+++ /dev/null
-#+TITLE: Battery charger and dual power supply unit
-#+AUTHOR: Svjatoslav Agejenko
-#+LANGUAGE: en
-
-* (document settings) :noexport:
-** use dark style for TWBS-HTML exporter
-#+HTML_HEAD: <link href="https://bootswatch.com/3/darkly/bootstrap.min.css" rel="stylesheet">
-#+HTML_HEAD: <script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
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-#+HTML_HEAD: pre {background-color: #111; color: #ccc;}
-#+HTML_HEAD: </style>
-
-* General
-+ DISCLAIMER: I DO ELECTRONICS AND 3D DESIGN SOLELY AS A HOBBY. THERE
- COULD BE ERRORS THAT CAN RESULT IN ALL KINDS OF DAMAGE. USE THESE
- DESIGNS AT YOUR OWN RISK.
-
-+ This design is released under Creative Commons Zero (CC0) license.
-
-+ Authors:
- - Svjatoslav Agejenko
- - Homepage: https://svjatoslav.eu
- - Email: [[mailto://svjatoslav@svjatoslav.eu][svjatoslav@svjatoslav.eu]]
-
- - Valeria Agejenko
-
-+ See also:
- - [[../../index.html][Other physical projects in this repository]]
- - [[https://www.svjatoslav.eu/projects/][Other projects hosted at svjatoslav.eu]]
-
-* Project description
-I needed dual voltage power supply for my lab that runs on mains
-electricity (wall power) and slowly charges attached 12V Lead-Acid
-battery. Lead-acid battery in turn provides high current when needed
-as well as power in portable situations or when mains electricity is
-not available.
-
-[[file:make.png]]
-
-Power supply provides about 13 Volts and 5 Volts simultaneously.
-
-!!!WARNING!!! I use USB-A connectors for power output, but IT IS NOT
-COMPATIBLE WITH USB DEVICES AND POSSIBLY WITH EXISTING USB CABLES.
-
-Normal USB devices and cables should not be plugged in! It would
-damage device/cable and likely power supply.
-
-I found USB-A connectors to be easily available, cheap, reliable and
-functional, so I re-purposed connector for my own needs but I'm using
-totally incompatible electrical wiring.
-
-[[file:connector%20terminal/USB%20hack.png]]
-
-As seen, it has dual voltage output. Additionally one wire is
-dedicated to data transmission and can be used with [[https://en.wikipedia.org/wiki/1-Wire][1-wire]]
-protocol. Power supply simply passively links all data wires together
-but does not participate in communication.
-
-Power supply uses 3D printed body with lots of holes, for fanless
-cooling.
-
-[[file:body%20and%20covers/body,%201.png]]
-
-Various modules are realized on top of prototype PCBs that slide into
-dedicated rails within the body.
-
-[[file:body%20and%20covers/body,%202.png]]
-
-Like this:
-
-[[file:make,%202.png]]
-
-When cover is closed, it blocks PCB movement:
-
-[[file:body%20and%20covers/cover.png]]
-
-There is still some empty space inside, so why not add dummy cover on
-top that can be replaced later with add-on functionality/expansion
-board/terminal :)
-
-[[file:body%20and%20covers/cover%20cover.png]]
-
-Download:
-+ [[file:body%20and%20covers/body.stl][Body STL file]]
-+ [[file:body%20and%20covers/cover.stl][Big cover STL file]]
-+ [[file:body%20and%20covers/cover%20cover.stl][Small dummy cover on top, STL file]]
-+ [[file:body%20and%20covers/body%20and%20covers.FCStd][Body and covers FreeCAD project]]
-
-* Transformer and AC to DC converter
-
-This is where high voltage from mains electricity enters the system.
-
-Schematic:
-[[file:transformer%20and%20AC%20DC%20converter%20board/schematic.png]]
-
-For safety I kept high voltage section as minimal as possible. That
-is, wall plug runs straight into transformer. Also I used [[https://www.amazon.de/gp/product/B07VGQKM3G/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1][UV hardening
-glue]] for extra safety and isolation on PCB.
-
-Power on/off switch operates on already reduced voltage of about 30
-volts. Power switch is located on [[id:c9a69490-f920-4a31-b32e-b101bfc3d01b][indicator panel]].
-
-[[file:transformer%20and%20AC%20DC%20converter%20board/make,%201.png]]
-
-DC current of about 30 volts is then routed to [[id:65d68227-4bf2-4c4f-b4d3-c390bc6a9c34][Main board]].
-
-[[file:transformer%20and%20AC%20DC%20converter%20board/make,%202.png]]
-
-[[https://www.amazon.de/gp/product/B07RLQH5TR/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1][Single sided prototype PCB is used]].
-
-* Main board
-:PROPERTIES:
-:ID: 65d68227-4bf2-4c4f-b4d3-c390bc6a9c34
-:END:
-
-This is logically main board because it appears to be central hub that
-connects all components. It also houses 2 [[https://www.amazon.de/gp/product/B072MQYJ93/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1][adjustable DC-DC Step Down
-voltage converters]].
