APOC Basic Kit & Usage Instructions


  • Soldering Iron & Solder (Leaded solder is much easier to work with than lead-free)
  • Electrical Tape (We recommend the high heat resistant kind which can withstand up to 220F i.e. 3M Super 33+)
  • Wire Clippers
  • Lighter/Matches/Hair Dryer for the shrink tubes (not necessary if not making the optional data cables)
  • Scissors
  • Phillips Head Screw Driver
  • Flat head Precision Screw Driver
  • Masking/Scotch Tape

Having Trouble? Post It On: /r/excelphysics!

This assembly guide assumes a basic knowledge of electronics, such as polarity and proper electrical connection. Basic competence with a soldering iron is also required. Before you begin assembling your APOC kit please check that your kit is not missing any parts by checking the list of included components in the Bill of Materials. If you discover that your kit is missing any components please email Support@excelphysics.com.









7   Photodiode  
 R1, R8 2  2.2MΩ Red-Red-Black-Yellow-Brown  
R2, R13 2 1KΩ Brown-Black-Black-Brown-Brown  
R3, R4 2 220KΩ Red-Red-Black-Orange-Brown  
R5, R10 2 4.7KΩ Yellow-Violet-Black-Brown-Brown  
R6, R7, R14 3 33KΩ Orange-Orange-Black-Red-Brown  
R11 1 20Ω Red-Black-Black-Gold-Brown  
R12, R15 2 100KΩ Brown-Black-Black-Orange-Brown  
R9 1 100KΩ Trimmer Potentiometer  
C1, C7 2 10μF

Smaller than C3

White Strip Corresponds to Negative

C2, C4, C6 3 0.1μF    
C3 1 100μF  White Strip Corresponds to Negative  
C5 1 1000μF  Black Strip Corresponds to Negative  
Q1, Q2 2   BC549  
Q3 1   PN2907A  
LED 1      
U1 - Socket 1      
U1 - IC 1   LM311P  
S1 1   Switch  
BT1 1  

9 Volt Battery Snap

Black = Negative | Red = Positive

LS1 1  


Black = Negative | Red = Positive

CLK RAW - Pin Header 1   4-Pin Header  
CLK RAW - Jumper 1      
IP - Pin Header 1   2-Pin Header  
IP - Jumper 1      
DATA - Right Angle Pin Header 1   3-Pin Right Angle Header  
DATA - Vertical Pin Header 1   3-Pin Header  
PCB 1   Printed Circuit Board  
Copper Tape 2      
Mounting Tape 1      
Case - Screws 8      
Case - Top 1      
Case - Bottom 1      
Case - Side Panel 1 1      
Case - Side Panel 2 1      
Case - Divider 1      
Case - Bottom End 2      
Case - Middle End 2      
Case - Top End 2      
iPhone Cable 1   4-pin cable with a 3-ring jack  
Stereo Cable 1    3-pin cable with a 2-ring jack  
Thick Shrink Tube 1      
Thin Shrink Tube 1  

*Note* Some kits came with transparent tubes

Servo Cable Female to Bare 2      
Servo Cable Female to Female 1      






Part One - Simple Components:

Start off with the 7 photodiodes (D1 – D7). The photodiodes are located on the opposite side of the PCB from the majority of components. These should be soldered on the side of the board that only has 7 silk-screened outlines of photodiodes. Polarity is important here so please note the side with the thin white strip. That should correspond to the white strip silk-screened on the board. After placing the photodiodes, tape them in place using masking or scotch tape. Make sure that the diodes are as flat as possible before soldering them in place.


Next we’ll do all the resistors (R1 – R15) except the trimpot (R9). Referencing the Bill of Materials, place each resistor in their respective spot outlined on the board. After all resistors are placed, tape them down and make sure they are as flat as possible before soldering.

Note: We do NOT recommend bending the pins of any components to

Now you should clip all the protruding leads from the resistors and photodiodes.

Note: When clipping, try to clip each lead so that it leaves a relatively flat stub behind. You DO NOT want to clip them flush with the board, this could prevent the part from making electrical contact with the pad. However, you do want to clip them so that it leaves a dull point. This is especially important for the components on the top half of the PCB (the side with the photodiodes separated by the long strip of tin) so it won’t cause issues with the electrical & copper tape later on.


