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tiny_tnc

Tiny_TNC

Introduction

Tiny TNC is a small interface allowing an Android or other phone with a standard headset jack to interface with a radio with a standard Speaker/Mic jack. In order to work, an external logic input must trigger the “key” to transmit over the air. In it's current revision, the Tiny TNC only passes audio from the phone to the radio. Future versions may allow the phone to receive as well.

Schematic

PCB

Top layer rendering of TinyTNC PCB. The PCB for the Tiny TNC measures 1.5in x .75 in. Features: *3 Pin header spaced at .1“ for Power, Ground, and Key *2 4 pin 4.5mm audio jacks for connecting phone to radio *Opto-Isolated relay circuit for keying radio by 3.3v logic input

Version 1 Bugs

*Silkscreen too small overall. *Silkscreen Diode orientation missing. *Silkscreen “Opto” inside footprint, change orientation marking to dot for simplification. *Silkscreen values instead of “R1” etc. *Alignment holes for audio jacks too small. *Some sort of ground loop problem. *Trim pot is worthless. *Header holes are too big and not wide enough.

Version 2 Fixes

*Silkscreen Improvement *Alignment holes for audio jacks *Remove Trim Pot *Install transformer, 2.2k resistor, and 100 ohm resistor to isolate circuits. *Transformer: 553-1580-5-ND *Update eagle part with bigger pads.

Parts List

{| class=“wikitable” style=“color: green;” !Quantity !Description !Part Number

tiny_tnc.txt · Last modified: 2014/09/04 14:31 (external edit)