2 layers202.2 × 229.8 mm
Switch boxes panelized
atait/DIPcap
Variable capacitor based on DIP switches ranging from 1nF to 1mF
881 parts
2 layers35.6 × 88.9 mm
Switch boxes
atait/DIPcapVariable capacitor based on DIP switches ranging from 1nF to 1mF
- Size
- 35.6 × 88.9 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 36
- Nets
- 32
- Pads
- 119
- Tracks, vias
- 133, 12
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 7 (file 20221018)
- Created
- 5 Jun 2026
- Updated
- 6 Jun 2026
Overview
Switch boxes is an open-source printed circuit board by atait, from the atait/DIPcap repository on GitHub. It is a 2-layer board of 35.6 × 88.9 mm with 36 parts on 32 nets, routed with 133 tracks and 12 vias.
It is built around the SMXS-08K-TP. Its parts include 27 capacitors, 4 connectors, 4 switches and 1 resistor.
Main components
1README
README.mdDIPcap
A variable capacitor bank built from DIP switches. Six decades of coverage (1 nF to 1 mF) for under $10 to build.
What it is
DIPcap covers six decades with 24 switches arranged in three groups of eight, using a non-standard but deliberate value series that guarantees full range coverage with the optimal number of switches per decade.
The calibration guarantee is the interesting part: even with ±10% tolerance on individual capacitors, some combination of switches will converge on any target value.
Specifications
| Parameter | Value |
|---|---|
| Range | 1 nF – 1,130 µF |
| Max voltage | 0-35V, or ±50V for values < 1 µF |
| Tolerance (dead reckoning) | ±10% |
| Parasitic capacitance (all off) | 28 pF (measured) |
| Output connector | BNC + screw terminal + pin header |
| Cost to build | ~$10/unit (panelized at 8) |
Why these switch values?
The values per decade are 10, 18, 33, 56 (in units of the decade's base, e.g. ×100pF, ×1nF, etc.). This is not a standard E-series but is drawn from E12 so that common components are available.
Full coverage means every value between 10–100 (in normalized units) is reachable within ±10% by some switch combination, and the next lower decade handles the remaining gap.
The choice of four switches per decade follows from a coverage argument:
- 2³ = 8 steps per decade — not enough; the gap between steps (100÷8 = 12.5) exceeds the range of the next lower decade group (0–10)
- 2⁴ = 16 steps per decade — sufficient; four is the minimum power-of-2 count that guarantees full coverage
Instructions
There are two ways to use DIPcap:
- Dead reckoning — set by remainder approximation to within ±10%
- Calibration — engage the series resistor, measure the RC time constant on a scope, and back out the exact capacitance regardless of component tolerance
The instructions are silkscreened on the back of the board.
What's next
DIPresi — the same concept applied to resistance. Binary-weighted resistor bank with DIP switches, covering several decades of resistance.
License
Hardware released under CERN-OHL-S v2. Design files are the Complete Source as defined by the licence.
© 2026 Alex Tait — source location: https://github.com/atait/dipcap
Parts
36| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 3.3 uF | Capacitor_SMD:C_0805_2012Metric | C14, C15, C25, C27 |
| 3 | SMXS-08K | atait-sensors:SW_DIP_SPSTx08_P2.54mm_easyEDA | SW2, SW3, SW4 |
| 2 | 180 nF | Capacitor_SMD:C_0805_2012Metric | C10, C26 |
| 2 | Conn_01x02 | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Horizontal | J1, J3 |
| 1 | 1.0 nF | Capacitor_SMD:C_0805_2012Metric | C1 |
| 1 | 1.0 uF | Capacitor_SMD:C_0805_2012Metric | C13 |
| 1 | 1.8 nF | Capacitor_SMD:C_0805_2012Metric | C2 |
| 1 | 10 nF | Capacitor_SMD:C_0805_2012Metric | C5 |
| 1 | 10 uF | Capacitor_SMD:CP_Elec_5x5.4 | C17 |
| 1 | 100 kΩ | Resistor_SMD:R_0805_2012Metric | R1 |
| 1 | 100 nF | Capacitor_SMD:C_0805_2012Metric | C9 |
| 1 | 100 uF | Capacitor_SMD:CP_Elec_10x10.5 | C21 |
| 1 | 18 nF | Capacitor_SMD:C_0805_2012Metric | C6 |
| 1 | 18 uF | Capacitor_SMD:CP_Elec_6.3x5.7 | C18 |
| 1 | 180 uF | Capacitor_SMD:CP_Elec_10x12.5 | C22 |
| 1 | 2.2 uF | Capacitor_SMD:C_0805_2012Metric | C16 |
| 1 | 3.3 nF | Capacitor_SMD:C_0805_2012Metric | C3 |
| 1 | 33 nF | Capacitor_SMD:C_0805_2012Metric | C7 |
| 1 | 33 uF | Capacitor_SMD:CP_Elec_6.3x5.8 | C19 |
| 1 | 330 nF | Capacitor_SMD:C_0805_2012Metric | C11 |
| 1 | 330 uF | Capacitor_SMD:CP_Elec_10x10.5 | C23 |
| 1 | 5.6 nF | Capacitor_SMD:C_0805_2012Metric | C4 |
| 1 | 56 nF | Capacitor_SMD:C_0805_2012Metric | C8 |
| 1 | 56 uF | Capacitor_SMD:CP_Elec_10x10 | C20 |
| 1 | 560 nF | Capacitor_SMD:C_0805_2012Metric | C12 |
| 1 | 560 uF | Capacitor_SMD:CP_Elec_10x10 | C24 |
| 1 | BNC | Connector_Coaxial:BNC_TEConnectivity_1478204_Vertical | J2 |
| 1 | Conn_01x02 | TerminalBlock_Phoenix:TerminalBlock_Phoenix_MKDS-1,5-2-5.08_1x02_P5.08mm_Horizontal | J4 |
| 1 | SW_Push_DPDT | atait-sensors:SW_DPDT_XKB_SS-3235S-L3 | SW1 |
Questions
How big is the Switch boxes PCB?
It measures 35.6 × 88.9 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Switch boxes use?
36 parts, built around the SMXS-08K-TP. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Switch boxes KiCad files?
From the atait/DIPcap repository on GitHub, at the commit this page was made from: the board is dipcap-src/Switch-boxes.kicad_pcb and its schematic dipcap-src/Switch-boxes.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Switch boxes design in my own project?
Its repository states no licence, so its author keeps all rights: ask atait before reusing the design.
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