This next part we’ll place & solder the following parts: C1, C2, C3, C4, C6, Q1, and Q2. Note that positioning affects all the transistors and capacitors except the 0.1μF capacitor (C2, C4, C6). For the transistors Q1 & Q2 place them on the board so that the rounded side of the transistor faces the same direction as the rounded outline on the board.  The capacitors have a white strip on one side detonating the negative side. When placing them on the PCB make sure that the negative side goes into the hole that is not labeled with a + symbol.

Most of the parts that are placed on the photodiode side of the tin strip (C1, C2, C3, Q1, Q2) you will need to place all of them EXCEPT C2 flat against the board. The easiest way to do this is to place the part in normally and then bend them so that they are flat on the board. Refer to the picture of the finished board above for guidance.


Part Two – Other Components:

Now that we have the easy parts done, let’s move on to the harder stuff such as the pin headers. All of the pin headers except for the right angle one is threaded from the bottom of the board (see reference image). Once you place the three sets of pin headers (CLK-RAW, IP, DATA) tape them down so they are secured in place and then solder the exposed pins on the top of the board onto the pads. When soldering be careful not to heat the pads for more than a few seconds because that will cause the plastic part of the pin headers to melt. If after one or two tries you can’t get the solder to flow around the pad let the pad cool for a minute before trying again. DO NOT CLIP ANY OF THE PIN HEADERS! After doing all the vertical pin headers, do the right angle DATA pin header. The right angle header is placed normally from the top of the board; the tricky part with this header is getting it to lie flat and not tilted on the board. One method we use is to solder only of the pins and then heating that pin while we quickly position the pin header. Be Careful not to burn yourself, the pin gets very hot!


Next place the switch (S1) and the IC socket. The socket is directionally biased so look for the notch on the socket. The side with the notch should correspond to the notch outlined on the board. Tape both parts down and solder them. If you’re having trouble keeping the part flat on the board, try soldering only one of the pins on each part and then quickly heating that pin while pushing the switch or socket flat on the PCB.

Once you’re done with that, you can place Q3, C7, and the LED. These three parts are pretty straightforward; they can be placed vertically unlike the parts near the photodiodes. One thing to note is that the LED has a flat side that corresponds to the flat side outlined on the PCB. It’s convenient to group this set of parts together because they are all relatively the same height making it easier to tape them down when soldering.

Now for the last two parts, the trimpot and the large blue C5 capacitor. When placing these two parts note that the trim pot has small protruding tabs. These match the outlined tabs on the board. The black strip on the capacitor corresponds to negative and should be placed in the hole that is not labeled with a + symbol.



Now that you've finished soldering most of the components, it is VITAL that you go back and double/triple check your soldering job! Pay special attention to the half of the board with the photodiodes, this is the half that will be covered with electrical and copper tape making it very difficult to troubleshoot any issues later.

Some questions you should ask yourself are:

  • Are all parts making electrical contact with the pads?
  • Did the solder flow all the way around the pad?
  • Did any of the leads get cut too short? (if so, you can solder it to the pad on the other side of the board just in case)
  • Are there any soldering that looks questionable? (it's better to run your iron over it again than to risk an issue later on)
  • Are all the parts placed correctly? (pay special attention to the photodiodes, capacitors, and transistors)


Part Three - Finishing the Detector:


After double and triple checking the soldering on your board it's time to move onto the final phase of the kit building process: shielding!

The first step in make the shielding for the APOC will be covering the top half of the board with electrical tape. To do this you will need to cut your electrical tape to the following specifications (you can cut them beforehand or you can cut as needed):

  • 1X 3.5in long piece of tape cut to 1/2in wide.
  • 1X 3.5in long piece of tape 3/4in wide (standard width for electrical tape)
  • 1X 1.5in long piece of tape 3/4in wide

Start with the 3.5in by 1/2in wide piece on the side of the board with the photodiodes. The purpose of this piece of tape is to cover the area just below the photodiodes and right above the grounding strip of tin. You do NOT want to cover any of the top area of the photodiodes (the sides are OK) OR any part of the tinned strip. If the piece of tape you cut was too wide, make the necessary adjustments so that it fits properly. Start from the edge of the board and first cover the area between the photodiodes and the tinned strip then wrap around to the side with the capacitors and transistors. Do your best to stay just barely above the tinned strip and cover as much of the capacitors as possible. This will make sure that no light penetrates the shielding and prevents the copper tape from making contact with any of the components covered by the electrical tape. The left over 1/2 inch of tape can wrap around again to the photodiode side, just make sure no photodiodes or tinned strip is covered.

