cyber_dev
Junior Member level 1
Hi everyone,
I am intented to design a universal input to interface a 3v3 MCU for a generic I/O module. I investigated some of commercially available modules. Each of universal inputs can be configured (user selectable) any of the following options :
Voltage input = 0-5V, 0-10V
Current input = 0-20mA, 4-20mA
Resistive input
PWM or Frequency input
To design such an input, im my mind a difference amplifier with programmable gain (1/2, 2) can be a good starting point. For voltage inputs, input impedance should be over 100K. For current sensing a 124R %0.1 resistor may work well. For PWM and frequency inputs (5V pulses) timer module of MCU can be used.
For 5V to 3v3 conversion a resistor divider with traditional %1 resistors may not be a good idea due to the high temperature coefficient. Low tolerance and low ppm resistors are very expensive. In this case what's your solution?
Let's design it together. Since it is open, everyone can use it. The key considerations for the design is less of complexity and low cost. I look forward to your response.
I am intented to design a universal input to interface a 3v3 MCU for a generic I/O module. I investigated some of commercially available modules. Each of universal inputs can be configured (user selectable) any of the following options :
Voltage input = 0-5V, 0-10V
Current input = 0-20mA, 4-20mA
Resistive input
PWM or Frequency input
To design such an input, im my mind a difference amplifier with programmable gain (1/2, 2) can be a good starting point. For voltage inputs, input impedance should be over 100K. For current sensing a 124R %0.1 resistor may work well. For PWM and frequency inputs (5V pulses) timer module of MCU can be used.
For 5V to 3v3 conversion a resistor divider with traditional %1 resistors may not be a good idea due to the high temperature coefficient. Low tolerance and low ppm resistors are very expensive. In this case what's your solution?
Let's design it together. Since it is open, everyone can use it. The key considerations for the design is less of complexity and low cost. I look forward to your response.