-
-[[file:main%20board/main%20board,%201.png]]
-
-High-level schematic of entire device:
-[[file:main%20board/schematic.png]]
-
-As seen from schematic, ~30 volts DC from transformer board is routed
-into first step-down converter that reduces it to about 15V. Reduced
-voltage is then directed to [[id:afc22d23-9bc4-421c-9cac-e0ce34bd36bc][Current limiter circuit]]. Current limiter
-loses about 2 volts. Now we have current and voltage limited power at
-about 13 volts. This power is used to charge connected 12V Lead-Acid
-battery. Also the same power is routed to [[id:e33940bd-652f-4ec0-b53b-1c03e16941c8][connector terminal]] to be
-consumed by connected devices.
-
-As seen from this schematic, device is not meant to provide high
-current for long periods of time. Instead it gets comparatively
-limited current to charge the battery and feed devices with low
-current requirements. Occasional current spikes are backed up by
-battery that stays in use-changing mode.
-
-Also about 13V output voltage is approximate and depends on connected
-battery charge level.
-
-Second Step-Down converter reduces voltage even further to quite
-precisely 5V DC. This resulting voltage is also routed to [[id:e33940bd-652f-4ec0-b53b-1c03e16941c8][connector
-terminal]].
-
-Both 13V and 5V lines are also routed to [[id:c9a69490-f920-4a31-b32e-b101bfc3d01b][indicator panel]] for
-monitoring.
-
-There is single on/off switch. In off position, it disconnects battery
-and transformer from the system effectively powering everything down.
-
-On schematic above, some wires are annotated with numbers from 1
-to 13. This corresponds to output pins on the board.
-
-[[file:main%20board/main%20board,%202.png]]
-* Current limiter
-:PROPERTIES:
-:ID: afc22d23-9bc4-421c-9cac-e0ce34bd36bc
-:END:
-
-Schematic:
-[[file:current%20limiter/schematic.png]]
-
-Simple LM317 based current limiter is used. I used 4.7 ohm
-resistor. It provides about 265 milliamps of current. See [[http://www.reuk.co.uk/wordpress/electric-circuit/lm317-current-calculator/][calculator]].
-
-[[file:current%20limiter/current%20limiter,%201.png]]
-
-Thermal paste below and UV hardening glue on top is used to attach
-LM317 to the heatsink. There is also jumper-like solution on top
-right. This is handy to attach multimeter tap to verify/monitor
-current during initial device calibration.
-
-If attached battery is really empty, significant voltage drop can
-occur in LM317. Heatsink is needed to dissipate that power.
-
-[[file:current%20limiter/current%20limiter,%202.png]]
-
-Note: resistor gets hot too.
-
-* Indicator panel
-:PROPERTIES:
-:ID: c9a69490-f920-4a31-b32e-b101bfc3d01b
-:END:
-
-[[file:indicator%20panel/indicator%20panel,%201.png]]
-
-Basically 2 digital DC voltmeters and main on/off switch.
-
-[[file:indicator%20panel/indicator%20panel,%202.png]]
-
-Download:
-
-[[file:indicator%20panel/indicator%20panel.png]]
-
-+ [[file:indicator%20panel/indicator%20panel.stl][STL file]]
-+ [[file:indicator%20panel/indicator%20panel.FCStd][FreeCAD project]]
-
-* Connector terminal
-:PROPERTIES:
-:ID: e33940bd-652f-4ec0-b53b-1c03e16941c8
-:END:
-
-Schematic:
-[[file:connector%20terminal/schematic.png]]
-
-As seen above, most of the USB connectors are used to deliver dual
-power output and 1-wire data connectivity, except one on the bottom
-right. This is used to attach 12V battery. Some capacitors are thrown
-in as well to stabilize against smaller current spikes.
-
-Electrically schematic is realized using smaller prototype PCBs.
-
-[[file:connector%20terminal/make,%201.png]]
-
-
-Those PCBs are wired to central small PCB that acts as a hub:
-
-[[file:connector%20terminal/make,%202.png]]
-
-PCBs are held together by being sandwiched between front panel:
-
-[[file:connector%20terminal/front%20panel.png]]
-
-and smaller back-end plate:
-
-[[file:connector%20terminal/back%20panel.png]]
-
-Result:
-
-[[file:connector%20terminal/make,%203.png]]
-
-
-Download:
-+ [[file:connector%20terminal/front%20panel.stl][front panel STL]]
-+ [[file:connector%20terminal/back%20panel.stl][back panel STL]]
-+ [[file:connector%20terminal/connector%20terminal.FCStd][FreeCAD project]]
-
-* Calibration
-
-Since device uses adjustable step-down modules, these need to be
-calibrated to provide correct output voltage. It is important that
-battery receives proper charging voltage otherwise either no charging
-occurs or battery starts gassing out and gets destroyed.
-
-See here for more details: https://www.powerstream.com/SLA.htm
-
------
-
-Happy building! :)
projects / physical.git / blobdiff