John WhittingtonI want the acrylic layer to be illuminated but also to act as a serial activity indicator. To ensure that the line signal does not deteriorate, I'm using a op-amp voltage follower as a buffer to drive the LEDs. I've also include a GPIO line to force the LEDs on and disable the activity indicator in-case it is annoying.
Here's a link to the simple circuit on Falstad: Op-amp buffer
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Modern day LED only require a few mA to drive. Not sure if you actually need to buffer the signals. A logic gate or a BJT or a MOSFET is a better buffer for that as you are buffering digital level signals not analog and can incorporate the gating function.
BTW I am building a very dumb terminal. :) The parsing of those ANSI code is going to be fun.
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I was thinking the same thing... A single MOSFET will do.
"very dumb terminal" is a misnomer : in these situations, you have to be extremely smart to afford to be so dumb ;-)
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Thanks Lee. Yes I saw your VGA terminal when I was looking on here to see if someone had done anything similar. I've already ordered the Pi screen otherwise I'd have been tempted to use your board and an old VGA PSOne screen I have. Great project by the way - fascinating and learnt lots reading it! I hope someone can combine the two down the line.
With regards to the buffer. I'm using a couple of 20mA super bright white LEDs in parallel I had kicking around so need something. You're right a MOSFET would be better.
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Thanks. I am glad that someone likes it. RPi path opens up a lot of possibilities - memory, open source code/frameworks, networks, I/O, colours, additional fonts/attributes, graphics etc. that my project can't do.
I am looking forward to seeing your build.
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