Pulse on emontx3.2 problems ds18b20


when i test the pulse with a loop from 5v to dig2 (pin4) i get pulse reading. but my ds18b20 temp sensor shows poor value. it changes from 260 to 850. anyone who can explain why it is like that?

I use emontx v3.2 just to log temp from different devices and power from a heat meter.
I use serial connection with rpi. without rfm.

i added the serial monitor log under:


Has it ever worked? Those sensors are very reliable but they do break (I’ve got one that has gone bad).

The pulse input and the one-wire input are two different things. Are you saying that activating the pulse input affects the temperature?

85°C is the “power-up” value for the register inside the temperature sensor that stores the reading between the sensor being told to measure the temperature and the emonTx requesting the answer. It usually means that the initial instruction from the emonTx to the DS18B20 to measure the temperature hasn’t got there.

Are you using a 2-wire or 3-wire connection to the temperature sensors?
And how long are the cables between the emonTx and the DS18B20?
Are the sensor connections secure?

yes sensor is connected secure.

I use 3wire. cabels are 1meter.
As long as there is no pulse i can get temp from sensors. as long as i jump between 5v and dig2 to make a pulse i get 850 reading from temp sensor. im not sure if i can test pulse by doing what i do.

This might be your problem. The emonTx V3.2 runs at 3.3 V, therefore you are putting a voltage that is too high on the input. You must connect your switch between the input pin (IRQ0) and 3.3 V.

It is possible that by connecting 5 V, you have forced the 3.3 V supply to the RFM12B radio module too high and damaged it.

I have an emonTx V3.2 here, so at some point over the next few days I will be able to test this for you.

I have now tested my emonTx V3.2 with this sketch from Github:

The emonTx is powered by the programmer, the temperature sensor is connected to pins 3, 5 & 6, and a switch to pins 2 & 4. The result via the Serial monitor:

emonTx V3 Discrete Sampling V1.2
Performing power-on tests.....please wait 10s
CT 1 Calibration: 90.90
CT 2 Calibration: 90.90
CT 3 Calibration: 90.90
CT 4 Calibration: 16.60
RMS Voltage on AC-AC Adapter input is: ~240V
AC-AC adapter detected - Real Power measurements enabled
assuming powering from AC-AC adapter (jumper closed)
Vcal: 276.90
Phase Shift: 1.70
CT 1 detected
CT 2 detected
CT 3 detected
CT 4 detected
Detected 1 DS18B20..using this for temperature reading
RFM12B Initiated: 
Node: 10 Freq: 868MHz Network: 210
1 3 2 0 23842 0
temperature: 26.30
0 3 2 0 23824 0
temperature: 26.30
0 2 5 0 23818 40
temperature: 26.30
1 1 3 0 23812 16
temperature: 26.50
2 3 4 0 23874 1
temperature: 26.60
2 3 7 0 23817 4
temperature: 26.60
2 4 3 0 23860 0
temperature: 26.70
0 3 0 0 23868 0
temperature: 26.80
2 4 4 0 23882 0
temperature: 26.80
0 3 3 0 23861 4
temperature: 27.00

Equally, when powered by the a.c. adapter only, the temperature still reads correctly.
(This shows 236.4 V, 25.3°C, 2 pulses, -84 dBm RSSI)

I cannot reproduce your problem.

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