Last Updated on January 7, 2020

Even though they’re oftentimes easy to find and buy, and they’re pretty cheap, too, there’s something about a homemade bug detector that makes it an attractive option for anyone who’s into DIY. If ever you’ve felt paranoid about sleeping in a random hotel room, or you’ve got reasons to believe someone is listening in on your conversations it might be a good idea to get one.

So, that being said, how do you make a homemade bug detector? It’s actually not that simple, but if you follow the things we mention below, you should be good to go.

What tools do you need?

In terms of tools, you’ll need a soldering iron and solder. You will also need needle nose pliers, wire cutters and strippers, and a small flat head screwdriver. A PCB clamp will come in handy, and you’ll need a solder pump. Last but not least, grab a hot glue gun and glue, and a magnifying glass to make sure you know exactly what you’re doing.

Start with the schematic

The first thing you’ll need to do is be able to assemble the basics. This schematic comes with a complete list of elements you’ll need to build a homemade bug detector that picks up all types of transmissions, so it’s going to be pretty versatile. In total, it should cost you no more than $15 to make this yourself. (1)

You’ll want to create a PCB layout from the schematic, and have it on a peg board. You can, for example, print the schematic, lay it out on the pegboard, and cut things to size. All parts will fit on the board, and the end result is to have all this fit in an Altoids tin box, so you can carry it around. Oh, and once you’ve cut the pegboard, you’ll want to sand the edges to smoothen them.  

Let’s begin

We’ll start things off with the capacitors. You already have a schematic, but a good advice would be to keep the board oriented the same way as the reference image, so you know you’re doing things right.

Make sure you pay attention to the electrolytic capacitor’s polarity, keeping in mind that the silver stripe down the side is the negative side (also the one with the shorter lead), which needs to be on the left hand side. In order for it to fit in the board well, straighten out the leads.

Also note that capacitors C2 through C5 are 0.22uF, while C6 is 470pF. Place the capacitors where needed, and bend the leads so they don’t fall out if you flip over the board. With the capacitors in place, flip the board over and solder them in place.

If you are looking to just buy, instead of building one, here is our list of the best bug detectors.

Resistors and inductor

The resistors will be clearly marked with the color code, with the exception of the R1 resistor, which has a value printed on it. If you get confused, use the reference image to help you. Place all of them, and the inductor, where they need to be. You can use the same trick of bending the leads to keep them in place. Then, flip the pegboard over and solder the leads in place, trimming any excess.

Diodes, Led and Transistors

The transistors are next. Make sure you orient them correctly, with the flat side facing the left of the board. Q4 is the C1674 transistor, and you’ll need to bend the leads out to fit the board. Q1 through Q4 are BC547 transistors.

When it comes to the diodes and LEDs, you should note which is the anode, and which is the cathode. The longer lead on the LED indicates the anode, and the cathode should be on the bottom side of the board. On a diode, the cathode has a white line around one end, and that line should be at the top of the board. As usual, bend the leads and solder them. (2)

Switch, piezo buzzer, coil and antenna

The switch should have its leads be spread out a bit wide, and the buzzer should drop into place. The leads should be just right to keep them in place for soldering. The coil should be made with a copper wire, and you should bend it around a 3mm diameter object. Make sure turns are nice and tight, and you could even dab a bit of hot glue to keep things in place. When done, strip the ends and place it on the board. You can have the coil placed anywhere along the right side, with the antenna being 100mm of wire, and you can place them wherever you need to.

Battery and tracers

Use two 10mm pieces of wire to create two U shaped pieces, and place them top to bottom and side by side in the Pad1 area. Place the battery clip on the board so you can insert the battery. Solder the clip in place.

Now, one thing at a time, you’ll want to bend the leads so they make contact with the components. Use excess wire to strip it and use it as a trace. Do things slowly and verify trace placements.

Wrapping things up

All that’s left is to cover the tin’s bottom to prevent the board from shorting out, and drilling holes in the side for the switch and LED to stick out. Once you do this, use hot glue to secure it to the tin, and that’s it – you have a homemade bug detector!

Resources

(1)-Schematic- https://upverter.com/design/mpilchfamily/09c849fbaa066e29/bug-detector-rev1/

(2) – LED and diode – https://circuitglobe.com/difference-between-led-and-diode.html