Posts Tagged ‘supernatural’

Supernatural Thermal Scanner Prop (Laser EMF Reader)

Tuesday, October 9th, 2018

Supernatural Laser EMF

This is my Laser EMF reader, aka Thermal Scanner prop. The Lasers, LCD, and Camera are all functional. In addition, I added gearing to the back so the Lasers could perform a synchronized linear scan.

From the supernatural TV show, there are a variety of EMF Readers used. Especially early on. This paper outlines many of the different variations.

The handheld device seen in episode S01E14 is not an EMF Reader, it is a Thermal Scanner.  I have made a few of these now and have enough pictures to make this write up.

Part List:


3D Printing:
The 3D printed parts are optional. I designed them to both hold the lasers and allow them to move in sync. If you opt not to use the 3D printed parts, you can substitute christmas light holders instead.

Supernatural Laser EMF Supernatural Laser EMF - 5

Some of the terminal blocks are blue and need to be painted silver. Poke the terminals into some cardboard to hold upright. Spray paint before soldering into the circuit board.

With the Screw Terminals installed, you have a sense of how the board is laid out. You can see that the breadboard is too long. Use a saw or dremel to trim the board shorter. If the edge is jagged, cover with electrical tape.

Supernatural Laser EMF

This is mostly a wiring project. Most of the wires you see running around the prop are real. There are two voltages on the board, 9V and 3V. Both run to the Slide Switch, which is DPDT with two isolated switching paths.

Wiring 9V Path: The 9V comes from a pair of 9V batteries wired in parallel to increase run time of the LCD. After the Slide Switch, the 9V is wired to power the LCD, Camera, and LEDs.

Wiring 3V Path: The 3V comes from the 2xAA and powers the lasers. After the Slide Switch, the 3V is wired to a momentary button, and finally the lasers. Polarity is not marked on the lasers, so be careful when soldering on some power wires. After powering on for the first time, the lasers need to be tuned. Take a screwdriver and spin the potentiometer on the lasers. 5 turns counter-clockwise to reset, then slowly bring the laser back on. The green lasers I linked are only 10mW, but they sell more powerful laser diodes that can be dangerous. Be careful when working with the lasers. You want them set to the lowest brightness that they can be seen across a room.

Supernatural Laser EMF

Camera Wiring: Before doing anything, test the LCD and Camera by using the cables supplied in the combo kit. Power up with a 9V battery. After confirming you did not receive a DOA device, you can proceed with cutting the cables.

The cables that come with the LCD and Camera are meant for automotive installs. I cut these wires much shorter and splice back together. Do note that the camera likely has a black lump on the cable. This blob likely contains a 12V -> 5V converter. When splicing the cables shorter, keep this block intact and splice around, do not remove.

Supernatural Laser EMF - 6

– Backup car lines on LCD are caused by the camera drawing them. Using a non-backup camera should fix.
– Lasers are difficult to tune so they are the same brightness.


Updated EMF Reader – Assembly Guide

Monday, May 30th, 2016


In 2015, I did a run of EMF readers with an updated design using an upgraded sound effects circuit.  This is an assembly guide for making that EMF reader. For my older EMF Reader design that is not dependent on custom parts, see here.

There are two custom parts that you can purchase from me: on etsy


Part List

The part list was moved to google drive so I can easily maintain it as links change. If you have trouble finding anything, do email me. I can help you track down the hard to find parts.

Note **: If the recommended Audio FX module is not available.  Here is how to wire the alternate modules.


Solder the Back Circuit

Tools Needed: Solder Iron, Solder, and a Wire Cutter.

Parts Needed: Circuit Board, Preprogrammed Chip, 5x LEDs, 6x Resistors 100 ohm, 4x Resistors 10k ohm, Capacitor 0.1uF, Button, Diode, Audio FX Circuit, Speaker.

Instructions: Assemble as shown in the picture.  The Audio FX Circuit needs 6 wires connected.  Vin, Gnd, Bus, TX, RX, UB.

