node-red-contrib-redplc-rpi-mcp342x v1.0.11

node-red-contrib-redplc-rpi-mcp342x

Node-Red node for mcp3421 .. mcp3428 analog to digital converter

Node Features

• mcp3421 1-channel, 12bit-18bit, one I2C address
• mcp3422 2-channel, 12bit-18bit, one I2C address
• mcp3423 2-channel, 12bit-18bit, eight I2C addresses
• mcp3424 4-channel, 12bit-18bit, eight I2C addresses
• mcp3425 1-channel, 12bit-16bit, one I2C address
• mcp3426 2-channel, 12bit-16bit, one I2C address
• mcp3427 2-channel, 12bit-16bit, eight I2C addresses
• mcp3428 4-channel, 12bit-16bit, eight I2C addresses
• Each input can be selected 12bit-18bit* or Disabled
• 12bit conversion time 5ms/channel
• 14bit conversion time 25ms/channel
• 16bit conversion time 100ms/channel
• 18bit conversion time 300ms/channel
• Output value is in mV
• Input range +/- 2.048V, 1.024V, 0.512V or 0.256V
• Scaling with factor and offset

*If set to 18bit on 16bit device, it changed to 16bit

Install

For using with Ladder-Logic install redPlc nodes

For using with other nodes, install module nodes

Install with Node-Red Palette Manager or npm command:

cd ~/.node-red
npm install node-red-contrib-redplc-rpi-mcp342x

Usage

This node writes to Node-Red global variables Update is triggered by redPlc cpu node or module-update node This node works only on Raspberry Pi with Raspberry Pi OS Enable I2C with raspi-config Consult datasheet for absolute maximum ratings

Analog Input (Variable IA):

mcp3421, mcp3425 |Input|Array-Index |:----|:---:| |CH1|0|

mcp3422, mcp3423, mcp3426, mcp3427 |Input|Array-Index |:----|:---:| |CH1|0| |CH2|1|

mcp3424, mcp3428 |Input|Array-Index |:----|:---:| |CH1|0| |CH2|1| |CH3|2| |CH4|3|

Scaling with Factor and Offset:

Formula:

Factor = (OH - OL) / (IH - IL)
Offset = OL - (IL * Factor)

Output = Input * Factor + Offset

Where:

IL = Input Low (mV), IH = Input High (mV) 
OL = Output Low, OH = Output High

Example:

Input: 0mV .. 2048mV, IL = 0, IH = 2048 Output: -20°C .. 60°C, OL = -20, OH = 60 Factor = (60 - (-20)) / (2048 - 0) = 0.04 Offset = (-20) - (0 * 0.04) = -20

Input = 500mV Output = 500 * 0.04 + (-20) = 0°C

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