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Arduino Nano Project Questions

e14 Contributor

I have a project that I would like to use the Arduino Nano . This project has the following requirements:

  • 1.       Run off a 12vdc power supply
  • 2.       To read a voltage that will vary form 0 - 12vdc volts, by a 90ohm pot.
  • 3.       Output a 0-12vdc voltage to an analog gauge.
  • 4.       Read an 8k pulse per single turn magnetic pulse generator. Output Voltage unknown as I am guessing somewhere in the MV range. Two wire system, GND and siginal.
  • 5.       0-12vdc Vacuum sensor.

Items 1 & 5 I know I can use the Analog input. It is item 3 & 4 I am not sure of. Any help with hardware and software would be appreciated.

  • 0

    Hi Phil,

    If this is a vehicle, keep in mind the nominal 12V signals can be as high as 14.4V when the vehicle is running, so your voltage dividers on "12V" sensors should reduce 15V to 5V (for a little safety margin).

    To amplify an analog signal from 5V to 12V you can use a non-inverting op-amp circuit such as in this app note:

    http://www.ti.com/ww/en/bobpease/assets/AN-31.pdf

    I would regulate the 14V battery to 12V with a low dropout regulator to supply voltage to the op-amp which would need to be a rail-to-rail model.

    The Arduino would use a 5V regulator.

    Magnetic pickup output voltage varies with gear speed and physical gap and different models output anywhere from zero to 200Vac, usually at least 7 Vp-p. They all output AC voltage, unless there is built-in circuitry. If there is no built-in circuitry, you can convert the AC signal to DC pulses using a diode to only pass the positive phase of the AC signal followed by a resistor and 4.7V zener diode to clamp the maximum to 4.7 volts. More sensitive circuitry is possible, but also more complex. This digital pulse signal may need to feed an interrupt pin or a counter.

    Doug

  • 0 in reply to dougw

    Thanks Doug for the reply. And yes this will go in to a car. I thought from the spec I read, the board was good up to 20vdc max. If I understand you correctly the inputs must be 5vdc max and all outputs will need to control 5vdc relays. And does the 5vdc max go for the Analog input to.

    If so any analog signals (0-12vdc) will need to be reduced to 0-5vdc for the Analog Input. And I guess I will need a DAC for the output of 0-12vdc.

    1 function of what need to control is my gas gauge. I replaced the tank in an old car and it does not have any baffles in it and the gas gauge bounces all around. I figured I would input the sending unit into an analog input. Write code so when I start the car it would take the current reading and output that voltage to the gauge then I would sample the sending unit every 1sec for 15sec's take the average of those readings and compare to the current output voltage and if within 95% of the current output then reset the output to the new reading then repeat. If it was not within the 95% then skip and repeat.

    Once I get this working I then want to add a Miles per Gal display which will require a Flow meter & a speed sensor, which I think I will use a proxy instead of the magnetic sensor.

    And the finial function would be to control the Lockup Torque Converter in the new transmission I installed. This will also require a Vacuum analog sensor and an analog Throttle Position Sensor along with the Speed Sensor.

  • 0

    Hi Phil,

    The power supply feeding your Nano can be up to 20V, but that voltage is internally regulated down to 5V. The CPU operates at 5 V so all digital and analog signals need to be at or below 5V. The CPU can output an analog voltage using PWM - this would require a simple RC filter to convert to a continuous analog voltage. It would then need to be amplified by a fator of 2.4 to provide a max of 12V.

    The gas gage could also be fed through an alalog filter with a very long time constant to help with your software filtering. For example in your scenario, if the gas splashed up every second just when you were reading the level, it would appear the tank was full. An analog filter with a cut-off frequency well below your sampling frequency will prevent this type of erroneous reading. It could be as simple as an extra resistor and capacitor.

    I think you could average your readings for at least a minute or two to improve accuracy on long curves where the gas will crowd over to one side.

    Doug