Diagram Guide

Saturday, November 8, 2014

Making a Solar Energy with iPhone Battery Charger

For faster charging, a larger solar cell can be attached to the bag. Enough power can be generated to fully charge an iPhone in about 5.5 hours and an iPod Touch in 4 hours using a slightly larger solar cell with 6V at 250mAh. The charger will automatically switch to trickle charging when the cell reaches full charge. The charging current is limited to 100mA when charging using the mini USB port and the charging is limited to 280mA when charging using the barrel plug jack

Source : http://witcircuit.blogspot.com/2013/04/making-solar-energy-powered-iphone.html

Soldering Iron Tip Preserver Circuit Diagram

Although 60/40 solder melts at about 200°C, the tip temperature of a soldering iron should be at about 370°C. This is necessary to make a good quick joint, without the risk of overheating delicate components because the iron has to be kept on the joint for too long. Unfortunately, at this temperature, the tip oxidises rapidly and needs constant cleaning. Thats where this circuit can help - it keeps the soldering tip to just below 200°C while the iron is at rest. Oxidisation is then negligible and the iron can be brought back up to soldering temperature in just a few seconds when needed. In addition, normal soldering operation, where the iron is returned to rest only momentarily, is unaffected because of the thermal inertia of the iron. Two 555 timers (IC1 & IC2) form the heart of the circuit.

Circuit diagram:

Soldering Iron Tip Preserver Circuit Diagram

IC1 is wired as a monostable and provides an initial warm-up time of about 45 seconds to bring the iron up to temperature. At the end of this period, its pin 3 output switches high and IC2 (which is wired in astable configuration) switches the iron on - via relay RLY1 - for about one second in six to maintain the standby temperature. The presence of the iron in its stand is sensed by electrical contact between the two and some slight modification of the stand may be necessary to achieve this. When the iron is at rest, Q1s base is pulled low and so Q1 is off. Conversely, when the iron is out of its stand, Q1 turns on and pulls pins 2 & 6 of IC2 high, to inhibit its operation. During this time, pin 3 of IC2 is low and so the iron is continuously powered via RLY1s normally closed (NC) contacts. Note that the particular soldering iron that the circuit was designed for has its own 24V supply transformer. Other irons may need different power supply arrangements. The warm-up time and standby temperature can be varied by altering R2 and R5, as necessary.

Friday, November 7, 2014

9 Volt Power Supply Circuit Diagram Using IC 7809

Description

Circuit showing a 9 volt power supply . Here we have used a bridge rectifier and 7809 ic for making this circuit.Where the ic regulate the output to 9 v,1 A .This voltage every time constant.Are you interested ?

Circuit diagram with Parts list.

Notes.

If a current of 300 mA or above is required, fit a proper heat sink to the IC 7809.
If 1A bridge is not available, make one using four 1N 4007 diodes.

uA 741 Square Wave Generator

A square wave generator with IC UA741 range shown here.The circuit uses positive feedback to the Schmitt trigger action and negative feedback to measure the time of the waveform.

Let us assume that the output is high and the capacitor C1 is fully discharged.C1 now begins to charge through R2 and C1 R1.When tension rises above the junction of R3 and R4, the output changes rapidly totally negative voltage.C1 Now begins the unloading and reloading in the direction.Again contrast, when the negative voltage across C1 falls below that at pin 3, the circuit is returned quickly to totally positive repetitions value.The output endless cycle.

The square wave frequency can be varied by varying POT R1.The frequency range of the circuit depends on the value of R3, R4 and C1.

Simple Gratis Symmetrical Opamp Supply Voltages

Many ways to obtain a set of symmetrical supply voltages for operational amplifiers and comparators from a single +5-V sup-ply voltage have been described already. The simplest option (including with regard to component availability and price) is to use a MAX232, which is available in the 16-pin DIP package for less than 30 p (50 eurocents).

In nearly all microcontroller circuits with an RS232 port, this IC is already present any-way to provide level conversion between TTl signals (5 V) and RS232 signals (nominally ±12 V), so you can obtain a set of symmetric supply voltages for opamps almost free of charge.

It ’s not even necessary to add any circuitry around the IC. Figure 1 shows how a MAX232 is typically wired in a microcontroller circuit.The symmetrical voltages (at around ±9 V) generated from the +5-V supply voltage can be taken from pin 2 (V DD; +9 V) and pin 6 (VEE, –9 V) of the IC.

As you can see from Figure 2, the no-load voltage is nearly 10 V and you can draw up to 5 mA at 9 V, which is enough for most standard opamps and plenty for low-power opamps.

