Pi-SPi-Series

Raspberry Pi as a PLC in Automation Applications

Posted by Vytas Sinkevicius on

Raspberry Pi as a PLC in Automation Applications

The Raspberry Pi is being used in more automation applications as a PLC replacement.  In this example, a Raspberry Pi 3 is being used as the main controller. The design spec called for: 16 Analog Inputs 4-20 mA 8 Digital Inputs 12 Relay Outputs for control 4 Analog Outputs 4-20 mA 120 VAC Prime Power 24 VDC Field Power Real TIme Clock Industrial Enclosure Here is a closer look at the interior panel: The enclosure is a BUD Industries ABS / Polycarbonate blend type with a clear cover and aluminum backpanel. The dimensions are 14" W x 16" H x...

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Raspberry Pi and GPIO Expansion Using the MCP23S08

Posted by Vytas Sinkevicius on

Raspberry Pi and GPIO Expansion Using the MCP23S08

The VP Process Inc. line of automation expansion modules for the Raspberry Pi uses the Microchip MCP23S08 GPIO Expander IC to maximize the number of modules that can be used with a minimum of Chip Select Lines.   In this example using the PI-SPI-DIN series of I/O modules, the Raspberry Pi reads 2 modules of 8 Isolated Digital Inputs for a total of 16 Inputs and controls 4 modules of 4 Relay Outputs for a total of 16 Relays. The sample code (written in "C") reads each input from the isolated digital inputs card and turns on the appropriate relay...

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Raspberry Pi DIN Rail Analog Output Interface

Posted by Vytas Sinkevicius on

Raspberry Pi DIN Rail Analog Output Interface

VP Process Inc has just released a new 4 channel Analog Output 4-20mA Interface, the PI-SPI-DIN-4AO. The 4AO is based on the Microchip MCP4728 12 bit DAC with I2C interfacing. The MCP4728 has up to 8 programmable I2C addresses, which means 8 of these modules can be daisy chained together for a total of 32 analog output 4-20mA signals. Combine this module with the other modules in this series, you now have some serious process control interfacing capability! The PI-SPI-DIN-4AO   The I2C interface has a bidirectional buffer that isolates capacitance and allows for up to 1MHz speeds and up...

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Raspberry Pi and the PI-SPI-2AO 4-20mA Output Interface

Posted by Vytas Sinkevicius on

Raspberry Pi and the PI-SPI-2AO 4-20mA Output Interface

The 4-20 mA analog signal is still a major part of process control infrastructure. The Raspberry Pi coupled with the PI-SPI-2AO Analog Output Interface provides 2 channels of 4-20 mA Outputs. The VDC outputs are the buffered VDC signal going to the output current generator.    The PI-SPI-2AO Interface uses a dual 12 bit DAC, the MCP4922. Each mA output has a mirror VDC output. The output circuit requires an external supply voltage. This example uses a wall adapter style 24 VDC power supply. Each output has a signal strength LED, in this example mA Output 1 is set to...

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Raspberry Pi DIN Rail I/O Interfaces

Posted by Vytas Sinkevicius on

Raspberry Pi DIN Rail I/O Interfaces

VP Process Inc has released three new modules in the PI-SPI-DIN series of DIN rail mountable interface modules: PCB's mounted with DIN rail clips:   and DIN Rail Enclosures:   At the heart of the PI-SPI-DIN Series is the main controller module that supports the Raspberry Pi: The PI-SPI-DIN-RTS-RS485 This main module accepts field power of 9 to 24 VDC and power the RPi through the 26 Pin GPIO interconnect cable. Basic specs are: Power Input: 9 to 24 VDC 5VDC @ 2.5A (Max 3Amp) Power Supply RS485 Output via RJ45 connector and Terminal Block 2 GPIO connectors - 1...

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