I'd like to use an LM3914 with a 10-segment tri-color LED bargraph to display the temperature from a motor which has a temperature sensor. The temperature sensor is a KTY84/130 (http://evmc2.files.wordpress.com/2013/02/kty84_ser_6.pdf). The motor must not exceed 140 degrees C. So I want to have the first LED come on at 40 C, and the next one at 50 C, and so on until the last LED comes on at 130 C. Using it in bar mode, so all LEDs should be lit at 130 degrees. The chart below shows the resistance values in this range:
So I've picked the following sample circuit from the LM3914 datasheet which should work well and would make the final LED flash which is a nice feature - but of course I need this to work with the thermal sensor input rather than a 0-5V input.
Also I will be using it with a 12V battery. Since the sample circuit is for 5V, I'll probably just add a 7805 regulator to power the circuit.
Finally, I want to add a relay to run a cooling fan when LED # 6 turns on. Ron H has posted a simple solution on this forum which I plan to use to make that work:
So my main roadblock right now is how to configure the LM3914 to read the resistance of the temperature sensor I'm using and map it out properly to the 10-LED bar?
So I've picked the following sample circuit from the LM3914 datasheet which should work well and would make the final LED flash which is a nice feature - but of course I need this to work with the thermal sensor input rather than a 0-5V input.
Also I will be using it with a 12V battery. Since the sample circuit is for 5V, I'll probably just add a 7805 regulator to power the circuit.
Finally, I want to add a relay to run a cooling fan when LED # 6 turns on. Ron H has posted a simple solution on this forum which I plan to use to make that work:
So my main roadblock right now is how to configure the LM3914 to read the resistance of the temperature sensor I'm using and map it out properly to the 10-LED bar?