Wiring Circuit: meter

Showing posts with label meter. Show all posts

Thursday, November 20, 2014

Audio VU Level Meter Circuit with LM324

The 1K resistors in the circuit are capital so that the LEDs about-face on at altered audio levels. There is no acumen why you cant change these resistors, although annihilation aloft 5K may account some of the LEDs to never about-face on. This ambit is calmly abundant with added op-amps, and is not bound to use with the LM324. Pretty abundant any op-amp will assignment as continued as you attending up the pinouts and accomplish abiding aggregate is appropriately connected.

The 33K resistor on the schematic is to accumulate the arresting ascribe to the ambit at a low level. It is absurd you will acquisition a 33K resistor, so the abutting you can get should do. The amount of this resistor may charge to be changed, so it is best you breadboard this ambit afore absolutely amalgam it on PCB. The ambit in its accepted anatomy will acquire band akin inputs from sources such as the aux out on a Hi-Fi, all admitting could be calmly adapted to acquire apostle inputs.

The audio + is affiliated to the capital absolute rail, while the audio - is acclimated for arresting input. The 50k pot can be acclimated to alter the acuteness of the circuit.

Wednesday, September 24, 2014

Loudspeaker Impedance Meter

Also suitable for Headphones Operates in conjunction with a DVM . A simple Impedance Meter can be useful to measure the actual impedance a loudspeaker or headphone is presenting @ 1kHz standard frequency. The circuit, designed on request, relies on an earlier design (Spot-frequency Sine wave Generator) to obtain a stable, low distortion 1kHz sine wave avoiding the use of thermistors, bulbs or any special amplitude-limiting device. The sine wave output, after some amplitude setting obtained by means of P1, is sent to the device under measurement through a resistor.

A regulated supply is necessary to obtain a stable output waveform. D1 and D2 force IC1 to deliver 6.2V output instead of the nominal 5V. The measurement is done in two stages: as a constant current supply of the device under test is necessary, this can be set at first by adjusting P1 and measured across the series resistor (R7 or R8, depending on the impedance value to be measured); then, the meter is switched across the device under test and the actual impedance will be read directly on the meter display.

Circuit diagram:

Loudspeaker Impedance Meter Circuit Diagram

Parts:

P1_______________4K7  Linear Potentiometer
R1______________12K  1/4W Resistor
R2_______________2K2 1/4W Resistor
R3_______________1K  1/2W Trimmer (Cermet)
R4_______________1K5 1/4W Resistor
R5_______________4K7 1/4W Resistor
R6_______________3K3 1/4W Resistor
R7_____________100R  1/4W Resistor (See Notes)
R8_______________1K  1/4W Resistor (See Notes)
R9_______________1K  1/4W Resistor (Optional)
C1______________22nF  63V Polyester Capacitor
C2_____________330nF  63V Polyester Capacitor
C3______________22µF  25V Electrolytic Capacitor
D1,D2_________1N4148  75V 150mA Diodes
D3_______________3mm  Red LED (Optional)
Q1,Q2,Q3_______BC550C 45V 100mA Low noise High gain NPN Transistors
IC1____________78L05   5V 100mA Regulator IC
SW1,SW2_________SPDT Toggle or Slider Switches
SW3_____________SPST Toggle or Slider Switch
B1________________9V  PP3 Battery

Clip for PP3 Battery

Circuit set-up using an oscilloscope:

Connect the oscilloscope in place of the DVM and rotate P1 fully clockwise.
Short the speaker output and adjust R3 to obtain a sine wave of about 2.2V peak-to-peak amplitude.

"By ear" circuit set-up:

Connect a small loudspeaker or one of the two earpieces forming a pair of headphones to the circuit output and rotate P1 to obtain a moderate output sound level.

Carefully adjust R3 until the output sound will stop; then turn back the trimmer very slowly and stop adjusting immediately when the sound will start again.

Measurement:

Connect a Digital Voltage Meter set to 200mV ac range to the DVM output terminals
Connect the device under test to the Speaker terminals
Switch SW1 in the position towards R7 if the impedance value to be measured is below 100 Ohm or towards R8 if above
With SW2 in the "Set" position power-on the circuit by means of SW3
Adjust P1 in order to read exactly 100.0mV on the DVM display
Switch SW2 in the "Measure" position and read directly the loudspeaker or headphones impedance value on the DVM display, e.g. 8.5mV = 8.5 Ohm
Please note that when measuring devices with impedance values above 100 Ohm (SW1 set towards R8), the decimal point in the DVM reading must be ignored. E.g. if the display shows 70.5mV, the impedance will be 705 Ohm

Notes:

For very precise measurements use 1% or 2% tolerance resistors for R7 and R8.
D3 LED pilot light and its current limiting resistor R9 are optional.