Step 1 - Back - Solder Parts

Click for larger image


Trim, Tape, and Needle

Tools Needed: Electrical Tape, Scissors, Glue, Solder Iron, Solder, and a Wire Cutter.

Parts Needed: Needle Graphic, Meter Parts, 6x Washers

Instructions: Take apart the meter and remove the plastic wheel.  You can now de-solder the potentiometer from the meter’s circuit board. Set aside.  Next, cut the wires to the meter’s needle assembly leaving enough length to re-attach to the emf circuit.  The needle assembly is screwed down and beneath the clear plastic housing that is also screwed down.  Remove both.  Be VERY careful with the needle assembly, it is fragile.  Re-use the two screws from the needle to help align with the emf reader holes.  You can use 6x washers to add some spacing between the needle assembly and the circuit board.  This helps provide clearance and allows free movement of the needle.  But be careful, as the washers are magnetic.

Step 2 - Front - Trim and Tape

Click for larger image


Solder the Front Circuit

Tools Needed: Screwdriver, Electrical Tape, Solder Iron, Solder, and a Wire Cutter.

Parts Used: 2x Yellow Square Capacitors, 2x Gray Square Capacitors, Toggle Switch, 2x Trim Pot, Rotary, Capacitor Blue 1uF, Capacitor Black 10uF, Potentiometer (salvaged from meter circuit).

Step 3 - Front - Solder Parts

Click for larger image


Meter and Coils

Tools Needed: Screwdriver, Solder Iron, Solder, and a Wire Cutter.

Parts Needed: Antenna, Magnet Wire, P-Clips, Solid Core Wire (strip off the rubber sheath)

Step 4 - Front - Meter and Coils

Click for larger image


Wire Clips

Tools Needed: Pliers, Solder Iron, Solder, and a Wire Cutter.

Parts Needed: Rainbow Wire, Solid Core Wire (strip off the rubber sheath)

Step 5 - Front - Wire Clips

Click for larger image


Battery Box

Tools Needed: Pencil, Drill, 1/8″ Drill Bit, Screwdriver

Parts Needed: 2x Screw Posts, 4x Screws, 6x Washers, Battery Clip.

Instructions: Make room in the battery box for the screws in the battery box by removing a bit of plastic from behind the switch.  No cutting needed, the plastic pops out.  Align the battery box cover with the circuit board.  Make two marks in the cover with your pencil.  Make 1/8 inch holes with the drill in the marked spot.  Use the washers as follows: SCREW |== (WASHER) |PCB| (WASHER) ==POST== (WASHER) |COVER| ==| SCREW

Assembly is now complete, calibrate and learn how to use your emf reader below.


Click for larger image

Load the Sound Clips

Adding new sound effects to the EMF Reader is simple.  Just plug into the usb port to a pc.  The EMF Reader will mount as flash storage on the pc.  Drag and drop the new .wav or .ogg file, then “eject” to safely remove the usb device.

Audio Files:



Next step is selecting the new sound on the EMF Reader.  The EMF Reader reads the first 5 files in storage and maps them.

To select the new sound, turn on the EMF Reader then move the mode select toggle switch to the center position.  There is no center position, so you will have to balance it there.  When you have correctly set the center position, the light on the back of the reader will rapidly flash.

With the EMF Reader in setup mode; press the button on the back to cycle through any of the first 5 files.  When the correct file plays, flip the toggle switch to exit setup mode.



EMF Reader Outline

Get to know your EMF reader.  Note the numbered arrows in the picture.

circuit outline with numbers v3

  1. Needle Calibration Screw Wheel, Sets high position
  2. Toggle Switch: Mode selection.
  3. Hidden Button: Located on the back of the EMF Reader, use this button to override normal EMF operation and force a “ghost” event.


Meter Calibration

Left blue screw wheel calibrates the analog meter needle high position.  Place the EMF Reader in interactive mode, and hold the hidden button. This will hold the meter needle high.  While holding the button, use a screwdriver to adjust the needle’s high position.


