When does mail arrive in my mailbox?Engineering Design ProcessMark Eimer and Josiah White

Remove unnecessary trips to the residential mailbox so that mail is retrieved during the first trip

Define The Problem

Sensor to indicate that the mailbox door has been opened or detects the weight of mail inside the mailbox

Flag that indicates that mail has been delivered

Wait until 9PM to get the mail Create a mail delivery service from the

mailbox to the home Train an animal to retrieve the mail

Brainstorm, Research, and Generate Ideas

Identify Criteria and Specify Constraints

Criteria Simple and easy to use Reliable and

predictable Affordable Installed by the home

owner Easy to maintain Discreet in appearance

and notification

Constraints Cost no more than

$100 Cannot obstruct the

delivery of mail Needs to work with

any USPS approved mailbox

Solution should meet the needs of handicapped residents

Sensor to indicate that the mailbox door has been opened or detects the weight of mail inside the mailbox

Flag that indicates that mail has been delivered

Wait until 9PM to get the mail Create a mail delivery service from the

mailbox to the home Train an animal to retrieve the mail

Develop and Propose Designs and Choose Among Alternative Solutions

A photosensitive sensor was chosen due to costs and simplicity. Some sensors have moving parts, which reduce reliability over time. Motion sensors and accelerometers are much more expensive than light sensors.

The receiver can be configured to notify the owner via different methods. A sound can play or a light can be turned on (or both). In addition, the receiver can even be configured to have a mechanical response that is tied to a motor.

Neither the transmitter or sensor have a requirement for power provisioning. Either can run on a battery system, a small solar panel with a battery backup, or be hardwired to a power source located elsewhere.

Implement the Proposed Solution

Make a Model or Prototype

Model is a three part system comprised of a light sensitive diode, a transmitter, and a receiver.

Image courtesy of: http://transistron.com/ Image courtesy of: http://www.electrodragon.com/

Compared to other systems on the market that serve the same purpose, this system is remarkably cheaper. Off the shelf pricing places this design at less than 50% the cost of other, similar systems.

Other systems use potentiometers that are only triggered when the door is opened to a certain degree. By using a highly sensitive photodetector, as long as it isn’t night time, the sensor will always trigger, regardless of if the door was opened completely.

Photodetector systems are very compact and use very little energy. This allows for a small form factor and a power system that can either be smaller or longer lasting.

Evaluate the Solution and Its Consequences

Because the sensor has to be exposed in order to detect light, there is an increased chance of damage when compared to other enclosed systems.

Transmission distance is reliant on many external factors that may cause interference.

Evaluate the Solution and Its Consequences

The system must be placed inside of the mailbox close, or attached to, the door itself for optimum results.

Transmission range directly proportional to power used. A 9v battery will provide transmission distances of 200-500 feet depending on environmental conditions.

Refine the Design

Final design will be very compact. Photodetector sensor located at a corner of the main face of the device to allow the most freedom in placement options.

Can be attached either via magnet, adhesive backing, or screwed into mailbox itself.

Receiver would have option for light/sound notification. Would have a reset switch to prepare for the next notification.

Create the Final Design