Hardware selection

Hi,

I am very familiar with the PLC world but this is my first project with Arduino products and I am a bit confused for hardware selection and compatibility. I have already identified that I need the Mega 2560 to get enough I/O. But then what?

My inputs should be at 24 Vdc and some outputs to be at 24 Vdc and 120 Vac. What are the I/O boards available?

I also want to command my project using my Iphone 6 as a Human Machine Interface so what shield do I need to get a Wi-Fi channel?

Finally, the controler should be housed into a box and used outside.

Is there somebody to help me with the selection of the hardware for such an application.

Hi,
Arduino is used in many industrial environments, and you need to do some research to handle the specific I/O devices you are involved with.

I suggest you look at THIS: section of ArduinoInfo.Info to see options about controlling power and higher voltages with Arduino.

There are some options for sensing voltages greater than 5V, but if it's on-off sensing, I am all for opto-isolation.

Hundreds of sensors such as temperature, humidity, acceleration, compass, gas sensors etc etc. are available for Arduino.

The physical environment and Nema enclosures are another challenge for you!

If you want several I/O connections shields may be too restrictive either by preventing access to certain I/O pins or by utilizing pins that you might want for something else. Some tasks (such as SPI) are restricted to certain pins.

For WiFi have a look at the cheap ESP8266 module.

...R

Thank guys for these answer but it is still not clear enough to place a purchase order.

If I use the 8-relay optically-isolated board, where I should connect it on the MEGA 2560? Then, do I still have space for remaining DIN (8) and AIN (4) I need?

The ESP8266 seems to be interesting but again, may I plug it directly on the MEGA 2560 without interfering the I/O numbers?

For the case, I understand that I will have to make one by myself but this not a big thing.

I offer a couple of relay module variants.
http://www.crossroadsfencing.com/BobuinoRev17/
This one uses D22-D29 to drive transistors to sink relay coil current.
The SPST relays are rated for 5A, 250VAC.
Here's a video of LED light strings being controlled by an Uno version of the small card (shift register controlled)

and of several that are daisychained (I got lazy for the demo and just shifted the same data out)


This one uses a shift register to sink relay coil current. Drive it with SPI.transfer() or whatever pins you want with shiftOut().

Robin_Boulianne:
If I use the 8-relay optically-isolated board, where I should connect it on the MEGA 2560? Then, do I still have space for remaining DIN (8) and AIN (4) I need?

The ESP8266 seems to be interesting but again, may I plug it directly on the MEGA 2560 without interfering the I/O numbers?

You need to post a link to the datasheet for the relay board so that we know what you are thinking of.

The ESP8266 is not a simple plug-in module. You will need to arrange the connections yourself.

I don't know what you are thinking when you say "interfering the I/O numbers"

It may be that you imagine the Arduino system to be a plug-n-play system similar to PLCs (which I know nothing about) but the reality is that you can get Arduino plug-in shields for some things but not for everything and it is quite possible that shield A will be incompatible with shield B. And shields for an Uno are not necessarily compatible with a Mega.

...R

Robin_Boulianne:
If I use the 8-relay optically-isolated board, where I should connect it on the MEGA 2560? Then, do I still have space for remaining DIN (8) and AIN (4) I need?

The Mega has 50-plus pins

Digital I/O Pins 	54 (of which 15 provide PWM output)

Analog Input Pins 16

If you keep the analog pins free for analog purposes, you still have 38 pins to play with. Keep 0 and 1 free (serial comms with PC via USB); you will only use those two if you really run out of pins as they are used for uploading of code and very useful for debugging.

Consider future expansion. You might want to use a second serial port in future; you might want to use PWM outputs in the future. Keep those (or a few of them) free if that is the case.

Next consider the wireless communication. Some shields / boards might have certain requirements with regards to pins.

SPI and I2C (and the serial ports as already mentioned) use specific pins; keep them free as well for future expansion (or for the wireless comms shield / board that you use).

And what is left can be used for the relay board.

Next physical layout might be a deciding factor which pins you will eventually use. You don't want a big spaghetti of wires if you can prevent it.

Note:
do not power the relay board from the Arduino.