This project is a metal travel pad used for DDR (Dance Dance Revolution) or ITG (In the Groove). It features aluminum construction, four acrylic panels, force-sensitive-resistor sensors, a custom PCB for I/O, and configurable addressable LED strips. This pad was built using items purchased online and fabricated using simple hand tools. Total cost is hard to estimate, as I had a lot of tools and parts lying around from other projects, but with shipping and tax I estimate I probably spent about $250-$300.

I'm not a good filmmaker but if you prefer to hear me ramble about this pad in video form you can check out this YouTube video.

Pad Description

The metal travel pad comprises mechanical and electrical components, as well as software running on the PC and microcontroller.

Mechanical Components

The pad frame consists of 1"x1" T-slot extruded aluminum arranged in a 17.5"x17.5" footprint. Interior rails form the mounting surface for the internal FSR brackets and the center panel, which is mounted on "low profile" 1"x0.5" extrusions. All components are retained with standard T-slot fasteners. Each panel is mounted via two hinges, which allow the panels to be easily flipped up for pad modding or cleaning.

The panels are 3/8" acrylic measuring 3" wide and 11" long. Enabling a flat upper surface, 1/4"-20 flathead screws retain each panel to its respective hinges. Low-profile lock washers secure the screws in place.

The center panel is a standard DDR center panel and is retained using double-sided mounting tape. The extrusion also provides screws as an alternative mounting option. Slippery plastic such as UHMWPE may be substituted for this center panel, although such parts may be cheaper to source locally.

Electrical Components

This pad features a custom printed circuit board (PCB). The PCB holds an Arduino Pro Micro, which features the ATMega32u4 chipset and breaks-out many I/O pins. The ATMega32u4 features a native USB interface and is supported by the Arduino IDE. The microcontroller acts like a joystick or keyboard, which permits modern Dance Game engines (Stepmania being the most prevalent) to interpret it as an input device.

The PCB is a very simple two-layer board with a few key features:

1. Spring-loaded, push-to-disconnect terminal blocks for the current divider fixed resistors. This is a tool-free way for the user to adjust the FSR sensitivity range without needing to de-solder or worry about the resistors falling out on their own.
2. Male header pins for dupont-style FSR terminals, connected in four current dividers to the swappable fixed resistors and analog pins A0-A3
3. Male header pins for WS2812 addressable LED strips and voltage-smoothing capacitor. Data pin is connected to the Microcontroller pin 6
4. A 5V barrel power jack for lights power, isolated from the microcontroller power. Also includes through-holes for the option of a 5V screw terminal
5. Four SMD LEDs that reflect whether the analog threshold has been reached, regardless of whether the main lights have power (useful if you don't want to pull up Test Input in Stepmania and don't have the lights plugged in)
6. Two mounting holes
7. A reset button

The lights are WS2812 addressable LED light strips. Each strip is daisy-chained off the last and requires no external circuitry besides what is present in the PCB.

Software

The pad uses teejusb's outstanding FSR software, which supports the PCB LEDs, several different microcontrollers, and includes a slick web interface for visualizing and adjust the FSR thresholds. My pad specifically uses a (slightly modified) dom-fastled-lights branch of Dominick's fork, with extends the code to support the panel lights and also includes a web frontend to modify the light colors.

Building Instructions

Here, I'll describe the steps that I followed to design and build this pad.

Bill of Materials

This first table describes the components I mailordered specifically for this project and where I obtained them. Note that I took advantage of Digikey's price breaks for higher order quantities and this table does not reflect these costs at single-quantity

