This project shows you how to make your very own effects stompbox! We'll go through the steps of downloading the .brd file, loading the file into our software, milling the board on the Bantam Tools Desktop PCB Milling Machine, and soldering the components. This is a great tutorial for those new to milling printed circuit boards (PCBs) or for those who want practice soldering components to the board as a part of a larger assembly.
Tools, Materials, Parts, and Files
- Flat end mill, 1/32”
- Digital calipers
- Bantam Tools Desktop PCB Milling Machine
- Computer with Bantam Tools Desktop Milling Machine Software installed
- Printed circuit board (PCB) blanks, single-sided, FR-1
Circuit Board Components
- C1 47uF 16V
- C2 0.1uF 100V
- C3 0.047uF 100V
- C4 100uF 16V
- C5 0.1uF 100V
- D1 1N4148
- D2 1N4148
- D3 1N5817
- R1 100 ohm 1/4W
- R2 3.3k 1/4W
- R3 1M 1/4W
- R4 1k 1/4W
- R5 2.2M 1/4W
- R6 240 ohm 1/4W
- R7 240 ohm 1/4W
- R8 200 ohm 1/4W
- Transistor 2N2222
Overdrive Pedal Kit
- 1590B Enclosure
- Mono output jack
- Stereo input jack
- +9V battery clip
- DC Power Jack
- A100K potentiometer (Volume)
- B50K potentiometer (Gain)
- 3DPT (On/Off)
- LED Bezel
- AWG 24 Hook-Up Wires
We'll start of by downloading a .brd file that was made in EAGLE, loading it into Bantam Tools Desktop Milling Machine Software, and milling a single-sided circuit board.
Step 1: Download the .brd file and set up your material.
If you haven't already, start out by connecting your computer to the milling machine with a USB cable, turning the milling machine on, and opening Bantam Tools Desktop Milling Machine Software.
You’ll be prompted to home your machine. Press the “Start Homing” button.
Install the 1/32” flat end mill into the milling machine, then click on the Tool “Change” button. If you haven't done this before, you can read more about the process in our Inserting and Locating a Tool guide.
Select the 1/32” flat end mill from the “New tool” drop down menu and click “Continue”. A new prompt window asking to verify tool position will pop up. Your machine will move the end mill to the right. Make sure there is no material under the end mill and that the spoilboard is free of debris. Click the “Locate Tool…” button. The end mill will slowly descend until it encounters the spoilboard. When it touches the spoilboard it will briefly pause, then retract upwards. This act of touching-off on the spoilboard lets the software know where the end mill’s tip is located in space. You are now ready to load your material.
In the the software menu that’s located at the top of the screen select Machine → Rapid to loading. The spoilboard should now be toward the front of the machine and ready for material loading.
Measure the thickness of your double-sided tape in millimeters using your digital caliper and enter the number into the Material Placement (Z) field.
Apply the tape to the back of a single-sided circuit board blank. Make sure the tape does not overlap, otherwise your z-axis will be slightly higher than intended. Be sure to cover as much of the back of the material as possible. Then place the PCB blank at the bottom-right edge of the spoilboard.
Select “Single-Sided FR-1” as your material type. The dimensions of the board should automatically default to the properties of a new board. It’s always a good idea to use digital calipers to measure the thickness (Z-axis) of your PCB Blank. Sometimes a board can be a little thicker than normal, and it’s important to enter this value into the Material Thickness (z) field of the software.
Now we’re ready to load the overdrive pedal.brd file into the software. Click the “Open File” button and select your brd file from its saved location.
Step 2: Look at the software preview and mill the board.
If you see any warnings or red on the board it means that the end mill you’ve selected to cut the board is too large to mill those areas. This is usually because your components or traces are too close together relative to the size of your cutting tol. To fix this, you will need to either select a smaller cutting tool, or open the .brd file in EAGLE and edit the layout to create sufficient space for the end mill to fit.
However, in the instance of the .brd file we’re milling here, as you can see in the image below, the board is free of any red markings and warnings. Because we see no red warnings, we know that the end mill we've chosen is small enough to successfully mill the board. This means we are ready to mill our board.
Move the “Parts to Mill” slider to the “bottom” setting and select your 1/32” flat end mill. You can click on the “Traces”, “Holes”, and “Outline” to get an idea of exactly what the machine is going to mill.
Now that our end mill is installed, our material is attached to the spoilboard, and our .brd file is set up in the software, we are ready to mill the board. We have only one file loaded, so we can either click the “Start Milling” button or the “Mill All Visible” button; they will both do the same thing and cut our file.
Click the “Mill All Visible” button and stay by your milling machine while it completes the job!
After the milling machine finishes cutting the board, use a scraper to remove the PCB from the spoilboard. Here is what your board will look like.
