Issues when powering thingy:91 from solar panel

RE: Issues when powering thingy:91 from solar panel

RichM — Fri, 18 Apr 2025 20:15:39 GMT

I have been testing with several solar panels and looking at voltages today. It seems like the beginning of the problem is that when the Thingy begins doing something that draws more power (like connecting to cell network), the input voltage (VBUS) from the solar panel which is running at 5 volts, can dip below 4.4 volts.I'm just using a meter on TP12 to watch this.

With the scope I see that Test points 3V3 and 1V8 and Li-Po and nRF52 are stable. nRF91 is bouncing around as the current draw does.

Since we only have high power draw a few moments per hour, is there a way we can disable the power charging before we do the cell transfers. It seems like this is the only time it is a problem.

Rich

p.s. - I am testing this using a 250W heat lamp aimed at the solar panel. That give me a lot of control. Everything works great when the panel is near the lamp or completely dark. Failure is when the panel voltage drops to about 4.7 volts and then drops further when cell is enabled.

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Mon, 17 Mar 2025 18:40:56 GMT

I have also been worried about the difficulties in upgrading the firmware, but hope it will be fine. However, I am worried that it will introduce more complexity as the nrf5340 has a network core and an application core, adding one more layer of things that can fail.

We also had a lot of issues getting the thingy 91 stable especially when using hci_lpuart. Since we use Bluetooth very frequently, we had to discard hci_lpuart and ended up using lpuart between the two devices, programming the nrf91 and nrf52840 separately, and only sending simple command messages between the chips.

Your products look really cool btw. We have started a company called botanist.ag, creating low-cost, accurate soil sensors for industrial use.

RE: Issues when powering thingy:91 from solar panel

RichM — Mon, 17 Mar 2025 14:30:50 GMT

I have the 91X and unfortunately it means new firmware... plus we use the hci_lpuart which has not been ported to the 91X yet. Something more to do... just a very busy time of the year for our small company with beekeeping season starting. Our group is BroodMInder.com, what is your's?

BTW, it took us a long time to get the T91 stable. We are (finally) quite happy with it and it is reporting all the connection parameters back to us as of about 4 months ago. Since we are installing globally, this is a huge help in problem areas.

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Mon, 17 Mar 2025 13:41:49 GMT

We have the same setup as you, where we use the Thingy:91 as a BLE to LTE-M/NB-IoT gateway. I have also considered using the V25 USB Battery Pack, but the whole setup becomes quite expensive.

I have also bought one of the new Thingy:91 X and will test if this has the same issue. The Thingy:91 X is also cheaper, so if this can be powered directly from a cheap 5V solar panel it is probably a nice solution.

RE: Issues when powering thingy:91 from solar panel

RichM — Mon, 17 Mar 2025 13:34:21 GMT

Rats,I was hoping for a cheap/easy solution. Currently we use Voltaic V25 plus solar panel. That works well, but is a bit pricey and requires a larger weatherproof enclousure. We use the Thingy91 inside a solar shield and it makes a great weather station / BLE receiver to read our sensors.

Maybe I will see about a custom solution from Voltaic. They have been a good partner for us.

It is hard when you see the very cheap panels that _almost_ solve the problem.

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Mon, 17 Mar 2025 13:21:07 GMT

Hi again,

I have actually tested this one:
https://voltaicsystems.com/solar-usb-regulator/?srsltid=AfmBOopYRxC9XLNVjKzA9O73vR363_SWk2QQ4Y-b0l6lik7y8aQQfee1

That also had the same issue as the solar panel.

I contacted Voltaic and they suggested something like this:
https://www.pololu.com/product/4085

Currently, I am testing an external voltage regulator/solar panel charger:

https://www.digikey.no/no/products/detail/dfrobot/DFR0559/9356334

This didn't work either and also has the same issue.

Now I am testing using DFR0559, an external battery and direct contact between the LIPO connected to the DFR0559 and the LIPO input on the thingy 91. This seems to work pretty well but is not optimal as it requires more installation steps and probably an EMC test.

RE: Issues when powering thingy:91 from solar panel

RichM — Mon, 17 Mar 2025 12:58:36 GMT

Yes I do. We are now just seeing a bit more sun in Wisconsin. I think it works great on sunny days, but has resets on cloudy days. I have only installed it outside on March 15. You can see from the graph that the device gets confused twice. We run every 10 minutes and upload to cell once per hour. If the cell can't get through, we also have an 8 hour watchdog. Hub status is just an up counter that increments on each good MQTT transfer. So it looks like we have 2 resets on March 16.

I'll leave it run for a while and see what happens. I will be out of the country for 2 weeks, so that shoudl be a good test. This is the panel I chose from Amazon.https://www.amazon.com/dp/B0CJ5C2QY5?ref=ppx_yo2ov_dt_b_fed_asin_title. It does not prevent low voltage output.

I wish I could find a panel that drops out below 4.5 volts... I don't want to make an adapter...

I also have a note into Voltaic, we have had good luck with them. They have a new part that might be a good answer (always looking....) https://voltaicsystems.com/solar-usb-regulator/?srsltid=AfmBOopYRxC9XLNVjKzA9O73vR363_SWk2QQ4Y-b0l6lik7y8aQQfee1

cheers,

Rich

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Mon, 17 Mar 2025 12:44:54 GMT

Hi!

Do you experience the same issue as I do? I have not had the chance to take the measurements as it is hard to reproduce due to the lack of sun in Norway at this time of the year.

-Jonathan

RE: Issues when powering thingy:91 from solar panel

RichM — Sat, 15 Mar 2025 13:40:34 GMT

I would also like to know this outcome. It seems like the PMIC is designed to handle this situation. I also tested with PPK2 and everything continues to work. Having an inexpensive solar option (like the ones available) would be a huge boon to our customers (beekeepers).

Thanks!

RE: Issues when powering thingy:91 from solar panel

Kenneth — Mon, 17 Feb 2025 11:58:21 GMT

Please share the measurements when you have time. Could be interesting to check if a shotkey diode on VBUS made any difference.

Kenneth

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Mon, 17 Feb 2025 11:25:07 GMT

Hi,

I have started doing some tests. The first test I did was powering the USB port with a power profiler kit to test multiple voltages. I did not recreate the problem with this method; the thingy switched between the battery and USB without any issues.

I have observed that using a solar panel makes the input voltage on the nrf9160 drop when it is connected and there is a medium amount of light shining on the solar panel.

-Jonathan

RE: Issues when powering thingy:91 from solar panel

Kenneth — Mon, 17 Feb 2025 09:27:28 GMT

Can you provide some measurements before I contact them internally? I suspect this is the first they will ask about.

Kenneth

RE: Issues when powering thingy:91 from solar panel

Kenneth — Fri, 14 Feb 2025 21:18:47 GMT

I will run this by the designers of Thingy:91, but an measurement on what voltage looks like on VBUS (e.g. voltage drops with a timescale) I think would be very helpful here.

Kenneth

RE: Issues when powering thingy:91 from solar panel

Jonathan E — Fri, 14 Feb 2025 09:38:24 GMT

Hi,

The issue also occurs when the onboard battery on the Thingy:91 is fully charged.

-Jonathan

RE: Issues when powering thingy:91 from solar panel

Kenneth — Thu, 13 Feb 2025 14:08:23 GMT

Hello,

I would likely have measured the VDD on startup, and made sure it's stable over a few seconds and (sufficient high) before starting to do something useful, also periodically measure VDD and enter power down immediately if VDD start dropping below operating conditions:
https://docs.nordicsemi.com/bundle/ps_nrf9160/page/recommended_op_conditions.html

Kenneth