Posts Tagged ‘prop’

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.


DIY Ammo Counter

Monday, December 21st, 2015

Do you need an ammo counter circuit for your project and are bummed that you have to wait for a spot in my build queue to open up?  Fret not, here is a step by step how to make one from scratch!

In this guide, I will detail how to build your own ammo counter for ~$25 and with only minimal soldering experience.




You can use other arduinos or switch and display choices.  The linked ones were chosen for number of pins and size.  This project uses 16 IO pins from the arduino and the trinket is the smallest arduino that can be programmed over usb.

If you get a different display, it must have the following traits:

  • Common Cathode, the common pin is ground (do not want Common Anode)
  • Two Single Digit 7 segment displays, with 10 pins on the back EACH.
    – OR –
  • One Dual Digit 7 segment display that is non-multiplexed, with 18-20 pins on the back (multiplexed only has ~10 pins)

Wire Display to Arduino:

Get out your solder iron, wire strippers, and some note paper.

  • Wire display digits 1 and 2 as shown below, diagram only shows one digit for simplicity.
    • The common pin (CC) goes to ground.
    • The period (DP) can be left unwired.
    • Each segment is wired to a unique pin on the arduino, can use any arduino pin marked as D or A.
    • The exact pins wired to are important, write them down for later.  To run the software without modification, use the default pinout table below.
    • Diagram shows resistors between the display and the arduino.  When using the 3.3 volt version of the arduino trinket, no resistors are needed.




Default Arduino Pinout

Arduino Trinket I/O Signal Type Name
3 ~3 O Display Output Digit 1, Segment E
4 4 O Display Output Digit 1, Segment D
5 ~5 O Display Output Digit 1, Segment C
6 ~6 O Display Output Digit 2, Segment E
8 8 O Display Output Digit 2, Segment D
9 ~9 O Display Output Digit 2, Segment C
10 ~10 O Display Output Digit 2, Segment B
11 ~11 O Display Output Digit 2, Segment A
12 12 I Switch Input Fire Switch
13 13 I LED Output LED
14 A0 O Display Output Digit 2, Segment F
15 A1 O Display Output Digit 2, Segment G
16 A2 O Display Output Digit 1, Segment B
17 A3 O Display Output Digit 1, Segment A
18 A4 O Display Output Digit 1, Segment F
19 A5 O Display Output Digit 1, Segment G
RST RST I Switch Input Reload Switch

Finish Wiring Assembly:

  • Wire the fire switch to a digital pin and ground.
  • Wire the reload switch to the reset pin (RST) and ground
  • Wire in the trinket to a 3.3 – 5 volt battery pack, blue and white color displays requires minimum of 3.2 volts.

Program Software:

You will need a micro usb cable.  No batteries needed yet, the trinket is powered by the usb for now.

Source Code:

  1. Follow the getting started guide from codebender to setup the website to talk to your arduino trinket, choose Adafruit Pro Trinket 3V USB when asked
  2. Open source code link
  3. Click Run on Arduino
    • If you get the error message, make sure to press the button on the Trinket to activate the bootloader before trying again.

Optional Software Changes

With the source code open on the website, find and click the edit button to make changes to the software.  After you have made changes, click Verify Code and resolve any issues, proceed to ‘Run on Arduino’ when the website indicates ‘Verification successful!’

  1. If you did not use the default pinout, you must update the pinMap list with where you wired each display segment. Use the pin numbers you wrote down
  2. If you want to use a different starting ammo count or firing types, scroll down and update ‘Starting Values’.
    • shotmode can be set to CONT for full auto or BURST for semi auto
    • burst_value is the number of ammo shot in each burst, default is 1.
    • counter_value is the starting ammo value.


  • shotmode = BURST; burst_value = 1; counter_value = 99; is used for paintball or nerf
  • shotmode = CONT; burst_value = 1; counter_value = 60; is used to match a Halo AR MA5B
  • shotmode = BURST; burst_value = 3; counter_value = 36; is used to match a Halo BR55


On startup, you will see the starting count of MODE1. Press the fire button and the number will go down 1 tick until 0.  The LED (pin 13) goes dark when the counter reads 00.
Press the reload button and the display will go blank, and then reset to the starting count.

Hold the fire button down while pressing reset, this will change between modes. Display will report the mode number as F1, F2, F3, and so on.

Feel free to play with the software further to tweak the features to your liking. Have fun :)