IIOT PLC based on Android things

Most of the industrial Equipment are operated and monitored by standard PLC(Programmable logic controllers) that has inputs and outputs that can be programmed based used based on application

The major Hurdle in using PLC for IIOT applications is the need of many external Components,Such as Protocol converter,gateways, External processors, cabeling , PLCs come in as many flavors and colors as the companies manufacturing them, some with proprietary programming software, which need to be bought at great cost; some with free software which requires various expertise.

Leveraging open-source Android things platform integrating IIOT in Android things based hardware PLC makes it simple to develop and helps to seamlessly connect with the cloud, Firebase , execute Machine learning and control industrial system with ease

Hardware interface

To use IMX6Ul as PLC we need to interface it with industrial standard Inputs and output such as.

• Digital I/O

• Analog I/O

• Communication

Digital I/O

24v Digital inputs

The industrial standard voltage for digital inputs is 24V to sense this voltage level we have to step it down to voltage level (3.3v) of the IMX6Ul controller. This could be done using Optocoupler.

B-6 will be the input from external industrial equipment which is reduced to voltage level and sensed as digital high or digital low in PICO-PI board

Relay Digital outputs

In order to control high power devices such as Motor,Contractors,Solenoid,Alarms IMX6UI should be able to control High voltage levels (230V,24V )for which we are using Relays

Any Pi device will have restricted current which will not be sufficient enough to drive a relay. In order to drive a relay we need a transistor such 2N3904 to drive the relay directly from the supply rail.

Analog I/O

Analog signals can use voltage or current with a magnitude proportional to the value of the processed sensor data

0-20ma Analog input (Current)

Industrial sensors gives out with a range of values between zero and full-scale which is mapped down to 0-20ma Output range of the sensor.

In order to measure the current we are using a (100ohm) shunt resistor and measuring the voltage across the shunt. This 0-20ma range is converted into 0-2V scale.

By Measuring the analog value 0-2V range with the PI device we will able to measure the sensor reading which could to processed accordingly.

0-10V analog input (voltage)

The other standard used in Industrial sensing is 0-10V output corresponding to the sensing value range.

In order to sense the voltage we have to step down the 0-10V range to 0-3.3V. We can use a simple voltage divider circuit to reduce the voltage level such a way when we get the maximum VIn voltage (10v) the Vout voltage should be 3.3V.

By selecting R1 as 200ohm and R2 as 100ohm we can convert the voltage level suitable to Pico-Pi.

Communication

There are several industrial standard communication interfaces such as RS232,RS485,Ethernet.CAN bus,Modbus,ProfiBus,etc .

There are plenty of communication converters available hence lets focus on most common interface used in the industrial data communication RS485 interface. Using RS485 our android things device would be able to communicate with industrial devices such Motor driver,Application specific controllers,Power meter,protection system etc.

Coming soon

We are working on a open source IIOT PLC for android things .

• Maker compatible HAT board (compatible with pi connector )

• Industrial compatible Carrier board

following are few pictures of the prototypes

The proto interface board consist of 6 digitals inputs , 3 relay for digital output and on-board power regulator that will enable pico pi to be powered directly for 24vdc line which is commonly available in the industrial panel.