This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band. Features * Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz * Correct rounding, reduced blinking of last digit * Over-range indication * Fast measurement - short measuring period * High input sensitivity in VHF/UHF band * Switchable intermediate frequency offset for use with receiver.
Posted on Friday, April 11, 2008 • Category: Timer Circuits
A small circuit that can find a lot applications of measurement time. She has the possibility us inform with sound signal from the BZ1. At the same time, exist the possibility drive a external circuit via the optocoupler IC2, after we connect the applicable circuit in contacts [ A ] and [ B ]. The circuit is based on IC1 (4060), which include in his inside, oscillator and a binary divider of 14 stage. The frequency operation of oscillator is determined by a circuit R-C that connected in pins 9,10,11 of IC1. We give supply in the circuit, with switch S1, is presented a pulse in 12 [ RESET ] via C1 and R3, null him counter, require the measurement of pulses to begin from the zero. Than the count get at in 14th digit then exit Q14 in the pin 3, acquire high logic level. This voltage drive the base the Q1-2, the transistors turn on, thus buzzer BZ1 sound, also the IC2 is ready to drive, via contacts [ A][B ], any suitable external circuit. The time delay is regulated with the potentiometer RV1, in time delay that begin from 1 minute up to 2 hours, proportionally with the combination of prices that they will have the RV1 and C2.
Posted on Friday, April 11, 2008 • Category: Amplifiers
GainClones have VERY few components and this one is based on the National Semiconductor LM3875 IC. The PCBs and components are very simple and quick to make, only took about 20 mins to assemble both amps and rectifier board. DC offset was about 80mV on one channel and about 40mV on the other. I used the optional Ci capacitor in the national datasheet for the IC which reduced it to between 0-4mV: This is the capacitor I chose, its an Elna Starget (expensive). The case was MUCH more time consuming and difficult to make though. I bought all the aluminum from a scrap metal yard including the heatsink. I got my aluminum panels cut at a sheet metal shop as I cant make straight cuts with a hack saw.
Posted on Thursday, April 10, 2008 • Category: Frequency Wave Generators
Frequency Generator is an essential laboratory equipment for every electronic. It allows a variety of measurements and experiments. The module described here is based on high quality XR2206 IC and is extremely compact and inexpensive. Output frequency is from 1Hz to 1MHz. It provides sine, square and triangle waves around 1Hz to 1MHz, depending on the timing capacitors used. Over two Potentiometers the amplitude and frequency can be set. About trimmers can also have the purity of the sine signal and the offset of the output voltage can be changed.
Posted on Thursday, April 10, 2008 • Category: Phone Circuits
It might be "yet another" «device» controller that operates over phone-line, but this one works for sure :) The task was to build a device that connects to the phone line and has a relay as an output switch. It should also sense if the connected «consumer» is turned-on or off and report to the administrator at the other end of the phone line. The administrator would then call-in the device, log in with the password, and check the state of «consumer», turn it on or off, change password or some other settings. Current version has only one relay.
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