2 layers67.4 × 44.8 mm
2 layers71 × 51 mm
Letitrain
bseibold/letitrain5An ESP32 board intended for use with TL-136 level sensors
- Size
- 71 × 51 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 47
- Nets
- 50
- Pads
- 170
- Tracks, vias
- 221, 69
- Pours
- 4
- Routed
- Yes
- KiCad
- KiCad 8.0 (file 20240108)
- Created
- 13 Sep 2024
- Updated
- 13 Sep 2024
Overview
Letitrain is an open-source printed circuit board by bseibold, from the bseibold/letitrain repository on GitHub, published under the MIT licence. It is a 2-layer board of 71 × 51 mm with 47 parts on 50 nets, routed with 221 tracks and 69 vias.
It is built around the ESP32-WROOM-32D, MCP9700B-E/TT and OP07, with the BSS84 and P4SMAJ30CA among its other parts. Its parts include 16 resistors, 11 capacitors, 9 connectors, 4 ICs and 1 diode. It belongs with the sensors and measurement boards and the ESP32 boards of this library.
Main components
5
ESP32-WROOM-32D
-- WiFi Modules ROHSEspressif SystemsWiFi Modules
MCP9700B-E/TT
SOT-23-3-40℃~+125℃ 2.3V~5.5V ±1℃ SOT-23-3 Temperature Sensors ROHSMicrochip TechnologyTemperature Sensors
OP07
SOP-8-20℃~+85℃ -22V~-3V、3V~22V 1 1.8nA 1.8uV/℃ 10nV/√Hz@1kHz 120dB 15pA/℃ 170V/ms 2.7mA 22V 500kHz 60uV 800pA SOP-8 Operational Amplifier ROHSSlkorOperational Amplifier
BSS84
SOT-23-55℃~+150℃ 1 P-Channel 130mA 2.8pF 24.6pF 2V 3.2Ω@5V 300mW 4.7pF 50V 590pC@10V SOT-23 MOSFETs ROHSDiodes IncorporatedMOSFETs
P4SMAJ30CA
SMA(DO-214AC)-50℃~+150℃ 1uA 30V 36.9V 400W@10/1000us 48.4V 8.3A@10/1000us Bidirectional TVS SMA(DO-214AC) ESD and Surge Protection (TVS/ESD) ROHSDIOTECTVS
README
README.mdLet it rain
An ESP32 board intended for use with TL-136 level sensors
Status
Version 1 was built and is running well.
Description
The sensor officially requires 24V, but in practice it runs well down to about 7V. An op-amp is used to limit the current through the sensor and protect the ADC in case of a short-circuit. The bias current of the op-amp has a small but measureable effect, however the voltage measured by the ADC is still very linear to the current through the sensor.
Software
The board can be used with ESPHome, see esphome.yaml for an example configuration.
BOM
-
1x TL-136 differential pressure level sensor
-
1x ESP32-WROOM-32x, can be any variant with the same footprint
-
1x MCP3421 ADC converter
-
1x OP07 Operational Amplifier
-
1x MCP9700B temperature sensor (optional)
-
1x DC-DC module with 780x compatible pins and 3.3V output. Must support 12-18V input
-
MLCC capacitors 0603, X5R or X7R, at least 6.3V
- 5x 100nF (C1, C2, C3, C5, C6)
- 1x 1µF (C2)
- 2x 10µF (C4, C9)
-
MLCC capacitors 0603, X5R or X7R, at least 25V (better 50V)
- 1x 100nF (C7)
- 1x 1µF (C8)
-
1x Polymer capacitor 5.0mm, at least 6.3V, 22µF (C10)
-
1x Polymer capacitor 6.3mm, at least 25V (better 50V), 10µF (C11)
-
1x Bidirectional TSV diode, SMA, voltage slightly above max. supply voltage (D1, optional)
-
1x Pin header 0,1" 1x3 Pins (J3)
-
1x BSS84 P-Channel Enhancement MOSFET (Q1)
-
8x Resistor 0603, 10kOhm (R1, R3, R4, R9, R10, R11, R12, R15)
-
2x Resistor 0603, 47kOhm (R2, R13)
-
3x Resistor 0603, 1kOhm (R5, R6, R7)
-
1x Resistor 0805, 100Ohm, high precision (R8)
-
1x Resistor 0805, 33Ohm (R14)
Optional pin headers are omitted. They are intended for later reuse of spare PCBs.
The enclosure is an RL6115 from Hammond Manufacturing.
Changelog
Version 1.1
- Made more room for DC-DC module, it was a tight fit next to the capacitors
- Rotated TSV diode so that silkscreen is correct for unidirectional diodes
- Changed temperature sensor from MCP9701 to MCP9700B, changed footprint from SC70-5 to SOT23-3
- Some cosmetic fixes
- Marked optional stuff as DNP
Parts
47| Qty | Value | Footprint | References |
|---|---|---|---|
| 8 | 10k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R1, R3, R4, R9, R10, R11, R12, R15 |
| 5 | 100n | Capacitor_SMD:C_0603_1608Metric_Pad1.08x0.95mm_HandSolder | C1, C3, C5, C6, C7 |
| 4 | MountingHole | MountingHole:MountingHole_3.2mm_M3 | H1, H2, H3, H4 |
| 3 | 1k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R5, R6, R7 |
| 2 | 10u | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C4, C9 |
| 2 | 1u | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2, C8 |
| 2 | 47k | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R2, R13 |
| 2 | Conn_01x02 | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J8, J9 |
| 2 | Conn_01x05 | Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Vertical | J1, J2 |
| 2 | Screw_Terminal_01x02 | TerminalBlock_MetzConnect:TerminalBlock_MetzConnect_Type073_RT02602HBLU_1x02_P5.08mm_Horizontal | J4, J7 |
| 1 | 100 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R8 |
| 1 | 10u | Capacitor_SMD:CP_Elec_6.3x5.8 | C11 |
| 1 | 220 | Resistor_SMD:R_0603_1608Metric_Pad0.98x0.95mm_HandSolder | R16 |
| 1 | 22u | Capacitor_SMD:CP_Elec_5x5.8 | C10 |
| 1 | 33 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R14 |
| 1 | BSS84 | Package_TO_SOT_SMD:SOT-23 | Q1 |
| 1 | Conn_01x03 | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J3 |
| 1 | Conn_01x03_Pin | Connector_PinHeader_2.54mm:PinHeader_1x03_P2.54mm_Vertical | J6 |
| 1 | Conn_01x04 | Connector_PinHeader_2.54mm:PinHeader_1x04_P2.54mm_Vertical | J5 |
| 1 | ESP32-WROOM-32D | RF_Module:ESP32-WROOM-32D | U2 |
| 1 | MCP3421A0T-ECH | Package_TO_SOT_SMD:SOT-23-6 | U3 |
| 1 | MCP9700B | Package_TO_SOT_SMD:SOT-23_Handsoldering | U1 |
| 1 | NetTie_2 | NetTie:NetTie-2_SMD_Pad0.5mm | NT1 |
| 1 | OP07 | Package_SO:SO-8_3.9x4.9mm_P1.27mm | U4 |
| 1 | P4SMAJ30CA | Diode_SMD:D_SMA_Handsoldering | D1 |
Questions
How big is the Letitrain PCB?
It measures 71 × 51 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Letitrain use?
47 parts, built around the ESP32-WROOM-32D, MCP9700B-E/TT, OP07 and BSS84. 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 Letitrain KiCad files?
From the bseibold/letitrain repository on GitHub, at the commit this page was made from: the board is letitrain.kicad_pcb and its schematic letitrain.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Letitrain design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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