Modes of Operation

How to Enter Primary Modes Alternate Modes
Prop Modes
Change toggle switch to the right position.
Pressing the hidden button will activate the sound and light pattern. Sound and light pattern will run in a loop, cycling between high and low readings.
Interactive Modes
Change the toggle switch to the left position.
Press the hidden button to activate the meter.  Meter and lights stay high until the button is released. EMF Reader will always read as high until the hidden button is pressed.

*Hold the hidden button while power cycling to enter an alternate mode.

**In modes that do nothing until the button is pressed, lights will blink every few seconds to indicate the meter is on.


Meter does not sweep or sweeps too high

  1. Needle is touching the back.  Use a tweezers to push away, bending slightly out.
  2. Meter potentiometer needs calibration.  See Meter Calibration above.
  3. Debris has gotten stuck in the meter’s electromagnet.  Gently spin the magnet and ensure that it doesn’t “catch” anywhere.  Even something as small as a hair can prevent free spinning.

Sound is garbled and sounds bad

  1. Voltage to the speaker amp is too low.  Replace the batteries.
  2. Not all sound files sound great on the small speaker, experiment with other sounds.

Note: Be sure to use good batteries.  Recommend: Energizer Ultimate Lithium.


Supernatural EMF Reader

Monday, November 10th, 2014

This is a summary post of my finished “revision 1” EMF Reader from Supernatural.  For revisions 2 and 3, please email me for the latest instructions.

Below you will find the following sections:

  • Description and Pictures
  • Part List
  • Rough Step by Step Build Instructions



Description and Background:

The EMF Reader in Supernatural is an excellent project for people like me that have some electrical knowledge. What I did was design a prop EMF reader around the Arduino platform so that it is actually functional while still looking like the prop from Supernatural.

I went to my local hardware store and bought an analog multimeter. After taking it apart, I played with it on an Arduino board and figured that it was possible to make a functional EMF reader using some off the shelf parts. I could even have the circuit play the telltale “erREEEEErr” sound on a speaker.

I finished the prototype circuit and proceeded to sourcing all the parts and designing a printed circuit board (PCB) that would do everything I wanted.

I measured the analog meter part with my caliper to ensure a good fit with the custom PCB.

In addition, this thread was very useful for finding reference pictures:


  • Meter with a pin that bounces to high when triggered
  • Five top LEDs that match meter display
  • Speaker that makes tone sweep sounds
  • Hidden trigger button to override EMF “readings”
  • Mode selector switch
  • When not activated, the lights will blink every few seconds to indicate the meter is on.

Pictures of my Completed Supernatural EMF Reader:

Link to full album on flickr.


Step by step build instructions

Review the part list is on google docs:

Once you have gathered all the parts, it is time to assemble. This does require minor solder skills.

If you have never soldered before, it’s easy! Get a $5 solder iron from the hardware store and the thinnest solder spool you can find. Then watch some YouTube videos to see how it’s done. Through hole soldering of big solder points (like in this project) is great for learning.

Salvage Parts and Test the Fit

Analog Meter

Take apart the multimeter to get at the analog mechanism inside. You will need the clear plastic from the front, the needle rotor, and the thumbwheel.

Cut a hole in the prototype board and do a “test fit” of the rotor. Make sure that it can spin freely. Eventually, it will be bolted down with washers to ensure the needle has enough clearance to move above the surface.

Switches and Knobs

Put all the various parts where you think they should go. Make sure that you have enough room for everything where you want them before you start soldering parts into place.

Assemble the functioning portion of the circuit


You have two choices to get the circuit functioning. Use an Arduino Pro Mini or use an Atmega328p chip. The Arduino is easier and recommended. I chose the Atmega328p chip because I was using a custom made prototype board that had wires pre-routed to the various switches.

  • Advantages of the Arduino Pro Mini: Easy to use and program over USB using the Arduino software. Use this for your source code:
    Note: there are 4 files to download.
  • If you choose the Atmega328p Chip, things get a little more complicated (you are on your own). More info here:
  • If you purchased a circuit board from Dustin (me), then there is nothing you need to do.  Your circuit is preprogrammed.

