Matt circuit

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. For a standard power amplifier hi-fi stereo, the output values ​​suggested are: D5 illuminates at 2W D4 illuminates at 12.5W D3 illuminates at 24.5W The above values ​​were selected for easy setup, but other options are possible. IC1A is the input buffer, feeding 3 voltage comparators and LEDs drivers by means of a variable DC voltage obtained by R5 and C4 smoothing action. In order to achieve stability of adjustment, the supply of IC1 and trimmers R6 and R7 is reduced and is subject to 5.1V by Zener diode D1.

If you, like so many other people in this day and age, arrive home from work stressed out and with the problems of the day still lingering,this simple little instrument will go a long way to relieving nervous tension. Of the various types of feedback devices, probably the best approach for the amateur experimenter is the Galvanograph, better known as the Galvanic Skin Response Monitor. The instrument described here relies for its operation on changes in skin resistance in sympathy with changes in emotional state. An increase in tension level reduces skin resistance and, conversely, a decrease in tension is accompanied by an increase in skin resistance. The correlation between emotional stress and skin resistance is still not fully understood. What is known, though, is that minute changes in the permeability of the skin produce corresponding voltage variations across two electrode pads attached to two fingers on the same hand. Tension Monitor meter circuit These signal fluctuations are ...

In most houses, water is first stored in an underground tank (UGT) and from there it is pumped up to the overhead tank (OHT) located on the roof. People generally switch on the pump when their taps go dry and switch off the pump when the overhead tank starts overflowing. This results in the unnecessary wastage and sometimes non-availability of water in the case of emergency.  The simple circuit presented here makes this system automatic, i.e. it switches on the pump when the water level in the overhead tank goes low and switches it off as soon as the water level reaches a pre-determined level. It also prevents ‘dry run’ of the pump in case the level in the underground tank goes below the suction level.   In the figure, the common probes connecting the underground tank and the overhead tank to +9V supply are marked ‘C’. The other probe in underground tank, which is slightly above the ‘dry run’ level, is marked ‘S’. The low-level and high-level probes in the overhead tank are marked ‘L...

Rotating laser levels, which are very handy  for setting objects in a room or garden at the  same height, are available at prices of a few  dozen pounds. At relatively large distances  and for outdoor use, the light from the rotating laser beam is often not easy to see, and  the laser beam detector described here can  be useful in such situations. The detector  works well at distances up to 50 metres (150  feet) and consists entirely of standard components. The detector is housed in a plastic case  that can be fixed to an object (such as a post  or a beam). It has three LEDs and a beeper that  indicate whether the object should be raised  or lowered. . . LEDs with a transparent package and integrated lens (round surface) are used as sensors. The top and bottom detection zones  each have five LEDs and two opamps (IC1a &  IC1b or IC1c & IC1d), which drive the ‘Move  Up’ and ‘Move Down’ indicator LEDs. The mi...

Here’s a simple water-level indicator for overhead tanks that uses three LEDs (LED1, LED2, and LED3) to indicate minimum, middle, and maximum water levels in the tank. The sensor probes comprise A, B, C, and D, where A is the common probe and B, C, and D are meant for sensing the minimum, middle, and maximum levels, respectively. When water in the tank touches sensor wires A and B both, a small current passes from A to B through water and to the base of transistor T1 via resistor R1. As a result, transistor T1 conducts, causing LED1 to glow. Similarly, when water touches sensor C, LED2 glows to indicate that the water has reached the middle level. Finally, when water touches sensor D, LED3 glows to indicate the maximum level of water. Thus all the three LEDs glow when the tank is full. At this stage, the motor should be switched off manually. Water-Level Indicator Schematic The circuit can be easily assembled on a general-purpose PCB and enclosed in a wooden box. The three LEDs should ...

Most water-level indicators for water tanks are based upon the number of LEDs that glow to indicate the corresponding level of water in the container. Here we present a digital version of the water-level indicator. It uses a 7-segment display to show the water level in numeric form from'0' to '9.' The circuit works off 5V regulated power supply. It is built around priority encoder IC 74HC147 (IC1), BCD-to-7-segment decoder IC CD4511 (IC2), 7-segment display LTS543 (DIS1) and a few discrete components. Due to high input impedance, IC1 senses water in the container from its nine input terminals. The inputs are connected to +5V via 560-kilo-ohm resistors. The ground terminal of the sensor must be kept at the bottom of the container (tank). IC 74HC147 has nine active-low inputs and converts the active input into active-low BCD output. The input L-9 has the highest priority. The outputs of IC1 (A, B, C and D) are fed to IC2 via transistors T1 through T4. This logic inverter ...

Here’s one for the books. This pedal had been exhibiting strange behaviour where it would work fine for ages, then suddenly the volume would drop to about 50% or so. It would stay this way for a while and then jump back up to 100%. Repeat ad infinitum. I wouldn’t really have jumped to a “dodgy jack” diagnosis, but decided to spray a little contact cleaner in there anyway, since it was cheap and easy to do so. It didn’t fix the problem. The next thing I decided to try was to spray some contact cleaner in the pots (after that, it was going to be a case of checking the electronic components), but they could only be accessed by opening the box. So I removed the back cover: Moved the insulating sheet to the side: Lifted the board, and immediately saw the problem. You see it? Let me show you a close-up: Yeah, you see it now, right? The jack on the right? The one that's supposed to be in one piece? Well here’s what it looked like: I think we can quite safely call that a “dodgy jack”. I ca...

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. 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 resistors with the 220k potentiometer. C...