Headphone Amplifier

R1-4= 1.2Kohm R12= 4.7 ohm C8-10= 470uF 25V
R2-3= 3.9Kohm RV1= 10Kohm  Log. pot. C9-11= 100nF 100V ceramic
R5-10= 10Kohm TR1= 10Kohm Trimmer Q1-3= BC184
R6=100Kohm C1= 4.7uF 63V MKT Q2-4= BC214
R7-9= 2.2Kohm C2-7= 100uF 25V Q5= BD136 or BD538
R8= 150 ohm C3-5= 100nF 100V  MKT Q6= BD135 or BD537
R11-13= 6R8 ohm C4-6= 100uF 16V All resistors is 1/4W 1%

Balanced Microphone Preamp

Car Voltage Gauge

The Car Voltage Gauge is based on 3 parts. The input circuit is an Analog to Digital Converter (IC2 CA3162E). The purpose of this chip is to sample an analog voltage and convert it to a decimal value which is read by a Display/Decoder Driver (IC1 CA3161E). This chip will turn each seven segment display on through the driver transistor Q1 - Q3. The power is derived from the car and is converted to 5 volts by the 5 volt regulator. The circuit works as follows: The 10uf capacitor is charged up by the cars voltage. Its value is then read by IC2 and a decimal value of that voltage is provided to IC1 which multiplexes the three display units. Each display is turned on sequentially with its appropriate value displayed. The transistors Q1 through Q3 control the drive to each seven segment display. By monitoring the cars voltage with an accurate multimeter you can adjust the "Zero Adj." pot and the "Gain Adj." pot for accurate readings. LED 1 and 2 are optional. They can be used to indicate power on or can light up a cut out display that says "Volts". This can be made by a plastic module that has a thin plastic cover on it with the word "Volts" cut into it. The LED's would be mounted inside the module.

R/C Car(27 MHz)

L1, L4=9 turns, .15mm wire on 4.5mm diameter tunable ferrite coil former
L2=15 turns, .5mm wire, 5mm diameter
L3=3.5 turns, .5mm wire, 5mm diameter

Step-Up Converter (MC34063A)

This solidstate DC switch can be assembled using just three transistors and some passive components. It can be used to switch on one gadget while switching off the second gadget with momentary operation of switch. To reverse the operation, you just have to momentarily
depress another switch.


The circuit operates over 6V-15V DC supply voltage. It uses positive feedback from transistor T2 to transistor T1 to keep this transistor pair in latched state (on/off), while the state of the third transistor stage is the complement of transistor T2’s conduction state.


Initially when switch S3 is closed, both transistors T1 and T2 are off, as no forward bias is available to these, while the base of transistor T3 is effectively grounded via resistors R8 and R6 (shunted by the load of the first gadget). As a result, transistor T3 is forward biased and gadget 2 gets the supply. This is indicated by glowing of LED2.


When switch S1 is momentarily depressed, T1 gets the base drive and it grounds the base of transistor T2 via resistor R4.


Hence transistor T2 (pnp) also conducts. The positive voltage available at the collector of transistor T2 is fed back to the base of transistor T1 via resistor R3. Hence a latch is formed and transistor T2 (as also transistor T1) continues to conduct, which activates gadget 1 and LED1 glows.


Conduction of transistor T2 causes its collector to be pulled towards positive rail. Since the collector of T2 is connected to the base of pnp transistor T3, it causes transistor T3 to cut off, switching off the supply to gadget 2) as well as extinguishing LED2. This status is maintained until switch S2 is momentarily pressed. Depression of switch S2 effectively grounds the base of transistor T1, which cuts off and thus virtually opens the base-emitter circuit of transistor T2 and thus cutting it off. This is the same condition as was obtained initially. This condition can be reversed by momentarily pressing switch S1 as explained earlier.


EFY lab note. During testing, it was noticed that for proper operation of the circuit, gadget 1 must draw a current of more than 100 mA (i.e. the resistance of gadget 1 must be less than 220 ohms) to sustain the latched ‘on’ state. But this stipulation is not applicable for gadget 2. A maximum current of 275 mA could be drawn by any gadget.

credit : PRAVEEN SHANKER

Stereo 1W audio amplifier with DC volume control

The TDA7053A is an integrated stereo audio power amplifier with DC volume control in a 16-pin dual-in-line plastic package. It is designed for use in TVs and monitors but is also suitable for battery-operated equipment.

The circuit used is straight out of the data book. PCB dimensions are a tiny 43mm x 40mm (1.7” x 1.6”).


TDA7053A SPECIFICATIONS

• 4.5 - 18V supply voltage range
• 1.5A max non-repetitive peak output current
• 1.25A max repetitive peak output current
• 1.1W output power using 6V supply into 8 load
• (THD = 10%)
• 20k internal input impedance
• 210uV noise output voltage
• 20Hz to 300kHz bandwidth (typical) at –1 dB

The kit is constructed on single-sided printed circuit board. Protel Autotrax & Schematic were used.

CONSTRUCTION

Start with the two resistors followed by the small monobloc capacitor. Next comes the IC socket with the electrolytic and polyester capacitors last. Be careful to get the electrolytic capacitors in the right way around. The positive lead is marked on the overlay. The negative lead is marked on the body of the capacitor.

