Need to get a notification when a parcel is dropped in my new letterbox

I have just bought and installed a new letter/parcel box for my home. These days we shop online A LOT and receiving parcels of varying sizes is an almost daily event. Previously with my old crappy letter box all the couriers came to the door and rang the bell so I always knew when something had arrived. My new letter/parcel box has a secure chute for the courier to open the front flap and place the parcel inside and when the flap is closed the parcel drops down into a secure area below. It works well and stuff cannot be stolen by other couriers.

So, what I have decided would be fun and useful would be to install some kind of photo beam like they have in front of automatic doors that when the parcel drops down it will break the beam and send a notification (via IFTTT or possibly WiFi if I have coverage there, not sure yet).

So that way when I am inside working at my desk I can get an SMS or an email or some kind of notification that tells me “Something just got dropped in your parcel box”.

Obviously power is a consideration but I was thinking maybe a small solar panel on the top of the box (which is essentially a pillar about 1.2 m tall) might be helpful in keeping a battery topped up. Not bulletproof obviously, but this isn’t rocket science !!!

I assume I can buy something close pre built off Amazon etc, or maybe from Core, but I’m also happy to play with building it - it would be a fun project.

Thoughts !!! (except that I am crazy, I won’t take that well!!!)

Hi Andrew.
Good idea if there is some way to make it (almost) foolproof.

AustPost (My preference) sends an SMS “your parcel from 'XXXXX” is out for delivery to-day, expect between ‘X’ and ‘Y’" and later "Your parcel from ‘XXXXX’ has been delivered.

Unfortunately most couriers don’t even get close to that. One recently gave me a time window of 8.5 hours. AND they expect you to sit around and sign for it. Some of these people forget just who is paying the wages. If a vendor insists on using a courier I consistently have trouble with and won’t use AustPost I just shop elsewhere.
Cheers Bob

1 Like

Hi Rob, Absolutely spot on observation. Having spent some of my IT life working for AusPost I have some inside info on how their systems work, but I want to avoid a defamation suit so I will refrain from comment !!!

Also, not everything that comes here is delivered via AusPost. In the last month I have had deliveries from DHL, Fedex and other private courier companies so my Nirvana solution is something actually connected to my parcel box so I know when something “actually” dropped in as opposed to when Auspost guess it might possibly arrive !!!

1 Like

Fun fact: Last year on a lazy Sunday afternoon I ordered 2 parts for a PC build I was doing. 1 part was ordered from a local PC store about 10km down the freeway near my home. The 2nd part came from a PC equipment manufacturer in Slovenia in Eastern Europe. The one from just down the road was delivered by AusPost/Star Track, the one from Slovenia was DHL.

Guess which part arrived first !

1 Like

I was thinking about this recently and arrived at the idea of using a Raspberry Pi Pico W and a Resistive Flex Sensor.

The flex sensor is an anlogue device, but they seem great for this application because they can be mounted basically anywhere. You don’t need perfect fit such as microswitches etc. Couple one with a comparator that is configured to go high when sensor is bent, and you’ve got an instant + reliable sensor. The flex sensor could be glued to the bendy side of a door, or anywhere that a bending action occurs.

The Pico can be woken up using a pin interrupt that is driven by a low-power comparator such as the TS3021 (or something similar).

Pico wakes up, connects to WiFi, fires off an email, and then goes back to sleep. If the battery is running low then send a second email.

Use a rechargeable 18650 battery, swap it out once a year (or longer) if all goes well.

In my case for a letterbox, I was just going to use two flex sensors inside a letter box hanging downward so that they interfered with letters being pushed through the gap.


Hey Andrew,
Welcome to the forums!

The first thing that came to mind when I read over this post was a recent project that @David191372 did! He used a P2P Lora network to see if his gate was open. I think that would be a great reference point for this project!

Obviously you wouldn’t be able to use the switch he used, however mixed with the use of a flex sensor like @Gramo mentioned, you may have something that would be perfect for your use case!


1 Like

Hi Guys,
I’m still adding features to my gate sensor :slight_smile:
I was having a hard time figuring out how to trigger the micro stitch without my cattle getting at the bracket or switch and playing with it. (Then run away laughing)
I came up with the idea of a picodev magnetometer.
I don’t really care about compass angles but if I mount the whole device in a nice secure box on the gate it will be able to sense when the angle of the gate changes. I just turn it on while the gate is closed and that becomes the starting point.
I’m in debugging mode at the moment. Once finished I’ll publish the code to GitHub. I’ve added a web page to the pico that records the time the gate was opened so I get a history. It’s obviously a very simple web page.
I have also added parameters to the config file so you can choose either type of detector.
I put the pico into light sleep mode for 10 seconds between testing the gate sensor and this extended the battery by several days. Not sure how the power usage will go with the magnetometer yet or how successful the solar panel will be but the pico uses so little power I think it will do it easily.

