A Coil Coupled Operation Metal Detector made from readily obtainable components and using an ordinary medium receiver as a detector. The metal detector shown here may well represent a new genre. At any rate, after some exposure, it is regarded as such by....

This circuit will detect AC line currents of about 250 mA or more without making any electrical connections to the line. Current is detected by passing one of the AC lines through an inductive pickup (L1) made with a 1 inch diameter U-bolt wound with 800....

This amplifier has about 20dB of gain, bandwidth of 100MHz and noise figure of about 7dB. The output transformer is 8 turns bifilar wound on a ferrite core. Use a medium power UHF transistor 2N5109, 2N3866, 2N4427 or similar. The transistor will need a small....

A MW AM radio like those you buy, or used to buy. Use just BC549 trannies, with the BC559 complement being allowed in the audio output stage. Buying RF antenna coils, oscillator coils and intermediate frequency transformers would be cheating - wind your own.....

The schematic of the SAVER V3.2 is depicted in Figure 1.A transformerless power supply uses Xc of a 0.22uF capacitor to limit current providing about 10mA current source. The diodes rectifies ac current to dc current which in turns charged to filtering....

Using a single 555 Timer IC and a small transformer to generate a high voltage, this circuit will test zener diodes of voltage ratings up to 50VDC. The 555 timer is used in the astable mode, the output at pin3 drives a small audio transformer such as the....

Using this circuit you can convert the 12V dc in to the 220V Ac. In this circuit 4047 is use to generate the square wave of 50hz and amplify the current and then amplify the voltage by using the step transformer. How to calculate transformer rating The basic....

This application note presents practical design considerations for battery chargers employing Green Mode FPS (Fairchild Power Switch). It includes designing the transformer and output filter, selecting the components and implementing constant current /....

This project is a piece of test equipment. It`s a square wave oscillator with 6 selectable frequencies from 1Hz to 100kHz, incrementing in decade values. It`s most useful application is as a Signal Injector for radios and TV`s. A square wave is the most....

The rechargeable Li-ion, I began to intensely interested last summer, when I managed to bring a holiday without a phone charger. After several experiments involving originated in Figure 1, which has proved. Involvement of the stage provides a limited current....

Here is a nice little receiver for narrow-band FM reception. It can also be used to receive FSK, RTTY and PACKET signals from the HF bands. Basic receiver sensitivity is in the region of 1uV PD and the receiver can be tuned to almost any frequency from....

The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so....

For it`s maximum result, the final stage of the amplifier should have the proper power supply, as the flowing, currents are very high. An Class A amplifier, requires attention. These are the rules for the power supply for the Class A audio amplifier. The....

A high voltage power supply is a very useful source which can be effectively used in many applications like biasing of gas-discharge tubes and radiation detectors etc. Such a power supply could also be used for protection of property by electric charging of....

I have received a few emails asking for a transformerless power supply. Here is such a supply. This supply uses no heavy step down transformer and has an extremely low parts count. The circuit can be built very small and can supply small currents for small....

This is a circuit to use a standard, low quality opto isolator to transfer an analogue signal with reasonable linearity and without complicated feedback loops to monitor and linearise it. The circuit was designed to interface a mains driven thryristor motor....

This power supply was designed for ham-radio use and has been in operation for over 10 years. Its design is very simple and practically immune to RF. It is assembled from discrete components, being the most costly element a 600VA toroidal transformer, which....

The transmitter is a very simple crystal oscillator. The heart of the circuit is the tuned circuit consisting of the primary of the transformer and a 10p capacitor. These two components oscillate when a voltage is applied to them. The frequency is adjusted....

The transformer has a 240V primary and has a secondary rated 24V at 2A. The bridge rectifier contains 4 diodes, their current rating needs to be high with respect to the transformers output current; if not the current may damage the diodes. I used MR751....

The 555 is wired as an astable and the capacitor is charged only through the 4,7Kohm trimmer (notice the diode) and discharged only through the 2.2 Kohm trimmer, making the duty cycle full adjustable. The square wave is then feed in a totem pole made up of a....

This simple circuit will find many applications as a battery eliminator for low power requirements. It consists of a transformer, a bridge rectifier and an electrolytic capacitor followed by a zener controlled series pass transistor. The output is stabilized....

The following circuit Diagram of (DUAL VOLTAGE POWER SUPPLY ) can be used for Misc.. application. It requires a few components to built. The most important components of this circuit are REGULATORS. 1 : (AN) 7812 and 2 : (AN) 7912 AN7812 is the Positive....

This very simple circuit uses a transformer ,two diodes , a capacitor and an ammeter. To charge a battery just connect the + and - terminals of the circuit to the corresponding terminals of the battery. When the battery is not charged, the ammeter reading....

This circuit will allow you to place a phone call on hold and if you wish to have them listen to music while they are on hold. The circuit operates as follows: The RED wire from the phone jack is typically positive and the GREEN wire is negative or ground.....

Pure A class is the most simple topology for designing an amplifier! The tube or the power transistor is loaded directly by the speaker (often thru a transformer, fro impedance matching!), and is biaised at the current necessary for full modulation (that....

A high voltage step-up DC power supply using adjustable flyback conversion...

Isolated flyback converters usually evoke thoughts-or bitter memories-of custom transformers, slipped delivery schedules, and agency-approval problems. Off-the-shelf flyback transformers carry isolation ratings of only 300 to 500V and rarely of as much as 1....

This circuit is a small +5V power supply, which is useful when experimenting with digital electronics. Small inexpensive wall tranformers with variable output voltage are available from any electronics shop and supermarket. Those transformers are easily....

The circuit in Fig. 1 uses a single bicolor LED to indicate both power-on and blown-fuse conditions. Regardless of the condition of the fuse, the green side of the LED is always on for each positive half-cycle of the ac input. With a 120Vrms ac input....

Since the circuit operates at greater than mains potential and is not isolated by a transformer, it is extremely dangerous. The DC operating potential is about 340V, and there is more than enough stored charge to kill you many times over (although in my....

This novel buzzer circuit uses a relay in series with a small audio transformer and speaker. When the switch is pressed, the relay will operate via the transformer primary and closed relay contact. As soon as the relay operates the normally closed contact....

The original TX was designed to be only PULSE Modulated for a proportional R/C system, but I later used the same circuit to make an HF bands Amplitude Modulation (AM) transmitter using PA-Base Modulation. It eliminated the need for a modulation transformer;....