‰  NOW 30 WPM  ‰  TEXT IS FROM MAY 2015  QST  PAGE 32 ‰

ON THE MONITOR.  PICAXE PROVIDES A CABLE WITH A SERIAL CONNECTOR OR A USB
CONNECTOR, AND A 1/8 INCH STEREO AUDIO PLUG.  TYPE THE PROGRAM INTO A TEXT
FILE AND PASTE INTO THE PICAXE EDITOR TO PROGRAM THE PICAXE 18M2.  THE
SAVED PICAXE PROGRAM BECOMES A BAS FILE.  SWITCH S1 SELECTS EITHER AN
INTERNAL 9 V BATTERY OR THE EXTERNAL BATTERY THAT THE CIRCUIT MONITORS.
THE WATTMETER FUNCTION REQUIRES THE INTERNAL BATTERY.  WHEN THE VOLTMETER
USES INTERNAL POWER ITS INPUT RESISTANCE IS MORE THAN 15 K.  SELECT THE
VOLTMETER OR WATTMETER FUNCTION WITH SWITCH S2.  THE WATTMETER REQUIRES A
PEAK VOLTAGE FROM AN RF DETECTOR AT ITS INPUT.  FIGURE 2 SHOWS THE RF
DETECTOR AND ITS CALIBRATING POTENTIOMETER R11.  THE VOLTMETER AND
WATTMETER FUNCTIONS USE TWO DIFFERENT PROGRAMS.  WHEN YOU SELECT THE
WATTMETER, S2 ALSO PULLS DOWN THE NORMALLY HIGH PIN C2 OF THE PICAXE TO
SELECT THE WATTMETER PROGRAM.  MY MONITOR CIRCUIT FIGURE 1 HAS AN INPUT
VOLTAGE DIVIDER TO SCALE DOWN THE INPUT TO THE 0 5 V LEVEL REQUIRED AT THE
ADC INPUT PIN C1.  THE PICAXE 18M2 PROVIDES A 10 BIT ADC USING THE 5 V
SUPPLY AS A REFERENCE, SO 5 V INPUT BECOMES DECIMAL 1024 WHEN CONVERTED.  A
‰  END OF 30 WPM TEXT  ‰  QST DE W1AW  ƒ