with a different address?
