Matt circuit

This alarm plays your prerecorded voice message. It is built around the readily available quartz clock. Take the buzzer out of the quartz clock and connect its positive terminal to pin 1 and negative terminal to pin 2 of optocoupler IC MCT2E (IC2). Pin 4 of IC2 is grounded and pin 5 is connected to trigger pin 2 of monostable multivibrator IC 555 (IC3) as shown in Fig. 2. Fig. 1: Voice recording circuit Fig. 1 shows the circuit for recording your voice message. When you press switch S2, it plays the meassage. The control circuit shown in Fig. 2 avoids the need for pressing switch S2 and thereby sounding the voice alarm automatically at the preset time. Connect points A and B of the recording circuit to the corresponding points A and B of the control circuit. After making the connections, press record switch S1 to record your 6-second voice message through condenser microphone. Set the desired alarm time in quartz clock. At the time of alarm, buzzer terminals provide voltage to the inte...

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 ...

TL431 and LM431 are relatively low-noise, stable and low-cost shunt regulators. These can be used to build all sorts of power supplies including programmable power supplies, advantages of which are enormous. You can program the output voltage with simple switches. You can also program the output voltage with digital codes coming from a microcontroller (MCU) or from the printer port of a PC. You can adjust any output voltage individually with resistors or trimmer potentiometers to the required values. This article presents a programmable power supply built around TL431 (IC1) and two bipolar transistors BD139 and TIP31 (T1 and T2). The circuit also includes an inverter 7406 (IC2), nine diodes 1N4007 (D1 through D9), a 12V regulator 7812 (IC3), a 5V regulator 7805 (IC4) and a few other components. Using this circuit you can obtain around 18V, 2A unregulated output and 3V to 15V, 1A variable regulated power supply based on digitally programmable input as shown in Table I. You can also obta...

‘Hello… HELLO! Are you deaf? Do you have disco ears?’ If people ask you this and you’re still well below 80 , you may be suffering from hearing loss, which can come from (prolonged) listening to very loud music. You won’t notice how bad it is until it’s too late, and after that you won’t be able to hear your favorite music the way it really is – so an expensive sound system is no longer a sound investment. To avoid all this, use the i-trixx sound meter to save your ears (and your neighbor's ears!). With just a handful of components, you can build a simple but effective sound level meter for your sound system. This sort of circuit is also called a VU meter. The abbreviation ‘VU’ stands for ‘volume unit’, which is used to express the average value of a music signal over a short time. The VU meter described here is what is called a ‘passive’ type. This means it does not need a separate power supply, since the power is provided by the input signal. This makes it easy to use: just conne...

The risks of installing your own auto sound system may be greater than you realize. The fact is that there are people that are professionally trained in the installation and proper handling of these delicate sound systems for a reason. If it weren't a difficult task they wouldn't be able to demand the rather hefty price tag that most installation centers charge. The problem is that mistakes can actually cost more than the installation. If you aren't one hundred percent certain that you can handle the installation process alone it is best to leave it up to the experts. To prove my point, I will give you my very own personal story of how auto sound system installations can go horribly (well, perhaps hilariously would be the better choice of words in my particular situation) of course. You see I wanted a CD player in my mini van about 13 years ago. This was back in the dark ages when these types of sound systems were still relatively new and on the 'cutting edge' when ...

  Running out of battery at the most inconvenient moment is a situation that happens more often than we would like. The services currently offered multiple cell phones lead to a continuous drain on the battery , having often upload at the end of the day as if our smartphone need rest as much as us. To try to make the battery last us a bit more, we offer these tips: 1. The screen is ample, which consumes more energy on our phone. Therefore, avoid looking at every minute cell would be to start with the best advice. Adjust the screen brightness will also help us better power consumption. Likewise, it is advisable to reduce the consumption of games, watch videos, or even record and take pictures. All these applications have a high battery consumption, and if what we want is that last a little longer, we have to reduce the time spent on these activities. 2. Any service to determine our location, such as GPS, it should be disabled if not in use at that time. There are many services th...