Diagram SOlution

Friday, October 24, 2014

Selector Antennas using PIN Diodes Circuit Diagram

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 circuit 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 circuit was designed for antenna input impedance of 50 or 75 ohms.

Selector Antennas using PIN Diodes Circuit Diagram

Selector Antennas using PIN Diodes Circuit Diagram

Selector Antennas using PIN Diodes Circuit Diagram

Low drop Regulator with Indicator Circuit Diagram

Even today much logic is still powered from 5 volts and it then seems obvious to power the circuit using a standard regulator from a rectangular 9-V battery. A disadvantage of this approach is that the capacity of a 9-V battery is rather low and the price is rather high. Even the NiMH revolution, which has resulted in considerably higher capacities of (pen-light) batteries, seems to have escaped the 9-V battery generation. It would be cheaper if 5 volts could be derived from 6 volts, for example. That would be 4 ‘normal’ cells or 5 NiMH- cells. Also the ‘old fashioned’ sealed lead- acid battery would be appropriate, or two lithium cells.

Circuit diagram :

Low-drop Regulator with Indicator Circuit Diagram

Using an LP2951, such a power supply is easily realised. The LP2951 is an ever- green from National Semiconductor, which you will have encountered in numerous Elektor Electronics designs already. This IC can deliver a maximum current of 100 mA at an input voltage of greater than 5.4 V. In addition to this particular version, there are also versions available for 3.3 and 3 V output, as well as an adjustable version. In this design we have added a battery indicator, which also protects the battery from too deep a discharge. As soon as the IC has a problem with too low an input voltage, the ERROR output will go low and the regulator is turned off via IC2d, until a manual restart is provided with the RESET pushbutton.

The battery voltage is divided with a few resistors and compared with the reference voltage (1.23 V) of the regulator IC. To adapt the indicator for different voltages you only need to change the 100-k resistor. The comparator is an LP339. This is an energy-friendly version of the LM339. The LP339 consumes only 60 µA and can sink 30 mA at its output. You can also use the LM339, if you happen to have one around, but the current consumption in that case is 14 times higher (which, for that matter, is still less than 1 mA).

Finally, the LP2951 in the idle state, consumes about 100 µA and depend- ing on the output current to be deliv- ered, a little more.

TV Video Transmitter Circuit Diagram

This circuit is a video transmitter that has many uses, such as video cameras, security cameras, satellite receivers, DVD, Video Games, etc. .. The circuit transmits 470-580MHz and can be tuned in the UHF channels 21-34. The video transmitter can reach up to 300 meters in open field using a wire antenna of 10-20 cm.

TV Video Transmitter Circuit Diagram

Video Transmitter

Transmitter can work with a voltage from 9 to 15 volts. However, you can also use a 9v battery. Oscillator is based around BF199 and BFR90 is the RF transistors. If necessary, the transmission power can be increased by replacing with BFR90 transistor 2N3886.

Lambda Probe Readout For Carburetor Tuning

A lambda probe (or oxygen sensor) can be found on the exhaust system of most cars running on unleaded fuel. Having reached its normal operating temperature (of about 600 degrees Celsius!) the lambda probe supplies an output voltage proportional to the amount of residual oxygen measured in the exhaust gas.

This information is indicative of, among others, the air/fuel ratio supplied by the carburetor(s) and hence the combustion efficiency. In modern car (and motorcycle) engines, this information is used to (electronically) adjust engine parameters like ignition timing and fuel injection. The indicator described here is intended for permanent installation on a motorcycle of which the air/fuel ratio needed to be watched, with the obvious aim engine power tuning after ﬁtting a different set of carburetors. Apart from this obvious technical use the unit’s bright LEDs will no doubt attract the attention of curious motorcyclists.

Lambda Probe Readout For Carburettor Tuning

At the local junkyard a single-wire lambda probe may be salvaged from a wrecked car. Once a suitable nut has been found, the probe can screwed into the exhaust pipe of the motorcycle, at about 30 cm from the cylinders. Since we’re talking of welding and drilling in an expensive (chrome-plated) exhaust pipe, you may ﬁnd that actually ﬁtting the probe is best left to specialists! The starting point for the design of a suitable electronic indicator is that in the noble art of carburetor tuning an air/fuel ratio of 14.7 to 1 is generally considered ‘perfect’, the range covering 16.2 to 1 (‘lean’) to 11.7 to 1 (‘rich’). The perfect ratio typically corresponds to a probe output voltage of 0.45 V.