Sunday, May 5, 2013

New Photo Meter Assesses Ambient Light Schematic

Most PN-junction diodes can be used as photodiodes. While not optimized for this application, they do work. When the diode is reverse biased, it will produce a small photovoltaic output as the light level is increased. LEDs are particularly suited for this task because their housings are transparent.

You can construct a simple circuit that will assess the condition of ambient lighting and, because many LEDs’ packages are tinted to enhance their emitted color, may even yield a reasonable evaluation of the detected color. The results are not as effective as those obtained using a high-quality optical filter, which typically has narrow bandpass characteristics, but they can be quite acceptable. Though the design described here does not produce the accuracy of designs with laboratory-grade photodetectors and transimpedance amplifiers, it can be quickly assembled and will produce usable results at a low cost.

Three LEDs are used; experimentation will indicate which device has the best sensitivity to which color (Figure 1). The ambient light falling on the LEDs causes some current flow—typically in the range of 10 to 100 nA—through each LED, depending on the applied illumination level. This current flows through the base of a transistor, Q1, and is amplified. Q1’s collector current then splits between potentiometer R4, which acts as a first-stage gain calibration, and the base of Q2.

Photo Meter Assesses Ambient Light Schematic

Q2 provides further amplification and drives the left side of a bridge circuit (D1A and D1B). Note that R2/D1 and R3/D2 form a balanced bridge. Q2’s collector current provides a slight imbalance to the bridge. The meter, M, measures this imbalance. R5 adjusts the sensitivity of the meter. Set R4 and R5 such that the meter has an appropriate deflection. R4 is useful for selecting the quiescent point; R5 is useful for adjusting the sensitivity.

Before building the circuit, check whether the LEDs can be used as photo sensors. To determine whether a given LED is a good photodiode, check the voltage across the LED using a common digital multimeter set to its most sensitive range—typically 200 mV. Typical output voltage should be approximately 0.3 to 1 mV with typical office illumination.

Friday, April 12, 2013

Temperature Meter

The
use of temperature devices in temperature measurement and sensing have
made tremendous progress in the last few decades. There are a few types
of measurement solutions that you can implement in your projects. The
use of thermistors or thermocouples are the two most widely used devices
in measurement solutions. The recent decade has seen the use of
integrated circuits devices in many temperature control related systems
because they are much smaller, provide a more accurate measurement and
simpler to be integrated to other digital control devices.

Most
of the digital temperature sensor system has a built-in communication
bus to enable it to communicate with the master control IC. The most
used communication interface is called I2C, a simple bi-directional
2-wire bus that was developed by Philips Semiconductors in the 1980s.
Since then, many devices has this built in communication protocol that
enables all devices that have this feature to be linked together without
any other additional components. The I2C interfacing standard has
become a world standard that are used in more than 1,000 integrated
circuits.

The
I2C standard basically define the start, stop, device selection
addressing and data transfer interfacing protocol. The hardware consists
of 2 I/O lines called SDA and SCL lines.

START Condition

The
Start Data Transfer is initiated when there is a change of state of SDA
line from HIGH logic to LOW logic while the SCL line is at HIGH logic.
This is the START condition.

STOP Condition

The
Stop Data Transfer is initiated when there is a change of state of SDA
line from LOW logic to HIGH logic while the SCLline is at HIGH logic.
This is the STOP condition.

DATA Transfer Condition

The
data transfer is done between the START and STOP conditions with the
data being transferred when SCL transition fromLOW to HIGH logic. Data
is read when SCL is at HIGH logic. SDA line data will only change when
SCL line is at LOW logic.There is no limit to the number of data bytes
transferred and is determined by the master device. Acknowledgement of
successful transfer of data is done between the master and the slave
devices at regular interval.

Digital Temperature Sensor Applications

If
you are into designing of thermostat controls for various buildings,
industrial controls or home appliances, you maywant to consider using
the TMP100 digital temperature sensor from Texas Instruments. This
device can be connected tothe microcontroller using the SCL and SDA
lines.

The features of the TMP100 sensor include:

* Low Quiescent standby current of 0.1uA means if you choose a proper
microcontroller, the device using battery powered could last for years
compared to the use of thermistor.

* Temperature range from -55 °C to 125 °C.

* Wide Power supply range from 2.7V to 5.5V.

* Accuracy of +/- 2.0 °C.

* Resolution up to 0.0625 ° C.

The typical application of the TMP100 digital temperature sensor is as shown in the diagram below.

Thursday, November 20, 2014

Audio VU Level Meter Circuit with LM324

Wednesday, September 24, 2014

Loudspeaker Impedance Meter

Parts:

Sunday, May 5, 2013

New Photo Meter Assesses Ambient Light Schematic

Friday, April 12, 2013

Temperature Meter

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