How to make a long range FM transmitter at low cost Description The use of transmitters which have a more powerful output than the ‘flea-power flea-power’’ are sometimes required when there are many obstacles in the path of the surveillance transmitter and monitoring station receiver, or the distance between them is too far so as to make a low powered device feasible. Whereas a typical micro transmitter will produce an RF power in the order of just a few milliwatts, i.e. a few thousandths of a watt, the VHF-FM transmitter described has a power output of between around a half and 2 watts, depending on the power source, which may be anywhere between 6 volts and 30 volts d.c. The battery or batteries should be of the alkaline high power type, since the current drain will be found to be relatively higher when compared to microtransmitter current drain. The power output of this device is somewhat proportional to the current drain and so therefore both may be decreased by altering the value of R6 to a higher resistance, or a variable resistor with a value of around 1k may be introduced in series with the existing R6, so as to give a variable power output. The variable The variable resistor resistormust must not be a wirewound device because this would act as an inductor which will cause feedback problems.The audio input to the power oscillator, which incidentally is formed by TR2 and associated components, is derived from a piezoelectric microphone which drives the simple audio frequency amplifier TR1. The input of the audio amplifier is controlled by the gain pot R1, which selects the correct amount of voltage that is generated by the piezoelectric microphone, then connects this signal to the base of audio amplifier TR1 via C7. It may be found that there is insufficient housing space for a bulky piezoelectric microphone, so with a slight modification to the circuit, it is possible to employ an electret microphone insert as shown. Since the RF field that is generated by this transmitter is relatively large, the problem of RF feedback may very well be encountered. This may be overcome by placing the transmitter transmitteriinside a metal enclosure, keeping all internal wiring as short as possible and the aerial wire.
Component listing for 1 watt transmitter Resistors Semiconductors R1 = 27k TR1 = BC547 R2 = 330k TR2 = 2N2219 fitted with heat sink R3 = 5k6 MIC = piezoelectric microphone R4, 5 = 10k R6 = 100R L = 6 turns 22 gauge enameled wire wound on 3⁄16″ former Capacitors C1, 2, 3 = 330 pF C4 = 2– 2 –10 pF trimmer C5 = 4p7 C6 = 1 nF C7,C8 = 40uF/25V Electrolytic
Circuit diagram for Long range FM Transmitter
2 km FM transmitter JOHN DECEMBER - 11 - 2009 274 COMMENTS
Description. With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier.C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna. Circuit diagram.
Notes. Assemble the circuit on a good quality PCB. The circuit can be powered from anything between 9 to 24V DC. Inductor L3 can be a VK220J type RFC. For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2. Frequency can be adjusted by varying C9. R9 can be used to adjust the gain. For optimum performance, value of C8 must be also adjusted. Using a battery for powering the circuit will reduce no ise.
Wireless FM Transmitter Circuit Posted by Popescu Marian in Radio with 4 comments More projects withfm transmitterswireless
•
1
Not logged in! See why you should become a member.
The wireless fm transmitter circuit described here has an extra RF power amplifier stage, after the oscillator stage, to raise the power output to 200-250 milliwatts. With a good matching 50-ohm ground plane antenna or multi-element Yagi antenna, this wireless fm transmitter can provide reasonably good signal strength up to a distance of about 2 kilometres.
The wireless transmitter circuit built around transistor T1 (BF494) is a basic low-power variable-frequency VHF oscillator. A varicap diode circuit is included to change the frequency of the fm transmitter and to provide f requency modulation by audio signals. The output of the oscillator is about 50 milliwatts. Transistor T2 (2N3866) forms a VHF-class A power amplifier. It boosts the oscillator signals’ power four to five ti mes. Thus, 200-250 milliwatts of power is generated at the collector of t ransistor T2.
FM wireless transmitter circuit diagram
For better results, assemble the circuit on a good-quality glass epoxy board and house the transmitter inside an aluminium case. Shield the oscillator stage using an aluminium sheet. Coil winding details are given below:
L1 – 4 turns of 20 SWG wire close wound over 8mm diameter plastic former.
L2 – 2 turns of 24 SWG wire near top end of L1.
(Note: No core (i.e. air core) is used for the above coils)
L3 – 7 turns of 24 SWG wire close wound with 4mm diameter air core.
