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[Tutorial] - Attaching DS18B20 temperature sensors to a Smart Implant


Tim__
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The Smart Implant can have up to 6 temperature sensors added to it, which makes it handy for climate control applications.  Here is a guide based on my experience, hopefully it helps you avoid the frustrations I had.

 

1.       Buy the sensors from a reputable source. The DS18B20 is manufactured by Maxim Integrated (ex-Dallas Semiconductor). There are many counterfeit sensors out there (eg Chinese company CXGAS) that either will simply not work, report incorrect readings, or stop working after a short period.  If the sensor is built into a probe it can be difficult to determine a counterfeit unless you open the casing, which can be difficult due to epoxy encapsulation. It seems most sensors bought on eBay, Aliexpress, Banggood etc are counterfeit.   See more on this here:

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2.       Keep the length of the lead between sensor and device under 3 meters, otherwise there may be synchronisation errors.

3.       A 4.7k resistor is required as a pullup from the DATA to VCC line.  If the DS18B20 is built into a probe, the resistor is probably not included.

4.       Where the DS18B20 device is soldered to a small daughter board, be careful as the PCB tracks may not connect directly to the corresponding jumper pins – instead the connections may be rearranged. Use a multimeter to confirm the pinout.

5.       Up to six sensors can be used, connected in parallel. The leads should all be the same length, to ensure the signals stay synchronised. Regardless of the number of sensors, a single 4.7k resistor is required as a pullup from the DATA to VCC line.

 

In order to show the temperature device slaves in your Home Center devices screen:

1.       Power down the device

2.       Wire the sensor(s) up, including the resistor

3.       Move the Smart Implant  very close to the Home Centre

4.       Power up and click the “Reconfigure Device” button in advanced options.

5.       You will need to delete the device and re-add it if you have changed sensors, as the internal sensor serial number identifiers will have changed.

6.       The temperature sensors will appear as additional Slaves.

 

When attempting to add the device, if you receive the error message: "ID xx: System hardware failure. Read the manual", this is a good indicator you have a clone sensor.

 

Set Parameters 67 and 68 as required, so that regular temperature reports are sent.

 

Note that the Smart Implant contains an internal temperature sensor.  This is likely to over-report air temperature, because the sensor is located inside the device and that will make it slightly warmer.

 

If this guide helped you, click the Heart symbol below to say thanks.

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  • 11 months later...

Hi Tim, 

 

thank you for your tutorial. Is it also possible to make a picture of your set up?

 

thanks in advance,

 

Joost

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  • Hi @Joost347, glad this was of use. Have a look in the manual, diagram 3 shows how to connect it:

     

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