Posts Tagged ‘guide’

EMF Reader – Assembly Notes for Wire Clips

Friday, August 3rd, 2018

This is to help out folks making my DIY kit.  I took some photos while assembling my latest batch of EMF Readers.  Routing the wires can be tricky.  My method uses spare 22 gauge solid core wire, a soldering iron, and hot glue.  Makes the wires stay put.

Click the infographic for a larger version.

EMF Assembly Notes - Wire Clips

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.


Light Break Sensor for Ammo Counter

Thursday, January 21st, 2016

I have offered ammo counter kits for nerf dart guns for a while now.  With a tweak to the ammo counter software’s min time between fire events and the addition of a photo sensor, you can install my ammo counter kit on a nerf gun and keep track of shots remaining in your clip even while full auto firing.

What allows this to work is a light break sensor.  The part number I recommend is the OPB100Z.  It comes with an IR LED and a Phototransistor.  The LED creates a beam of light, and the phototransistor acts as a switch.  When the light shines on the sensor, the transistor conducts and the ammo counter reads voltage.  However, when a shadow is cast on the sensor the circuit is broken and the ammo counter fire input is grounded.

More info on how Phototransistors work:

Below is how to wire the light break sensor into an ammo counter.  The wire leads on the light break sensor are color coded, follow the colors in the diagram below.  Place the sensor and light on your barrel so each dart fired creates a shadow between the sensor and light.


  • During your install and testing, you will be unable to see the light with your eyes.  Your human eyes are not sensitive to IR light.  Instead, point a camera or smartphone at the light and you should see the white/blue light on the screen.
  • I do not currently sell light break sensors, but do tell me when purchasing a kit that you intend to use one.  I will program with special software and include the extra two resistors seen in the diagram.
  • Places to buy a light break sensor, part number OPB100Z:

Cropped - Light Break Sensor Wiring Diagram for Ammo Counter

Xbconnect Wireless Guide Updated

Friday, January 23rd, 2009

Major overhaul to the layout and format of this page to bring it up to date with the rest of the website. No new content, sorry.