Usually, Low-Cost Stereo Level Indicator home stereo power amplifiers don’t have output level indicators . An output power level indicator can be added to each channel of these stereo power amplifiers . As low levels of the output power are not disturbing and damaging to the people, there is no need to add a preamplifier and low-level detector before IC LM3915. But you should know when the output power becomes considerably high. Here we present a very simple, low-cost stereo-level indicator circuit for home power amplifiers with power rating of around 0.5W. The circuit is built around two LM3915 dot/bar display driver ICs (IC1 and IC2). LM3915 senses analogue voltage levels to drive ten LEDs, providing a logarithmic 3dB/step analogue display. Stereo Level Indicator Circuit Diagram The voltage levels below 1V are not important because these correspond to a low level of the audio signal. Similarly, input voltage levels above 30V correspond to too high levels of the output power, which ...
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This stereo balance indicator circuit diagram is designed using few common external components .The schematic circuit is very simple to build and will provide an visual indication with LEDs for left , right and center balance . Stereo Balance Indicator Circuit Diagram Outputs from each channel are fed to the two inputs of IC1 connected as a differential amplifier . Output of the IC1 is connected to the noninverting inputs of the IC2 and IC3 . If the outputs of the IC1 approaches the supply rail , the outputs of the IC2 and IC3 will go high illuminating the LED 3 , this will show that the right channel is dominating . If the sound is balanced to the left channel , the Ic2 and IC3 will go low and the LED1 will light . If both channels are equal in amplitude the outputs of the IC2 and IC3 would be low and high respectively , lighting up LED2 .
This temperature indicator indicates the temperature of a heat sink in high power circuits .In this temperature indicator, diode voltage drop in ambient temperature is used as reference level. Temperature is measured by a transistor mounted on a radiator or near power transistor controlled.T1 temperature sensor and voltage to the base - emitter is compared, through potentiometer P1, with the common point of reference in its D1 and R1. Transistor remains blocked as long as temperature remains below a certain level, which is set to P1. Base-emitter voltage of transistor will decrease by about 2 mV for a temperature increase of about 1 ° C. When the emitter voltage of transistor voltage falls below the cursor P1, the transistor will go into conduction and D2 will light.The values of R1 and R2 are voltage dependence of Ub and relationships can be calculated: R1 = [(Ub - 0.6) / 5] k, R2 = [(Ub - 1.5) / 15] k. Temperature Indicator Schematic
This circuit, designed on request, has proven to be useful to indicate when the voltage in a power supply line is changing from 120V to 240Vac. It can be used in different circumstances and circuits, mainly when an increase in ac or dc supply voltage needs to be detected. D3 illuminates when the line voltage is approaching 120V and will remain in the on state also at 240V supply. On the other hand, D6 will illuminate only when the line voltage is about 240V and will stay on because the latching action of Q1, Q2 and related components. C1, D1 and D2 provide a low dc voltage in the 4.5V - 6V range in order to allow proper operation of latch circuit and LEDs. Circuit diagram Parts: R1_____________470R 1/2W Resistor R2_____________220K 1/4W Resistor R3,R7__________470R 1/4W Resistors R4_______________1K 1/4W Resistor R5_______________2K2 1/4W Resistor R6_____________330R 1/4W Resistor C1_____________330nF 630V Polyester Capacitor C2______________10µF 25V Electrolytic Capacitor D1,D2_...
Mains/Fuse Failure Indicator Circuit Diagram. The indicator shows when the mains is present at its output by a continuous glow of a neon bulb, La1, and when the fuse is blown by flashing of the neon bulb. When the fuse is intact, capacitor C2 acts as the series resistance for the neon bulb, so that this glows continuously. When the fuse has blow, the mains voltage across diode D1 is applied as a pulsating direct voltage to network R1-C1. Capacitor C1 charges slowly and when the voltage across it reaches 80–100 V, the neon bulb comes on. Capacitor C1 is then discharged slowly via diode D2 and the bulb. Mains/Fuse Failure Indicator Circuit Diagram When the voltage across it has dropped sufficiently, the bulb goes out, whereupon C1 slowly charges again. This process repeats itself, so that, provided the values of R1 and C1 are right, the bulb flashes visibly. The potential across capacitor C2 is a ramp with a peak value of 30 V (which is, of course, applied to the load). Note that the neo...
This circuit indicates which of three voltages in the range from about about -4V to about +4V - at A, B and C - is the highest by lighting one of three indicator LEDs. Alternatively, it can be wired to indicate the lowest of three voltages or to indicate both the highest and lowest voltages. Op amps IC1a, IC1b & IC1c are wired as comparators, while the three indicator LEDs and their series 1kO current limiting resistors are strung across the op amp outputs to implement the appropriate logic functions. Maximum Minimum Voltage Indicator Circuit Diagram For example, LED A will light only when pin 8 of IC1c is low (ie, A greater B) and pin 7 of IC1b is high (ie, A greater C). Similarly, LED B will light only when pin 8 of IC1c is high (ie, B greater A) and pin 1 of IC1a is low (ie, B greater C). LED C works in similar fashion if the voltage at C is the highest. Note that if all the LEDs and their parallel 1N4148 diodes are reversed, the circuit will indicate the lowest of the thr...
