Diagram Guide

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.  

Most engineers will recognise the problem: Your circuit needs a stable 1 or 2 MHz clock generator (in the author’s case it was for a Pong game using an old AY3-8500). A suitable crystal is not to hand so you cobble together an RC oscillator (there are plenty of circuits for such a design). Now it turns out that you don’t have exactly the right capacitor so a preset pot is add e d to allow some adjustment . Before you know it the clock circuit is taking up more space on the board than you had hoped. 

Providing the application does not demand a precise clock source a tiny 8-pin microcontroller may offer a better solution to the problem. It needs no additional external components and an old ATtiny15 can be found quite cheaply. Another advantage of the solution is that clock frequency adjustment does not involve changing external components and is not subject to component tolerances. 

The microcontroller’s internal RC oscillator is already accurately calibrated to 1.6 MHz. With its inbuilt PLL, internal Timer 1 can achieve up to 25.6 MHz [2]. By configuring internal dividers the timer can output a frequency in range of roughly 50 kHz up to 12 MHz from an output pin. The difference between calculated and the actual output frequency increases at higher frequencies. A meaningful upper limit of about 2 MHz is a practical value and even at this frequency the deviation from the calculated value is about 15 %.

The circuit diagram could hardly be simpler, aside from the power supply connections the output signal on pin 6 (PB1) is the only other connection necessary.The example program, written in Assembler is just 15 lines long! With a program this short comments are almost super fluous but are included for clarity. The code can be downloaded from the Elektor website [1]. 

The program only needs to initialise the timer which then runs independently of processor control to output the clock sign al . The processor can then be put into sleep mode to memory used up the remaining 99 % is free for use for other tasks if required. 

The OSCCAL register contains a calibration byte which allows some adjustment of the CPU clock. This gives a certain degree of fine tuning of the output frequency. A recommendation in the Atmel data sheet indicates that the CPU clock frequency should not be greater than 1.75 MHz otherwise timer operation cannot be guaranteed. 

The more recent ATtiny45 can be substituted for the ATtiny15. In this case the CK SEL fuses should be set to put the chip’s Timer 1 into ATtiny15- compatible mode [3]. After adjustment to the program it will now be possible to obtain a higher (or more exact) frequency from the timer, the ATtiny45’s PLL can operate up to 64 MHz.

The schema diagram shows the over voltage protection as a feature of LM317 linear voltage regulator.Over voltages come from several source or factors which are usually in the form of transients. Transients are represented in spikes which are short and fast disturbance or change in the voltage and current component.

It only occurs in diagram containing conductance and capacitance. The causes are typically from power outages, short diagram, tripped schema breakers, lightning spikes, inductive spikes and other malfunctions from power company.

 As an example using a 12V battery source, the LM317 voltage regulator can be used to obtain 6 Volts. To protect any device from over voltage, there are ways such as adding relays or a zener diode. A relay switch functions by opening or closing under the command of another schema. But finding a relay that would limit the output from 6 V to 12 V is not easy.

Fortunately, zener diodes are more abundant. A 6.2V zener diode rating can be used to surpass any excessive voltage set by the voltage regulator, to prevent more damage to the schema. The components will be as follows:

ZD1 – 6.2 Volts
R1 – 1K ohms
R2 – 1K ohms
T1 – NPN Transistor (low power)
T2 – NPN Transistor (acts as a switch)

Every schema design needs to be tested carefully as to avoid further damage to the equipment that will be connected. The trial can be done by using a multimeter, and gradually increasing the schema voltage. Once the schema turns off the supplied voltage, take note of the reading which will signify the threshold voltage of the zener diode.

This Selector Antennas using PIN Diodes Circuit Diagram selector antennas uses PIN diodes, was designed using common components and is very useful when used various external antennas, this antenna selector uses PIN diodes that eliminate disadvantages of mechanical switches especially at high frequency. 

Capacitors C1 to C4 and C9 are used to prevent the input and output schema DC. Shock L1 to L5 prevent leakage of HF signal.Shock L1 to L5 can be wound on a ferrite core, using enameled copper wire of 0.3 mm in diameter, two rounds will suffice for entries for VHF and UHF 5 (1 mH is required for VHF and UHF about 5 uH). The schema was designed for antenna input impedance of 50 or 75 ohms.