Next, take your 3.5in by 3/4in wide tape and once again start from the side with the photodiodes. This time you will want that piece of tape to fully cover all the photodiodes from the top edge of the board to overlapping some of tape from the previous step. Once again you will want to wrap this tape around the board and cover the capacitors and transistors and then wrapping it back to the side with the photodiodes and then cutting the tape so it doesn't cover the photodiodes twice.

With your last strip of tape, tape across the top edge of the photodiode side of the board taking care not to cover the top of any photodiodes and then wrapping the tape over the top part of the board to seal the exposed capacitors and transistors on the other side.

Once this part is done the top half of the board should be fully covered in electrical tape. If there are a few gaps here and there, you can cut small strips of electrical tape to cover them. Just make sure not to cover the photodiodes twice. Afterwards, flatten the tape with your fingers to push out any air pockets especially the layer covering the photodiodes.

Now you're ready to apply the copper tape! You only need one piece of the copper tape, the second piece was included in case you mess up and need to try again. Start by carefully removing the copper tape from its packaging making sure not to crinkle it. Line up the edge of the short side of the copper tape with the tinned strip on the board, you will want to center it so that there is a little bit of overhang on each side of the board. We recommend doing this from the photodiode side since it is flatter and easier to adhere to. The copper tape should cover about 50% of the tinned strip, this will allow it to be grounded properly. After covering the photodiode half of the board, you should cut notches into each side of the tape so that the left and right sides can be folded onto the sides of the board with a bit overflowing to the other side. Next fold the remainder of the tape over the capacitor and transistor side of the board. You want the copper tape to cover about 50% of the tinned strip on this side as well. Cut any excess off the copper tape if covers more than 50% of the tinned strip. Afterwards fold the flaps on both sides over its respective edge of the board which should overlap some of the copper tape. Once you have applied the copper tape take your soldering iron and apply solder to the  exposed tinned strip and the copper tape. Although the adhesive on the copper tape is conductive and should already be grounded to the tinned strip, we prefer to solder them together again for insurance. When soldering the copper tape to the tinned strip, be careful not to solder the two gaps where the traces pass though.


Congratulations! You are almost there! All you need to do now is to solder the speaker and 9-volt battery snap to the board. As specified in the Bill of Materials, the black wires are negative and the red wires are positive. First thread the two sets of wires through the stress relief holes (see reference image) and then solder them to their respective pads. Sometimes it's easier to thread and solder only the battery snap before threading and soldering the speaker. Choose whichever way works best for you as long as it gets the job done!


Part 4 Calibration and Enclosure

For this next part you will need a flat head precision screw driver to calibrate the APOC by turning the trimpot and a Phillips head screwdriver to put together the case. You'll also need to put the CLK RAW Jumper on the two pins labeled CLK otherwise it won't actually output anything.

Start by connecting connecting a 9-volt battery to your APOC and flip the switch to on (this is the middle of the three settings). If your APOC immediately starts squawking and the LED is flashing red, this is a good sign. Take the precision screwdriver and slowly turn the knob on the trimpot counterclockwise. The squawking should die down into intermittent clicks. Once that happens, turn the knob about a 1/4 counterclockwise every minute or so. During that time count the number of clicks you hear until you only hear about one click every minute or so. Now your APOC should be properly tuned to detect mainly gamma radiation and high energy x-ray.

For those of you who turned on the switch only to find that it's silent, there is still hope! First turn the knob counterclockwise for a while, if you don't reach a point where the device starts squawking then try turning it clockwise. Once you hit that area where it starts squawking follow the instructions outlined in the previous paragraph.

Some of you might turn it on to find that the APOC is squawking but the LED is green instead of red. If this is the case, try turning the trimpot clockwise until the squawking dies down and then start turning it counterclockwise. Sometimes this fixes the problem and the LED flash red as usual.

If none of the above solutions solved your problem then your best bet is to try to go over all the soldering again to make sure everything is soldered properly. If that still doesn't work then try to post your problem with pictures to the our subreddit.


 Case assembly



Data cables and interfacing.