How do you know?

Like i come up with amazing ideas sometimes, but i wouldn't know how to design it myself. Like what parts do i need, stuff like that. I Can follow tutorials but as far as setting down and designing and figuring out what i need, i just don't know where to start.

I Had an idea last night and i thought (well how do i do this?????) Like my grandmas mail box is 196 steps (guessing 196ft give or take a few ft) and i was wanting to make something that i could mount something on the inside of the mailbox when the door opens it will release a button turning a light on (Blue led) letting her know that the mail has came. When the mail person closes the door, it wont turn off the light in the house until my granny pushes a button turning the light off.

This would have to be wireless, but that's a long distance to be wireless so could a booster be installed halfway?

My granny is 70yo and she trivial to the mail box 3 or 4 times a day because she doesn't know when the mail runs, because sometimes they run at 10am, sometimes the run at 12pm, sometimes the run at 2pm, or even 4pm, you never know when they run because its different everyday.

I Wouldn't no where to begin

The distance is not too far for wireless. I would do it like this: Get a promini, 100mAH LiPo or LiIon battery, 315 MHz or 434 MHz RF transmitte, and a switch that closes a normally open contact when the mailbox door opens (look for microswith with a lever arm). When the door opens, it creates an interrupt, wakes up the promini from powerdown sleepmode, it reads the battery voltage and sends a message, goes back to sleep. The receiver, another promini running from a wallwart, with a matching receiver and a couple of lights and an acknowledgement switch, receives the message and lights up the You've Got Mail light, and if the battery needs recharging, lights up the Battery Low light as well.

No need for an arduino you can simply do it with a holding relay. The radio link fires the relay, which is wired so that the normally open contacts feed current to the coil as well. Therefore once fired it holds. The reset button is a push to break button in line with the normally open contacts that breaks the circuit and releases the relay. Another set of relay contacts light the lamp.

If you don't want to spend too much money on new equipment, I would suggest this:

1) Buy a wireless doorbell (battery powered) set for $7-8

2)Open up the receiver and there should be 4 wires, a red and a black connected to the battery and another pair to power the board in the receiver module. When the doorbell is rung, there is a 2-3V signal across the two wires, perfect for "turning on" a transitor which will control the input signal to your Arduino (I'm assuming you know how to use pull-up/pull-down resistors and transistors).

3)Depending on the tune selected, the signal will be be a pulsing for a few seconds. You can work around this by shorting out two of contacts on the sound chip in the receiver. This is different for each model, but you'll find it in a couple of minutes with trial and error.

4) Now you should have a signal only when the button is pressed. Open up the transmitter and remove the pushbutton switch. Replace that with a switch of your choosing to mount on the mailbox: reed switch, hall effect sensor, LDR etc.

5) Stick your Atmega chip (in your Arduino works but standalone on a tiny breadboard works great!) in the mailbox and write the code to make it do what you want!

There are I'm sure much more elegant ways to do this but for a quick and dirty project, this should function just fine. A suggestion I would make would be to set it up so that the transmitter is NOT transmitting when the mailbox door is closed, in other words, reverse the operation of the switch. I'll leave that for you to figure out ;).

Hope this helped!

I would go with Mike's suggestion. You don't need a microcontroller, unless the whole point is to experiment with the Arduino. You should be able to buy a suitable DPST relay for about a dollar. I think you can also implement an equivalent circuit using a couple a transistors if you don't want use the relay.

I would also follow Cacofonix's suggestion and use a wireless doorbell as the transmitter/receiver.

Hell, you don't even need electricity for this. Put a small flag on the end of a spring. Tuck the spring inside the door such that when the mailman opens the door to insert the mail the flag pops up. When granny goes out to get the mail she resets the flag.

EdSmelly: Hell, you don't even need electricity for this. Put a small flag on the end of a spring. Tuck the spring inside the door such that when the mailman opens the door to insert the mail the flag pops up. When granny goes out to get the mail she resets the flag.

You might not even have to do that. Granny should just raise the flag on the mailbox when she goes to get the mail. When the mail is delivered, the postal worker will put it down. No flag - the mail has been delivered. If the postal worker doesn't put it down - stick a postcard inside with the mailing and return address the same as the mailbox - don't even bother with a stamp. If it is taken (and the flag put down), it will be returned as "undeliverable" or some-such. Just put it back in, and raise the flag (you might need a few of these cards as they take time to circulate thru the system).

cr0sh:

EdSmelly: Hell, you don't even need electricity for this. Put a small flag on the end of a spring. Tuck the spring inside the door such that when the mailman opens the door to insert the mail the flag pops up. When granny goes out to get the mail she resets the flag.

You might not even have to do that. Granny should just raise the flag on the mailbox when she goes to get the mail. When the mail is delivered, the postal worker will put it down. No flag - the mail has been delivered. If the postal worker doesn't put it down - stick a postcard inside with the mailing and return address the same as the mailbox - don't even bother with a stamp. If it is taken (and the flag put down), it will be returned as "undeliverable" or some-such. Just put it back in, and raise the flag (you might need a few of these cards as they take time to circulate thru the system).

She cannot do this because you can't see the mailbox until you go around the bend just so you can see far enough past the tree line to see the flag, and by than she has already walked over halfway up there.