Category	Part	Vendor	Vendor Part#	Detail	Quantity	Cost/Ea [USD]
Pad Frame	Front Rail / Rear Rail (17.5")	TNUTZ	EX-1010	NO MACHINING	2	3.90
Pad Frame	Side Rail / Inside Rail (15.5")	TNUTZ	EX-1010	Ø9/16" COUNTERBORE @ "A" (both ends)	4	5
Pad Frame	Inside Interior Rail (8.75")	TNUTZ	EX-1010	Ø9/16" COUNTERBORE @ "A" (both ends)	2	3.60
Pad Frame	Interior Top Rail (10.75")	TNUTZ	EX-1050	NO MACHINING	2	1.46
Pad Frame	Inside Interior Top Rail (8.75")	TNUTZ	EX-1050	NO MACHINING	2	1.70
Pad Frame	10 Series Single Anchor Fastener Assembly	TNUTZ	AF-010		14	1.40
Pad Frame	10 Series 1/4-20 Economy T-Nut & 1/2" lg screw	TNUTZ	COMBO-010-A		40	0.19
Pad Frame	10 Series 2 Hole Inside Corner Gusset	TNUTZ	CB-010-A		4	1.95
Pad Frame	10 Series 6 Hole Inside Corner Bracket	TNUTZ	CB-010-F		4	2.25
Pad Sensor	FSR	Interlink	FSR X 402	Female contacts and housing	4	3.49
Panel Mount	Panel Hinge	McMaster-Carr	1514A11		8	0.75
Panel Mount	Flathead Screw	McMaster-Carr	93791A552	1/4"-20 x 5/8" (pack of 25)	1	5.53
Panel Mount	Acrylic Panel	McMaster-Carr	1227T359	3" Wide x 3.8" Thick, 4' Long	1	19.36
Panel Mount	Panel Nut	McMaster-Carr	90566A029	1/4"-20 Nylon-insert, low-profile (pack of 100)	1	4.08
PCB Components	Fixed Resistor Terminal	Digikey	732-11090-ND	Würth Elektronik / 691411410008	1	2.93
PCB Components	PCB LED Resistor	Digikey	P123823CT-ND	0805 package, 220 Ohm	4	0.094
PCB Components	FSR Male Header	Digikey	2057-PH2RA-08-UA-ND	8-position, 90-degree	1	0.24
PCB Components	Lights Male Header	Digikey	2057-PH1RB-03-UA-ND	3-position, 90-degree	1	0.11
PCB Components	Fixed Resistor	Digikey	CF18JT1K00CT-ND	1k Ohm (swappable)	4	0.0248
PCB Components	LED Data Resistor	Digikey	YAG3733CT-ND	0805 package, 470 Ohm	1	0.050
Pad Light	LED Bars	Ebay		WS2812B, 1m. Optional	1	9.99

In addition, you'll want the following components. I had these laying around already or got them separately. Different people may be able to source these at different costs so I've removed the "cost" column here. I personally acquired most of these items through Amazon.com or Ebay.com for different projects. I'd strongly encourage you to check polarities and package sizes on all electronic components.

Category	Part	Suggested Vendor	Detail	Quantity
Pad Frame	Center Panel	McMaster-Carr, local plastics supplier, your DDR/ITG arcade pad	Approx 11"x11"	1
Pad Frame	Base Panel	McMaster-Carr, local plastics supplier	Approx 17.5"x17.5". Not necessary if you mount the PCB elsewhere	1
Pad Frame	Center Panel Fastener	Local hardware store	I used 3M mounting tape. Screws should work too!
Pad Frame	Hinge-to-rail screws	Local hardware store	I used button-heads but you could use other varieties	16
Pad Sensor	Wire	Local electronics supplier	Various colors are helpful. I used 22 AWG	Several feet
Pad Sensor, Lights	Double-Sided Tape	Local supplier	I used standard Scotch
Pad Sensor / Lights	DuPont-style crimps	Local electronics supplier	I used both female and male pins/housings	8 per FSR, 6 per panel light
Lights	3-across Male headers	Local electronics supplier, Digikey.com	I bent straight headers but 90 degree headers would be prefferable	7
Lights	Lights power supply	Local electronics supplier	5V, I used 31 LEDs that pulled about about 770ma peak	1
PCB	Electronics base	JLCPCB.com, ALLPCB.com, Oshpark.com	ALLPCB fabricated mine for free.	1
PCB Components	Lights power barrel jack	Digikey.com	Make sure to check your polarity :)	1
PCB Components	Microcontroller Pro Micro	Sparkfun.com	I use a 5V Arduino, not sure if the 3.3v works	1
PCB Components	Lights voltage-smoothing capacitor	Digikey.com	The PCB is designed for a through-hole electrolytic cap, I used 470uF	1
PCB Components	PCB LEDs	Digikey.com	0805 package. Note these are optional	4
PCB Components	Reset switch	Digikey.com	I used a omron-style tactile switch	1
Modding	Gorilla Tape	Local supplier	Replace with your preferred mod tape
Cable Management	Zip Tie mounts	Local supplier	I used these to hold the wires down
Communication	Micro USB cable	Local supplier	Connects directly to the Pro Micro

In addition, I'd recommend the following tools. Several of these I bought for other projects and several I borrowed from my local tool-share.