Referring to the circuit diagram, that is the input level at which 5 of the 10 LEDs will light, including the green one, D5. If one of the red LEDs lights, the mixture is definitely too rich. Note that in general it is better to have a mixture that is a little to rich than one that’s on the lean side, hence a yellow LED lights between the green LED and the ﬁrst red one. Also note that the engine needs to be at its normal operating temperature before a meaningful indication is obtained.

5 Watt Class A Audio Amplifier Circuit diagram

This solid-state push-pull single-ended Class A circuit is capable of providing a sound comparable to those valve amplifiers, delivering more output power (6.9W measured across a 8 Ohm loudspeaker cabinet load), less THD, higher input sensitivity and better linearity. Voltage and current required for this circuit are 24V and 700mA respectively, compared to 250V HT rail and 1A @ 6.3V filament heating for valve-operated amplifiers. The only penalty for the transistor operated circuit is the necessity of using a rather large Heatsink for Q2 and Q3 (compared to the maximum power delivered).In any case, the amount of heat generated by this circuit can be comparable to that of a one-valve amplifier. An optional bass-boost facility can be added, by means of R5 and C5.

Circuit diagram:

Parts:

P1 = 47K
R1 = 100K
R2 = 12K
R3 = 47K
R4 = 8.2K
R5 = 1.5K
R6 = 2.7K
R7 = 100R
R8 = 100R
R9 = 560R-1/2W
R10 = 1R-1/2W
Q1 = BC560
Q2 = BD439
Q3 = BD439
C1 = 10uF-63V
C2 = 10uF-63V
C3 = 47uF-25V
C4 = 100uF-35V
C5 = 150nF-63V
C6 = 220uF-25V
C7 = 220uF-25V
C8 = 1000uF-25V
SPKR = 5W-8R Speaker

Notes:

If necessary, R2 can be adjusted to obtain 13V across C8 positive lead and negative ground.
Total current drawing of the circuit, best measured by inserting the probes of an Avo-meter across the positive output of the power supply and the positive rail input of the amplifier, must be 700mA. Adjust R8 to obtain this value if necessary.
Q2 and Q3 must be mounted on a finned Heatsink of 120x50x25mm. Minimum dimensions.
Add R5 and C5 if the bass-boost facility is required.

Portable 230v Lamp Flasher

Here is a portable, high-power incandescent electric lamp flasher. It is basically a dual flasher (alternating blinker) that can handle two separate 230V AC loads (bulbs L1 and L2). The circuit is fully transistorised and battery-powered. The free-running oscillator circuit is realised using two low-power, low-noise transistors T1 and T2. One of the two transistors is always conducting, while the other is blocking.

Circuit diagram :
Portable 230v Iamp Flasher-Circuit-Diagram

Portable 230v Lamp Flasher Circuit Diagram

Due to regular charging and discharging of capacitors C1 and C2, the two transistors alternate between conduction and non-conduction states. The collector of transistor T1 is connected to the base of driver transistor T4 through current-limiting resistor R5. Similarly, the collector of transistor T2 is connected to the base of driver transistor T3 through limiting resistor R6. These transistors are used to trigger Triac1 and Triac2 (each BT136) through optotriacs IC1 and IC2, respectively, and switch on the power supply to external loads L1 and L2.

IC1 and IC2 operate alternatively at a low frequency determined by the values of capacitors C1 and C2. The oscillator circuit built around transistors T1 and T2 generates low frequencies. When transistor T3 conducts, IC1 is enabled to ire Triac1 and bulb L1 glows. Similarly, when transistor T4 conducts, IC2 is enabled to ire Triac2 and bulb L2 glows. Connect the power supply line (L) of mains to bulbs L1 and L2, and neutral (N) to T1 terminals of Triac1 and Triac2.

You can also connect neutral (N) line of the external 230V mains supply to both loads (bulbs L1 and L2) as a common line and then route supply line (L) to respective loads (bulbs L1 and L2). The circuit works off only 3 volts. Since current consumption is fairly low, two AA-type cells are suficient to power the circuit. Assemble the circuit on a general-purpose PCB and enclose in a suitable plastic cabinet with integrated AA-size pen-light cell holder. Drill holes for mounting the ‘on’/‘off’ switch and power switching terminals. Also connect two bulb holders for bulbs L1 and L2.

The circuit works off only 3 volts. Since current consumption is fairly low, two AA-type cells are sufficient to power the circuit. Assemble the circuit on a general-purpose PCB and enclose in a suitable plastic cabinet with integrated AA-size penlight cell holder. Drill holes for mounting the ‘on’/‘off’ switch and power switching terminals. Also connect two bulb holders for bulbs L1 and L2. Refer Fig. 2 for pin configurations.