Heltec CubeCell - part 1

FYI: Topic title was updated.

Hi,
May I kindly ask regarding CubeCell module (meaning CubeCell chip, not developers board) - what is input voltage tolerance, Is it ok to powered it by 3,6V - LS14500STD 3,6V 2450mAh?? Or should I use regulator to convert it to 3.3V?
Ciao
Lukas

According to Heltec’s specifications max power supply voltage (VDD) is 3.5V.

See Tech Specs tab on the HTCC-AM01 product page.

An alternative is put a low forward voltage Schottky diode (e.g. 1N5817) in series with the (plus of) the battery. This will cause a voltage drop of around 0.3V to 0.5V and also provides reverse polarity protection.

Hi,
may I kindly ask a few questions. I tested your sketch but it really was not working based on my expectations. Using ABP I was able to send data. Using OTAA I always get response “unable to join” - I saw requests coming but no success.

Is it also possible to share sketch with download handling? Like ability to receive the response and parse data and apply it - like change wakeup time, or handle GPIO (low/high), or any other operation?

I would really appreciate any kind of support.
Maybe I am doing something totally wrong, but not sure
Ciao
Lukas

The standard LoRaWAN example already automatically enters deep sleep between upload cycles and automatically wakes up by timer.

I did a small test with the standard LoRaWAN.ino example.

When powered by LiPo battery via the battery connector the CubeCell board uses only 8.5 uA during deep sleep! :smiley: :+1:

When externally powered directly on the 3.3V pin, either by LiFePO4 (3.2V nominal) or by two Alkaline batteries (2 x 1.5V = 3.0V nominal) the CubeCell board uses only 3 to 3.5 uA in deep sleep.

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Powering the CubeCell HTCC-AB01 board with batteries

Important: It is easy to connect batteries incorrectly and reverse their polarity (50% probability) which can permanently damage the board. I’m not sure if there is reverse polarity protection when using the battery connector (often not) but there definitely is not when directly powering the Vin or 3.3V pins. Also take care that AA, AAA, 18650 model batteries can accidentally be inserted in reverse when using a battery holder.

Powering with a Li-ion or LiPo battery:

Li-ion and LiPo batteries must be connected via the battery connector.
The battery will be automatically charged when a (powered) USB cable is connected or when a solar panel is connected.

Important: To prevent damaging the board, first check the polarity of the battery cable before connecting the battery to the board. It is not uncommon that polarity (plus and minus) of separately bought cables is reversed to that of the board - which can permanently damage it.
Some of these batteries have built-in protection but I’m not aware if that will also protect the board from damage if the battery is connected in reverse.

Powering with a LiFePO4 battery:

Connect the plus directly to the 3.3V pin and do not use the battery connector.
The battery connector only supports Li-ion and LiPo batteries. LiFePO4 battery have a lower output voltage and have different charging requirements. When using a LiFePO4 battery, it cannot be charged via the USB port.

Important: The board does not provide over-discharge protection for the battery. When using a battery holder it is possible to insert the battery reversed which can damage the board. Adding a reverse polarity protection with a MOSFET will protect against this.

Powering with regular Alkine batteries:

Note that directly powering the 3.3V pin with two regular Alkaline batteries is less suitable because the batteries provide only 3.0V nominal output which steadily decreases to below 2.0V during discharge, so it will not be possible to use their full capacity (maybe only half of it).

In case use of Alkaline batteries is preferred (e.g. because they are cheap and readily available) it will be better to use three Alkaline cells in series. In this case the plus must be connected via a Schottky diode in series to the Vin pin. Use a Schottky diode with low forward voltage (e.g. 1N5817).

Important: The Schottky series diode is required to protect the batteries. The diode prevents the batteries from being powered with Vin or Vusb (5V). This protection is important but is not provided on the board. The diode also provides reverse polarity protection.


Connecting a solar panel

The board can be connected to a 5V or 6V solar panel. The plus of solar panel must be connected via a Schottky diode in series to the VS pin. Use a Schottky diode with low forward voltage (e.g. 1N5817). The solar board will be used for charging the Li-ion or LiPo battery.

Important: The Schottky series diode is required to protect the solar panel. The diode prevents the solar panel from being powered with Vin or USB (5V). This protection is important but is not provided on the board.

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This is so true about Alkaline batteries.

If you want to avoid rechargebles for whatever reason, a good alternative to Alkalines is the Lithium Energizers, almost the full 1.5V till exausted. Good down to circa -40C.

Not as cheap as Alkaline unfortunately.

https://data.energizer.com/pdfs/l91.pdf

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I didn’t know that 1.5V Lithium batteries exist.

Hi,
and may I asked for your recommendation regarding LS14500, which is 3.6V No-rechargeable lithium ion battery. Which way to connect to CubeCell board. Shall I use VIN pin and regulator? I would rather use it without regulator.

Have you used one to power a node before ?

Datasheet I have for a LS14500 suggests the output voltage is around 2.5V at 50mA current drain.

I am using LS14500 mainly to power esp8266 or esp32 for my nodes. I do not tested using cubecell yet, but I plan to test it soon. Looking for recommendation regarding proper setup/configuration/connecting to CubeCell. I am really satisfied with the battery performance with my existing projects… Measured battery output is approx. 3.4V at 100mA.

Thanks for the update, interesting although not cheap.

I had looked at them for very low temperature use, thats where the voltage performance suffers.

@LoRaTracker - I am using it mainly nodes which are placed under the ground, so there is no such low temperature (-3 was the lowest temp, so I do not challenge such an issue).

That was exactly the reason why I did not include 3.6V Lithium Thionyl Chloride batteries in above overview (and I have no personal experience with these batteries).

A sufficiently large capacitor as buffer could help to stabilize input voltage for short periods between deep sleeps.

The next issue to solve would be to which power input pin to connect it.

When connecting directly to the 3.3V pin:

  • The 3.6V of the battery is too high for this (max supply voltage VDD of the CubeCell module is 3.5V). A series diode would probably cause a too high voltage drop (especially under load).

    Or just connect it without series diode but that would run the CubeCell module (and connected sensors) (a bit) out of spec. This could work fine but can also cause degrading issues on longer (or shorter) term.

When connecting to Vin:

  • Vin is parallel to Vusb (5V) which is error prone and may cause damage when a USB cable is connected. Using a series diode for protection is not an option here because it will cause a too large voltage drop. Vin is input to a 3.3V voltage regulator of which VDD 3.3V is the output so voltage would drop twice when using a series diode.

So what would be the best choice?

During Wifi transmissions ESP8266 (ESP32 is probably similar) can have peaks of 200+ mA which will require use of a sufficiently large capacitor as buffer.

I have tested cube cell with TTIG indoor Gateway and join problems.
Can some report else such problems?
See:
@wasn do you have also such problems? Is it the indoor gateway or my node?
What can I throw away?

@MOS-FET i have several CubeCell devices running andu havenNo more problems than with other nodes.
Most times the problems is that the TTN servers are not sending the accept fast enough.

I can see those join accept problems only when using TTN, when i use our own chirpstack servers these problems dont accure.

@wasn Join not accepted by node
Could it that the library is waiting to short time for join a acceptance?

@MOS-FET Stop asking the same questions in different threads! Join not accepted by node

You were asked for information in the linked post and to do a test and observe the results but you did not and instead repeat your question here. Stop wasting others’ time if you don’t want to follow provided suggestions and don’t want to provide requested details.