2 layers70 × 30 mm
Pi485bearer
bvarner/pi485
An open-source TTL UART <-> RS485 converter, intended for a Raspberry Pi or Arduino
25 parts41MIT
2 layers63 × 46 mm
Pi485
bvarner/pi48541An open-source TTL UART <-> RS485 converter, intended for a Raspberry Pi or Arduino
- Size
- 63 × 46 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 31
- Nets
- 22
- Pads
- 85
- Tracks, vias
- 219, 0
- Routed
- Yes
- KiCad
- KiCad 5 (file 20160815)
- Created
- 9 Jan 2017
- Updated
- 10 Nov 2021
Overview
Pi485 is an open-source printed circuit board by bvarner, from the bvarner/pi485 repository on GitHub, published under the MIT licence. It is a 2-layer board of 63 × 46 mm with 31 parts on 22 nets, routed with 219 tracks and 0 vias.
It is built around the MAX485ED, RS485 and NE555, with the BAT43 among its other parts. Its parts include 12 resistors, 5 connectors, 4 capacitors, 4 diodes and 4 transistors. It belongs with the interfaces and adapters boards of this library.
Main components
4
MAX485ED
SOP-8-40℃~+85℃ 1 1 1mA 32 4.75V~5.25V 5Mbps Half-Duplex Transceiver ±8kV SOP-8 RS-485 / RS-422 ICs ROHSHTCRS-485 / RS-422 ICsRS485
SOP-81 1 1.2mA 2.5Mbps 256 5V Half-Duplex Transceiver ±4kV SOP-8 RS-485 / RS-422 ICs ROHSGRRS-485 / RS-422 ICsNE555
SOP-8-20℃~+70℃ 1 1.5mA 200mA 4.5V~15V Adjustable duty cycle oscillation、Reset function、Duty cycle stabilization SOP-8 555 Timers / Counters ROHSGRTimers / Counters
BAT43
DO-204AH-65℃~+125℃ 1 Independent 1V@0.2A 200mA 30V 4A 500nA@25V DO-204AH Schottky Diodes ROHSSTMicroelectronicsSchottky Diodes
README
bearer/README.mdPi485 Bearer Module
Based upon what I learned while creating the Standalone pi485, this board is meant to function as a carrier / bearer for an LC Technologies RS485 module, adding the RX / TX LEDs, power controll, and latched DE / RE pin driving to this very inexpensive and commonly available module.
Unlike the standalone board this layout prioritizes compactness over ease of use for beginners. The trace clearances are tighter and you'll need to remove five surface mount resistors from the RS485 module. In practice, I've found these boards are reasonably easy to produce with a laser printer hot iron transfer.
PCB Layout
is designed to hold these RS485 modules
Schematic
Design Goals
- Add the functions and features of the standalone module in a slightly more compact layout that can accomodate inexpensive 485 modules.
- Leverage the RS 485 module due to the module cost being less than the the cost of a discrete terminal block header, max485 IC, power LED, LED resistor, and filtering capacitors. These boards do shave a couple USD off the cost of UART based RS-485.
- Latch the DE / RE pins on the Max485 based upon the UART TX activity, but allow that to be disabled (force read-only mode)
- Include jumper termination for the A/B lines of the RS485 bus.
For in-depth details on the function of the circuit refer to the Standalone Module README.
Build Instructions
- Start off by customizing the resistor values for your LEDs. I used [http://ledcalc.com/] to help inspire my choices.
- Use KiCad's PCB editor (pcbnew) to customize any footprint changes.
- Print the back copper layer on a laser printer, using glossy photo paper.
- Print the front layers on a laser printer, using glossy photo paper.
- Cut your board (62mm x 30mm)
- Transfer the copper printout using a hot iron and some water.... (youtube reference coming). Touchup with a resist pen if necessary.
- Etch the board.
- Clean the board.
- Tin the board.
- Reflow the board (bake it in an oven).
- Drill the component holes.
- Place & solder components.
- Assemble!
- Remove the 120Ohm resistor (R7), and the 4 10kOhm pull-up resistors (R1 - R4) from the LC Tech 485 Module.
Parts
31| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 270 | Resistors_THT:Resistor_Horizontal_RM10mm | R8, R9, R10, R11 |
| 3 | 2N3904 | TO_SOT_Packages_THT:TO-92_Inline_Wide | Q1, Q2, Q3 |
| 2 | 200 | Resistors_THT:Resistor_Horizontal_RM10mm | R3, R7 |
| 2 | 20k | Resistors_THT:Resistor_Horizontal_RM7mm | R4, R6 |
| 1 | 0.1uF | Capacitors_THT:C_Rect_L7_W2.5_P5 | C2 |
| 1 | 10k | Resistors_THT:Resistor_Horizontal_RM7mm | R12 |
| 1 | 10nF | Capacitors_THT:C_Rect_L7_W2.5_P5 | C3 |
| 1 | 10nF | Capacitors_THT:C_Rect_L4_W2.5_P2.5 | C4 |
| 1 | 10uF | Capacitors_THT:C_Radial_D5_L11_P2 | C1 |
| 1 | 120 | Resistors_THT:Resistor_Horizontal_RM10mm | R5 |
| 1 | 200 | Resistors_THT:Resistor_Horizontal_RM7mm | R1 |
| 1 | 2N3906 | TO_SOT_Packages_THT:TO-92_Inline_Wide | Q4 |
| 1 | 3.9k | Resistors_THT:Resistor_Horizontal_RM10mm | R2 |
| 1 | BAT43 | Diodes_THT:Diode_DO-35_SOD27_Horizontal_RM10 | D4 |
| 1 | MAX485 | Housings_DIP:DIP-8_W7.62mm_LongPads | U2 |
| 1 | NE555 | Housings_DIP:DIP-8_W7.62mm_LongPads | U1 |
| 1 | PWR | LEDs:LED-3MM | D1 |
| 1 | PWR | Pin_Headers:Pin_Header_Straight_1x02 | P2 |
| 1 | RO | Pin_Headers:Pin_Header_Straight_1x02 | P4 |
| 1 | RS485 | Connectors_Terminal_Blocks:TerminalBlock_Pheonix_MPT-2.54mm_2pol | J1 |
| 1 | RX | LEDs:LED-3MM | D3 |
| 1 | Rasperry Pi | Pin_Headers:Pin_Header_Straight_1x05 | P1 |
| 1 | TERM / BIAS | Pin_Headers:Pin_Header_Straight_2x03 | P3 |
| 1 | TX | LEDs:LED-3MM | D2 |
Questions
How big is the Pi485 PCB?
It measures 63 × 46 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Pi485 use?
31 parts, built around the MAX485ED, RS485, NE555 and BAT43. 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 Pi485 KiCad files?
From the bvarner/pi485 repository on GitHub, at the commit this page was made from: the board is standalone/pi485.kicad_pcb. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pi485 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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