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Dual Tone Air Raid/Security Siren

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MOST Delta filament as guide.JPG This page was part of an MTU course MSE4777 OA and MSE4777 OB/MSE5777/EE4777/EE5777: Open-source 3-D printing

Please leave comments using the discussion tab. The course runs in the Fall semester. It is not open edit.

Dual Tone Air Raid/Security Siren - OSAT project[edit]

Project developed by Peter Gorecki (talk) 3:00, 8 December 2015 (PST)]
This OSAT has been designed but not yet tested - use at own risk.
This OSAT has been prototyped.

You can help Appropedia by contributing to the next step in this OSAT's status.


This is a 3D printed Security Siren that could be used in low income areas where theft or other problems are an issue. The purpose of the siren is to get the attention of others nearby when a crime or other emergency is happening. Because crime rates are sometimes higher in lower income areas it would be beneficial to provide a low cost alternative to these areas.

This siren has a 5:6 frequency ratio, also known as a untempered minor third. Having two clashing tone simultaneously makes the siren more noticeable.

This has been improved from other designs, having fewer parts for ease of assembly, using an electric motor rather than a hand crank ed siren, and by having 2 tones instead of 1


Bill of Materials[edit]

Non-Printed parts

  1. 2 X 3mm dia X 10 mm length fine thread socket cap screws ~ $0.66 total
  2. 2 X 3mm dia split lock washers ~ $0.50 total
  3. 13.6 V 6290 RPM Johnson electric motor part number: 9167AJ ~ $3.95
  4. 12 V 4 amp AC-DC power supply ~ $2.99
  5. 2mm hex wrench ~ $0.30

Printed Parts

  1. Stator ~ $5
  2. Rotor ~ $6

Total Cost ~ $19

Source and STL files[edit]

The STL files are available on thingaverse, here is the link:


Tools needed for fabrication of the OSAT[edit]

  1. 3-D printer, I used the Athena: MOST Delta RepRap3-D printer
  2. 2mm hex wrench
  3. Wire stripper or something to strip wires safely

Skills and Knowledge Necessary to Make the OSAT[edit]

  1. soldering

Technical Specifications and Assembly Instructions[edit]

  1. Stator print time estimate ~ 5 hours
  2. Rotor print time estimate ~ 5 hours
  3. Include assembly time estimate - 30 minutes

To assemble:

  1. Print stator and rotor
  2. Cut and solder power supply wires as show in picture
  3. inset motor into hole in stator and secure with screws and lock washers using the 2mm hex wrench
  4. Insert motor shaft into rotor. This is a pres fit onto a spline shaft, so it will require a bit of force, make sure to push the rotor on straight as shown in picture.

Common Problems and Solutions[edit]

  • Include common mistakes/problems to avoid in building your OSAT and how to overcome them
  1. Make sure to tighten screw snugly onto lock washers so they don't come loose from vibration
  2. Make sure to push the rotor straight onto the motor shaft, or the hole might get damaged and the rotor could be off center and unbalanced

Cost savings[edit]

  • If your solution is not a low cost one then it is not really appropriate.
  1. Estimate your costs : Approximately 390 g pla ( ~ $11), cost of non-printed parts ( ~ $8 ) = Total: $19
  2. Similar sized air raid style sirens were anywhere from $35.15 to $89.99
  3. This means percent savings is somewhere between 46% and 79%