You now have a circuit board that’s ready to be populated with components!
Step 3: Place the components and solder them to the board.
In this next step we'll take the components, place them in the appropriate place on the circuit board, and solder the parts to the board.
This is what the board will look like when we're done soldering the components to the board.
Notice that the parts are sitting on the side of the PCB that does not have the copper coating.
This is what the other side of the board will look like when finished.
The .brd file we are using was created in Eagle. When placing the components we can refer to the .brd file as it is viewed in Eagle to see where the parts should go.
The image below shows the .brd file as seen in Eagle. The blue lines indicate the traces. Notice that the blue lines are the mirror image of the traces on the milled PCB board. In other words, if you horizontally flip the image on the left (the .brd file as viewed in Eagle), then you'll get the image on the right (the PCB board). This is helpful to keep in mind when placing the components on the board.
Now let's place our components on the board. Here's a quick diagram to show where each of the components goes. Some of the components need one leg to go in a specific hole. Other components, like the resistors, do not have polarity and so the legs can go in either hole. If you're interested, you can read more about polarity here.
After you have placed the components in their appropriate place, the copper side of the PCB will look something like this.
Now it's time to take out your solder and solder iron, and solder the legs to the board. If you're new to soldering then check out Adafruit's Soldering Guide. After soldering, use diagonal cutters to cut the legs off.
Now that the components are soldered to our circuit board, it's time to prepare our enclosure to hold this circuit board.
Step 4: Drill the enclosure.
In this project the container that will hold our pedal is a 1590b enclosure. When you purchase the enclosure it does not come with holes for the components to fit into, so we'll add those now. Begin by printing the 1590b enclosure template (which you can download here) and cutting it out along the outside edge.
Fold the flaps down along the center rectangle edge, then tape it together.
Place enclosure inside your drilling template. Tape the template onto the enclosure so that it does not move when you're drilling. If the paper does not move you will have an easier time drilling the holes in the correct location.
We’ll be using a stepper bit attached to a drill press to make our holes. This is the specific stepper bit we used, and we liked it because it has diameters in 1mm increments, ranging from 4mm to 12mm. When using a stepper bit, keep drilling downward up until the stepper bit diameter matches the diameter on the drilling template.
If you don’t have access to stepper bits you can use regular drill bits intended to drill into metal. However, it won’t be possible to get exact hole diameters.
Use the following as reference when using regular drill bits:
- --3PDT Switch: 12mm stepper bit = 1/2” drill bit (~12.7mm hole)
- --DC Power Jack: 12mm stepper bit = 1/2” drill bit (~12.7mm hole)
- --Input/Output jacks: 10mm stepper bit = 3/8” drill bit (~9.5mm hole)
- --Potentiometers: 7mm stepper bit = 5/16” drill bit (~7.9mm hole)
- --LED: 6mm stepper bit = 1/4” drill bit (~6.35mm hole)
If you don’t have a drill press a hand drill will do; a steady hand goes a long way.
Notice that we have taped the enclosure drill paper template to the metal enclosure so the paper does not move.
You are now ready to drill your enclosure holes.
After drilling the holes, take a look to see if there are any sharp edges or burrs. If you see any, you can use scouring pad to smooth the edges.
This is what the enclosure will look like once all the holes have been drilled.
Now that the holes have all been drilled, we are ready to begin adding the hardware to the enclosure.
Step 2: Installing and Soldering the Components
Here is where all the parts are going to be placed.
Begin by inserting the DC Power jack, the B50K potentiometer, and the A100K potentiometer. Tighten the nut on each component just enough so they don’t move, but leave them loose enough so that you can still move the components. This makes soldering much easier as you can spin the components if needed.
Next insert the 3PDT switch, the Mono Jack (the pedal's output) and the Stereo Jack (the pedal's input). When looking down at the open enclosure be sure that the stereo jack is on the left, and the mono jack is on the right side. Again, tighten the components just enough to hold them in place, but not so tightly that they can’t be moved.
Notice that we have not inserted the LED/Bezel into place. We’re going to do a bit of soldering before adding the LED/Bezel.
Step 5: Solder the components.
Now we will begin soldering our components. If you're new to soldering, or would like a refresher, check out Adafruit's Soldering Guide.
We’ll begin by soldering the positive wire from the battery clip into the DC power jack.
Next solder the wire that will connect to the 3PDT switch and a ground wire. So far your enclosure should look like the image below.
Next, put some masking tape below the potentiometers to prevent your circuit board from touching the enclosure and becoming grounded. It’s not always necessary, but we recommend adding this masking tape just to be safe!
The 3DPT switch has nine lugs. Use the image below as a reference for how each lug is numbered. From this point forward we will refer to each lug on the 3DPT switch by the number assigned to it.
