|
Simple electronic S-meter |
|
|
|
I have tried an electronic S-meter developed by Mike Martell N1HFX and this is my favourite circuit. It is a low cost alternative to panel meters. Although this S meter has only 4 LEDs, it can be easily enhanced to any number of LEDs.
This circuit is really a low-level voltage meter and could even be used for audio purposes. Pins 4, 6, 8 and 10 of IC1 are connected together and are connected to the AGC line or the input to the last audio stage.
Adjust R9 for the desired sensitivity. Resistors R5 through R9 provide voltage references for each of the OP Amps. R5 has the lowest reference voltage while R8 has the highest. As the input voltage exceeds each OP amp's reference voltage, the output goes low causing the corresponding LED to light. R1 through R4 drops the voltage to allow the use of standard 1.5 volt LED's. If you absolutely have to use 12 volt LEDs then eliminate resistors R1 through R4.
Enhancement to more LEDs is done by resistor bridge and more ICs. If non-linear scale is needed, change R5 - R8 values depending to the scale you want.
|
