27MHz 555IC Simple Transmitter & Receiver

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RMMK
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27MHz 555IC Simple Transmitter & Receiver

Postby RMMK » Mon Jul 28, 2014 1:59 pm

I followed this project http://www.pyroelectro.com/projects/pyr ... dware.html and built the receiver and transmitter on a veroboard but sadly enough i dont get any reception at the receiver end until and unless i place the transmitter too close that is less than a foot and then the green led glows otherwise not. Also previously i built this transmitter on a breadboard and found out the same problem and interestingly even if i removed the 27MHz crystal from the transmitter i get the same signal until i remove power from the 555IC. Its as if i am not getting my crystal to oscillate...... I tried replacing the crystal but to no avail...... i even tried to place the crystal b/w the base and the ground rather than the collector and base but with the same results........ Can u plz help me on this???

Thanks

RMMK
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby RMMK » Mon Jul 28, 2014 2:04 pm

I have also tried tuning the LC tank circuit by using a 2.2uH fixed Axial leaded Inductor and a trimmer capacitor (4.2-20pF) but to no avail....... on a specific position (which i think its 12-15pF) of the trimmer capacitor i get these rogue signals on the receiver end observed by the glowing of the green LED. Also, I have used Axial leaded Inductors (the green coloured ones :roll: ) for the 2.2uH RFC u advised...... is it okay to have these 2.2uH inductors placed on the transmitter? are they the correct radio frequency choke?? You advised a torroidal inductor hand made for receiver but i failed with it as well......

ThePyroElectro
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby ThePyroElectro » Thu Jul 31, 2014 11:02 pm

RMMK wrote:Also previously i built this transmitter on a breadboard and found out the same problem and interestingly even if i removed the 27MHz crystal from the transmitter i get the same signal until i remove power from the 555IC.


Hi. You can't build this on a breadboard it won't work. You need to use protoboard or a PCB. The reason it works without the crystal when transmitter and receiver is close by is because the transistor will become a very noisey oscillator the way that it is configured when you pull out the crystal. However it is not a powerful signal, so it only makes it a 6inch - 1 foot transmitter.

RMMK wrote:Its as if i am not getting my crystal to oscillate...... I tried replacing the crystal but to no avail...... i even tried to place the crystal b/w the base and the ground rather than the collector and base but with the same results........ Can u plz help me on this???


If you have access to a signal analyzer, it will tell you whether or not your transmitter is working correctly. You would see something like this on the output side:
http://www.pyroelectro.com/projects/pyro_rf_transmitter_27mhz/theory3.html or you would see something different if your transmitter isn't working.

RMMK wrote:I have also tried tuning the LC tank circuit by using a 2.2uH fixed Axial leaded Inductor and a trimmer capacitor (4.2-20pF) but to no avail....... on a specific position (which i think its 12-15pF) of the trimmer capacitor i get these rogue signals on the receiver end observed by the glowing of the green LED.


A tuning capacitor is not a bad idea, just make sure that the L+C value will be resonant for 27 MHz!! If you don't have a textbook nearby you can find some online calculators that do the math for you: http://www.daycounter.com/Calculators/LC-Resonance-Calculator.phtml. When the transmitter/receiver work, its obvious they work, no glowing LEDs. Again you can use a signal analyzer on the front-end of your receiver to know you are receiving the 27 MHz signal http://www.pyroelectro.com/projects/pyro_rf_receiver_27mhz/theory2.html.

RMMK wrote:Also, I have used Axial leaded Inductors (the green coloured ones :roll: ) for the 2.2uH RFC u advised...... is it okay to have these 2.2uH inductors placed on the transmitter? are they the correct radio frequency choke?? You advised a torroidal inductor hand made for receiver but i failed with it as well......


The 2.2uH / 1uH inductors are simply chokes preventing high frequency AC noise from messing with the 27 MHz signal on both transmitter and receiver. The toroidal inductor is your RF inductor used for the LC tank circuit. Depending upon how many turns, the length of the coil and the AL value of the core, you will get a different inductance value. So since you have a tuning capacitor, it's just a matter of finding the matching capacitance for whatever inductance your coil has to tune to resonant 27 MHz frequency.

RMMK
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby RMMK » Sun Aug 03, 2014 6:30 am

Thanks for the help! I did some changes to the transmitter and built it on a veroboard and its working now! I am getting a range of 3-4 meters out of this. Here is the modifications i did to my transmitter! The beow pic shows only the first transistor T1 arrangement! I kept the T2 the same way u did!
Attachments
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Untitled.png (25.75 KiB) Viewed 10751 times
Last edited by RMMK on Sun Aug 03, 2014 7:01 am, edited 1 time in total.

RMMK
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby RMMK » Sun Aug 03, 2014 6:38 am

But do u think that the range i am getting can be increased even furthur by some tinkering in this existing circuit or do i have to apply some pre-amplifier and RF Power Amplifier stages??? thanks!

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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby ThePyroElectro » Mon Aug 04, 2014 7:06 pm

RMMK wrote:But do u think that the range i am getting can be increased even furthur by some tinkering in this existing circuit or do i have to apply some pre-amplifier and RF Power Amplifier stages??? thanks!


Hello,

That is good news.

I believe you can get more range by tinkering with the circuit.

Some suggestions I can think of:

[1] Use 1/4 wave antenna designs for transmitter and receiver
[2] Verify power output & frequency of transmitter is significant (5-10dm) (Use Signal Analyzer)
[3] Verify Receiver circuit is tuned for ~27MHz (Use Signal Analyzer) -- The receiver circuit will actually oscillate when powered up, so you can easily find the frequency that it is tuned for and adjust it as necessary.

Alternatively. There is virtually no filtering done in this circuit and only basic amplification.

If you added more filtering to the transmitter, then the Harmonic frequencies wouldn't be as amplified, only our carrier frequency.

Similarly, if you added more filtering to the receiver end before the amplifiers, noise wouldn't be amplified as much and a much cleaner signal would make it though.

Just a few suggestions....Good luck!

AAbd9
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby AAbd9 » Mon Dec 01, 2014 11:18 am

Hi!
I was working on a school project involving 555 timers and I was looking to make my prototype wireless. The circuit I've built uses a 555 timer and 8 resistors all hooked up to a speaker. When each resistor is connected one by one(switch is turned on) it makes a different sound(for each resistor). I was wondering whether it would be possible to make it wireless using the base of this project and I'd appreciate any help in regards to moving forward on this project
Thank you :)

hnoor0055
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Re: 27MHz 555IC Simple Transmitter & Receiver

Postby hnoor0055 » Sat Mar 26, 2016 11:29 am

The circuit I've built uses a 555 timer and 8 resistors all hooked up to a speaker. When each resistor is connected one by one(switch is turned on) it makes a different sound(for each resistor).
thinks for sharing


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NOOR


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