2 layers66 × 99.1 mm
2 layers52.1 × 65.4 mm
Continuity tester
vpatkov/continuity-tester2Ultra low-voltage, low-current, and fast continuity tester
- Size
- 52.1 × 65.4 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 38
- Nets
- 39
- Pads
- 125
- Tracks, vias
- 238, 36
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 1 Jul 2023
- Updated
- 8 Jun 2026
Overview
Continuity tester is an open-source printed circuit board by vpatkov, from the vpatkov/continuity-tester repository on GitHub. It is a 2-layer board of 52.1 × 65.4 mm with 38 parts on 39 nets, routed with 238 tracks and 36 vias.
It is built around the ATMEGA88PA-AU, MCP6V61-E/OT and TLV431ASN, with the BAV199, BAS316 and CR2032 among its other parts. Its parts include 17 resistors, 6 capacitors, 4 diodes, 3 ICs and 3 connectors. It belongs with the AVR (ATmega, ATtiny) boards of this library.
Main components
9
ATMEGA88PA-AU
TQFP-32(7x7)-40℃~+85℃ 1.8V~5.5V 10bit 1KB 20MHz 23 512Byte 8 Bit 8KB AVR Built-in FLASH TQFP-32(7x7) Microcontrollers (MCU/MPU/SOC) ROHSMicrochip TechnologyMicrocontrollers (MCU/MPU/SOC)
MCP6V61-E/OT
SOT-23-5-40℃~+125℃ 0.45V/us 1 1MHz 1pA 8uV Zero drift / auto-zero、Reverse-phase input protection SOT-23-5 Precision Op Amps ROHSMicrochip TechnologyPrecision Op Amps
TLV431ASN
TSOP-5-1.5mm-40℃~+85℃@(Ta) 1.24V~16V 150nA 20mA 80uA Adjustable Parallel ±1% TSOP-5-1.5mm Voltage Reference ROHSonsemiVoltage Reference
BAV199
SOT-231 Pair Series Connection 1.25V@150mA 160mA 4A 5nA@75V 85V SOT-23 Diodes - General Purpose ROHSNexperiaDiodes - General Purpose
BAS316
SOD-3231.25V@150mA 100V 250mA 400mW 4A 4ns 500nA@80V Independent SOD-323 Switching Diodes ROHSNexperiaSwitching Diodes
CR2032
-- Unclassified goods ROHSMaxellUncategorisedIRLML6402
SOT-23-55℃~+150℃ 1 P-Channel 1.3W 110pF 12nC 145pF 20V 3.7A 400mV 633pF 65mΩ@4.5V P-Channel SOT-23 MOSFETs ROHSGuangdong HottechMOSFETsPESD3V3U1UA
SOD-323ESD And Surge Protection (TVS/ESD)TECH PUBLIC
PKLCS1212E4001-R1
SMD,12x12mm-20℃~+70℃ 12mm 12mm 3mm 4kHz 84dB Passive (Externally Driven) Piezoelectric ±12.5V SMD,12x12mm Buzzers ROHSMurataBuzzers
README
README.mdContinuity Tester
Ultra low-voltage, low-current, and fast continuity tester.
-
Open circuit voltage is 100 mV, short circuit current is 100 μA. No risk of damaging sensitive components. Keep semiconductor junctions closed. Multimeters usually apply much higher voltage and current to the probes (and not always specified).
-
Resistance-dependent beeper tones with chromatic steps. Allows to differentiate resistance by ear. The range is 0–10 Ω with 1 Ω steps. Multimeters usually have a pretty big threshold and require you to look at the screen to read the resistance, e.g., to catch a bad connection.
-
Detects shorts of 150 μs. Minimal beep duration is 100 ms (latching). Suitable for finding connections by sweeping and brushing without the risk of missing a beep. Gold-plated probes are recommended.
-
Inverted mode. If probes are shorted during power-on, the tester turns into inverted mode: silent for < 10 Ω, beeps otherwise. Beeps are still latched for 100 ms to not miss them. If normal mode is to find shorts, inverted mode is to find opens, e.g., intermittent bad connections, even very brief.
-
Auto-hold the minimal resistance (in normal mode). Helps against unstable contacts, e.g., on dirty, oxidized, or lacquered boards. The hold resets when the resistance becomes greater than 10 Ω.
-
200 working hours on a single CR2032 cell. The tester consumes approximately 1 mA. After 5 minutes of inactivity it turns off automatically.
-
30 V continuous input protection. The tester should not be used on a powered circuit, but just in case. Also saves against charged capacitors. The input impedance of the tester is 1 kΩ, so the risk of damaging an accidentally powered circuit under test is also low.
-
Quick self-test on power-on. Ensures the ADC, reference, and battery are fine. In case of failure, the tester beeps shortly two times and turns off.
