Have you been a victim of the so-called “salisi gang”? A group of individuals who just set an eye on you and wait until you drop your valuables and immediately take them as you lost your attention. They are very common in restaurants, bus terminals and almost everywhere.

The solution:

I built a portable device that you can place inside your bag to monitor whether the bag has been moved. When the bag has been moved (the device will think that it was stolen), the loud piezo buzzer will sound and distract the intention of the thief. Unfortunately, the thief will not be able to switch off the device because the device needs passcode before shutting off. Also, the battery cannot be easily accessed because it is protected by pair of screw.

How it works:

The device has a power button that will turn on the device once pressed. The device will blink a green status LED which means that the device is asking for the passcode. The device will automatically shut off if the user fail to supply the passcode. This way, the device ensures that only the owner can use the device and passcode is not forgotten. After encoding the passcode, the device will give few seconds to set your bag stationary. After this, the device will start monitoring your bag. You can turn off the device by encoding the passcode.

VIDEO AT THE LAST STEP!!!!!!!!!!!! :)

Suggestions please!

I always believe in continuous improvement. If you guys have some suggestions to help improve the device, comment it out below. I will be very happy to hear from you guys! If you think that this instructable entry deserves to win, vote for it! Thanks ahead! :)

Step 1: Gather the Parts

Here are the electronic components, tools and materials that you are going to use.

Parts:

· Tactile switch

· 9x 10K Ohms resistor

· 2x 330 Ohms resistor

· 1x 47K resistor

· 2x P-channel MOSFET

· 2x N-channel MOSFET

· 1x IN4001 Rectifier Diode

· 1x 7805 5Volt regulator (I used the one in TO-92 Package)

· MPU6050 Accelerometer with Gyro

· Arduino-compatible MCU

· Battery clip

· Header pins and connector wires

· Project box

Materials (consumables)

· Etching Solution (Ferric Chloride)

· PCB

· Fine tipped marker (for correcting PCB, optional)

· Ruler (optional)

· Glossy paper / magazine paper

· Sanding paper

Tools:

· Mini drill (Dremel)

· Flat iron

· Laser printer/photocopier

· Latex gloves (for protection against corrosive etching solutions)

· Eye protection(for safety purposes)

Step 2: Schematics

The Arduino-compatible MCU that I’m using is far different to the existing arduino(s) in terms of pin layout. It’s locally made here in the Philippines (www.e-gizmo.com.ph). However, I still made to show you the PCB layout of the circuit and it’s up to you to modify it according to the pin layout of your chosen MCU. This also means changing some pin in the arduino code (step 8). The raw Fritzing file is available for download at the next step. Modify it to suite to your preferred MCU.

Try comparing the pin assignment of the MCU i used to the Arduino mini.

Step 3: Print PCB Layout

Print the layout using a Laser Printer or a Photocopying machine. Inkjet printers will not do the trick. Also, print the layout in a glossy paper such as a photo paper or magazine paper. The device consist of two boards, the mainboard where the MCU and the MOSFETs are attached and the keyboard where the pushbuttons and indicators were attached.

Summary:

Printer to use --------- Laser Printer or Photocopier

Paper to use ---------- Glossy paper, Magazine paper, Photo paper

The raw Fritzing file is available for download as well as the pdf file i used.

Step 4: Iron the Layout to the PCB

If you’re already a master degree holder or familiar in PCB fabrication, then you can skip the following steps and jump straight to step 7.

Do these steps for both the circuit board (mainboard and keyboard). Use a laundry iron to iron your layout to the PCB. Ironing the layout transfers the ink from the paper to the PCB. You need to set the iron’s temperature to the highest setting if your paper is thick and medium setting if your paper is thin. Sometimes, it is necessary to tape your layout to the board to prevent it from moving. Adding additional layer of paper between the iron and the layout is optional. Iron the layout until the ink is fully transferred. In my case, I’m using a photo paper, after 5 minutes of ironing, I try to peel off the paper and it goes off easily. Some prefer to soak the board with water first then remove the paper. In my experience, soaking it with water gives a dirty work than just carefully peeling it off while its quiet hot (I mean tolerable). Don’t forget to check the PCB for worn paths, restore them using a marker. I prefer cutting the PCB to its size after etching it. This is to prevent damaging the layout.

Step 5: Etch

Safety first! Use latex gloves and eye goggles.

There are different variety of etching solution but the most common is Ferric Chloride. Get a plastic container (never use any kind of metal container) and pour the etching solution to it. Place the PCB in the container. Agitate it from time to time to speed-up the etching time. After about 5 – 10 minutes, check if it is fully etched. If yes, remove it immediately and wash.

Step 6: Cut to Size, Drill Holes and Sand the PCB

Now that you have a neatly etched PCB, it’s time to cut it to its size. Use a hacksaw to cut it. Using a mini-drill or dremel, drill holes to the PCB. After drilling holes and making sure no holes were skipped, sand the PCB to make sure that the next step will not be messy – Soldering time!!!

Step 7: Solder Components

Use step #2 as reference. Solder the smaller parts first such as resistors, pushbuttons, diode and LEDs. You can solder directly the MCU or use headers to make it detachable. Since this device is still a prototype, I made the MCU and the accelerometer detachable by using header pins. Solder then the connecting wires between the mainboard and the keyboard.

Step 8: Program the Arduino-compatible MCU

The code will work to any arduino-compatible MCU. If you are using the same arduino-compatible MCU and PCB layout as mine, you don’t need to modify the code anymore. However, if you modify the layout or use different pin, make sure to update the arduino code. The code is downloadable below.

The arduino code i used is available for download below. Modify and be merry! :)