The Household Informer

Who wants to go outside to see if the mail has arrived? In the cold winter or rain I’d rather not have to put on a jacket and shoes, only to find that there was no mail. This project will notify you of the mail carrier’s visit, and as a secondary function it will remind you that the garage door has been left open. It can even be expanded to include other sensors

Step 1 Schematic

The project is based on the Atmega 168 chip. Since the design requires only minimal resources, most of the AVR chips would be acceptable substitutes. But having extra resources means adding functionality is easier than a redesign.

The device contains only a minimum number of parts (see schematic) .
The design has two sensors, the Garage door magnetic reed switch, and the Mailbox Light Dependent Resistor (LDR).

Comments

[Ksw1234]

Love your project. Awsome when people build their own solutions. You seem like a no-nonsene guy and would value your opinion. I know there are dedicated burners, but not sure how those folk prototype. I was thinking of trying an Arudino board for prototyping, and there appears to be a way to use the board to burn the bootloader and later upload the program on a separate AltaMega chip (link below). As there are apparently infinite ways to get started, could you describe your setup for prototyping/burning?
( http://arduino.cc/en/Tutorial/ArduinoToBreadboard )

[diy_bloke]

"Any suggestions?"
The possibilities seem endless:
A humidity sensor to remind you to water the garden
Indicators for other doors/windows you may forget to close
A PIR or an optical interrupter to give advance warning someone is coming up to the house (can double to see if you had any visitors while u were absent)
Switching on/off lights to make potential burglars think you are at home while u r not (switch off the main light downstairs, followed by briefly switching on the light in the bedroom)
A switch alarming you when your daugther is climbing down the pergola at nite to be off with her boyfriend who rides a motorcycle (just referring to a classic theme in american movies)


Just one question: What happened to the custom that mailmen wld push down the flag on yr mailbox to indicate 'you've got mail' :-)

[pmounica]

can i do it using PIC microconroller

[diy_bloke]

Yes, you can. You can do it basically with any microcontroller, but You'd have to write your own code, unless you can copy what someone else might have done for you.

I bet somewhere there is a project like this with a PIC controller and a guy asking: "Can I do this with an Atmel?"

[jkster107]

I'd like to make something like this, but I'm concerned about the distance to my mailbox (one of those community box things). How long were your wiring runs? And have you run into any interference issues using the coaxial line as signal line?

I don't have good line of sight for wireless communication either, which makes me sad, since a small wireless sensor would probably be less suspicious then running a wire up to the back of a community mailbox.

[BrianH]

I ran about 40 feet of coax from the house, under the driveway to the mailbox. Inside the house there is perhaps another 40 feet of twisted pair to get to my office. I'm not a big fan of wireless since there is always the possibility of RF interference.
I've had no false triggering due to noise with the wired solution. The readings from the LDR are relatively stable. In a test version of the project, I had the readings from the sensor displayed on a LCD. This was how I decided on the threshold value.

Perhaps you might want to try a combination of wired and wireless.
Run a wire where you can, and wireless for the rest of the way.

[placko]

Why are there 5 wires coming out of the enclosure? shouldn't there only be 4? (2 for reed switch, 2 for LDR)

[BrianH]

The power also comes in on this connector, and used a common ground.
I get the power from my doorbell transformer which is rectified, filtered and reduced to about 7 volts before it enters my little box. Once in the box, it is regulated down to 5v.

Actually the connector has one more unused pin, I may use this for another input in the future. I've learned to leave room for expandability during the design - it makes upgrading easier in the future.

[scottinnh]

You could use some cheap wireless daughterboards and save yourself a lot of wiring:
http://shop.moderndevice.com/products/rfm12b-radio

I don't get why these things are not more popular... people always think wireless is expensive, requiring ZigBee or 802.11..

Hope this reminder helps someone. :-)