Sensitive Audio Power Meter Circuit Diagram

As a follow-up to the simple audio power meter described in [1], the author has developed a more sensitive version. In practice, you rarely use more than 1 watt of audio power in a normal living-room environment. The only time most people use more is at a party when they want to show how loud their stereo system is, in which case peaks of more than 10 W are not uncommon. With this circuit, the dual LED starts to light up green at around 0.1 watt into 8 ohms (0.2 watt into 4 ohms). Naturally, this depends on the specific type of LED that is used.

 
Sensitive Audio Power Meter Circuit diagram:

Sensitive Audio Power Meter Circuit Diagram

 

Here it is  essential to use a low current type. The capacitor is first charged via D1 and then discharged via the green LED. This voltage-doubler effect  increases the sensitivity of the circuit. Above a level of 1 watt, the transistor limits the current through the green LED and the red LED con ducts enough to produce an orange hue.The red colour predominates above 5 watts. Of course, you can also use two separate ‘normal’ LEDs. However, this arrangement cannot generate an orange hue. For any testing that may be necessary, you should use  generator with a DC-coupled output. If there is a capacitor in the output path, it can cause misleading results.

Reference: Simple Audio Power Meter, Elektor July & August 2008.

Read More

Peak Reading Audio Level Meter

This simple schema will indicate peak audio response on an analogue meter, similar to a tape recorders meter. The schema uses an opamp as a non inverting amplifier, but with one addition - a diode in the feedback loop. The schema has a fast response time and slow decay time to indicate peak readings. The 1N4148 diode provides half wave rectification of the input signal, the dc output being smoothed by the 22u capacitor. the capacitor will charge to the peak value of the input waveform, and then discharge via the meter and 18k resistor. I used a meter with a FSD of 150uA, but any meter with a FSD in the range 50-250uA may be used. The discharge time is around a quarter of a second. Increase the 22uF cap for a longer discharge time, or omit altogether to make an instantaneous reading level meter.

This schema will only work with a MOSFET type op-amp, bipolar types i.e. 741 and J-FET op-amps such as LF351 will not work in this schema.

Read More

Sound Level Meter Wiring diagram Schematic

The NE604`s signal-strength indicator section is used, based on an internal logarithmic converter. This enables a lineardecibel scale so that the moving-coil meter (shown in the diagram) can be replaced by a digital instrument. The signal source is assumed to be an electret microphone that converts ambient noise into an electrical signal. Because this type of microphone normally contains a buffer stage, R7, R8, and C13 have been included to provide the supply voltage for this stage. The NE604 delivers an output current (at pin 5) of 0 to 50, which causes a potential difference across R2 + R3 of 0 to 5 V. 

 Sound-Level Meter Circuit Diagram

The input and output signal range is equivalent to a sound range of 70 dB. lb compensate for the effects of temperature changes, the required resistance of 100 KOhmhm is formed by two resistors (R2 and R3) and a diode (Dl). Any ripple remaining on the output voltage is removed by R4/C9/C10 before the output is buffered by IC2. The indicating instrument, here a moving-coil meter, is connected to the output (pin 6) of IC2 via a series resistance, R^ + . 

The preset is adjusted to give full-scale deflection (FSD) for an output voltage of 4 V. Calibrating the meter is a little tricky, unless you have access to an already calibrated instrument. Otherwise, if you know the efficiency of your loudspeaker, that is, how many decibels for 1W at 1 m, you can use that as reference. The scale of the meter can then be marked with the (approximate) value. In any case, the meter deflection must at all times be seen as an indication, not as an absolute value: it was not thought to be worthwhile to add a filter to the schema to enable absolute measurements to be made.

Read More

LM2901 LED bar graph meter

Several LED above and other components used to determine the signal amplifier, when in a state of high and low . If the signal received from the amplifier circuit is high then the LED lamp are lit up everything and more bright LED lamps, but otherwise if the received signal is low then the lights on only one or two , even absent or faint.

To use the circuit you can connec with the output amplifier or speaker output , if there is reinforcing the other in the amplifier , can be connected to the output.

Read More

Audio Power Meter Wiring diagram Schematic

This is an audio power meter simple with this schema, dual LED starts to light green around 0.1 watts into 8 ohms (0.2 watt into 4 ohms). Naturally, this depends on the specific type of LED is used. Despite being a simple equipment he is impressively bench since with a load resistor connected to output of speakers is possible to measure the sound level up, or just check its output.

Audio Power Meter Circuit Diagram

Read More