X-Git-Url: http://www2.svjatoslav.eu/gitweb/?p=physical.git;a=blobdiff_plain;f=misc%2F12V%20Lead-Acid%20battery%20changer%20and%20terminal%2Findex.org;fp=misc%2F12V%20Lead-Acid%20battery%20changer%20and%20terminal%2Findex.org;h=36baa7fabd7d5435ca096802e2605a5d1766c163;hp=0000000000000000000000000000000000000000;hb=19af345819ef415d6685de55eb218367baa47b33;hpb=365f953bb4a379fb74f7ec49244484f75362c684 diff --git a/misc/12V Lead-Acid battery changer and terminal/index.org b/misc/12V Lead-Acid battery changer and terminal/index.org new file mode 100644 index 0000000..36baa7f --- /dev/null +++ b/misc/12V Lead-Acid battery changer and terminal/index.org @@ -0,0 +1,252 @@ +#+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: +#+HTML_HEAD: +#+HTML_HEAD: +#+HTML_HEAD: + +* 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! :)