Sơ đồ mạch phát FM dùng transistor

sơ đồ mạch phát fm dùng transistor

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Đây là mạch phát thanh FM ,tôi đã xây dựng từ năm 2001 , mạch có tần số rất ổn định không bị trôi, công suất phát khoẻ Xa 200 mét vẫn thu được bằng Radio dân dụng có tần số 144MHz Mời các bạn ráp thử chúc các bạn luôn trau dồi kiến thức, học tập mau tiến bộ Sáng tạo được các mạch , đề tài khoa học mới

( chú ý tất cả các transistor đều dùng C9018)

Thân : Quế Dương

Đừng lo đây là số liệu cuộn dây : Dây tráng men đường kính 0,56mm Lấy cái đầu mũi khoan đường kính 5 mm quấn lên đó 5 vòng sát nhau sau đó rút lõi ra là được, nên nhớ quấn theo chiều kim đồng hồ Quấn ngược cũng được nhưng đôi khi không xảy ra dao động và không tập trung năng lượng sóng ( không biết có đúng không vì khi tôi làm tôi quấn theo chiều kim đồng hồ thì sóng tốt hơn)

Bạn nói về mạch điều khiển nào, Tôi đang làm cái mạch inter net modem không dây ,chuột và bàn phím Hiện tại trong nhà tôi tôi đã làm các mạch không dây để điều khiển.

- Điều khiển đen bật tắt từ xa, điều khiển quạt, chuông cửa v.v bạn nào có ý tưởng gì xin hãy post lên đây Tôi sẽ cố gắng giúp các bạn trong phạm vi kiến thức của mình.

- Có thể nói tôi đã có ý định làm một trang web về điện tử từ lâu, tôi tức vì hội vô tuyến điện tử việt nam kinh doanh quá, bắt đóng tiền cho hàng tháng truy cập vào mạng của họ.

Tôi đã tìm gặp một web hiếm hoi như của các bạn nói về điện tử, rất hoan nghênh các bạn, tôi được biết có thêm một diễn đàn điện tử nữa của mình Hãy phát triển thêm nhé.

Còn nói về điện tử thì tôi đã tiếp xúc với nó từ hồi 6 tuổi cơ, hơn nữa lại ở trong một gia đình chuyên về điện tử nên cũng có tý chút mánh khoé và kinh nghiệm ( mặc dù tôi vốn rất lười) Quế Dương

Thử cái này xem Tuy chỉ phát được 30m nhưng đơn giản hơn nhiều:

www.boondog.com/%5Ctutorials%5CrfTransmitter%5CrfTransmitter.htm

http://tacashi.tripod.com/elctrncs/smplfmtr/smplfmtr.htm

http://web.telia.com/~u85920178/tx/bug.htm

Simple FM transmitter with a single transistor

Mini FM transmitters take place as one of the standard circuit types in an amateur electronics fan's beginning steps When done right, they provide very clear wireless sound transmission through an ordinary FM radio over a remarkable distance I've seen lots of designs through the years, some of them were so simple, some of them were powerful, some of them were hard to build etc

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Here is the last step of this evolution, the most stable, smallest, problemless, and energy saving champion of this race Circuit given below will serve as a durable and versatile

FM transmitter till you break or crush it's PCB Frequency is determined by a parallel

L-C resonance circuit and shifts very slow as battery drains out

Simple FM Transmitter involves on a single transistor oscillator

Technical datas:

Supply voltage : 1.1 - 3 Volts

Power consumption : 1.8 mA at 1.5 Volts

Range : 30 meters max at 1.5 Volts

Main advantage of this circuit is that power supply is a 1.5Volts cell (any size) which makes it possible to fix PCB and the battery into very tight places Transmitter even runs with standard NiCd rechargeable cells, for example a 750mAh AA size battery runs it about 500 hours (while it drags 1.4mA at 1.24V) which equals to 20 days This way circuit especially valuable in amateur spy operations :)