L4 – 7 turns of 24 SWG wire-wound on a ferrite bead (as choke)
Potentiometer VR1 is used to vary the fundamental frequency whereas potentiometer VR2 is used as power control. For hum-free operation, operate the wireless fm transmitter on a 12V rechargeable battery pack of 10 x 1.2-volt Ni -Cd cells. Transistor T2 must be mounted on a heat sink. Do not switch on the transmitter without a matching antenna. Adjust both trimmers (VC1 and VC2) for maximum transmission power. Adjust potentiometer VR1 to set the fundamental frequency near 100 MHz. This fm wireless transmitter should only be used for educational purposes. Regular transmission using such a transmitter without a licence is illegal in most countries.
DIY Water Softener System Posted by Popescu Marian in 555, DIY with 4 comments More projects withwater
•
4
Not logged in! See why you should become a member.
Hard water has a high concentration of minerals, and of these calcium salts are the most troublesome. But there is a solution coming in form of a cheap diy water softener system built with the well-known 555 IC. Actually the price of this diy system is so low that even if this doesn’t work you won’t be upset.
The working principle of the water softener is based on a theory from 1930 which states that an electromagnetic or electric field causes small crystals of calcium carbonate in the water to join together to form larger crystals. One of the methods to obtain a strong magnetic field is to put a powerful magnet (2.5 gauss) near the water pipe. The second method is the el ectronic one. Studying a water filter purchased from stores we found that it produces a frequency of about 15 kHz a t an amplitude of 15V.
Water Softener Circuit Schematic
cheap diy water softener system circuit schematic
Extension: water softener power indicator The values of the coils are not known, but my guess is L1 has 9 turns and L2 has 7 turns. Actually you should consider this circuit as a theoretical one. Therefore this water softener system uses one 555 IC to obtain a rectangular signal that is applied to the water pipe by wrapping two coils with one open ending around it. The coils must have good isolation. Make sure to power the water softener from a isolated power supply because in some areas the water pipes are connected to ground
DIY Solar Tracker System Posted by Popescu Marian in DIY, Solar with 8 comments More projects withLM324solar panels
•
8
Not logged in! See why you should become a member.
The solar panels are operating at optimal parameters when they are at the perfect right angle to the sun. Unfortunately this is accomplished only if solar panels are rotated by the sun. This is the purpose of this di y solar tracker system.
The solar tracker circuit uses a window comparator to maintain the motor in a i dle state as long as the two LDRs are under the same illumination level. In this case, half the voltage is applied to the noninverting input of A1 and to the inverting input of A1.
Solar Tracker Circuit Schematic
simple diy solar tracker system schematic
solar tracker components
T1, T3 = BD239, BD139
T2, T4 = BD240, BD140
A1, A2 = 1/2 of LM324
Diodes = 1N4001
When the sun position is changing so does the illumination level on the LDRs and the input voltage for the window comparator is no longer half of the supply voltage thereby the output of the comparator generates informations for the motor that rotates the solar panels for tracking the sun. diy sun tracking sensor
diy sun tracking sensor
P1 and P2 are adjusted in such way that the motor stands still when the LDRs get th e same amount of solar light. If less light reaches LDR2 than LDR1, the voltage in point A increases to more than half of the power supply voltage. As a result the output of A1 is HIGH and T1 and T4 transistors conduct. In this situation the motor is starting. If the angle of the solar light is changing again and the voltage i n point A decreases at less than power supply voltage, the output of A2 g oes HIGH and T3 and T2 transistors conduct. As a result the motor is rotating in opposite direction. For solar panels control is best to use small motors with a suitable voltage and a maximum working current of 300 mA. This solar tracker system is used for tracking the sun only in one plane, the horizontal one. If you want to track the solar light in the vertical plane you need to build a separate sun tracker circuit. Analog Solar Tracker by Bien Fallaria
analog solar tracker circuit schematic by Bien
This is a simple and practical analog solar tracker circuit. Using four LDR (light dependent resistor) as a sensor in detecting the light source arranged as illustrated. When the light hit the LDR in a certain position, it will activate the circuit and trigger the relay to turn the slewing motor in the right direction until the sensor is fully shaded under its cover stopping the motor to its rest condition.
Solar Panel Power System Posted by D Mohankumar in Power supply with 3 comments More projects withsolar panels
•
0
Not logged in! See why you should become a member.
The PhotoVoltaic (PV) power system uses solar panels to harvest energy from the sunlight. The PV panel is a packaged assembly of solar cells. A PhotoVoltaic power system typically includes an array of solar panels, Maximum Peak Power Tracking (MPPT) controller, inverter system and batteries. For efficient use of the PV power system, it is necessary to select suitable solar panel and battery. Here describes some tips to select the panel and battery for the PV power systems.
