Hi,
I'm working on reading the value of a pressure sensor. The pressure sensor is a variable resistance between 10-180ohm with a working voltage between 6-24V. I'm using a voltage divider to read the voltage and convert the value to pressure through a polynomial formula.
The sensor is powered by a car battery, but because the voltage fluctuates a lot I had to put a voltage regulator in front of the voltage divider. I'm using a L7808, 8V, 1.5A and 2 x 10uF caps. The second resistor in the voltage divider is 47ohm, 3W. There is also a Zener diode at 4.7V 5W that protects the Arduino input.
The problem I'm facing right now is that the voltage regulator and the caps get very very hot. I knew I had to get a high power rated resistor to use in series and I figured out I also had to use a high power Zener diode. But now the voltage regulator and the 2 caps get incredibly hot. I can't figure out why and I'm also out of ideas on how to fix this.
I believe the voltage regulator and the caps get hot only when the Zener diode lets the current pass through, but I can't test right now because I have to generate a lot of pressure on the sensor to get the resistance up. Is this right? How can this be avoided? Maybe it's stupid, but moving the ground of the zener diode from the caps/voltage regulator will have no effects, right?
Thanks,
Andrei
I'm working on reading the value of a pressure sensor. The pressure sensor is a variable resistance between 10-180ohm with a working voltage between 6-24V. I'm using a voltage divider to read the voltage and convert the value to pressure through a polynomial formula.
The sensor is powered by a car battery, but because the voltage fluctuates a lot I had to put a voltage regulator in front of the voltage divider. I'm using a L7808, 8V, 1.5A and 2 x 10uF caps. The second resistor in the voltage divider is 47ohm, 3W. There is also a Zener diode at 4.7V 5W that protects the Arduino input.
The problem I'm facing right now is that the voltage regulator and the caps get very very hot. I knew I had to get a high power rated resistor to use in series and I figured out I also had to use a high power Zener diode. But now the voltage regulator and the 2 caps get incredibly hot. I can't figure out why and I'm also out of ideas on how to fix this.
I believe the voltage regulator and the caps get hot only when the Zener diode lets the current pass through, but I can't test right now because I have to generate a lot of pressure on the sensor to get the resistance up. Is this right? How can this be avoided? Maybe it's stupid, but moving the ground of the zener diode from the caps/voltage regulator will have no effects, right?
Thanks,
Andrei
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