The article explains a very simple circuit of a wireless speaker system which can be used for playing hi quality music wirelessly from your TV set, DVD player, Ipod, cell phone or from any music system. The speaker thus can be placed in any corner of the house within a radial distance of 50 meters and high quality music can be enjoyed without the hassles of long connecting wires.
For implementing the entire wireless speaker system, we actually need to make two sets of circuits, a transmitter circuit for transmitting the music signal from the source input as discussed above and a receiver circuit for receiving the transmitted music signal and for playing it in the attached speaker.
As shown in the figure, the configuration looks a little different from the usual single transistor transmitter circuits where a single stage is used for the audio amplification and for the generation of the modulated carrier waves.
The usual single transistor transmitter circuit has the advantage of smaller and compact size and minimal power consumption, but is not suitable for long and strong signal transmissions.
However since such circuits are commonly used for wireless microphone applications, the distance is not a factor but compactness and low power consumption is definitely a must, and therefore becomes quite suitable for the intended application.
The present design is not intended for the above application so the first two features are not important, however the proposed idea of a wireless speaker system surely requires a long range and a distortion free power transmission, so that the reception can be heard at any corner of a particular premise or even across an apartment.
Therefore a stronger signaling or transmission of stronger carries RF signals becomes a necessity.
That’s exactly why we have incorporated a couple of extra stages in addition to the central carrier wave generator stage.
The first transistor and its associated components form a neat little audio amplifier stage and also a buffer between the audio source and the transmitter circuit.
This stage amplifies the received signal to stronger levels, and this stage also allows keeping the volume of the source signal to minimum levels.
The amplified signal is passed on to the next stage, which is the actual RF signal generator stage.
This stage is basically a simple feedback type of oscillator, wired to produce RF signals in the range of around 90 to 100 Mhz.
The amplified signal from the collector T1 start forces T2 to modulate the generated RF with the injected audio signals.
The modulated signal from the collector of T2 can also be directly used for the intended wireless music receiving.
However since we are interested in making it more powerful, we introduce another stage which becomes responsible for amplifying the modulated signals to much stronger levels so that it may be heard across many 10s of meters away and even in cell phone radios.
How to Make L1
The inductor L1 is the most critical part of the circuit. Its dimensions are: 1mm, super enameled copper wire, having 5 turns of 6mm diameter. The tap to C6 is taken by scratching the second last turn of the coil toward the positive side end.
The whole transmitter circuit can be built over a small piece of veroboard and housed inside a suitable sized metal box along with the required power supply section enclosed.
This concludes the transmitter circuit.
The Receiver Circuit
Ideally you won’t need to build this as the receptions can be heard crystal clear over an ordinary FM radio set. Therefore you might just want to use the FM radio itself as the wireless loudspeaker, or probably add an ampli-speaker box in conjunction to you FM receiver.
That’s it, your wireless speaker box system is ready and may be used for listening to any audio transmission without connecting wires across a radial distance of more than 50 meters, if the antenna is made large enough, the range may be well increased to beyond 90 meters.
- R1 =1M,
- R2 = 2K2,
- R3 = 470 Ohms,
- R4 = 39K,
- R5 = 470 Ohms,
- C1 = 0.1 uF,
- C2 = 4.7 uF,
- C3, C6 = 0.001uF,
- C4 = 3.3pF,
- C5 = 10pF,
- C7 = 100uF/16V
- D1----D4 = 1N4007
- L1 = See Text
- T1, T2 = BC547B,
- T3 = BC557B
- TR1 = transformer, 0-9V, 100mA
Another Wireless Music Transmitter Circuit
The following diagram shows another miniaturized FM transmitter circuit that can be hooked up with a music source to send the music into the air in the wireless mode. A distant FM radio could be used as the wireless speaker is able to receive the signals and play the music.
The inductor L1 can be built by winding a piece of super enameled copper wire having a length of 6.5 inch, and thickness of 20 SWG over an air cored former having a diameter of around 1/4 of an inch.
Meaning, take a 6.5 inch long, 20 SWG super enameled copper wire and wind it over a 1/4 inch diameter air core former.
