I want to simulate a linear resistor (temperature sensor)... I want to use instead of the sensor, something else (arduino?) and be able to set my own values...
How can I do this?
With Arduino?
I want to simulate the temperature sensor which is a linear resistor...
So how can I do this with arduino?
I have a cool LCD display for temperature (with a linear resistor temperature sensor) and I want to use it in order to show different readings from different sensors....
Which sensor would that be?
You could use a servo coupled to a pot.
A linear pot, of course.
It is a NTC 10K like sensor...
and what are the inputs to the simulation going to be?
(jeez, this is like pulling teeth)
It is likely that a solid state potentiometer would work for you. Maybe like this one: http://www.analog.com/en/digital-to-analog-converters/digital-potentiometers/ad5235/products/product.html
Google will be happy to suggest other models.
I assume what you have is an existing circuit that you can't mess with, but it has a temperature sensor that you intend to spoof with an Arduino-based circuit of some sort.
In this instance, it would be wise to look at how the existing circuit biases the sensor, what potential either of the sensor leads has to power supply ground and/or earth ground, what is the actual resistance range of the existing sensor. These factors will influence what means will be practical.
You are correct... It looks like that I need a digital potentiometer...
The device is: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=150433276940 and it has s sensor like this: http://www.seeedstudio.com/depot/temperature-sensor-with-steel-head-p-78.html?cPath=6... Both of them are similar to a NTC 10K sensor...
With the digital potentiometer is it possible to set values in the range of 133.500KOhm-0,339968KOhm? As you can see in the second link...
You can do that with this Resistor ladder - Wikipedia if you don't need too many steps and their other limitations won't effect what you are doing.
Can I use a resistor ladder with this range of values? (see 2nd link)
I want to cut the sensor (of the 1st link) and connect "something" in order to set the desired value in the display (arduino)...
Thinking outside the box, since the digital thermometer almost certainly uses the thermistor against a fixed resistor in a voltage divider to generate a voltage that is fed into an ADC of some description, I'd measure the voltages on either side of the probe against 0v (Gnd) at various temperatures. Almost certainly one contact will be a fixed voltage and the other will vary with temperature. You then remove the probe and feed the varying end from a PWM pin maybe with a RC low pass filter to smooth it out. (connect the grounds obviously). Has to be a lot cheaper than a digital potentiometer........
You will also likely find that a very small part of the range of Resistance from 0 to 10K is of any interest to you. Maybe 6K through 7K will be the range corresponding to useful temperatures.
If this is the case, you can series in 6K and then parallel up your digital pot with another resistor to have it cover the narrow range of interest, with all the resolution it has. If you make the resistors 10-turn trimmers, you will have total adjustability.
I like the idea of using the PWM in arduino and supply the correct voltage to the contact with varying voltage...
Can you be more specific with the RC low pass filter? I read about it but I am a little confused...Do you mean passive or active? What are the values of the resistor and the capacitor for my purpose?
OK I see...
So what do you propose? What is the best approach?
One more thing... I know that there is one type of transistor which can be used as a variable resistor... Do you know more details about it?
I know that there is one type of transistor which can be used as a variable resistor.
Really? Tell us more about this...
OK Sorry for the misunderstanding... It is not linear, it has list of values... see: http://www.seeedstudio.com/depot/temperature-sensor-with-steel-head-p-78.html?cP