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Author Topic: Catibrating a Vellman k8067  (Read 819 times)
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I already had this board in hand. I want to use it with the Duemilanove. The specs on this board say 12V for 5 Vout and 15V for 10V out. but the calibration steps call for 15V in and set for a certain output. I assume that is calibrating it for 0-10 V output. I want  0-5V output to interface with the analog inputs of the Duemilanove. Would the procedure be the same as far as values used for calculation is concerned? Should I limit the output with a 5V zener to protect the input pin of the Duemilanove? I don't have a 15V power source.

Jim
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I already had this board in hand.
This one? Or this one? A link would be most useful.
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This looks like the manual:

http://www.vellemanprojects.com/downloads/0/illustrated/illustrated_assembly_manual_k8067.pdf

It looks like the device is designed to drive 0-20mA output in proportion to temperature. It also looks like you could muck with resistor R9 in the circuit (change to 250 ohms) for a nominal 5V output.

I believe the circuit is relatively insensitive to voltage V+ (within reason) thus the output current (hence calibration procedure) shouldn't depend too much on whether you use 12V or 15V. What voltage source do you have?

Yes, I would definitely limit the output with a 5V zener (really 4.7V since 5V zeners can go quite a bit higher before they actually break down). Also I would use a series resistor of 1k before the zener (but after the load resistance of the sensor) to limit zener current. The zener *shouldn't* ever have to turn on, but......

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I believe the circuit is relatively insensitive to voltage V+ (within reason) thus the output current (hence calibration procedure) shouldn't depend too much on whether you use 12V or 15V. What voltage source do you have?
Check out our new shield: http://www.ruggedcircuits.com/html/gadget_shield.html


Thanks for the helpful reply. I have a 12V supply i saved from a scanner which died. It had the same connector as the Duemilanova used.

The gadget shield looks like a complete overkill for my application. I just want to be able to remotely monitor the temperature in my observatory from m,y house via a WiShield. Then I will turn on/off a heater remotely.

Jim
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The gadget shield looks like a complete overkill for my application. I just want to be able to remotely monitor the temperature in my observatory from m,y house via a WiShield. Then I will turn on/off a heater remotely.

You might use a thermistor in a voltage divider or similar to input an analog input pin for temperature reporting.

http://en.wikipedia.org/wiki/Thermistor
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