Hi everyone.
I have an Innovate LC-1 AFR controller for my car. It has a wire which outputs 0-5 volts suitable for calculating AFR (Air Fuel Ratio) with a microcontroller or be connected to a gauge or something. This wire is connected to one of the analog inputs of my Arduino Duemilanove.
I have set my Arduino Duemilanove up with a 20x4 blue LCD and used the LiquidCrystal library to print some stuff on it, including the AFR value that I get from the controller.
The problem is, with the above setup, after a while the LCD shows unreadable characters. Restart the Arduino and everything is fine for a while again.
When I disconnect the AFR 0-5 volts output wire from the Arduino analog input, everything seems to be fine.
What could be the issue here? Anyone has ever experienced anything like this before?
Someone told me I can use an OpAmp, but unsure how to or even why I should?
Any help is appreciated. Thanks.
How does the board ground to the sensor output ground?
Doc
There's also a black negative cable from the AFR controller, which I've connected to GND of the Arduino board.
I have set my Arduino Duemilanove up ... What could be the issue here?
I suppose there is something wrong with your setup. That would include both the physical connections and the program (sketch). Unfortunately we have no real information about either of these.
Don
One real issue could be the Grounds... If the Arduino is connected to a computer that is also connected to the vehicle 12V there is a high current common ground path from the charger that will slightly raise the Arduino's ground potential relative to the ground of the sensor and this voltage is also common to the analog input as well.If for example if the ground lead from the 12V to the computer was part of a 1A load and perhaps there was a quarter of an ohm of resistance from the charger ground to the car ground there would be 1A X.25 ohms or .25V difference between the 2 grounds this voltage or a part of it will show up on the input pin as an offset voltage it's called 'common mode' offset or differential offset and frequently seen as noise... It is noise as any signal added to a desired signal is noise.
Doc
I have a Innovate LC-1 and I have taken it apart to look it over. If I remember correctly, it has an Atmega 8 as the main chip, it uses a separate eeprom for memory, a chip for shmitt trigger input, and they are using an op-amp for the 0 - 5 volt analog output.
It uses a non-switching regulator for the 12volt to 5volt conversion. It has a fet or transistor, to control the heater for the O2 sensor.
Some of the chips were hard to read but, at one time I had made a list of all of the chips on the board.
This is very similar to the Innovate design. Wideband LD2B DIY Kit Construction (Tech Edge)