Wednesday, October 1, 2014

Minima working with rotary encoder

I have gotten Wayne, NB6M's Minima hardware working with a rotary encoder, thanks to the great work by Eldon, WA0UWH.  Eldon has come up with a clever way to implement an encoder on top of his button structure that only requires a single input pin on the ATMega328 to handle all 7 buttons, plus the rotary encoder.  Check out his blog for all the details.

I am sitting here listening to 75 meters tonight to the group that meets around 3.885 MHz on AM.  Most of these guys are running old AM ham gear.

I have replaced the audio section with an LA4425 power amplifier chip.  This is a 5W amplifier that typically is found in a automotive applications.  It requires very few external parts and has sufficient drive to comfortably drive an unpowered speaker.

I have inserted this circuit between the volume control wiper and the speaker.  Here is a shot of the ugly-style build in Wayne's Minima.

I like the end result, but it actually has a little more gain than it needs for this application.  It is nice not needing to use amplified speakers just to hear the radio.  I have not yet screwed down the component.  It runs cool enough in this application, but the additional heat sink couldn't hurt.

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