Transistor is not a critical part of the circuit, but selecting a high frequency / low noise one contributes the sound quality and range of the transmitter PN2222A, 2N2222A, BFxxx series, BC109B, C, and even well known BC238 runs perfect Key to a well functioning, low consumption circuit is to use a high hFE / low Ceb (internal junction capacity) transistor

Not all of the condenser microphones are the same in electrical characteristics, so after operating the circuit, use a 10K variable resistance instead of the 5.6K, which supplies current to the internal amplifier of microphone, and adjust it to an optimum point where sound is best in amplitude and quality Then note the value of the variable resistor and replace it with a fixed one

The critical part is the inductance L which should be handmade Get an enameled copper wire of 0.5mm (AWG24) and round two loose loops having a diameter of 4-5mm

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Wire size may vary as well Rest of the work is much dependent on your level of

knowledge and experience on inductances: Have an FM radio near the circuit and set frequency where is no reception Apply power to the circuit and put a iron rod into the inductance loops to chance it's value When you find the right point, adjust inductance's looseness and, if required, number of turns Once it's OK, you may use trimmer capacitor

to make further frequency adjustments You may get help of a experienced person on this point Do not forget to fix inductance by pouring some glue onto it against external forces If the reception on the radio lost in a few meters range, than it's probably caused

by a wrong coil adjustment and you are in fact listening to a harmonic of the transmitter instead of the center frequency Place radio far away from the circuit and re-adjust An oscilloscope would make it easier, if you know how to use it in this case Unfortunately I don't have any :(

Every part should fit on the following PCB easily Pay attention to the transistor's leads which should be connected right Also try to connect trimmer capacitor's moving part to the + side, which may help unwanted frequency shift while adjusting PCB drawing should be printed at 300DPI, here is a TIFF file already set

PCB design for the FM Transmitter

The one below is a past PCB work of mine, which was prepared to fit into a pocket flashlight Since it was so crowded, use the new computerized PCB artwork instead, yet very small Take a look at my PCB design page to get information on my work style

Transmitter PCB compared in size with an AA battery

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Here is a completed and perfectly running circuit, mounted in a pocket light, taking the advantage of the 1.5V AA cell slot near it Microphone is fixed into the bulb's place and antenna is made out of a 30cm soft cable When cover is placed, it becomes very handy!

Transmitter placed in a pocket flashlight

Do not forget, restrictions on radio frequency transmitting devices may differ in your local area This circuit has a power output that should be less than 1mW so have to be safe under many kinds of legal conditions but particular attempts such as listening to other people's private life will always be disapproved everywhere

E-mail me at : incepinar@yahoo.com

Back to the electronics page

File gửi kèm :

Mach fm khac

Mình đã lắp 1 micro FM :

File gửi kèm :

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L1 và L2: 6 vòng bk 3mm, dài 6mm, dây 0,4mm

L2 có lối lấy tín hiệu ở giữa.

Mình thấy máy này phát xa nhất là 30m khi anten dài 1m.Mình đã thử ghép thêm vài tầng khuếch đại như ở tầng Q2 nữa nhưng ko thấy xa hơn gì.Các bạn xem và chỉ mình cách nâng cao công suất nha!

Mgdaubo

http://myhome.hanafos.com/~tk1999/2248.pdf

http://myhome.hanafos.com/~tk1999/2249.pdf

(Right click and save target as )

Các bạn thân mến !mình biết một trang web rất hay về các mạch điện thông dụng Dường như

nó có tất cả những gì mà các bạn cần về các sơ đồ mạch ,nó sáp sếp theo từng loại từ mạch nguồn ,ampli , cho đến các mạch kỹ thuật số Nói chung là dư sức thỏa mãng yếu cầu của các bạn Đây là www.commlinx.com.au/schematics.htm

chúc các bạn tìm được những gì mà bạn cần tìm

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