Wiring Schematic Diagram

3V FM transmitter Circuit

This 3V FM transmitter Circuit is about the simplest and best basal transmitter to body and accept a advantageous transmitting range. It is decidedly able admitting its baby basic calculation and 3V operating voltage. It will calmly access over three floors of an accommodation architecture and go over 300 meters in the accessible air.

The ambit is basically a radio abundance (RF) oscillator that operates about 100 MHz. Audio best up andamplified by the electret microphone is fed into the audio amplifier date congenital about the aboriginal transistor. Output from the beneficiary is fed into the abject of the additional transistor area it modulates the beating abundance of the catchbasin ambit (the 5 about-face braid and the trimcap) by capricious the alliance capacitance of the transistor. Alliance capacitance is a action of the abeyant aberration activated to the abject of the transistor. The catchbasin ambit is affiliated in a Colpitts

Place the transmitter about 10 anxiety from a FM radio. Set the radio to about about 89 - 90 MHz. Walk aback tothe FM transmitter and about-face it on. Spread the ambagious of the braid afar by about 1mm from anniversary other. No coilwinding should be affecting addition winding. Use a baby spiral disciplinarian to tune the trim cap. Remove the screwdriverfrom the trim spiral afterwards every acclimation so the LC ambit is not afflicted by devious capicitance. Or use a plasticscrewdriver. If you accept adversity award the transmitting abundance again accept a additional being tune up and downthe FM punch afterwards every adjustment. One abounding about-face of the trim cap will awning its abounding ambit of capacitance from 6pF to 45pF. The accustomed FM bandage tunes in over about one tenth of the abounding ambit of the affability cap.

So it is best to acclimatize it in accomplish of 5 to 10 degrees at anniversary turn. So affability takes a little backbone but is not difficult. The acumen that there charge be at atomic 10 ft. break amid the radio and the FM transmitter is that the FM transmitter emits harmonics; it does not alone afford on one abundance but on several altered frequencies abutting to anniversary other. You should accept little adversity in award the Tx abundance back you chase this procedure.

Wireless Headphones Receiver

The wireless headphones receiver presented is an accepted appliance of ZN415 produced by Ferranti ( abbreviate beachcomber receiver). ZN415 assures a affection reproduction, has a 1.5 array alimentation and contains a MA detector and audio amplifier.

The accepted burning is < 5mA, L1 has 40 turns, 0.2 Ø chestnut and 20mm Ø ferrite. C1 is adjuted with an non metal screw, the accession abundance of this wireless headphone receiver is amid 1.7MHz and 3.4MHz – shortwave receiver. This wireless receiver is to be acclimated with this wireless headphones transmitter.

12V Low side PWM Motor/Light Controller

12V High side PWM Motor/Light Controller

These two schematics are variations on addition PWM circuit that I designed. The diagrams are for 12V operation alone and there are aerial ancillary (common ground) and low ancillary (common +12V) versions. The low ancillary adaptation of the ambit uses an N Channel FET, the aerial ancillary adaptation of the circuit uses a P Channel FET. N Channel accessories tend to handle added accepted than P Channel devices, they are additionally beneath expensive. The aerial ancillary adaptation of the ambit is advantageous back one ancillary of the bulk has to be grounded.

This Circuit can about-face a adequately aerial bulk of current, an IRFZ34N MOSFET can handle over 35 Amps if affiliated to a able calefaction sink. Higher ability FETs, such as the IRFZ48N or IRF1010Z can be commissioned if alike beyond currents are required. It is additionally accessible to affix assorted FETs in alongside for alike added accepted capacity. Always use thermally conductive grease amid the FET and the calefaction sink, and bethink that the calefaction bore is electrically live.

Inductive endless (motors) may crave appropriate affliction back they can accomplish ample voltage spikes that can accident the MOSFET. Replacing the 1N4002 with a fast accretion diode may advice blot the about-face voltage bang back active an anterior bulk such as a motor. If you use these circuits for abstracts with electric vehicles, be abiding to install a ambit breaker in alternation with the battery, the ambit breaker should be accessible to ability by the driver. This is abnormally important due to the actuality that back MOSFETs fail, they generally abbreviate out, abrogation the motor on at abounding speed.

Note that the pwm ascendancy has an adverse aftereffect on these two circuits, the low ancillary adaptation is on with a aerial pin 7 achievement voltage and the aerial ancillary adaptation is on with a low output.

The inductor on the aboideau ancillary of the ability MOSFET transistor can be a ferrite bean or a few turns of wire captivated about a 10 ohm, 1/4W resistor. The purpose of this allotment is to anticipate RF oscillations from occurring in the MOSFET circuitry.

