Almost was home, back from a client where I fixed some computer problems. Then I realized that I had left my usb memory stick in my client’s computer. Now I had a hard choice, drive back 100 km or let my client send back the usb stick with lots of information he does not need to know. Do you recognize this and do you have fine soldering skills? Then this instructable is something for you. This is an usb cap that sounds an alarm when it has been empty for 5 minutes. The alarm is repeated every minute. When you always keep the cap with you, you will never forget an usb stick again.

Step 1: Parts and Tools

Parts needed:

3 batteries size AG5
PIC12F629-I/SN microcontroller (soic 8 package)
piezo beeper 20 mm diameter
100nF capacitor (size 1206)
4M7 resistor (size 0804)
Some abs plastic
Some stripped wire wrap wire (30AWG)
Some lacquered wire
Small piece of foam

Tools

3d printer
Soldering iron
Tweezers
Wire cutter
Wire stripper
Glue gun
pic programmer (pickit 2)
5 pin pin header
1 mm drill

Step 2: Programming the Microcontroller

Connect the microcontroller to the programmer according to the schematic with lacquered wires

program the hex file into the pic chip.

I compiled the source file with the HI-TECH compiler (ver 9.60) in mplab IDE (ver 8.00) If you want to adapt the program and use other versions of the compiler beware that the timing can be different. I found that newer versions of HI-TECH actually are slower. This means that the frequency of the sound is lower.

Step 3: Build the Enclosure.

Print the model from the stl file usb_bleeper.stl You might have to scale the model so that the batteries and usb stick fit. You could also make the casing by other means. My initial prototype was made with instamorph moldable plastic

usb_bleeper.stl
Download View in 3D

Step 4: Contacts for Detecting USB-plug

Drill 4 1mm holes in the corner of the rectangular area under the round area. Put some 30AWG wire through the holes. They must contact the metal of the usb plug when it is in.

Step 5: Connecting the Electronics.

Solder the electronics according to the schematic. This very simple schematic can be built without a pcb. Solder the piezo beeper with lacquered wire.

The sens contacts are the 2 wires that go through the holes. The smaller electrode of the batteries is the minus side. On the picture I use smaller type batteries than for what I designed the casing.

Step 6: Close Battery Cap

Put the batteries in together with a piece of foam. The foam must push the wires against the batteries. Glue the battery cap with some hot melt glue. For replacing the batteries the glue can easily be removed by applying some isopropyl alcohol.

Step 7: Glue the Piezo Beeper

Put some tape over the electronics and glue the piezo beeper on top with hot melt glue. For best sound quality the whole rim of the beeper must be covered with glue.

Step 8: Testing

Whenever you put in or take out a usb-plug the device produces a single beep. When you take the plug out and wait 5 minutes you must here 7 beeps. The timing of this chip is not very accurate.