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SmoothBus-T2A

theHeathLee·SmoothBus-T2A·hardware/SmoothBusT2A.kicad_pcb

SmoothBus-T2A PCB layout, top view — open source AVR/Arduino board by theHeathLee

About the SmoothBus-T2A PCB

SmoothBus-T2A is an open source AVR/Arduino PCB design by theHeathLee, published on GitHub. It is a 2-layer board measuring 31 × 31.8 mm, with 14 components from 10 distinct parts.

Its main chip is the ATTINY85-20SU, from the AVR/Arduino family. Other key parts include the MC7805BDTRKG. By type, the board carries 6 resistors, 3 diodes, 2 ICs, 2 connectors and 1 capacitor.

From the project

analog to digital to analog fuel gauge for VW Bus ⛽

An adaptation of the SmoothBus project for the early VW bay window bus (Type 2A). Replaces the original fuel gauge mechanism with a servo-driven needle controlled by an ATTiny85 microcontroller, providing smooth movement and a low-fuel LED warning.

- Smooth servo motion — moves in 1° steps with a moving average filter (35-sample window) to eliminate sender noise - Low-fuel LED warning when the sender reads in the reserve range - Boot sweep sequence (empty → full → empty) to verify servo operation - Compact PCB (~32mm × 14mm) designed to fit within the original gauge enclosure - 3D-printable…

SmoothBus-T2A, from the project README
From the project README

Main components on the SmoothBus-T2A

ATTINY85-20SUMC7805BDTRKG

SmoothBus-T2A bill of materials (BOM)

14 components, 10 distinct parts.

QtyPartRefs
1
ATTINY85-20SU
U1
1
MC7805BDTRKG
U2
1
BM03B-SRSS-TB_LF__SN_
J2
1
SM03B-SRSS-TB_LF__SN_
J4
2
OF-SMD3528WC
D1, D2
1
WL-SMCD_0603
D3
1
EEE1AA101WAR
C1
1
R100
R1
3
R300
R2, R3, R4
2
R10k
R5, R6

SmoothBus-T2A design files

The KiCad project lives in the theHeathLee/SmoothBus-T2A repository on GitHub; these links point at the commit this page was built from.

SmoothBus-T2A: common questions

What microcontroller does the SmoothBus-T2A use?

The SmoothBus-T2A is built around the ATTINY85-20SU, from the AVR/Arduino family.

How big is the SmoothBus-T2A PCB?

The SmoothBus-T2A measures 31 × 31.8 mm, has 2 copper layers and is 1.6 mm thick.

How many components are on the SmoothBus-T2A?

14 components, from 10 distinct parts. The full bill of materials is listed on this page.

Where can I download the SmoothBus-T2A design files?

From the theHeathLee/SmoothBus-T2A repository on GitHub, which has the KiCad layout and the schematic; the links under Design files point to each one.

Can I use the SmoothBus-T2A design in my own project?

The repository has no license, so all rights stay with theHeathLee. Use it as a reference, and ask the author before reusing the design.

Can I test firmware for the SmoothBus-T2A without the hardware?

Yes. HardLabs builds a simulation of the board from its netlist and BOM, so you can run and debug AVR/Arduino firmware against it before you order a PCB.

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