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Topic: Temperature sensor not working with battery (Read 1 time) previous topic - next topic

Uncle82

Does anyone tried to acquire DHT or OneWire temperature with MKR1000 and LiPo battery?

I did a project DHT22 sensor acquired with MKR1000 (pin 5) that sends data to ThingSpeak. Everything works fine until the MKR is connected to the PC via USB (with or without the battery). When I unplug the USB and power the MKR with the battery, sensor is not acquired. I tried also with the OneWire sensor, the TMP36 nd others. The problem is always the same. I tried also different batteries, but the result is the same.
When using the DHT and OneWire, I put the pullup resistence (tried with 10 ad 4.7 k). Is this problem common for MKR or it is just my board's problem?

Thanks

frogger3d

Are you powering onewire with 3.3v or with 5v? I think the 5v cuts out when the MKR1000 is connected to a battery. Onewire should work fine on 3.3v.

Uncle82

How was powring with 5V. Now I tried with 3.3V (Vcc pin) and it works well with both dht and onewire.

I measured the output of 5V pin when battery powered and confirm that its output is null.

Thank you very much for the suggestion!

ballscrewbob

Have used both external power, battery, and connected to computer with a selection of DHT's and TMP sensors to Thingspeak.

They do work on all the sources of power.

However I gave up using the battery as the power consumption was too high to maintain long term use.
Once the voltage started to drop the data was unreliable.

It also meant that the Wi-Fi was also unreliable at this point too.

The max I got out of it was around 12 hours with an 1200mAh LiPo.

Also check the sensor specs as many of the older ones require a little more than 3.3 V to be stable.
DHT needs 3.5 to 5 V
TMP is 2.7 to 5.5 so should be better
It may not be the answer you were looking for but its the one I am giving based on either experience, educated guess, google or the fact that you gave nothing to go with in the first place so I used my wonky crystal ball.

Uncle82

Have used both external power, battery, and connected to computer with a selection of DHT's and TMP sensors to Thingspeak.

They do work on all the sources of power.

However I gave up using the battery as the power consumption was too high to maintain long term use.
Once the voltage started to drop the data was unreliable.

It also meant that the Wi-Fi was also unreliable at this point too.

The max I got out of it was around 12 hours with an 1200mAh LiPo.

Also check the sensor specs as many of the older ones require a little more than 3.3 V to be stable.
DHT needs 3.5 to 5 V
TMP is 2.7 to 5.5 so should be better

Yes, it works fine with all the power sources now that I have connected sensors to 3.3V.  I am testing the battery life, but given that I will acquire every 15 min, I would include some deepsleep logics.
The measuremet done until now are quite stable, let's seen during next hours.

thanks

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