Burglar alarm help

I am in the process of making a burglar alarm system. There will be a main box with arduino nano in, that will be connected to the sensors (PIR Ect.) This will be in our back utility room.

I then want a pannel about 10- 20 meters away at the front door that will have an RFID reader and a I2c LCD panel. The plan at the moment is to have another Nano in here. This panel at the front door will send a digital pins out 5v signal back to the main Nano to turn the alarm on or off. The wiring will be the existing burglar alarm wireless installed in the house. 12v will be supplied down the cable to power the Nano at the front door.

Question 1. Will the nano 5v pin out be able to work over that distance?

  1. Any other better ideas?

I know that I could use a relay either end but I don't really want to have a big relay at the front door. (Maybe transistors?) I am not very experienced so go easy please!

  1. Will the nano 5v pin out be able to work over that distance?

As an on-off signal, yes.

If you're running power over a distance you might get voltage drop (depending on the current, the wire gauge, and the distance).

I know that I could use a relay either end but I don't really want to have a big relay at the front door. (Maybe transistors?)

A relay or transistor for what? For the 5V, you don't need it.

The wiring will be the existing burglar alarm wireless installed in the house. 12v will be supplied down the cable to power the Nano at the front door.

If you are mixing the existing 12V system with the 5V electronics, you'll need to accommodate that. The Arduino can be damaged by 12V, and if you send a 5V signal into the 12V alarm, it may not be enough.

use 12 volts. it is very easy to power the Arduino with 12 volts. it is very eary to put in a voltage divider or even an opto-coupler to work with 12 volts in and 5 volts out.

I intend to power the Nano at the front door by putting 12v into the Vin pin, as opposed to usb power. the door nano will only send the 5v output as a signal to the main Nano.

Sure you need two Nanos for this? If the one at the front door is reading the RFID it (the RFID module) can be supplied with power via the cables that have to run to/from it anyway (to send the data back, or as you propose send a signal back).

I would only use a single Nano unless there were design constraints preventing me doing this (perhaps the distance from the door to the main panel is an issue but you are going to send a signal voltage out anyway).

Just ponderin' ;)

Ralph_S_Bacon: Sure you need two Nanos for this? If the one at the front door is reading the RFID it (the RFID module) can be supplied with power via the cables that have to run to/from it anyway (to send the data back, or as you propose send a signal back).

I would only use a single Nano unless there were design constraints preventing me doing this (perhaps the distance from the door to the main panel is an issue but you are going to send a signal voltage out anyway).

Just ponderin' ;)

Along with the RFID reader I also want a I2c LCD. I am also worried that the I2c won't communicate over that distance. I know the project I got the idea from uses Software serial LCD but I don't want to spend the extra!

In that case you will need two boards as I2C is meant for short (Intra board comms) distances - even at 3 feet you will probably get corruption (and that's at 100Khz not the faster 400Khz)!

Thanks for clarifying.