nikisalli

modified 9 years ago

Fm transmitter with 555

1261

14:36:51

This circuit uses a 555 for frequency modulation and an opamp to amplify the signal (AC source, i put the frequency to 10MHZ to see if it was working or not but in real life that's sound input)
The transmission frequency it's about 100MHz
I don't know if this works in real life (i'm waiting hurz's opinion ;-).)
-nikisalli

published 9 years ago

thebugger

9 years ago

Now, restore.

Karsten

9 years ago

This is more like PWM

nikisalli

9 years ago

@thebugger what?

rich11292000

9 years ago

I want a 555 that goes that fast. Where can i get one?

nikisalli

9 years ago

The 555niki can go over 9000 Ghz XD

WTFCircuit

9 years ago

Rich112292000 it's the cmos version of the ne555, named 7555

nikisalli

9 years ago

Yes wtfc but it can oscillate at 500khz max

WTFCircuit

9 years ago

No, it's limited to 10MHz, i rechecked the datasheet

NateDogg1232

9 years ago

WTF, just stopping by, that's dedication to put the full user name. Niki, I don't think this will work, because it looks too square wavy, and it's more PWM and not FM. You only changed the duty cycle, not the frequency.

WTFCircuit

9 years ago

What do you mean about my name Nate? Anyway I have a possible solution to the pwm problem

NateDogg1232

9 years ago

WTF, I meant putting all the numbers in rich's name, but I would like to hear your solution.

WTFCircuit

9 years ago

It's quite easy. Put a capacitor between pin5 of the 555 and the output of the opamp and reduce the amplitude of the wave to 500mV. It doesn't solve completely the problem but it reduce it a lot

jpoulin0901

9 years ago

The 555 datasheet states the max frequency of the device is 300 kHz. I could see pushing it as high as 1MHz with some bugs but 100MHz is virtually out of the question.

Gizmo

9 years ago

555 cannot work. Even the C-MOS version fT is 1MHz

nikisalli

9 years ago

Hey don't take this circuit too seriously

NateDogg1232

9 years ago

So, I've been analyzing the circuit, and on the rising edge of the sine wave the frequency does increase, but as the change slows down and the wave goes down in voltage, the frequency decreases. So it is FM, but inaccurate, because it only detects change, not amplitude in the wave.

nikisalli

9 years ago

Yep in fact that was just a try i'm not so stupid to try to build this in real life

ezequiel72

9 years ago

Eso te podría servir, conectado a un parlante para una alarma

NateDogg1232

9 years ago

Esa es una buena idea.

colloquiallyineffable

9 years ago

Although it may not be feasible to use a 7555 much above 10MHz, it doesn't necessarily mean the topology is without merit. There's nothing saying FM can only be applied to carrier above 87 MHz. All you need is a broad band receiver to transmit to. A tuned output stage would be a good idea to clean up the harmonic content of the o/p tho.

zorgrian

8 years ago

Have you looked for a 555 style timer that might operate at the carrier wave frequency?

zorgrian

8 years ago

As i pointed out to a similar offering, this might work very well for modulation of infrared LEDs. This style of modulation used for infrared light transmission of audio might offer a relatively noise free communication. Far better than any form of amplitude modulation.

zorgrian

8 years ago

It should be possible to use the 555 for demodulation. However, I am not sure if this is pulse width modulation rather than frequency modulation, although both are strongly related

Bablee

8 years ago

Hello... I'm new here... Please can Anyone help to show me how to build RC drone receiver circuit?

cannellajs2

7 years ago

Wow, that’s pretty cool.

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