This article is a detailed description of how to source and assemble a wonderful little project originally published by Dave NZ1J. It takes a TDOA project documented on this site elsewhere to a new level. The original TDOA, built with a 555 timer, is extremely easy to build, but only gives an audio indication of the direction of the fox.
This project uses a PIC mcu and LED's to indicate the direction to the fox. It requires a bit more hardware to construct, but with a group buy, we were able to source the PCB and parts for around $26 ea.
See this video by Dave NZ1J of a demo ==> https://www.youtube.com/watch?v=mNqUKYkifOo
Below is the schematic and some photos to help with your build.
Note: that the electrolytic Capacitor C2 goes with the ground at the bottom, not according to the symbol, but rather the + sign on the top.
The BOM (Bill of Materials) is the following:
|Item||QTY||Part||Digi-key Part Number||References|
|2||1||14 Pin Socket||ED3114-ND||U1|
|5||2||PIN Diode||568-1922-1-ND||D1, D4|
|6||4||Green LED||C503B-GCN-CY0C0792CT-ND||D5, D6, D8, D9|
|8||4||1k Resistor||1.0KQBK-ND||R3, R6, R13, R17|
|9||8||4.7k Resistor||4.7KQBK-ND||R2, R5, R10, R11, R12, R14, R15, R16|
|10||2||470k Resistor||470KQBK-ND||R1, R4|
|13||3||0.1uF Cap||399-4264-ND||C1, C3, C4|
|14||1||10uF Cap||493-17435-1-ND||C2 (Note: align according to the + symbol up)|
|15||1||1uH Inductor||78F 1R0K-TR-RCCT-ND||L1|
|17||1||9V Battery Clip||36-232-ND||TP+|
The files that were provided by Dave NZ1J to me so that we could get our own PCB's made and PIC chip programmed are available to our club members by contacting me by email at ve6pds @ this domain (caraham.org)
Also, Here is a blog posting: https://aerobatgeek2.blogspot.com/2022/03/blinky-tdoa-rdf-detector.html