The music is fed from the input indicated as PL1
Mfumo wa sauti ya wireless unaweza kutumika kwa kucheza muziki wa ubora wa juu bila waya kutoka kwa TV yako, DVD player, iPod, simu ya mkononi au kutoka kwa mfumo wowote wa muziki. Kwa hivyo, msemaji anaweza kuwekwa katika kona yoyote ya nyumba ndani ya umbali wa mita 50 na muziki wa ubora wa juu unaweza kufurahishwa bila shida ya waya ndefu za kuunganisha. Kwa ajili ya kutekeleza mfumo mzima wa spika wireless, tunahitaji kufanya seti mbili za mzunguko: mzunguko wa transmitter kwa ajili ya kupeleka ishara ya muziki kutoka chanzo cha pembejeo kama ilivyojadiliwa hapo juu, na mzunguko wa mpokeaji kwa ajili ya kupokea ishara ya muziki na kucheza katika spika iliyounganishwa. Kama inavyoonyeshwa katika picha, muundo unaonekana tofauti kidogo na mzunguko wa kawaida wa transmitter ya transistor moja ambapo hatua moja hutumiwa kwa amplification ya sauti na kwa kizazi cha mawimbi ya kubeba. Transistor moja kawaida mzunguko transmitter ina faida ya ukubwa mdogo na compact na matumizi ya chini ya nguvu, lakini si yanafaa kwa ajili ya muda mrefu na nguvu ishara maambukizi. Hata hivyo, kwa kuwa mizunguko kama hiyo hutumiwa kwa kawaida kwa matumizi ya kipaza sauti bila waya, umbali sio sababu, lakini compactness na matumizi ya nguvu ya chini ni lazima, na kwa hivyo inakuwa sahihi sana kwa matumizi yaliyokusudiwa. Kwa kuwa muundo huu haukusudiwa kwa matumizi ya hapo juu, kwa hivyo sifa mbili za kwanza sio muhimu, hata hivyo wazo lililopendekezwa la mfumo wa spika zisizo na waya hakika inahitaji umbali mrefu na usafirishaji wa nguvu bila kupotosha, ili mapokezi yaweze kusikilizwa katika kona yoyote ya eneo fulani au hata katika ghorofa. Kwa hiyo nguvu ishara au maambukizi ya nguvu hubeba ishara RF inakuwa uhitaji. Hiyo ni hasa kwa nini sisi wamejumuisha hatua chache za ziada pamoja na hatua ya kati carrier wimbi jenereta. Transistor ya kwanza na vipengele vyake vinavyohusiana huunda hatua ndogo ya kuimarisha sauti na pia buffer kati ya chanzo cha sauti na mzunguko wa transmitter. Hatua hii huongeza ishara iliyopokelewa kwa viwango vikali, na hatua hii pia inaruhusu kuweka kiasi cha ishara ya chanzo kwa viwango vya chini. Ishara amplified ni kupitishwa juu ya hatua ya pili, ambayo ni halisi RF ishara jenereta hatua. Hii ni moja ya njia rahisi ya kusonga kwa oscillator, ambayo hutumia frequency ya RF ya 90 MHz. Msaada wa sauti kutoka kwa mkusanyaji T1 unafanya T2 kugeuza RF iliyotengenezwa na ishara za sauti zilizopigwa. Mfano wa T2 ni pamoja na ishara ya moduli ya T2 ambayo inaweza kutumika kwa njia ya wireless kwa ajili ya kupokea muziki. Hata hivyo, kwa kuwa tunapenda kuifanya iwe na nguvu zaidi, tunaanzisha hatua nyingine ambayo inakuwa na jukumu la kuimarisha ishara za moduli kwa viwango vyenye nguvu zaidi ili iweze kusikilizwa katika mita nyingi za mita na hata katika redio za simu za mkononi. Jinsi ya kufanya L1 inductor ni sehemu muhimu zaidi ya mzunguko. Urefu wa waya ni 1mm, super enameled shaba waya, na 5 turns ya kipenyo 6mm. C6 ni kuchukuliwa kwa scratching pili ya mwisho wa kugeuka ya coil kuelekea upande chanya mwisho. Mzunguko mzima wa transmitter unaweza kujengwa juu ya kipande kidogo cha veroboard na kuwekwa ndani ya sanduku la chuma la ukubwa unaofaa pamoja na sehemu ya usambazaji wa umeme inayohitajika. Hii inamalizia mzunguko wa transmitter. Mpokeaji Circuit Kimsingi huna haja ya kujenga hii kama mapokezi inaweza kusikilizwa kioo wazi juu ya kawaida FM redio seti. Kwa hiyo, unaweza kutumia redio ya FM kama msemaji wa wireless, au kuongeza sanduku la msemaji wa amplifier pamoja na mpokeaji wa FM. Kwa hiyo, mfumo wako wa sanduku la spika bila waya uko tayari na unaweza kutumika kwa kusikiliza maambukizi yoyote ya sauti bila kuunganisha waya katika umbali wa radial wa zaidi ya mita 50, ikiwa antenna imefanywa kubwa ya kutosha, safu inaweza kuongezeka hadi zaidi ya mita 90. R1 = 1M, R2 = 2K, R3 = 470 Ohm, R4 = 39K, R5 = 470 Ohm, R1 = 0.0UF, R2 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0UF, R3 = 0.0F, R3 = 0.0F, R3 = 0.0F, R3 = 0.0F. Kwa mfano, kuna aina ya kipaza sauti ya sauti inayoitwa FM, ambayo inaitwa FM. Kwa mfano, redio ya FM inaweza kutumika kwa njia ya wireless, ambayo inaweza kuwasiliana na sauti ya sauti na kuwasiliana na sauti ya sauti. Induction L1 inaweza kujengwa kwa winding kipande cha super enameled shaba waya kuwa na urefu wa 6.5 inchi, na unene wa 20 SWG juu ya hewa cored zamani kuwa na kipenyo cha karibu 1⁄4 inchi. Kuchukua 6.5 inchi kwa muda mrefu, 20 SWG super enameled shaba waya na wind juu ya 1⁄4 inchi kipenyo hewa msingi zamani. Muziki ni kulishwa kutoka pembejeo iliyoonyeshwa kama PL1