AM Transmitter Double Side Band

The ambit of AM transmitter is advised to address (amplitude modulated) DSB (double ancillary band) signals. A articulate AM arresting consists of a carrier and two symetrically spaced ancillary bands. The two ancillary bands accept the aforementioned amplitude and backpack the aforementioned information. In fact, the carrier itself coveys or carries no information. In a 100% articulate AM arresting 2/3 rd of the ability is ashen in the carrier and alone 1/6th of the ability is independent in anniversary ancillary band.

In this transmitter we abolish the carrier and transmitt alone the two ancillary bands. The able achievement of the ambit is three times that of an agnate AM transmitter.

Op Amp IC741 is acclimated actuality as a microphone amplifier to amplify the articulation best up by the condenser microphone. The achievement of the op amp is fed to the bifold counterbalanced modulator (DBM) body about four IN4148 diodes. The accentuation akin can be adapted with the advice of preset VR1.

The carrier is generated application clear oscillator active about BC548 transistor T2. The carrier is added amplified by transistor T1, which additionally acts as a absorber amid carrier oscillator and the counterbalanced modulator. The alive abundance of the transmitter can be afflicted by application crystals of altered frequencies. For multi abundance operation, alternative of altered crystals can be fabricated application a selector switch.

Ths achievement of the DBM contains alone the artefact (of audio and carrier) frequencies. The DBM suppresses both the ascribe signals and produces bifold ancillary bandage suppressed carrier (DSBSC) at its output. However, back the diodes acclimated in the counterbalanced modulator are not absolutely matched, the achievement of the DBM does accommodate some balance carrier. This is accepted as carrier leakage. By adjusting the 100 ohm preset VR2 and trimmer C7 you can absent the carrier leakage.

To accept DSB signals you charge a exhausted abundance oscillator to reinsert the missing carrier. If you don’t accept a exhausted abundance oscillator, or appetite to transmitt alone AM signal, acclimatize preset VR2 to aperture some carrier so that you can accept the signals on any accustomed radio receiver. In AM approach 100% accentuation can be accomplished by adjusting preset VR1 and VR2.

Range of the circuit depends on the type of antenna used. It is very important to use matched antenna to radiate the signals effectively. I used horizontal dipole antenna, which is simple and easy to construct. For 7 MHz, ie 40 meter ham band the length of dipole antenna will be 20 meter. Use 75 Ohms co-axial cable to connect antenna and transmitter. I was able to get 57 report from station 80 kilometer away. You can easily add a Linear RF amplifier using IRF830 to get more power.

Car Alarm Arming Horn Beep Canceller Circuit diagram

It's a abundant accessibility that best avant-garde cars appear with a congenital in alarm, about it is annihilation but babble abuse that the horn sounds back the anxiety is armed. Disconnecting the anxiety arrangement from the horn broadcast will annihilate this, but anticipate the horn from aural in the alike of an absolute alarm.

This circuit serves to blackout the arming beep yet advance the anxiety by introducing a baby adjournment into the signal. It sits amid the anxiety and horn relay. The anxiety charge accommodate a connected horn arresting for at atomic 3 abnormal afore the horn broadcast is activated. That way the quick "beep" will never actuate the horn relay, while the connected anxiety arresting will.

40 Segment LED S-Meter Circuit

Provide your radio with a actual cord signal, again acclimatize the HIGH LEVEL pot to the beginning of anecdotic the aftermost LED (all LEDs on). Remove the arresting completely, again acclimatize the LOW LEVEL pot to the beginning of no LEDs illuminated.

If your radio's S-meter achievement is greater than 5 volts, you mau ambition to alter the HIGH LEVEL pot with a 10K resistor, and accommodate pin 6 of the right-most 3914 with the cathode of a 6.1 volt zener diode, pulled up to 13 volts with a 1K resistor. The anode should be affiliated to ground. You may use a college voltage zener if necessary.

This agreement provides 10ma per LED segment. Change the ethics to the resistors and pots to change the drive accepted to the LEDs. R1=12.5/I R2=25/I R3=37.5/I R4=50/I area I = the adapted LED current

40 m Band Direct Conversion Receiver

Building a applied and accessible absolute about-face receiver for the 40 m CW bandage is not as simple as it ability appear. Broadcast base signals from the adjoining 41 m band, will calmly afflict best absolute about-face mixer designs with their exceptionable (and absolutely nearby) S9 +40 dB signals. My band-aid incorporates a diode-ring mixer and a attenuated bandage rf ascribe filter. These choices aftereffect in empiric all-embracing receiver activating ambit than that accomplished back application an IC mixer bore (such as a NE612). Comfortable and undisturbed operation in the black was accessible back activated application my Windom antenna. Some of this project's objectives included:

• High dynamic range diode-ring mixer
• Stable oscillator with a 30 kHz tuning range
• Tuning range from 7005 kHz to 7035 kHz
• Narrow front end band pass input filter
• Broadband 50 Ohm termination
• Audio selectivity used in the AF amplifier
• Symmetrical (differential coupling) design
• Low battery / power supply current consumption
• 60 Ohm headphone output impedance