|
|
PTT Switch Box
 After
finishing the BM-800 PC Microphone
project, I wanted to be able to use
it with my portable ham radio transceiver as well, and so some kind of
interface would be required that incorporates a PTT switch. I also
decided that it should have an internal battery to power the microphone
instead of using 5 volts from a USB port, so that it's a completely
'stand alone' unit. As the BM-800 is designed to work on 5
volts, I used a 4 x AA battery box mounted on the inside of the front
panel supplying 6 volts. The preamp in the microphone only consumes
about 1.5mA so the battery should last several months with intermittent
use. Mostly though, this project is more about the different
connection cables and their pinouts.
 The switch box
consists of two 5 pin DIN sockets, one being the input from the microphone and the
other an output to a PC or radio. There are also two
latching push switches,
one is the PTT of course and the other is an on-off switch to cut power to the
battery when not in use, coloured red and green
respectively.
A 10uF capacitor was added to block any DC voltage on the mic input of
the radio (there to power electret mic capsules) and is not used when a PC is connected. The pinouts for the
DIN sockets are such that if the plugs are accidentally reversed no damage will occur.
 Pinouts for PTT switch box to microphone.
 Pinouts for PTT switch box to PC line input.
 Pinouts for PTT switch box to Baofeng or similar type radio.
 Pinouts for PTT switch box to Anytone AT-778UV radio.
 The PTT switch box is housed in an extruded aluminium enclosure that matches the BM-800 microphone.
|