1w Limits??

[Lazzz]

Is there such a thing as too many 1w connections. 

I now have 7 @ DS18B2 senders & they are occasionally spiking??

[sebba]

It seems you have some DS clones, not originals.

[Lazzz]

It seems you have some DS clones, not originals.

I removed the latest "cheap" DS sender but I'm still getting spikes, sometimes up & sometimes down, on different senders which I didn't get with OP3 on the Pi4.

Any ideas??

EDIT: I did a bit of looking & came up with this:

Electrical Interference: The DS18B20 is sensitive to noise on the data line, especially if the wiring is long or runs near sources of interference (like motors or other high-power devices). Ensure that the data wire is properly shielded or consider adding a capacitor (typically 100nF) between the VCC and GND close to the sensor to help filter out noise.


Weak Pull-up Resistor: The DS18B20 sensor uses a 1-Wire protocol, which requires a pull-up resistor on the data line (typically 4.7kΩ). If this resistor is too high or too low, it could cause unstable readings. Double-check that the pull-up resistor is correctly rated and connected.

Power Supply Issues: If the power supply to the DS18B20 is unstable, it could cause the sensor to send erratic readings. Ensure that the power supply is stable and that there is no significant voltage drop.

Grounding Problems: Inconsistent grounding can lead to voltage fluctuations, which may cause the sensor to produce spikes. Ensure that all components share a common ground and that there are no loose connections.

Long Cables: If the sensor is connected via long cables, the added resistance and capacitance can cause spikes in the readings. Consider shortening the cables if possible or using higher-quality cables.

Temperature Sensor Issues: The DS18B20 itself might be faulty, especially if it has been exposed to extreme conditions or physical damage. Try swapping the sensor with a known good one to see if the problem persists.

Software Glitches: There might be issues with the software reading the sensor values. Ensure that the software properly handles erroneous readings, such as by filtering out unrealistic temperature values or implementing averaging to smooth out spikes.

Moisture or Corrosion: If the sensor or connections are exposed to moisture, it can cause temporary shorts or signal degradation


Is the resistor on the MacArthur Hat 4.7kΩ ????????????????????? EDIT: NO it's 1.6k. 
I might look at this first because this is different to what I had on my Pi4 setup with no MacArthur Hat!! 

Would it be possible to add a 3k resistor between the VCC & Data terminals to bring it to 4.6k???????


Is there any filtering in the software that is different from OP3??????

I might try re-running the wiring with shielded cable & adding a 100nFcapacitor between the VCC and GND close to the sensor.

[Boatingbaileys]

Isn't there a distance limit of about 10m of cable?, could the combined length of cable to all your sensors be dropping the voltage?

[Lazzz]

Isn't there a distance limit of about 10m of cable?, could the combined length of cable to all your sensors be dropping the voltage?

It worked great with the same sensors on the Pi4 / OP3 with the 4.7K resistor.

see here:
1 w resistor (openmarine.net)

[WoodTyra]

I've had similar issues with too many DS18B20 sensors. I was running 6 of them and noticed spikes too. Adding a couple of 4.7k pull-up resistors to the data line really helped stabilize things for me. Also, make sure your wiring is solid—bad connections can cause those spikes. Sometimes less is more if you can't get the stability you need.

[Lazzz]

I've had similar issues with too many DS18B20 sensors. I was running 6 of them and noticed spikes too. Adding a couple of 4.7k pull-up resistors to the data line really helped stabilize things for me. Also, make sure your wiring is solid—bad connections can cause those spikes. Sometimes less is more if you can't get the stability you need.

Just to make sure here: 

You had more than one 4.7k resistors between data & power along your wiring??

Was this in addition to the 1.6k on the MacArthur hat, or not using the hat??