Shop OBEX P1 Docs P2 Docs Learn Events
2-10vdc control [ stamp - prop ] — Parallax Forums

2-10vdc control [ stamp - prop ]

Larry SutherlandLarry Sutherland Posts: 77
in General Discussion
2-10vdc is a common industrial control method. I was wondering about interfacing this method with a stamp or propeller. 
  1. Any ideas on making an output [ power design ] controlled by the micro controller [ code ].
  2. Any ideas on making an input  interface [ design ] read by the micro controller [ code ].

Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    In short:

    Prop -> RC filter -> opamp -> optional emitter follower for 0-10v output

    For 0-10V input for the Prop it's best to use an ADC chip and simply use a resistor divider on the input to scale that down to the ADC range. Use either I2C bus or SPI chips such as the MCP3208 etc.

    Of course you could also implement an RC DAC fed into a comparator to measure an analog voltage but ADC chips are cheap.

  • Duane DegnDuane Degn Posts: 10,588
    I knew 0V to 5V output and 4ma to 20ma output were common industrial control interfaces but I hadn't heard of 2V to 10V before.
    I'd think Peter's suggestion of a voltage divider and a ADC should work fine.
    I'm very curious if anyone has used 2-10VDC interface with a Prop before.
  • Larry SutherlandLarry Sutherland Posts: 77
    I starting this thread to start up some conversation about applying Parallax products to the everyday world of industrial control. I would be very interested in using the Propeller to control a VFD, Belimo actuators, heater elements and temperature sensors.
    I figured control voltage signals would be a good starting point.
    There are basically three types of analog input signals; voltage, current and resistance.
    VoltageCommon voltage signals used in the controls industry are 1-5 Volts Direct Current (VDC), 2-10 VDC, 3-15 VDC, 0-5 VDC, 0-10 VDC and 0-15 VDC.
    CurrentThe 4-20 mA signal has become the industrys standard current signal for use with analog and digital controllers. A variation of the 4-20 mA signal is 0-20 mA.
    ResistanceResistance measurement is most commonly associated with direct inputs from temperature sensing devices, such as thermistors and RTD's. RTD nominal resistances are typically 100 W, 500W, 1000 Wor 2000 W. Common thermistor nominal resistances are 2252 W, 3k W, 10k W, 20 kWor 100 kW.
  • kwinnkwinn Posts: 8,697
    2-10 volts is what you get when a 4-20mA signal is connected across a 500 ohm resistor, and the 4-20mA standard is what made the 2-10V convention so popular.

    Of course the availability of cheap ADC's for measuring voltage made the conversion from a current signal to a voltage one so popular.
Sign In or Register to comment.