Solar radio, Solar Radio
Keywords: solar radio
Solar radio
Solar energy is exhausted, inexhaustible energy. The solar energy (or other light energy) is directly converted to a device, referred to as a solar cell. With the continuous increase in people's energy saving and environmental awareness, solar cells are rich in energy, no pollution, long life, easy to maintain and maintain advantages, and more reliable performance, and become more loved.
Make a small medium wave amplitude radio with solar cell power supply, how interesting and pleasant things: in the sun during the day, in the evening, you can use it to listen to news broadcasts, learn foreign languages. By making, you can also master and understand the knowledge of solar cells, broaden the horizons, and further develop and use solar energy for future human beings. String 6
I. Working principle
The circuit of the small solar radio is shown in Figure 1. It uses a miniature radio-specific integrated circuit A to do high-frequency amplification and detection, and then use two triodes VT1, VT2 to low frequency amplification and emitter output, and finally push 8Ω low-resistance ear plug. String 6
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A (Model YS414) is a direct enlarged detection radio-specific integrated circuit, which uses TO-92-type plastic packaging, and the packaging form is identical to ordinary 9014-type plastic small power crystal triodes, and the shape and pins are arranged as shown in Figure 2. (A) shown. Each pin function: The G pin is a common ground end, the I pin is the input, the O pin is the output. The YS414-type integrated circuit consists of 9 triiod, 16 resistors, and 4 capacitors, including first-level high-resistance input buffer, three high-frequency amplification and primary detection, and its internal circuit diagram is shown in Figure 2 (b) Show. The YS414 integrated circuit has the high input impedance, large gain, power saving, less peripheral components, no need to debug, etc., is ideal for making mini simple radios.
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When sun glare (or light) is irradiated onto the solar panel BP, the BP surface is a photovoltaic effect, and the two ends output a power of power, and the radio circuit is operated. The magnetic antenna L and the variable capacitor C1 constitute a tuning loop, which is a parallel resonant circuit that adjusts C1 to change the resonant frequency, and serve the role of the station signal to receive. The magnetic antenna L uses a medium-wave special magnetic bar with a high sensitivity, and there is no exterior antenna, and there is a certain direction when receiving the station. Since A has a very high input impedance, the tuning loop can be directly connected to the input terminal I of A and the input of C2 without having to couple the secondary coil as a secondary coil. The radio signal sent to a, and then output an audio signal from its O pin after multi-stage high frequency amplification and detection via an internal circuit. R1 is the input stage bias resistor of A. It is connected to the BP positive electrode by the output load resistor R2 of A, and A can also have an automatic gain (AGC) control capability. If the signal received by the radio is strong, the working current of A will increase, and the voltage drop on R2 also increases, so that the operating voltage of A is lowered, the internal circuit gain also decreases, resulting in a decrease in the output signal, so The automatic gain control role was completed. When R2 is large, the AGC control is too strong, which will make the circuit gains decrease; when the R2 is small, the AGC control is too weak, which will cause the circuit to produce self-excited. C3 is a high frequency bypass capacitor, which can filter the unwanted high frequency components contained in the detection signal; C3 selects the appropriate capacity, not only good sound quality, but also preferably automatically gain control characteristics.
The audio signal output from the O pin of A. The volume adjustment is sent to the potentiometer RP by the coupling capacitor C4, and then the low-frequency amplifier circuit composed of VT1, VT2 is sent by the coupling capacitor C5 to power amplification, and finally push the 8Ω earphones. . VT1 constitutes a front amplifier, which is voltage amplifier; VT2 constitutes an emitter follower, converts the impedance of the 8Ω earplugs in the jack XS to the vT2 current amplification coefficient (ie β × 8Ω), Solving the high impedance output from VT1 that cannot be directly matched with the 8Ω earpiece; the adult follower has a current amplification, which makes the earplug machine sound more loud. R3 is a DC bias resistor of VT1. Since the base of VT2 is connected directly to the collector of VT1, the modulated R3 resistance can simultaneously adjust the operating point of VT1 and VT2; R4 is the emitter current negative feedback resistor of VT1, Its role is to further stabilize the work points of VT1 and VT2.
Second, the component selection
The BP adopts a finished solar panel having a size of about 35 mm × 10 mm, an open circuit voltage ≥2V, and a short circuit current ≥ 8mA. Such solar panels are made of single crystal silicon wafer process, and photoelectric conversion efficiency is stable, which has been widely used in weak current appliances such as calculator. The power output capability of the solar panel is closely related to the size of the area, the larger the area, the greater the output power under the same illumination conditions. The advantages and disadvantages of solar panels are mainly measured by two indicators of open circuit voltage and short-circuit current. The amateur test method is to place the solar panel in the sun direct-illuminated environment, and the output voltage can be measured with the multimeter, which is considered to be an open circuit; and then the multimeter directly connects the output current on both ends of the solar panel. It is considered to be a short circuit current. String 5
If the solar panel is not purchased at a time, the three-piece size of 10 mm × 5mm, the open circuit voltage is 0.5 to 0.6V, and the short circuit current ≥9mA is used in series after being substituted. The shape of such silicon photovoltaic cells is shown in Figure 3, and its light-receiving surface is blue, there is a few silver-white gate lines, which leads to two wires as the battery positive; backlight surface is silver (tinned), lead two The root lead is a battery negative electrode. Be
A uses the YS414 type micro radio dedicated integrated circuit. Its main feature: the working voltage is low, it can be satisfied with normal operation; power consumption, no signal is only 0.4mA, the working frequency bandwidth, can reach 150 ~ 3000kHz; the amplification capacity, power gain Up to 72dB, the automatic gain control range is up to 20 dB. The same is exactly the same as YS414, but the different integrated circuits of manufacturers include: D7642, TA7642, CTC7642, YS7642, BS414, MK-484, 2N414, etc., they can be used directly.
