Problems with OneWire protocol

Using Arduino Programming Questions
1

Hi,
I am building an induction heater controlled by an Arduino UNO.
The intention is to use a DS18b20 temperature sensor to check that the circuit does not overheat.
The induction heater is controlled by a Fostek relay with a trigger tension of 3V Vcc minimum. The relay is on pin 6.
The DS18b20 Data pin is connected to pin 15.

When I poll the temperature sensor on pin 15 (or any other pin, I tried several) via

sensors.getTempCByIndex(0)

the tension on pin 6 raises so much that it triggers the relay.

The temperature sensor connected to +5V, GND and Data (Pin 15) with a 4K7 resistor between Data and +5V

It seems to me that when the sensor gets polled, the level of all the pins is raised above 3V.

Any help is much appreciated.

Stefano

2

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3

Hi,

It looks like the problem was the polling interval.

Reducing the read frequency by using asynchronous reads with a 120 msec polling interval fixed the problem.

Stefano

4

The DS18B20 requires between 94 and 750 ms (depending on selected resolution) to do a single temperature conversion. If you need fast temperature readings, you're using the wrong sensor.

5

Hi,
Thank you for your answer.
I need one reading/sec, so the DS18b20 works for me.
What I did not know is that if you try to poll it faster that its conversion time allows for, it sends a spike that raises the tension of other pins to ca. 3Vcc.

6

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