The MAX232 has two charge pumps, each of which has two external capacitors for voltage doubling. These are 10-µF electrolytic capacitors in Figure 1, which yields a somewhat stabler output voltage than the standard circuit with 1 µF as shown in Figure 2. The charge pumps of the MAX232 are operated at an oscillator frequency of around 50 kHz, so the amount of ripple on the output voltage is quite small (typically less than 10 mV with a 2-mA load).

This means that in most cases you can manage without any additional filtering of the output voltage. In sensitive applica-tions, such as amplification of small audio or measurement signals by one or more opamps, it’s a good ideal to use a small gyrator circuit for additional suppression of the residual 50-kHz signal. Figure 3 is an example of such a circuit that has been proven frequently in practice. Of course, you can use other types of complimentary small-signal silicon transistors, such as the BC547 (NPN) and BC577 (PNP), in place of the BC550 (NPN) and BC560 (PNP) shown on the schematic.

Transistors in the current gain class ‘B’ (such as the BC547B and BC557B) are also suitable, and the values of the capacitors between the bases of the transistors and ground can also be increased (e.g. 100 µF) or decreased (e.g. 1 µF).

Thursday, November 6, 2014

Audio Visual Ringer Circuit Diagram

Many a times one needs an ex- tra telephone ringer in an ad- joining room to know if there is an incoming call. For example, if the telephone is installed in the drawing room you may need an extra ringer in the bedroom. All that needs to be done is to connect the given circuit in parallel with the existing telephone lines using twin flexible wires. This circuit does not require any external power source for its operation. The section comprising resistor R1 and diodes D5 and LED1 provides a visual indication of the ring. Remaining part of the circuit is the audio ringer based on IC1 (BA8204 or ML8204). This integrated circuit, specially designed for telec- om application as bell sound generator, requires very few external parts.

It is readily available in 8-pin mini DIP pack. Resistor R3 is used for bell sensitivity adjustment. The bell frequency is controlled by resistor R5 and capacitor C4, and the repeat frequency is controlled by resistor R4 and capacitor C3. A little experimentation with the various values of the resistors and capacitors may be carried out to obtain desired pleasing tone. Working of the circuit is quite simple. The bell signal, approximately 75V AC, passes through capacitor C1 and resistor R2 and appears across the diode bridge comprising diodes D1 to D4. The rectified DC output is smoothed by capacitor C2. The dual-tone ring signal is output from pin 8 of IC1 and its volume is adjusted by volume control VR1. Thereafter, it is impressed on the piezo-ceramic sound generator Audio Visual Ringer Circuit Diagram

DC Coupled Audio Amplifier

Designs for audio amplifiers with DC coupling to the load are not often encountered these days, even though they offer definite advantages. One advantage is that there is no need for the complication of a second (symmetric) power supply; another is good frequency and phase response. Also, no special electrolytic capacitors are needed for voltage stabilisation, and switch-on ‘thump’ is much reduced. To try to rescue this class of circuit from obscurity the author has designed a headphone amplifier working along the lines illustrated in Figure 1.

DC-Coupled Audio Amplifier Circuit Diagram

It consists of a voltage divider, a voltage follower and the loudspeaker in the headphones, whose other side is connected to the junction of two electrolytic capacitors, providing the virtual earth. The potential at this point is, of course, half the supply voltage. All we need to do now is suitably couple in the audio signal to be amplified. Figure 2 shows a practical realisation of this idea in the form of a stereo headphone amplifier. The amplifier itself consists of IC1 and P1, R3 and R4 (giving a gain of 11).

DC Coupled Audio Amplifier Circuit Diagram

This part of the circuit demands no further explanation, and the same goes for the voltage divider mentioned above, formed by R1a and R1b. The signal is coupled in via the potentiometers. C2 and R2 have a special purpose: C2 connects the bottom end of the potentiometers (ground for the input signal) to the virtual earth. However, this capacitor creates a feedback path which can lead to oscillation of the amplifier under some circumstances. R2 damps this tendency to oscillate.

It is possible to calculate suitable values for these components, but it is better to determine them by experiment. C2 must be sufficiently large that stray electric fields do not cause unacceptable hum at the output. R2 must be sufficiently large that the voltage at the amplifier’s virtual earth stabilises quickly enough after switch-on. The polarity of the electrolytic is unimportant as no significant voltage appears across the network. It is possible to try the circuit out with the C2/R2 network shorted and observe the behaviour of the circuit at switch-on using an oscilloscope. Depending on the degree of asymmetry in the circuit, the voltage at the virtual earth point can take a considerable time to stabilise.