Solar Panel parameters The Solar panel uses photons of sunlight to generate electric current through the Photovoltaic effect. Most of the solar panels use wafer like crystalline silicon cells or thi n film cells. Crystalline Silicon is widely used as the semiconductor in solar cel ls. Electrical connections in the solar panel are made in series/parallel to get desired output voltage and current. Electrical characteristics of solar panel includes nominal power PMax measured in Watts (W), open circuit voltage (Voc), short circuit current(Isc) measured in amperes etc. Peak power output of the solar panel i s represented in Kw. Nominal voltage of the solar panel refers to the battery voltage that the panel is best suited to charge. The actual output from the panel depends on the amount o f sunlight falling on the panel, load characters, temperature etc. Most of the light spectrum cannot be used to generate electricity. So the efficiency of most solar panel is limited. Open circuit voltage of the panel i s the maximum voltage that the panel can produce when not connected to a load. Open circuit voltage can be measured with a volt meter directly on the panel’s terminals. Load Power consumption The power efficiency of the PV power system depends on the selection of suitable solar panel and battery. It is better to calculate the total power consumption of the load that i s to be used with the inverter. The load rating of individual appliance is represented in terms of Watts or VA (Volt Ampere). For example a 20W CFL consumes 0 watts power in 1 hour. Before selecting the battery, inverter and solar panel, it is better to add all the power ratings of the loads together. For example if you wish to connect Four 20 Watts CFL, One 60W TV and One 40W Fan, then the total power consumption of the load i s 20+20+20+20+60+40 = 180Watts. This is the minimum power rating of the Inverter system. But consider the power l oss also. So it is better to use a higher rated inverter, say 300 VA or 500 VA to run 180 W load. Solar panels power efficiency
To calculate the power efficiency, it is necessary to calculate the power consumption in hours also. This can be done by multiplying the total load in watts by the time required. So if you want to run 180 W load for 5 hours, then 180W X 5h = 900Wh(Watts Hour). So a 300 Watts inverter is necessary for the purpose. Battery efficiency and selection The battery capacity is also important. The battery should have sufficient charging capacity to store 900 Wh energy to run the load and not the 180 watts of the load. Battery capacity is usually represented in Ah (Ampere hour). For example a 40 Ah battery can run 1 ampere load for 40 hours. If a 12 volt 40 Ah Lead Acid or Tubular battery is used, then the energy storage capacity of the battery is 12 x 40 = 480 Wh. So if the load requires 900 Wh energy, then a 12 volt 80 Ah battery can hold 960 Wh energy which i s the minimum rating. Consider the power loss also. Then it is better to use a 100 Ah 12 volt battery so that it can give 1200 Wh efficiency. Solar panel selection Before selecting the Solar panel, it is necessary to calculate the energy efficiency of the battery. For example, if you want to use a 60 W fan for 10 hours, then total energy requirement is 600 Wh. Using this example, add the wattage of all the appliances and multiply by the hours of use t o get the energy efficiency of th e power system. If the load rating is 180 watts as the example cited is running for 5 hours, then the energy consumption is 180W x 5 h = 900 Wh. Solar panel can give current only for 5-6 hours per day. More over only 70-80 percent efficiency can be expected from the panel. That is a 100 Watts (Wp) solar panel can give only 80 watts maximum power for 6 hours. This gi ves the energy of 5 h x 100 x 0.7 = 420 Wh. 0.7 is the minimum power loss in the system. So t o get sufficient energy for the 900 Wh, it is necessary to use a 300 Wp solar panel so that i t can give 1050 Wh energy to store in 12 volt 100 Ah battery.
Maximizing Solar Panel Efficiency and Output Power Posted by Jim Keith in Solar with no comments yet More projects withsolar panels
•
3
Not logged in! See why you should become a member.
Improve Solar PV Panel Efficiency and Output Power There are a number of means available to increase solar panel output and efficiency — some of which may be utilized by the serious experimenter. These are listed as follows: Solar Cell Technology
There are a number of technologies being researched and there are continual advancements. Experimental technologies and highest efficiencies include:
Multi-cell gallium arsenide – 44%
Single cell gallium arsenide – 29%
Crystalline silicon - 25%
Thin film copper-indium-gallium-selenide – 20%
Emerging PV technologies (dye-sensitive cells etc.) – 11% (low efficiency, but very inexpensive)
DIY Solar Birdhouse Light Posted by T.K. Hareendran in Light, Solar with 12 comments More projects withsolar chargers
•
0
Not logged in! See why you should become a member.
