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Two things became very clear to me once I got into the detailed testing of the project: I have completely stuffed up the grounding and layout of the components.  In particular the Switching Regulator has a convoluted route back to Vin -ve and the route it does have takes it right under the sensitive components (until I bodged in a couple of wires).  Layout is too far apart for many components, including the bypass and decoupling caps, and non-conducive to managing noise.  There a ...
EDITS: 21/07/19 - added a PDF of the schematic             11/08/19 - updated navigation links   Introduction My intention was to document, in some detail, testing of the power supply with both a 10 Ohm and 5 Ohm load (to drive the current from 0A to 3A.)  To summarise, I’m seeing a number of problems - see later - and I thought I’d document where I’ve got to as I need to do some thinking about this.  See my ...
EDITS: 17/07/18 - updated links   It’s been some time since I last posted on this project because I’ve been busy with the museum and away for a few days.  It only took about 4 days to get the new PCBs manufactured and delivered from China, which is pretty amazing.  As it turns out, it was a bit of a blessing in disguise making the mistakes on the PCB as it gave me time to create the 4Duino interface which has proved very useful here.   I soldered up the Control ...
Edits: 15/6/19 - embedded YouTube video rather than just have a link.            9/7/19 - updated link to part 10   Whilst waiting for the new PCBs to be manufactured and delivered, I started on the Interface for monitoring the supply.  I prototyped this in Part Seven, so I know the fundamental code works.  To create the interface I want requires the use of 4D Systems Workshop 4 IDE so that I can make use of the graphical environ ...
EDITS:    14/6/19 - updated navigation link                27/6/19 - updated post for built power stage Prototyping Board I'm waiting for new PCBs to come before cracking on with this but whilst I'm waiting I will work on the 4Duino interface and I created this prototyping board.  The PCBs are the old ones (but don't change in size or appearance much).  I've kapton taped the switch as well as used hea ...
EDITS: 6/11/19 - Fixed broken links; Added link to Part Eight.   I'm going with an Arduino interface to display voltage, current, power and temperatures.  In the first version this will be display only - controls for setting voltage and current limits are manual (10 turn potentiometers) - but can be extended with more functionality in the future.   The 4Duino from 4D systems is an Arduino compatible (Leonardo I believe) device with a built in touch-enabled LCD, wifi and SD card ...
The KiCad files are available on Github. Custom footprints and custom symbols can be downloaded from Github.  You’ll need to add a link to these in KiCad’s preferences so that the projects don’t error when opening.  I’m assuming that if you have KiCad you know how to do that, but please ask below.   There are two projects, one for the Power Stage and one for the Control Stage (actually called Power Supply.)   I have produced precisely zero PCB desig ...
EDITS: 6/11/19 - Fixed broken links; Updated calculations for LM7805   Thermal Calculations The biggie!  In theory, the design should run without generating high temperatures but I want to be sure.  I have calculated power dissipation and temperature rises for key components both at ambient and with a heatsink attached.  I’m aware that ambient really reflects the ‘enclosure’ temperature, mitigated by passive ventilation (vents) and active ventilation (fan), ...
EDITS: 6/11/19 - Fixed broken links   LTC1624 Calculations I have spent a fair bit of time trying to get a good understanding of this part of the design (and to be honest, I’m still working on that!).  I have used the data sheet to make the necessary calculations for the selection/confirmation of various components in the design as well as the power dissipation of MOSFET and Schottky Diode.   Rsense selection This is the resistor used as an external current sense.  Calc ...
EDITS: 11/6/19 - Fixed broken links   As part of the analysis I was doing into the design and selection of parts, I ran up some calculations.  I also validated the thermal characteristics of the key parts to see how likely they were to need heatsinking.  I’ve captured, and attached, these in an Excel spreadsheet if you want to take a look and put it on Github.  There are two attachments now: the first, original one, and the second, updated one - see the comment I've po ...
EDITS: 11/6/19 - fixed broken links   LTSpice files are available on Github.  You will need to put the directory ‘Andrews Parts’ in the sym directory for LTSpice library but you can delete it when finished.  It’s just used to hold the .asy file for the LM7805.   I had to learn how to use the application which isn’t the most intuitive, especially the Mac OS version, but I found it extremely useful and I’m really pleased with what I achieved. There ...
EDITS: 11/6/19 - Fixed broken links; Changed schematic for low voltage supply following change of LM7805              21/7/19 - Attached a PDF containing the whole schematic   The first step in producing this was to install and learn KiCad!  I did start out with Omnigraffle - just a tool I had - but Frank Milburn posted a good response on one of my questions so I switched over and spent a bit of time picking it up.   KiCa ...
EDITS: 6/6/19 Updated navigation links.             11/6/19 Added link for part 8; fixed broken links.             14/6/19 Updated navigation links.              9/7/19 Updated navigation links.             17/7/19 Updated navigation links.       ...
EDIT: 6/6/18 - fixed broken links; updated link to part 7   The BOM is in the attached spreadsheet (and Github) but I haven’t copied it here: I suspect that it’s only of interest to those people who want to download it.  There are two copies: the original parts list, and the updated one with a DC-DC Switching Regulator swapped for the LM7805.   Wherever possible I selected parts available from uk.farnell or cpc.farnell but they don’t carry everything needed so ...