Solder a wire from lug 3 to lug 9 on the 3DPT switch.
For the mono output jack, here are how the lugs are numbered. In the next step we'll be soldering to lug 2 on the mono output jack.
Solder a wire from lug 8 on the 3DPT to lug 2 on the mono output jack.
For the stereo input jack, here are how the lugs are numbered. In the next step we'll be soldering to lug 1 on the stereo input jack.
Solder the negative battery wire to lug 1 on the stereo input jack.
Solder a wire from lug 2 of the 3PDT switch to lug 3 of the stereo input jack.
Next we will be soldering to the positive and negative leg of the LED. The longer leg of the LED is the positive leg, and the shorter leg is the negative leg.
Solder a resistor to the positive leg of the LED. Cut the positive leg of the LED so it’s shorter, cut the leg of the resistor so it’s shorter too, and then solder them together. See the image below for an example of how this should look.
Next, cut the negative leg of the LED and solder a wire to it. This wire will serve as the resistor’s ground wire.
One thing to keep in mind when selecting a resistor in a project like this one, where the pedal is powered by a battery, is that the value of the resistor used with the LED will affect the battery life. A lower resistor value that allows the LED to burn at its brightest will drain the battery more quickly. A higher resistor value that keeps the LED more dim will prolong the battery life. In this tutorial we are using a 56k resistor, which is a high enough value that the LED will not burn too brightly and therefore the battery will not prematurely be drained.
Use some heat shrink tubes on your connections and you should have something that looks like the image below.
Insert the LED bezel into the enclosure from the top side of the enclosure. Then insert the LED into the LED bezel from the inside of the enclosure. Next, cut the positive wire and solder it to lug 5 of the 3PDT switch.
Insert the negative wire from your LED into lug 2 of the stereo input jack (on the left) but do not solder it yet. Next, insert the negative wire from the DC Power Jack into lug 1 of the mono output jack (on the right) but do not solder it yet. Then route the positive wire from the DC Power Jack along the edge of the enclosure and leave it near the 3PDT switch for later use.
Notice that the area with the tape is clear of wires and that the wires are being run along the edge of the enclosure. While this is not necessary for the pedal to work correctly it is good practice to keep your wires nice and tidy.
Next we’ll be soldering our circuit board to both the A100K potentiometer and B50k potentiometer. As a reference to know where to solder the components, look at the .brd file as viewed in Eagle.
The lugs on the A100K potentiometer and B50k potentiometer are labeled like this.
Begin by soldering the B50K (gain) potentiometer to the board. First, solder GAIN-1 to lug 1 of the potentiometer. Next, solder GAIN-2 to lug 2 of the potentiometer. Finally, solder GAIN-3 to the lug 3 of the potentiometer.
Refer to the board diagram to see where Gain-1, Gain-2, and Gain-3 are located.
Next, solder the A100k potentiometer to the board. First, solder the VOL-1 wire from the circuit board to lug 1 of the A100K (volume) potentiometer. Next, solder the VOL-2 wire to lug 2. Finally, solder the VOL-3 wire to lug 3.
Position your board into the enclosure and route the input (green) wire toward the 3PDT switch and solder it to lug 1 on the 3PDT switch.
If you recall a few steps ago, you inserted the negative wire from your LED into lug 2 of the stereo input jack. Now run the negative (black) wire from the circuit board and insert it into lug 2 of the stereo input jack. Next, cut some hookup wire that is long enough to reach lug 1 of the mono output jack.
You should now have three wires going into lug 2 of the stereo input jack. Solder these three wires into lug 2.
Again, recall from a few steps ago, the negative wire from the DC Power Jack should be in lug 1 of the mono output jack. Insert the hook up wire from lug 2 of the stereo input jack from the previous step and solder the two wires into the lug.
Next, insert the positive (red) wire from the circuit board and the positive wire from the DC Power Jack into lug 4 of the 3PDT switch and solder them.
Finally, insert the output wire (blue) from the circuit board into lug 7 of the 3PDT switch and solder.
Remember how earlier we left the input/output jacks, potentiometers, DC power jack, and 3PDT switch only partially tightened? Now you can tighten all.
Last, add the knobs to the potentiometers and test your pedal! Plug your guitar into the pedal, and then connect the pedal to an amp. Congratulations, you just milled your very own overdrive guitar effect pedal!
This is what your completed pedal will look like.
If the pedal doesn't work, check your soldering connections one by one. Make sure that there isn’t a cold solder joint or loose wire. If you have a multimeter, you can use it to make sure that the joints aren't cold. If you haven't used a multimeter before, check out Sparkfun's How to Use a Multimeter guide.