This solar birdhouse light is an economical circuit of a mi ni solar lighting system circuit i s presented here. At the heart of the circuit is a mini 6V/2W solar panel. Here, this solar panel is used to charge a 4V/800mAh rechargeable battery through a charge current limiter circuit built around an adjustable 3-pin regulator LM317T (IC1).
Resistor R1 sets the output current. The lighting circuit comprising 20 white LEDs are directly powered the battery. Swich S1 is a simp le on/off switch. Assemble the circuit on a small PCB and enclose in a suitable cabinet. Fix the solar panel on the top of the cabinet and power switch and LEDs on the front side. Specification of a typical 6V/2W solar panel:
Maximum Power (Pm) :2W
Working Voltage (Vmp):9V
Working Current (Imp) :220mA
Open Circuit Voltage (Voc) :10.5V
Power Tolerance:-3% to +5%
Assuming a 6 hour sunlit day, a 2 watt panel (near 150mA current set by the regulator IC1+R1) will pump about 900mAh into the battery. Solar charging current can be reduced by increasing the value of R1 ,say from 8.2 Ohm to 10 Ohm.
Solar Birdhouse Circuit Schematic
SMD FM Transmitter Circuit Posted by Popescu Marian in DIY, Radio with 8 comments More projects withfm transmitters
•
1
Not logged in! See why you should become a member.
Let’s construct a low-power FM transmitter using surface-mount devices (SMD) that will be received with a standard FM radio. Soldering surface mounted devices is not so hard and actually is quite easy. There are many designs for small FM transmitters but they have some problems. First, you need an audio amplifier to get enough modulation. Second, the antenna is attached directly to the collector. Third, the coil L must be wound by hand and adjusted by stretching. It all ads with a weak signal that tends to drift in frequency. In contrastm the transmitter schematic we present here eliminates some of those problems, using varactor diode for tuning and modulation, givind great sensitivity without an audio amplifier.
FM Transmitter How it works The figure below shows the schematic of the transmitter which consists of two stages: an oscillator and an output amplifier. Modulation is from an electret microphone but you can use a low power audio source. –
Oscillator stage Transistor Q1 is a Colpitts oscillator where the frequency is determined by the parallel resonant circuit formed by inductor L, varactor V1 and capacitors C7 and C8. Q1 is a common-collector amplifier where the power gain counts. V1 is actually a dual varactor that eliminate the possibility of forward conduction at the sinewave peaks.
The frequency of oscillation is set by adjusting the DC voltage on V1 with potentiometer R2. R4 and C3 form a low-pass filter to prevent RF from feeding back onto the DC. Capacitors C7 and C8 form an AC voltage divider to provide feedback at the emitter of Q1 to sustain oscillation. A necessary condition for oscillation to start is for the radio (C7+C8)/C7 to be sufficiently bigger than 1.
SMD transmitter circuit schematic
Frequency Modulation Modulation is done by superimposing an audio signal from the el ectret mic onto the DC bias applied to V1. R3 and C1 form a low-pass filter to prevent RF from feedi ng back to the mic. R3, R4 and R2 form a votage divider f or the audio. Transmitter output stage The output of the oscillator is fed through C9 to the Q2 emitter-follower. The output of Q2 drives the antenna through C11. The Q2 emitter-follower it ensures that the oscillator is not loaded down by the impedance of the antenna and it provides power gain to drive the antenna. SMD Transmitter layout The figure below shows the layout of the PCB and it uses surface-mounted devices like resistors and capacitors (non-polar devices). All the caps are size 0805 and all resistors are size 1206. use through-hole components for Q1, Q2, IC1 and V1. You can use an SOT-89 device for IC1 and an SOT-23 device for V1. Use MPSH10 or a transistor equivalent. Here you can learn how to solder smd chips
The inductor A coil would consist of two or three turns of wire but for thi s schematic we will use an inductor with loops of copper on the PCB. Such fl at spiral inductor are common at these frequencies. One formula for flat spiral inductors is:
where L = inductance in uH r = radius of coil (outer radius + inner radius divided by 2 ) i nches N = number of turns d = depth of coil (outer radius minus inner radius) inches Tuning range While commercial FM band goes from about 88 MHz to 108 MHz, the L and C values used in this design allow tuning up to 100 MHz. Transmitter testing You will need a portable FM radio and an assistant. First, find an empty spot on the FM dial and set your radio about 30 feet away (9 m eters). The radio’s volume control should not be set too high to prevend feedback. Next, power-up your transmitter and talk to yourself as you adjust the frequency with the trim-pot. When your assintant hears you, your transmitter is tuned. You might have to adjust the radio’s tuner slightly for best reception. Have fun with it but remember that using the transmitter as a bugging device may not be legal in your country. To use the circuit as a wireless microphone, increase the value of R3. The transmitter range is about 100 feet (30 meters) inside a building.