Now I’m thinking I should also monitor my mailbox!

Hope these ideas help.


Hey Andrew,

Keeping the battery topped up will be no easy feat!

I’d recommend going for a nano power timer (the HAT variant makes it easy to connect to a Pico W).

In terms of measuring a package, a load cell combo with a break-beam sensor would provide some more information if a package has been delivered.
This way you are sensing the presence of something instead of looking to catch when the letterbox door is opened (this lets us use the power timer HAT).

Super keen to see this come together!

1 Like

Thanks for all the feedback guys, this is great. i have some research to do now which i will pick up tomorrow. Great stuff.

Hi Liam,

Thanks for the feedback. To be honest the battery life is not a deal breaker for me. I currently have a drawer full of 2032s we found in a bargain pack on Amazon, so realistically if I have to change a battery every 3-4 months that’s still way better than the video doorbell I have at the moment (Brand name hidden to protect the innocent!!!)

I am going to look into this Pico thing over the weekend. That seems to be a favoured option and I am keen to understand its capabilities.

1 Like

Hi Andrew
I doubt that a 2032 cell would go anyway near powering what you have in mind. Ok for Real Time Clocks and other devices that only require a few µA but a micro controller with wireless capabilities I think not.

I reckon it could be back to the drawing board for your power requirements.
Cheers Bob

Hi Andrew
Check out this awesome project on Hackaday website. It uses a reed switch on the letterbox flap to trigger it so it is off most of the time. It then powers up briefly, sends the notification and shuts down. So it lasts for a year or so on one battery.

1 Like

Not really, I wasn’t actually suggesting using the 2032s, my point was that I can treat the power requirements as a separate issue once I understate the shape of the solution and what kind of power delivery I will need. I never really imagined the 2032s would do, so possibly shouldn’t have mentioned them !!!

Nice idea Basil, Thanks for that !!!

Hi Andrew

What a breath of fresh air. There are in my opinion (for what it is worth) far too many who think the opposite. Start off with a power supply they THINK might do then try to fit everything into that.

My general take on things is to work how much I will or am likely to need, Double that then go for the next size up. That way everything sings along quite happily well within capability without any supply worries. Takes care of anything you may have forgotten or want to add too.

I usually have at the back of my mind things like the last major project I was involved with while still working full time. EVERYTHING had to be de-rated to 50ºC (yes 50). so mundane things like switch mode power supplies suddenly went from 100W to something like 300W. You might be surprised what comes to light when you can prise this sort of information out of a supplier. Probably impossible in the domestic market. Fortunately our supplier (local, Sydney) did not have any problem doing so. probably as it was a customer requirement and written in the specs and if they couldn’t or wouldn’t another supplier would have to be found may have had a bearing.

Even in a hobby or domestic environment something like 40ºC would not be unheard of. You might be surprised what a nominal 50W power supply actually is at that ambient temperature. Could conceivably reduce to 30W or so and if you are too border line could spell potential trouble. Batteries could be especially prone to a bit of derating. But I have yet to see some numbers published. I am not suggesting they are not published, I just have not seen any reference to this. Could have a large bearing for projects that spend time in sunlight.
Cheers Bob


Sorry I did not include a link. Here it is in case you did not find it. A Battery Sipping Cellular Mailbox Notifier | Hackaday
OOPS wrong one… This is the one I was talking about.
Moving The Snail Mail To WiFi | Hackaday

1 Like

Could not agree more !!

I am an IT guy and I build PCs for fun and amusement (sad isn’t it). The one component I pay the most attention to when building a new PC is the power supply. It is the only component in a PC that if not appropriately specced can destroy every other component in the box. It amuses me to see people fret and sweat over the exact CPU or GPU for their build and they max them out and then to recoup some of the spend they buy a cheaper PSU and then wonder why the whole thing went up in smoke !

I truly have no idea what the power draw of my solution is going to be so once I know the shape of that I will explore an appropriate solution. Obviously this is not a PC so the solution is vastly different, but that’s all part of the fun !!!

1 Like

I thought it was me who couldn’t find the link !!! Thanks for the update !

1 Like

Hi Andrew

So very true. Especially if the P is expandable with fancy graphics cards etc.

Not rocket science to measure once design finalised is it. The only problem is technique with things like “Voltage burden” on mA meter ranges. The part solution here is use the 10A range. Should get down to mA resolution.
I have a non invasive unit in the form of a small Uni-T clamp meter. Gets down to measuring mA with surprising accuracy if the wire is through the centre of the aperture. Plenty accurate enough for estimating power requirements. Nice little meter actually, goes up to 200A.
Cheers Bob

1 Like