Solder the power and audio cables (supplied by you) directly to the pads provided on the PCB.

CIRCUIT DESCRIPTION

All the work is done internally in the IC. The internal circuit consists of a differential input stage with integrated DC volume control, two class AB output stages and a stabiliser circuit.

Resistors R1 and R2 provide a DC input impedance to ground. The input signal is AC coupled into the amplifier via capacitors C3 and C4. The output stages are a BTL (Bridge Tied Load) configuration, resulting in increased output power at low supply voltages.

The gain of each amplifier channel is controlled by the DC voltage level on pins 2 and 8. This voltage is derived from the DC supply using a simple voltage divider network of resistor R3 and potentiometer VR1. Capacitor C5 across the potentiometer provides power supply decoupling of the volume control inputs. If the DC volume control voltage falls below 0.4V the chip will switch to mute mode.

The maximum voltage gain of the amplifier is internally fixed at 40.5dB. The DC volume control has a logarithmic characteristic. The total gain can be controlled from +40.5 to –33 dB.

Due to the BTL output configuration the outputs are floating with respect to ground. Therefore the outputs of the amplifier should never be connected to ground.

Capacitors C1 and C2 provide power supply decoupling.

IF IT DOES NOT WORK

Poor soldering (“dry joints”) is the most common reason that the circuit does not work. Check all soldered joints carefully under a good light. Re-solder any that look

suspicious. Check that all components are in their correct position on the PCB. Are the electrolytic capacitors the right way round?

PARTS LIST – K107A

Resistors (0.25W carbon)

4K7 yellow violet red .........R1,2 .............................. 2

27K red violet orange .........R3 ................................. 1

Capacitors

100nF monobloc 104 ..........C1 ................................. 1

470nF polyester 474 ...........C3,4 .............................. 2

1uF 16V electrolytic ...........C5 ................................. 1

220uF 25V electrolytic .......C2 ................................. 1

Semiconductors

TDA7053A......................... IC1 ................................ 1

Stereo Audio Amplifier IC with DC volume control

Miscellaneous

Potentiometer, 10K.............VR1 .............................. 1

Single gang, PCB mounting

IC socket, 16 pin, for mounting IC1 .......................... 1

PCB, K139................................................................. 1

credit : kitsrus.com

Deer Repellent/ Seismic Sensor

Here is a simple sensor which can detect the seismic vibrations caused by a person or
large animal walking nearby. A representative application for the sensor is a deer
repellent for the vegetable garden. When a deer steps near the sensor a loud buzzer or
beeper sounds for a few seconds startling the would-be vegetable thief away. The
sensor also makes an effective intruder detector to catch trespassers as soon as they
step on the property!


The unit is designed to consume minute amounts of power when not rattling to provide
many months of unattended protection (practically set by the battery shelf life). The
seismic sensor is built from an ordinary 2 inch speaker by gluing a mass to the speaker
cone to lower its resonance frequency. A lid from a baby food jar with a little extra
weight glued to the inside will work fine.

The CA3094 I.C. is an unusual op-amp consisting of a programmable transconductance
amplifier connected to a darlington transistor. In this circuit the darlington is combined
with a pnp transistor to form a monostable timer which determines how long the buzzer
sounds. When the ground shakes, the vibration sensing speaker generates a small voltage
which is amplified causing the voltage on pin 1 to go high. The darlington in the IC and
the 2N4403 turn on with regenerative feedback provided by the diode. The 2N4401 turns
on, powering the buzzer until the monostable resets.

The circuit may be used to activate a variety of devices including a relay to control line
voltage devices, a transmitter to telemeter an alarm from a remote location, a battery powered walkway light, or even one of those battery powered squirt guns! The output
transistor may be replaced with a power darlington transistor for directly controlling
higher current loads.

The circuit may be built into ordinary plumbing PVC pipe or practically any
weatherproof enclosure. A larger detection area may be accomplished by burying a long
pole or PVC pipe just below the surface of the ground with the seismic sensor located
above the pole. Vibrations will readily travel down the pole whenever a footstep occurs
anywhere along its length.

The seismic sensor may be replaced with other sensors for different applications. A
photocell/ resistor divider will sense changes in light level, a microphone will sense fairly
low sound levels, and a diode detector will sense a low-level RF field.

Deer Repellent/ Seismic Sensor

Noise Gate

The parts for this Noise Gate are:
J1 - J2: 1/4 INCH MONO FEMALE CHASIS MOUNTING JACKS
C1 - C5: 0.1 MICROFARAD CERAMIC DISC CAPACITORS AT 50V
P1: 10k POTENTIOMETER
P2: 100M POTENTIOMETER
R1: 1K RESISTOR
R2: 100K RESISTOR
IC1: 741 OP AMP

HF / VHF / UHF Active Antenna

R1 = 1 Mega Ohm
R2 = 220K
R3,R6 = 100K
R4 = 100 ohm
R5 = 10K potentiometer, (pc mount)
C1,C2,C5,C6 = 0.01microF, ceramic disc
C3 = 100pF ceramic disc
C4 = 4.7 to 10microF, 16WVDC, radial lead electrolytic
B1 = 9-volt alkaline battery
S1,S2 = DPDT PC mount pushbutton switch
J1,J2 = PC mount RCA jack
 ANT1 = Telescoping whip antenna (screw mount)
 MISC = PCB materials, enclosure, enclosure, battery holder and connector,
        wire, solder, etc.