Transistors Vt1, Vt2 are all 9014 or 3DG8 silicon NPN small power low noise triode, and the current amplification coefficient β value of VT1 is between 40 and 150, and the β value of Vt2 is between 20 to 60.
The magnetic antenna L needs to be strokes themselves. Specific methods: use φ0.15mm single-shaped high strength paint line, single layer wrapped around 82 laps on the medium wave magnetic rod of φ5mm × 35 mm. Attention to the wrapping, in order to make the coil are disrupt, apply a quick-drying glue (or white wax) to stick the starting place and the end. For the convenience of debugging, it is best to make a coil skeleton with a cardboard before the winding, so that the coil made can be moved around the magnetic rod.
The C1 is selected from the 5 ~ 200PF ultra-small sealing variable capacitor; C2, C3 and C6 are used in CT1 type ceramic capacitors; C4, C5 are used with CD11-10 type electrolytic capacitors. R1 ~ R5 all use RTX-1 / 8W carbon film resistors. RP is selected with a small synthetic carbon film potentiometer that does not switch with the WH15-1A type. XS selects two-core jacks that are commonly used by CKX2-3.5 (φ3.5mm caliber) earphitch headphones. The headset is a 8Ω low-resistance earbeliner with CSX2-3.5 (φ3.5mm) two-core plug.
Third, production and use
Figure 4 shows the printed circuit board wiring diagram of the radio. The printed circuit board is processed by a single-sided copper, and the actual size is about 75mm × 35 mm.
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The machine debugging is very simple: in the solar panel BP accepts a good sun, the 8Ω low-resistance earbuffer is inserted into the XS, and the total current is adjusted by adjusting the R3 resistance, so that the total current of the whole machine is about 4 mA; Next, the rotation C1 knob You can listen to the radio broadcast. In general, the components are required as required as required by Figure 1, and the welding is guaranteed, and no commissioning is required to work. Since the gain of the integrated circuit A is large, it is possible to produce self-excited calls when the alignment position of the circuit board is not at that time. If self-exchancing occurs, it can be eliminated by appropriately adjusting the position of the component, or using a method of increasing the R2 resistance.
If it is found that the radio receiving frequency range cannot cover the medium wave 535 ~ 1605kHz band, the magnetic antenna coil can be moved to the position on the magnetic rod, and the correction can be obtained; if it is not effective, it can be adjusted by appropriately increased or decrease the number of turns. . When adjusting, you can use a finished radio to do a reference. The adjustment ends, and the coil is sealed with white wax or glass glue. Specific adjustment method: When the C1 knob is spin to the head in the pressing direction, the radio signal near the high frequency end (1605kHz) can be received, and the magnetic antenna coil can be moved to the end of the magnetic rod, and it can be appropriate when necessary Reduce the number of turns; if the C1 knob is converted to the head in the counterclockwise direction, the radio signal near the low frequency end (535kHz) can be received, and the magnetic antenna coil can be moved to the intermediate position of the magnetic rod, if necessary, can be appropriate Increase its number of turns.
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The outer shape of the solar radio is shown in Figure 5. The casing can be made of plastic plates, and the existing plastic small box can also be used, and the size is preferably the circuit board is appropriate. The tuning knob hole of C1 is opened on the front side of the casing, and the volume adjustment knob hole of the RP is opened on the back side of the casing; the mounting holes (φ6mm) of the plunger jack XS is opened on the right side of the casing, and is installed XS. The solar panel BP is fixed to the top of the casing, and the "+" of the back surface, "-" pole leads through the small holes on the casing, and is connected to the shell circuit board. If the BP is powered in series with three 2Cr32 silicon photovoltaic cells, a thin colorless transparent organic glass should be covered with a silicon photoelectric battery to avoid damaging the silicon photovoltaic cell. However, it should be noted that the transparency of the organic glass sheet must be good, otherwise it will affect the conversion efficiency of the photovoltaic cell.
Since this machine uses a dedicated integrated circuit, it is not only small, easy to make, but also high sensitivity, good selectivity, and ideal. When you listen to the language broadcast, you will feel pure; when you listen to the music program, you will feel clear that the high and low level is clear. If you can listen to a stereo headset (left, right headphone parallel), the sound effect will better string 2
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