Tool	Purpose(s)
Power drill / Drill Press + Bits	Drill-out clearance holes on hinges and top rails, create countersinks in panels
DuPont-style crimper	Crimp FSR and LED cables
Soldering iron	Solder through-hole components
Reflow station	Solder surface-mount components
Hand Saw	Cut acrylic panels to length
Ball-ended allen keys	Assemble frame
Threadlocker	Secure fasteners
Ratchet / Wrenches	Secure fasteners
Exacto Knife / Deburring tool	Clean up aluminum
Tweezers	Position SMD components
Flux	SMD soldering
Wire stripper	Prepare FSR and lights wire

Assembly Instructions

Hardware Components

1. De-burr all the T-Slot extrusion. I used an Exacto knife but a deburring tool is the right tool for the job.

2. Use the anchor fastener assemblies to fasten the inside interior rails to the interior rails. Make sure to include two t-nuts for each of the FSR brackets in the future. Also include two t-nuts on each of four rails for the top rails in the future.

3. Use anchor fasteners to fasten the interior rails to the side rails. Install the corner gussets (I removed one gusset to leave more clearance for the PCB). You may also want to install extra t-nuts to retain the base panel. Make sure you include two t-nuts on the side rail outsides for each of the panel hinges in the future.

4. Install the front/back rails. I personally applied threadlocker after checking all the alignments but you can do it as you go.

5. Prepare the interior top rails and the inside interior top rails. Since I used used flat-head screws to retain the top rails, I had to drill a 1/4"-20 clearance hole in the center and a screwhead clearance hole through the faces. Secure these in place to the previously-installed t-nuts.

6. Drill and countersink clearance holes in the acrylic panels. I'd recommend using your hinges as a guide.

7. The stock holes on the hinges are slightly too small for a 1/4"-20 clearance, so drill those out using a 1/4" clearance bit. I'd also recommend removing the burrs at this step.

8. Install the hinges to the panels and the assemblies to the outer surface of the side and front/back rails.

9. Prep and secure the base plate (if desired)

10. I'd do this last, but also prepare and secure the center panel. You can screw into t-nuts located in the top rails, or use double-sided tape like me.

Electronic Components

PCB Assembly

You'll need a PCB or another circuit board to handle the microcontroller-FSR interface. A breadboard works as well, it just may not fit in the arrow cavity. Gerber, drill and assembly files can be found in the ./cam/ directory. I personally used ALLPCB for this one - they currently have a "free prototype" promo. I've also used JLCPCB in the past - they ship fast and boards are good quality. If you want something domestic to the US and like purple, I've had colleagues recommend Oshpark.

I like to hand-solder PCB components but if you like the stencil-solderpaste-reflowoven method, go for it!

1. Tape the board down to a bench. Using flux, solder the SMD current-limiting LED resistors. I used 220 ohm.
2. Solder the SMD LEDs (I used blue). Solder the LED signal resistor. I used 470 ohm.
3. Solder the TH components (FSR header, lights header, capacitor, reset switch, barrel jack)
4. Solder the Pro Micro sockets and the swappable PCB terminals. I do these last since they are plastic and can be melted by the reflow station.
5. Install the microcontroller and fixed current-divider resistors.

Lights Preparation

1. Cut the LED strips as desired. I used 7 LEDs for left and right, 7 LEDs for up, and 8 LEDs for down.
2. Solder 3-wide male headers to the LED strips.
3. Prepare your daisy-chain wires. Please ensure that you don't cross-over the power and data pins! I've heard WS2812B has reverse polarity protection but I can confirm crossing-over the data and power pin will kill at least one LED ;)
4. I'd highly recommend testing out the LEDs on a bench before installing them to confirm the integrity of your joints and crimps.

Final Assembly

1. Secure the PCB to the baseplate or a rail if desired. Prepare and plug the FSR cables into the male headers, as well as the first leg in the lights daisy-chain. I installed my PCB on the far-left hand up arrow cavity.
2. Attach the FSRs to the brackets using double-sided tape. Attach the lights to the inside of the top/bottom and side rails using double-sided tape. Mod the FSRs as desired using double-sided tape. I also used a few zip tie mounts to handle the wires.

Software Instructions

As I didn't write the vast majority of the code, I'll point you first to teejusb's FSR software, and next to the dom-fastled-lights branch of Dominick's fork. I made a couple small modifications to get Dom's light setup to work with four-panel.