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  • JanRose commented on ajoyraman's instructable DIY - USB OSCILLOSCOPE IN A MATCHBOX3 years ago
    DIY - USB OSCILLOSCOPE IN A MATCHBOX

    Hi all, I recently completed this nifty Scope project and am very satisfied with the outcome.With the blessing of Mr Ajoy Raman, I would like to share two "mods" or changes I made, with the hope that others may benefit.1. For the FTDI 232 USB , I used a commercial FTDI break-out board. These are nifty little units and very inexpensive on the net..£3.00 or so. (E-bay, Sparkfun etc)I have included a stock photo, showing the connections. For our application we only need four pins, +5v, 0V (Gnd), RX and TX. It is now very easy to incorporate this little board as a "component" on your PCB layout. (JPG is attached of my PCB layout, from which you can see the general idea.) This then solves the difficulty of soldering directly on a SM chip.(Please note here that the...

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    Hi all, I recently completed this nifty Scope project and am very satisfied with the outcome.With the blessing of Mr Ajoy Raman, I would like to share two "mods" or changes I made, with the hope that others may benefit.1. For the FTDI 232 USB , I used a commercial FTDI break-out board. These are nifty little units and very inexpensive on the net..£3.00 or so. (E-bay, Sparkfun etc)I have included a stock photo, showing the connections. For our application we only need four pins, +5v, 0V (Gnd), RX and TX. It is now very easy to incorporate this little board as a "component" on your PCB layout. (JPG is attached of my PCB layout, from which you can see the general idea.) This then solves the difficulty of soldering directly on a SM chip.(Please note here that the photos of my actual board do NOT match the PCB layout 100%...I made changes to the layout afterwards -- once I saw where I could improve the layout. Never happy are we?)2. The second "change" I made was to use MCP6S21, instead of MCP6S22 as used by Ajoy....The xxx6S21 is a single channel version, and the xxx6S22 a dual channel version.The reason for this is simply because of difficulty I had in sourcing the dual channel in DIP package. The single channel in DIP package I found readily available. No other reason.BUT please take note: When using MCP6S21 (single channel), that Pin 3 on this chip is a V ref input, and for our application needs to be tied to GND. On my PCB layout you will observe pin 3 and 4 joined together to GND respectively.(On the MCP6S22, Pin 3, is isolated and not connected to anything).Don't forget the heatsink..On my PCB layout I have allowed for two mounting holes on the ends of the PIC, offset a little bit toward the MCP's. This allows the heatsink to "pull down" on the MCP's a little, so that the heatsink don't rock on the PIC....I tested the working of my unit on a simple 555 astable, adjustable over a wide range by trimpot. Brilliant results..Finally I built the whole unit into a plastic case, job done.Hope this is of some insight to others..Jan

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