Mode Select Switch

Solder in place the toggle switch. Depending on your Arduino, pull up resistors may be required. More info here:

Wire one of the toggle switch’s two side pins to pin 2 on the Arduino. The center is the common pin, wire to ground on the Arduino.


Install the 5 LEDs at the top of the prototype board. The short lead from the LED goes to ground. The long lead from the LED goes to the Arduino.

Wire the LEDs to the Arduino pins in the following order: 2,4,6,7,8 (pin 5 is reserved for the meter output)

You can also install the white and yellow dummy square capacitors now if you like. These are cosmetic only and are not wired to the circuit. Solder them to the prototype board normally.

Cover the LED leads with electrical tape. This too is cosmetic, but also helps hold the LEDs down when you are handling the EMF reader.

Meter Potentiometer

Solder in place a blue square potentiometer. This will be used to adjust the meter sensitivity.

Pictured is my custom PCB. If you are using a different prototype PCB board, yours will look different.

Analog Meter

Install the meter onto the PCB, use two washers between the meter and the PCB to give the needle more clearance over the surface. Attach the meter using 2 screws, 8 washers, and 2 hex standoffs.

The washers on the backside of the PCB will help spread out the squeeze from the screw and hex standoff.

Wire the red wire from the meter to the analog output pin 5 of the Arduino through a potentiometer. The black wire goes to ground.

The potentiometer is used to “tune” the max point of the meter. The analog meter has a screw in the center; this is used to set the min point of the meter.

Later, when you are ready to power up, you can adjust the potentiometer with a screw driver until it performs right.

Printed Graphic

Download the .psd file here:

Print onto peel and stick adhesive photo paper, then trim the print then stick on the protoboard behind the meter’s needle.

Use hot glue or epoxy to affix the clear plastic cover over the meter.

Assemble the cosmetic portion of the circuit


There are two round capacitors in the upper left corner of the board. Solder them in place. It is ok if they are not straight up and down.


Solder on the thumbwheel below the meter.

Antenna P-Clips

Place the antenna clips on the antenna and drill the prototype board so you can eventually bolt the antenna in place. Do not bolt down yet. Right now we just need to get the spacing between the P-clips in the correct position.

Coil 1

The first coil goes on the right hand side of the meter. Use your magnet wire to create this coil by winding the 22 gauge bare copper wire around a pen or screwdriver. Once the coil is long enough, cut off the excess and solder down.

With the coil soldered down, re-insert your pen or screwdriver and straighten the coil out.

Coil 2 (antenna)

The second coil is wrapped around the antenna between the two Pclips. Use the red magnet wire. This wire is a lot thinner and will take many layers. Just keep wrapping around until your coil looks right.

Antenna Bolts

It is now time to bolt the antenna in place. Use the screws, washers, and nuts.

Rainbow Wire

Take approximately 10 inches of rainbow ribbon wire and split them apart into separate strands. Half of the strands will run from the top right to the lower left. The second half of the strands will run from the lower right to the lower left.

Use more of the 22 gauge bare copper wire to create U shaped cable ties. Thread the ribbon wire under the U, then press down with a plyers and solder the U wire down.

If you look closely in the pictures, you can see these cable ties are used in the corners to hold down the ribbon cable.

Final Hex Standoffs and Battery Holder

Place the last two hex standoffs between the LEDs. With all four hex standoffs now attached, use them as a guide to cut holes into the battery holder and affix the battery holder to the EMF reader with more screws and washers.

Sound and Speaker

Pin 11 from the Arduino outputs the sound. However, if you connect a speaker directly to pin 11 and ground, you will have little volume. You need a speaker amplifier.

The PAM8403 is a cheap (under $2) small amplifier board. Wire the amplifier board to the battery power input, 4.5 volts. Then wire pin 11 from the Arduino into the input of the amplifier board. Lastly, wire the two wires from the speaker into the amplifier board’s output.