i need help with my simple electronic radio proyect?

Thread Starter

leonheard

Joined Jan 8, 2013
48
hi!

i started to do electronic stuff few month ago, i study in internet, i made many proyects
succesfully, ( i do really love electronic, its my passion these days ) well... now i have a problem with my new proyect.... i want to make a radio controller with 4 mhz 4 legs crystall oscillator , so when i press on switch in the emisor, then the receptor switchs on, and then led turns on, but it didnt work...

what am doing wrong? i need help, i will appreciating a lot.

the 2 crystalls i use are:
- 4 legs crystall oscillator MURATA ERIE m 7160 83 28 4,0000 ( i didnt find its datasheet, but i saw 1 in google that looked like this model...)

here is my circuit schematics:

http://s8.postimage.org/63z2zop6t/my_circuit_help.png


Información adicional
when i touch the base of the transistor the led turns ON, so i dont think i puted the transitors wrong...
 

SPQR

Joined Nov 4, 2011
379
Hi and welcome to the forum.

Well, I wonder where you got the schematics from?

Usually you need things like transistors and resistors to go along with the crystal on the transmitter side.
Something like THIS.
 

Thread Starter

leonheard

Joined Jan 8, 2013
48
well its my own schematics :p ( i thought this was gonna works by pure logic :p) i have also a 2 legs crystal, but they said that a 4 legs crystal would be better because its a complete circuit ( thats why my transmitter rf circuit doesnt have any added transistors, just vcc, ground and antenna ) dunno maybe they lie to me or something xD


i bought a crystall oscillator ( so i dont need to build a lc circuit ) i thought this crystall was gonna make some ac, sign wave to make some radio waves...
 

Audioguru

Joined Dec 20, 2007
11,248
A "crystal" with 4 legs is a crystal oscillator. If the antenna is the correct length and is connected to its output then it is a very crude radio transmitter.

But we don't know what the "receiver circuit" is since it is hidden inside a box.
The oscillator is not modulated so the "receiver" will simply saturate when it receives the signal.

Oh yeah. The LED is connected backwards and does not have a current-limiting resistor so it will not light if the receiver receives the signal but it might burn out immediately when the base of the darlington is touched.

The darlington-connected transistors need a very high signal level to turn them on since they are followers. A follower has a voltage loss and has no voltage gain.
 

Thread Starter

leonheard

Joined Jan 8, 2013
48
crude radio transmitter? how can i make it a good radio transmitter?

okei i suppose that i will have to make a LC circuit as a receiver, it have to be 4 mhz also isnt it? :)

mmm yea sorry i forgot to put the MINUS/line sign behind the triangle xD

thanks for ur time :)
 

Audioguru

Joined Dec 20, 2007
11,248
crude radio transmitter? how can i make it a good radio transmitter?
A transmitter has a sine-wave output that has no harmonics that cause interference to othew radio systems. But the oscillator has a square-wave output full of harmonics.
The harmonics are reduced with an LC filter that your circuit is missing.

ok i suppose that i will have to make a LC circuit as a receiver, it have to be 4 mhz also isnt it?
A radio receiver has many LC tuned circuits but yours has none.
A radio receiver also has an amplifier with a high voltage gain but your darlington transistor follower has a voltage gain of only almost 1.

i forgot to put the MINUS/line sign behind the triangle
What triangle? We are talking about an electronic circuit not about triangles.
The symbol for the LED is almost a triangle but it is shown connected backwards.
 

Audioguru

Joined Dec 20, 2007
11,248
The LC tuned circuit is a fairly good filter if it is in the correct circuit.
The circuit you found of an "FM receiver" is garbage that probably will not work.
 

Thread Starter

leonheard

Joined Jan 8, 2013
48
okei, thanks for the advice.... well yesterday i builted a new circuit, just improvising, and i made it actually work! :D this is somehow strange cuz i didnt use a lc circuit, or crystall oscillator for transimmer first... i only used 3 transitors, 5v power supply, and many resistors not even any antenna.....


then i switched my radio from fm to MW ( it think its same as am ) and put a long antenna to it, and finally tunet to... about 500 Khz... and i could heard my mp3 song that was in my other room.... ( a friend called me and i heard also his voice in my radio :D )
it was not clear voice(noise) but still could heard 70% well...

what was that? why it works? did i actually made some radio waves? or was my radio soooo sensitive that it could detect my simple circuit inductions without antenna or something?

then i made this circuit also, and it worked, not so good as my early circuit but it was okei

http://postimage.org/image/cn3wzwoup/



damn, am comfused but want to learn :)

thanks ;)
 
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