The modem off indicator is intended especially for serious Internet surfers. It will be seen that the circuit of the indicator cannot be much simpler, or there might be nothing left. In spite of its simplicity, it may prove to be a cost-saving device, since it shows at a glance whether the telephone line is free again after the modem has been used. This obviates high telephone charges in case for some reason the modem continues to operate. The circuit depends on the fact that there is a potential of about 40 V on the telephone line when it is not busy. This voltage drops sharply when a telephone call is being made. If, therefore, the circuit is linked to telephone terminals a and b, the lighting of the green LED shows that the line is not busy in error. Circuit diagram: Modem Off Indicator Circuit Diagram The bridge rectifier ensures that the polarity of the line voltage is of no consequence. This has the additional benefit that polarity protection for the LED is not necessary. To mak...
This ULN2004 electronic project circuit diagram design is a very simple water level indicator circuit project . This ULN2004 water level indicator circuit is very simple and require few external electronic parts . ULN2004 is a high voltage, high current darlington arrays that contain seven open collector darlington pairs with common emitters . Each channel rated at 500mA and can withstand peak currents of 600mA. ULN2004 Water Level Indicator Circuit Diagram As the water level rise in the tank , it comes in contact with probes P1 through P7 and thereby makes pins 7 trough 1 high sequentially . The corresponding output pins 10 trough 16 go low one after other and LED1 through LED7 will light up . When water comes in contact with the last probe P7 , the buzzer connected to the last pin 16 will sound . This electronic circuit project must be powered from a fixed output DC voltage that will provide an output voltage between 9 and 12 volts .
The following sequence is useful to show the battery voltage (battery) 12 volts. Voltage level is shown with four lights led. To facilitate the reading of the led is arranged in a vertical array. Led top three chosen by the green LED while the lowest is selected the color red. If the battery voltage continues to decline (because of usage), the Led-Led will turn off sequentially from the top to the bottom. Until if battery voltage is below 11.83 volts then only the red LED that lights up which means that the charge batteries are empty. Even this red Led will die if the stress continues to drop to below 11.5 volts. The working principle of this circuit is a comparison of battery voltage with a reference voltage. Schematic Battery level indicator
This series is made to indicate that the amplifier has been given the maximum signal, the amplifier has the ability to be at its peak. if the lights do not mean the signal-plus volume.the way it works is the LED lights will light up when given a signal that more than 1.8 volts, the average amplifier will be saturated (maximum) if the signal was given more than this. The circuit is very simple to the point that we forget that making a series of peak signal can in this way. circuit is mounted on the output tone control IC, master mixer output, or input power amplifier. This series does not impose on other circuits.survived the experiment!
Signals when an on-circuit battery is exhausted 5V to 12V operating voltage. A Battery-status Indicator circuit can be useful, mainly to monitor portable Test-gear instruments and similar devices. LED D1 flashes to attire the user's attention, signaling that the circuit is running, so it will not be left on by mistake. The circuit generates about two LED flashes per second, but the mean current drawing will be about 200µA. Transistors Q1 and Q2 are wired as an uncommon complementary astable multivibrator: both are off 99% of the time, saturating only when the LED illuminates, thus contributing to keep very low current consumption. Flashing-LED Battery-status Indicator Circuit diagram : Flashing-LED Battery-status Indicator Circuit Diagram The circuit will work with battery supply voltages in the 5 - 12V range and the LED flashing can be stopped at the desired battery voltage (comprised in the 4.8 - 9V value) by adjusting Trimmer R4. This range can be modified by changing R3 and/or...
The normal level-indicator circuits which are available in the market require connections to be made to the output of the player, which may not be easily accessible. The audio level indicator circuit described here removes this restriction as it may be placed close to the player’s speakers and yet the desired effect can be realised. Remote Audio Level Indicator Circuit diagram : Remote Audio Level Indicator Circuit Diagram As shown in the circuit, signals are picked up by the condenser microphone, which get further amplified by the noninverting amplifier built around one of the four op-amps of LM324. The remaining three, along with four op-amps of the second LM324, are used as seven comparators to work as the level detector, giving seven output levels through seven coloured LEDs. The sensitivity of the audio level indicator circuit may be improved by varying the 220k potentiometer. If a fine adjustment is desired, a 4.7-kilohm potentiometer may be connected in series resis...
