Externally power Thingy:91 without battery

[Roshan Nepal]

Hi,

I’m exploring options to externally power the Thingy:91 while isolating it from the battery. I noticed that the board offers three external supply points: P3, P4 and P5. Could you advise on which one would be more appropriate for stable operation, especially for temperature data transfer to cloud?

Additionally, what’s the best way to establish the external power connection? Would placing a jumper in the designated holes suffice, or is there a specific process or configuration to follow?

Lastly, is there a practical way to disable battery power without physically disconnecting it? The battery is mounted inside a hard plastic enclosure, making manual removal quite difficult.

I’d appreciate your guidance on these points. Thank you!

[Achim Kraus]

In my experience, the easiest way is to use a JST 1mm 3pin wire. You will find them in several web-shops.

[Roshan Nepal]

Hi Achim,

Thank you for the suggestion! Could you please clarify how the signal port of the JST connector should be handled? Should it be left floating? I tried leaving it unconnected, and while the Thingy:91 powered up, it didn’t seem to search for an LTE signal or attempt to send one.

[Achim Kraus]

The JST connector has GND, temp sensor, VAT.

What is the "signal part"? The temp sensor? I use a 10k resistor to GND. AFAIK, that's only required, if the battery is replaced by an other battery.

> I tried leaving it unconnected, and while the Thingy:91 powered up, it didn’t seem to search for an LTE signal or attempt to send one.

Interesting. Maybe I find some time to retest it, but in my memory, it's not required to connect the temp. sensor.

From other tickets (and my experience), if LTE doesn't work, your power supply is too weak. How much current will that deliver? Go for at least 500mA.

[Roshan Nepal]

Yes, I was referring to the temperature sensor. I powered the Thingy:91 using a DC power supply set to 3.7V with a current limit of 1A. The the device never drew more than 30 mA of current.

I noticed that the battery it came with has a small PCB attached. Do you know the purpose of this PCB? I even attempted to connect the two terminals of the PCB directly to the DC power source instead of the battery, but it still didn’t work. However, when I reconnected the original battery, the device suddenly worked again.

[Achim Kraus]

AFAIK, that's a charging protection including the temp. sensor.

I will (re-)check that with one of my Thingies in the evening.

[Achim Kraus]

"works on my machine".

The 3pin 1mm JST has different colors compared to the battery.

red is VBAT+ (PPK II VOUT)

yellow is GND (PPK II GND)

black is temp. sensor.

The picture unfortunately doesn't show, that I removed a jumper, which connects the resistor as temp sensor, so that's wire is left open.

[Roshan Nepal]

Thanks. It might be the case that my JST connector is broken, since I cut it off from the battery. I have ordered a couple of them and will do a test with the new one tomorrow. Just to make sure I understand your setup correctly, you kept the temp sensor (black wire) floating, right? 

[Achim Kraus]

Roshan Nepal said:

you kept the temp sensor (black wire) floating, right? 

Yes, in that test.

If I use a larger 2 pin battery, I connect that with 10k resistor to ground in order to be able to charge it.

[Achim Kraus]

Before causing damage, let me clarify:

The original 3pin plug uses red for VBAT, yellow for TEMP, and black for GND.

Just the 3pin plugs I bought use other colors. So you need to check your 3 pin plugs not to cause damage.