Parts list
Intercom Circuit Posted by Popescu Marian in DIY with 13 comments More projects withLM386
•
0
Not logged in! See why you should become a member.
In this intercom schematic, the 8 ohm speakers is used as microphone and listening speaker. The 10K potentiometer controls volume and the total gain can be set with de 5k R. Use a double switch with 2 positions so when one i s used to talk and the other one to listen. The switch will be in the house.
Intercom circuit diagram
12v to 240v INVERTER This circuit will produce 240v at 50Hz. The wattage will depend on the driver transistors and transformer.
This is a simple circuit of 12V rechargeable smart battery charger circuit. You can use this best battery charger circuit as car battery chargers, Inverter battery charger, Emergency battery charger etc. Automatic indicator alarm circuit is also comes along with this battery charger schematic. The main advantage of this indicator is that a buzzer informs us when the battery needs recharge. This circuit schematic definitely helps for your daily life battery charging applications.
Circuit diagram of battery charger
Click on the image for enlarged view
Components required 1. Transformer (230V to 15V or 110V t0 15V) 2. Bridge rectifier (1N4007 x 4) 3. Capacitor (470µF, 50V) 4. Voltage regulator IC 7815 5. 12V rechargeable battery 6. Diode (1N4148) 7. LED Zener diode 9V 8. Transistor (BC547 x 2) 9. Resistors (10kΩ, 1.5kΩ, 100kΩ Each ¼ Watt) 10.
Buzzer (12V)
Working of battery charger circuit
The charging circuit is build around voltage regulator IC 7815 and two transistors BC 548.
The main supply 230V or 110V is step down using a step down transformer, and then it is rectifiered and filtered out.
That DC voltage is fed to the voltage regulator IC 7815; the output will be regulated 15V.
12 volt rechargeable battery is connected at the output of voltage regulator and it charges when main power is available.
This circuit indicates the charging status that is the LED1 is glows when the battery charged (Above 10.5V).
When battery voltage goes below a particular value LED1 stops glowing and the buzzer produces sound indicating that the battery has been discharged and it needs recharge.
This article explains What is inverter? And how can you construct your own simple low cost 12V to 220V inverter circuit. An inverter is nothing but a DC to AC converter. Inverters are very useful electronics products for compensating emergency power failure, as it performs DC to AC conversion. CBZ4DUQZD2JF AC can’t be stored for future use but DC can be stored for future use in a battery. The stored DC can be converted back to AC by using power inverters. Here is the simple inverter circuit diagram using 555 timer IC. The astable multivibrator mode operation of 555 timer utilized here for AC oscillations and these oscillations are switched via transistor 2SC4029 to a transformer. The transformer step ups the voltage to 220V AC. Use a 12V battery and Battery charger circuit for this project. Design of inverter circuit is also given.
Circuit diagram of DC to AC inverter
Components required 1. Power supply (12V) 2. Resistors (3kΩ x 2; 1kΩ, 2W x 1)
3. Capacitor (10µF) 4. 555 timer IC 5. Diode(1N4007) 6. Transistor (2SC4029) 7. 9V to 220V Step up transformer
Working of DC to AC inverter
This is a simple inverter circuit based on 555 timer IC. Here timer IC wired as an astable multivibrator mode.
We have already discussed about Astable multivibrator using 555. Here the oscillation frequency is set to 50Hz, supply frequency in India.
The diode 1N4007 is used to get 50% duty cycle for the pulses from 555, it also reduces the design complexity.
The output pulse from the 555 astable multivibrator is fed to the base of power transistor 2N5192. The 2N5192 transistor works as a switch, so the 12V DC supply passed through the transformer at a rate of 50 times per second.
Transformer step up the 12V to 220V, thus we got 50Hz, 220VAC supply at the output of transformer secondary.
Use a 12V battery along with a battery charger circuit to power this DC to AC inverter.
Design of Inverter circuit 555 timer Astable designed about to oscillate at 50Hz, line frequency. Frequency of astable multivibrator is given by,
Choose C=10µF, then
Use R1=R=3kΩ
