OpenLCB Development Board (AT90CAN ver.) REV B
Update 09 March 2011: Of course, one should always order parts and try placing them on a printout of the PCB before one ever commits to a layout. Naturally, that’s what I did, and indeed I found mistakes in some of the footprints (for example, in the AT90CAN128 footprint—that would have been a problem!). So, please note, I’ve just now uploaded an updated PCB and schematic file; check the date on the schematic, it should read “2011-03-09″. Schematics and PCB layout for my latest project, the OpenLCB Development Board, are now available. I expect to have these off for...
read moreLOLbooster: Input and Fault Detetction Stages
Here’s the final major piece of LOLbooster: input handling, and the logic for detection of a DCC signal and of faults in the booster. This entry completes the first round of the booster’s design, and what remains is to test it (already begun!), and design a PCB for the first prototype. Here’s what I hope to achieve with the input and fault-detection stages. Compliance with NMRA RP-9.1.2 Over-temperature shutdown. Auto-resetting short-circuit detection. Shutdown on loss of DCC signal. Here is the schematic to reference as I discuss how I’ve attempted to meet the...
read moreLOLbooster: Power Supply
Next up: The power supply. LOLbooster includes one 6V regulator for the various logic chips, but where most DIY designs defer track-level voltage regulation to the wall-wart, I’ve opted to include it on the board. Why? Because wall-wart regulators are very good at keeping a steady voltage—at the power jack. But we, finicky modelers that we are, want to keep a steady voltage not at the power jack, but at the rails. Which is an entirely different bucket of colored horses: It means we need regulation on the booster itself. Read on. 1 Nov 2010: Turns out the load regulation circuit below...
read moreLOLbooster: Output Stage (Part 2)
Having selected the LMD18200 as the h-bridge driver for the LOL booster, what remains in designing the output stage is to select a heatsink, and to draw up the auxiliary circuitry.
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