Power Supply for Projects. Design Note 43

IMAGEFor bread board assembly of Micro controller and Arduino projects ,we need  well regulated  5 V and 3.3 V DC power supply. Here is the simple but efficient regulated power supply that gives four stage power outputs  – 12 V unregulated, 9 V, 5 V and 3.3 V regulated DC .
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How Capacitor functions as a Transformer? Design Note 42

is used to convert high volt AC to low volt AC (Step down) or low volt AC to high volt AC (Step up). So step-down transformer is generally used to convert 230 Volt AC to low volt AC which can be used to make a DC power supply after rectification and smoothing. But a Non polarized capacitor can act like a transformer to step down the high volt AC to low volt AC. Say, 230 V AC to 40 VAC. Let us see how the capacitor is doing this.
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Mini Inverter. Design Note 41


Here is a simple Mini Inverter circuit to light 11 Watts CFL from 12 volt battery. It is an ideal gadget to check the vehicle engine or electrical circuit in night. It can be hooked in the vehicle’s battery and the CFL will light. It can also be used in home as emergency lamp using the 12 volt UPS battery. An AC socket provision is also added to charge Mobile phone or other low watt gadgets while travelling. The 12 volt DC can be tapped from the Cigarette lighter socket of the car. The Inverter has maximum 18 Watts power.
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LED Driver CC Chip .Design Note 40

High current White LED requires constant current for giving maximum brightness. Connecting 1 Watt LED to the DC source using a current limiting resistor gives poor performance and the LED will be either too bright or too dim. More over, the low value resistor (10 Ohm or less) will heat up since the LED consumes around 200 to 350 milli ampere current . So here is a simple LED driver chip AMC 7135 that gives constant current (CC) to LED to give maximum brightness. It also increases the life of LED. It is too simple and enjoy the project.
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Transformer less Power supply Problems. Design Note 39

To reduce size, and cost, Transformer less power supply is now used. If it is a well regulated SMPS power supply, output will be stable. But simple Transformer less power supply is not ideal for many circuits as observed in my experience. I have designed different types of Transformer less power supply but none of them is showing good performance. It can be used to power simple circuits like LED lighting. If sensitive semiconductors are present in the circuit, this kind of power supply creates many problems including erratic response. This is very high in sensor based circuits and oscillators. So to get a perfect output voltage, it is ideal to use a Transformer based power supply or SMPS. These are the problems I noticed in the Transformer less power supply.
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Short Circuit Indicator for Bread board. Design Note 38

Here is a solution to protect your circuit assembly on Bread board. Usually we test the working of a circuit first on bread board before making the PCB assembly. Sometimes due to mistake in wiring, valuable components may destroy through short circuits. With the power on , we still continue the trouble shooting which may further destroy many components. Only after sensing heat or burning, we realize the problem. So here is the simple solution to assemble the circuit on bread board safely. If there is any short circuit in the bread board, the power to the board will cut off and Red LED lights. So immediately we can detach the board from power supply.
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LED as Zener diode. Design Note 37

What will do if you want a low voltage less than 3 volts as reference voltage for a circuit? Usually we use a low volt Zener to give low voltage to a particular section of the circuit. But Zener below 3.1 V is not available. So do this simple method. The LED can act a Zener to give a reference voltage. Each type of LED has a forward voltage drop that range between 1.7 V to 3.3 V. This forward voltage drop slightly increases when the input voltage increases. This is due to the increase in the luminosity of the LED. So let us exploit the LED to do the job of the Zener.
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