Comparison with some popular multimeters
| Multimeter | Open circuit voltage, V | Short circuit current, mA | Capture time, ms | Threshold, Ω |
|---|---|---|---|---|
| Keysight 34461A | (9.4) | 1 | ≤ 3.3 | 10 |
| Keysight 34401A | (7.0) | 1 | ≤ 3.3 | 1–1000 (adjustable) |
| Keysight U1282A | ≤ 2.7 | (1) | ≤ 1 | 25±11 |
| Fluke 8846A | (6.2) | 1 | ≤ 3.3 | 1, 10, 100, 1000 (selectable) |
| Fluke 45 | ≤ 3.2 | 0.7 | ≤ 0.05 | 30 |
| Fluke 117 | ≤ 2.7 | ≤ 0.35 | ≤ 0.5 | 20–250 (hysteresis) |
| Fluke 179 | ≤ 8.0 | ≤ 1.1 | ≤ 0.25 | 25–250 (hysteresis) |
| Fluke 289 | 5 | 1 | ≤ 1 | 40 (depends on range) |
| Fluke 87V | ≤ 7.9 | 1 | ≤ 1 | (?) |
| Brymen BM235 | (1.7) | (0.16) | ≤ 15 | Between 30 and 480 |
| Brymen BM869s | (2.9) | (0.38) | ≤ 0.1 | Between 20 and 200 |
| Hioki DT4256 | ≤ 1.8 | 0.2 | ≤ 0.5 | 20–245 (hysteresis) |
| Hioki DT4282 | ≤ 2.5 | 0.64 | ≤ 10 | 20, 50, 100, 500 (selectable) |
| Rigol DM3068 | ≤ 8 | 1 | ≤ 3.3 | 1–2000 (adjustable) |
| Siglent SDM3065X | ≤ 8 | 1 | ≤ 3.3 | 1–2000 (adjustable) |
| This tester | 0.1 | 0.1 | ≤ 0.15 | 1–10 (different tones) |
Values in parentheses are not specified.
Parts
38| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 10k | Resistor_SMD:R_0603_1608Metric | R1, R9, R13, R15, R16 |
| 4 | 100n | Capacitor_SMD:C_0603_1608Metric | C2, C4, C5, C6 |
| 3 | 1k | Resistor_SMD:R_0603_1608Metric | R5, R6, R14 |
| 2 | 100 | Resistor_SMD:R_0603_1608Metric | R7, R10 |
| 2 | BAV199 | Package_TO_SOT_SMD:SOT-23 | D1, D2 |
| 1 | 0 | Resistor_SMD:R_0603_1608Metric | R17 |
| 1 | 1.1k | Resistor_SMD:R_2512_6332Metric | R4 |
| 1 | 10 | Resistor_SMD:R_0603_1608Metric | R11 |
| 1 | 100p | Capacitor_SMD:C_0603_1608Metric | C1 |
| 1 | 12.4k | Resistor_SMD:R_0603_1608Metric | R3 |
| 1 | 1n | Capacitor_SMD:C_0603_1608Metric | C3 |
| 1 | 30k | Resistor_SMD:R_0603_1608Metric | R12 |
| 1 | 5.1k | Resistor_SMD:R_0603_1608Metric | R2 |
| 1 | 560k | Resistor_SMD:R_0603_1608Metric | R8 |
| 1 | ATmega88PA-A | Package_QFP:TQFP-32_7x7mm_P0.8mm | U3 |
| 1 | AVR ISP | Connector_PinHeader_2.54mm:PinHeader_2x03_P2.54mm_Vertical | J3 |
| 1 | BAS316 | Diode_SMD:D_SOD-323 | D3 |
| 1 | Banana | Connector:Banana_Cliff_FCR7350B_S16N-PC_Horizontal | J2 |
| 1 | Banana | Connector:Banana_Cliff_FCR7350R_S16N-PC_Horizontal | J1 |
| 1 | Button | Button_Switch_THT:SW_PUSH_6mm | SW1 |
| 1 | CR2032 | Battery:BatteryHolder_Keystone_3034_1x20mm | BT1 |
| 1 | IRLML6402 | Package_TO_SOT_SMD:SOT-23 | Q1 |
| 1 | MCP6V61 | Package_TO_SOT_SMD:SOT-23-5 | U2 |
| 1 | PESD3V3U1UA | Diode_SMD:D_SOD-323 | D4 |
| 1 | PKLCS1212E4001 | Buzzer_Beeper:Buzzer_Murata_PKLCS1212E | BZ1 |
| 1 | TLV431 | Package_TO_SOT_SMD:SOT-23 | U1 |
The 37 most common of 38 parts.
Questions
How big is the Continuity tester PCB?
It measures 52.1 × 65.4 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Continuity tester use?
38 parts, built around the ATMEGA88PA-AU, MCP6V61-E/OT, TLV431ASN and BAV199. 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 Continuity tester KiCad files?
From the vpatkov/continuity-tester repository on GitHub, at the commit this page was made from: the board is pcb/ct.kicad_pcb and its schematic pcb/ct.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Continuity tester design in my own project?
Its repository states no licence, so its author keeps all rights: ask vpatkov before reusing the design.
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