The modem off indicator is intended especially for serious Internet surfers. It will be seen that the circuit of the indicator cannot be much simpler, or there might be nothing left. In spite of its simplicity, it may prove to be a cost-saving device, since it shows at a glance whether the telephone line is free again after the modem has been used. This obviates high telephone charges in case for some reason the modem continues to operate. The circuit depends on the fact that there is a potential of about 40 V on the telephone line when it is not busy. This voltage drops sharply when a telephone call is being made. If, therefore, the circuit is linked to telephone terminals a and b, the lighting of the green LED shows that the line is not busy in error. The bridge rectifier ensures that the polarity of the line voltage is of no consequence. This has the additional benefit that polarity protection for the LED is not necessary. To make sure that the telephone line is not loaded unnecessa...
This is a Simple Emergency Lamp and Turning Indicator Circuit Diagram .White LEDs are replacing the conventional incandescent and fluorescent bulbs due to their high power efficiency and low operating voltage. These can be utilised optimally for emergency lamp and vehicle turning indication. The circuits for the purpose are given here. Emergency Lamp and Turning Indicator Circuit Diagram fig 1 Fig. 1 shows the circuit of a white-LED based emergency lamp . You can also use arrays of white LEDs as daytime running lamps in automobiles. In the emergency lamp , seven 1.2V AA-size Ni-Cd cells giving 8.4V have been used as the power source. The brightness is controlled by duty-cycle variation of an astable multivibrator working at 1 kHz. The astable multivibrator is built around IC1. Its output is connected to LED-driver transistor T1. Up to six branches of white LEDs can be connected in parallel, with each branch containing two LEDs in series (only three branches are used here). Depending o...
This circuit will illuminate a LED if one of your telephones is in use. It should work in all countries (Including UK) that have a standing line voltage above 48 Volts DC. Please note that it is illegal to make a physical permanent connection to your telephone line in some countries (this includes the UK and Ireland). If building this circuit it is advisable to use a plugin cord so that the unit can be unplugged should a fault occur. If in doubt consult either your telephone or cable operator. If all extension phones are on-hook and the line voltage is around 48 V, Q1 will conduct thus effectively shorting the gate of Q2 to its source, so it will be off and the LED will be disabled. Lifting the handset of any phone on the line causes the line voltage to drop to 5-15 V. The gate voltage of Q1, equal to some 6% of the line voltage, will then be too low and Q1 will be turned off. So Q2's gate is now biased at approximately 1/2 of the line voltage, Q2 turns on and the LED indicate...
This is a Simple Telephone In Use Indicator Circuit Diagram . With this circuit mounted in or near every phone in the house, it will allow users to know if the phone is being used and not to pick up the phone. When a phone is taken off hook, the voltage across the tip and ring terminals drops to 10 volts or less. This will cause the FET (2N4360) to turn on and also turn on the transistor (2N2222). When the transistor turns on it will allow current to flow through the LED and make it light. A blinking LED could be used to make the effect better. Simple Telephone In Use Indicator Circuit Diagram
This circuit is designed to indicate the power level output of any audio amplifier. It's simple, portable, and displays three power levels can be adjusted to any desired value. 3 Level Audio Power Indicator Circuits Diagram Parts: R1__________100K 1/4W Resistor R2___________50K 1/2W Trimmer Cermet R3__________330K 1/4W Resistor R4____________ 1M2 1 /4W Resistor R5__________470K 1/4W Resistor R6 ,R7 _______500K 1/2W Trimmers Cermet R8____________ 1K5 1 /4W Resistor R9-R11______470R 1/4W Resistors C1___________ 47pF 63V Ceramic Capacitor C2__________ 100nF 63V Polyester Capacitor C3___________47µ F 25V Electrolytic Capacitor C4____________1µ F 25V Electrolytic Capacitor D1______BZX79C5V1 5.1V 500mW Zener Diode D2_________1N4148 75V 150mA Diode D3-D5________3mm. Yellow LEDs IC1_________ LM339 Quad Voltage Comparator IC...
Some types of electronic equipment do not provide any indication that they are actually on when they are switched on. This situation can occur when the back-light of a display is switched off. In addition, the otherwise mandatory mains power indicator is not required with equipment that consumes less than 10 watts. As a result, you can easily forget to switch off such equipment. If you want to know whether equipment is still drawing power from the mains, or if you want to have an indication that the equipment is switched on without having to modify the equipment, this circuit provides a solution. One way to detect AC power current and generate a reasonably constant voltage independent of the load is to connect a string of diodes wired in reverse parallel in series with one of the AC supply leads. Here we selected diodes rated at 6 A that ...
The following sequence is useful to show the battery voltage (battery) 12 volts. Voltage level is shown with four lights led. To facilitate the reading of the led is arranged in a vertical array. Led top three chosen by the green LED while the lowest is selected the color red. If the battery voltage continues to decline (because of usage), the Led-Led will turn off sequentially from the top to the bottom. Until if battery voltage is below 11.83 volts then only the red LED that lights up which means that the charge batteries are empty. Even this red Led will die if the stress continues to drop to below 11.5 volts. The working principle of this circuit is a comparison of battery voltage with a reference voltage. Schematic Battery level indicator