Circuit will expand the district, 3-30Mhz = area high-frequency (HF), 3-300Mhz = areavery-high frequency (VHF), 300-3000MHz district ultra-high (UHF) frequency.
Select Allow a Dog When SW 1-a to the amplifier Q1 = a district. high-frequency (HF).
Select Allow a Dog When SW 1-a to the amplifier Q2 = a district. high-frequency (HF)area, and very-high frequency (VHF).
R5 = adjust the gain of the circuit SW2-a, b ON-OFF signal expansion.

PCB

ADD - ON STEREO CHANNEL SELECTOR by PRABHASH K.P.

The add-on to the circuit presented here is useful for stereo systems.
This Circuit provided for connection Stereo outputs from four different
Sources / channels as inputs and a single chosen by them is / are connected
Exit at any time.

When power is turned "on" Channel A (A1 and A2) is selected. If not,
The audio is on Channel A, the circuit waiting for some time and then
the next channel (channel B), The The search operation continues until it is detected
The audio signal on a channel. The other channels have to wait or delay
The time can be set by Preset VR1. If the time longer
necessary, you can replace C1 Capacitor with a higher value.

Suppose that is, Channel A-line is connected to a tape recorder and the channel B
a radio receiver. The first time A channel is selected, the audio
the tape recorder be present Edition. After the tape is played entirely
or if you have enough rest between successive shots, the circuit automatically launch
radio receiver. To manually from a jump (selection) active channel, press the jump
switch (S1) at the time, one or more times until the desired input channel
selected. The selected channel (A, B, C, or D) is indicated by a light
LED (LED 11, LED 12, LED13 and LED14, respectively).

Analog IC CD4066 contains four switch. These switches are four separate channels. For stereo operation, two similar chips CD4066 as shown in the circuit. These analog
The switches are controlled by IC CD4017 outputs. CD4017 is a 10-bit ring
IC against. Since only one of its outputs high all the time, only a
Switch is closed at a time. IC CD4017 is a ring of 4-bit configuration
Connecting the fifth counter output Q4 (pin 10) on the reset pin. Capacitor
C5, in conjunction with R6 forms a power-on reset circuit for IC2, so that
the first step "in the" power Supply, output Q0 (pin 3) is always 'Strong'. The watch is expected CD4017 IC1 (NE555), which acts as a astable multivibrator when transistor
T1 is in state court.

IC5 (KA2281) is not used here just to point out that the audio level
selected channel stereo, but also transfer Polarization of the transistor T1. Only
a certain threshold of audio detected in a selected channel, the pin 7 and /
or pin 10 of IC5 goes "low." This low Level is the base of the transistor, along
T1 with diode-resistor combination of D2-R1/D3-R22. As a result, the transistor
T1 conducts and the cause of the output IC1 to remain "low" (off), if
selected channel's output exceeds audio threshold setting.

Preset VR2 VR3 were recorded and Set individual audio- The thresholds of the left stereo channels, if desired. Once the multivibrator Effect of IC1 is disabled, the output of IC2 does not change. Therefore, research through the channels until receives an audio signal and "higher preset threshold. The jump S1 is also used to move a channel when the selected sound in the channel. The number of channels can extended to ten, the use of new 4.066 chips.

Audio Isolation Amplifier

• R1, R11 56 kOhm   C1, C11 470 nF 
• R2, R12 39 kOhm C2, C12 2,2 uF (mikrofarad) 
• R3, R13 180 kOhm C3, C13 4,7 uF (mikrofarad) 
• R4, R7, R14, R17 15 kOhm C4, C14 15 pF, Ceramic
• R5, R9, R15, R19 10 Ohm C21, C22, C25, C31, C32, C35 100 nF, Ceramic
• R6, R16 120 kOhm C23, C33 1000 uF (mikrofarad) / min. 16 V 
• R8, R18 470 Ohm C24, C34 100 uF (mikrofarad) / min. 10 V 
• R10, R20 100 kOhm C26 10 nF/630 V= (275 V~)
• R21, R31 390 Ohm T1, T3, T11, T13 BC559C (BC177, BC308, BC558 ...) 
• R22, R32 1,8 kOhm T2, T4, T12, T14 BC549C (KC238, BC238, BC548 ...) 
• R23 4,7 kOhm U21, U31 B250C1000DIL, diode stek DIL / DIL bridge 
• P1 10 kOhm / N, potenciometr D21, D22, D31, D32 1N4148, KA262 apod./or eq. 
• IO21, IO31 LM317L 
• Transformor 0,5 W
• 230 V / 2x 9 V LED LED 2 mA 

PCB

40 LED for Bikecycle

Light flashes alternately the rhythm of the IC

PCB : 1

PCB : 2