TTL Power Supply using protection circuit diagram

TTL Power Supply using protection circuit diagram

Power supplies that are intended to be used with TTL logic circuitry must guard against over-voltage, which can destroy TTL chips very rapidly. The duration of over-voltage that can destroy TTL chips is much too brief to trigger any conventional fuse

TV RF Amplifier 5W With BLW98 circuit diagram

TV RF Amplifier 5W With BLW98 circuit diagram

This application circuit is a TV RF amplifier for driving small UHF TV transmitters, with gain is 7dB and can amplify a signal between 470-860 MHz. Drive input the circuit with 1 to 1,5 Watts signal. Better use double layer PCB with the second layer connected to earth.

Use a stabilized power supply 24 volts and at least 5 Amps.

TV Signal Amplifier circuit diagram

TV Signal Amplifier circuit diagram

Broad band, signal amplifier which covers the frequencies from 40 to 900 MHz. These frequencies include TV in VHF and UHF and also the radio broadcasting frequencies in the 88 - 108 MHz FM band.
It is connected between the antenna and the input of your receiver and boosts the signals by up to 20 dB, thus making it possible to receive even the weakest signals.

PARTS
R1 = 120 Ohm (brown, red, brown)
R2 = 1,5 KOhm (brown, green, red)
R3 = 270 Ohm (red, violet, brown)
R4 = 82 KOhm (gray, red, orange)
C1,C5 = 100pF (ceramic)
C2,C3 = 1nF (ceramic)
C4 = 2,2pF (ceramic)
D1,D2 = 1N4148 diode
Transistor = BFR90, BFR91, BFW92
Misc = PCB, 6pins, solder, 9V battery clip
L1,2:
diameter : 5mm
wire thickness : 0,5mm

15 W transmitter power amplifier 88-108MHZ Circuit diagram

15 W transmitter power amplifier 88-108MHZ Circuit diagram

The power amplifier can be reactive 1-2 W ,88-108MHZ power FM transmitter As for the expansion of 10-15W, a single C Larger and multi-level low pass filter components, has a high conversion efficiency and strong Yi-wave suppression.
Circuit see attached map shows, using high-power launch of C1972, its parameters are as follows: 175 MHZ, 4A, 25W, power gain ≥ 8.5 db, as shown by parameters, circuit work center frequency of about 98 MHZ, the importation of about 2 W of RF power , The rated output up to 15 W.

Video Signal Amplifier circuit diagram

Video Signal Amplifier circuit diagram

The construction should not present any difficulties if you follow the circuit diagram carefully and place the components in their place as it is outlined on the component side of the p.c. board. Solder first of all the pins, then the resistors, the capacitors making sure that the electrolytic are connected correctly with respect to their polarity and finally insert the transistors in their places and solder them very carefully as overheating during soldering can destroy them. When all the components have been soldered make a careful inspection of the circuit and if you are satisfied that there are no mistakes make the following connections:
- Supply voltage at points 3 (+12 VDC) and 4 (-)
- Input signal at points 1 (signal) and 2 (common).
- Outputs 5,6,7 (signal) and 4 (common).

Electronic mosquito repeller circuit diagram

Electronic mosquito repeller circuit diagram

Here circuit diagram of an ultrasonic mosquito repeler.

The circuit is based on the theory that insects like mosquito can be repelled by using sound frequencies in the ultrasonic (above 20KHz) range.The circuit is nothing but a PLL IC CMOS 4047 wired as an oscillator working at 22KHz.A complementary symmetry amplifier consisting of four transistor is used to amplify the sound.The piezo buzzer converts the output of amplifier to ultrasonic sound that can be heard by the insects.

Soft start PSU circuits diagram

Soft start PSU circuits diagram

The output voltage rises slowly and reaches 15 V in 5 seconds.

In order to perform this soft-start function, the LM317 voltage regulator IC requires an external universal PNP transistor and the L200 uses its internal comparator (pin 2).

After switch-on, the rising voltage on the positive side of the charging electrolytic capacitor slowly turns the (initially conducting) transistor off, thus raising the voltage (relative to ground) on the adjustment pin of the LM317. In the L200 circuit, the corresponding electrolytic capacitor's rising voltage gradually relaxes the current-regulation loop inside the L200.

Sound Operated Switch circuit diagram

Sound Operated Switch circuit diagram

This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electric microphone.

LED Lighting flip flop circuit diagram

LED Lighting flip flop circuit diagram

Using light effects for decoration on festive occasions is a normal practice. Designers are coming up with varieties of electronic circuits to fill the imagination of users.

Radio Remote Control using DTMF circuit diagram

Radio Remote Control using DTMF circuit diagram

Here we make use of DTMF (dual-tone multi frequency) signals (used in telephones to dial the digits) as the control codes. The DTMF tones are used for frequency modulation of the carrier. At the receiver unit, these frequency modulated signals are intercepted to obtain DTMF tones at the speaker terminals. This DTMF signal is connected to a DTMF-to-BCD converter whose BCD output is used to switch-on and switch-off various electrical appliances (4 in this case)

The remote control transmitter consists of DTMF generator and an FM transmitter circuit. For generating the DTMF frequencies, a dedicated IC UM91214B (which is used as a dialer IC in telephone instruments) is used here. This IC requires 3 volts for its operation. This is provided by a simple zener diode voltage regulator which converts 9 volts into 3 volts for use by this IC. For its time base, it requires a quartz crystal of 3.58 MHz which is easily available from electronic component shops. Pins 1 and 2 are used as chip select and DTMF mode select pins respectively. When the row and column pins (12 and 15) are shorted to each other, DTMF tones corresponding to digit 1 are output from its pin 7. Similarly, pins 13, 16 and 17 are additionally required to dial digits 2, 4 and 8. Rest of the pins of this IC may be left as they are. .

Single chip FM transmitter circuit using Maxim semiconductors IC MAX2606

Single chip FM transmitter circuit using Maxim semiconductors IC MAX2606

 single chip FM transmitter circuit using Maxim semiconductors IC MAX2606. The MAX2606 is a compact, high-performance intermediate frequency VCO specially designed for wireless communication circuits.
They have monolithic construction with low-noise and a low-power operation in a compact 6-pin SOT23 packing .Th1s low-noise IC feature an on-chip varicap diode and feedback capacitance that avoid the need for external tuning components, making the MAX2606 perfect for portable systems. Only an external inductor is needed to set the oscillation frequency.In addition to this,integrated differential output buffer is also there for driving a mixer or prescaler.The MAX2606 can be operated from a single +2.8 V to +5.4V supply and consumes very less current .The chip can be operated from 45MHz to 650MHz .

Subwoofer filter circuit diagram

Audio filter circuit diagram
The circuit is designed around the TL072 dual BIFET opamp IC. Out of the two opamps inside the chip, IC1A is wired as a buffer. The left and right audio inputs after mixing is fed to the input of the IC1A using the DPDT switch S1. Switch S1 is the phase control switch which can be used to make the subwoofer in phase with other speakers.