I looked on instructables and I found an interesting(at least for me) AM transmitter made with a 555 timer which acts as the oscillator:http://www.instructables.com/id/555-AM-Transmitter/ Is this idea feasible?Will it work?
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4\$\begingroup\$ adapting a 555 to an AM transmitter is rather like adapting a chainsaw to drive your washing machine. \$\endgroup\$– user16324Sep 3, 2015 at 10:20
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3 Answers
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No, it's rubbish: -
Look at the circuit - where do you connect a modulating input (such as a microphone or signal generator) - if you attached its output to an antenna it would be creating so many harmonics the whole of the AM broadcast band would be corrupted in the near vicinity.
Accepting that it's likely illegal to connect an antenna to the circuit there are far more practical circuits around like this: -
Taken from here. Or, there is this FM (not AM) one: -
Taken from here. Just Google "Simple AM transmitter" and look at the images of circuits you get. Choose one that is within your capabilities and go to the source page for instructions and help.
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I see no capacitor in the schematic (where there should be one for normal operation) so it probably works on parasitic capacitances of which there will be plenty on a breadboard.
The 555 timer is not meant to be used at 500 kHz or higher. There's no antenna connected which is actually good because if the circuit worked you'd be transmitting illegally.
Sure it might "work" but more as a toy/gimmick than anything else. And if your 555 would be from a different manufacturer the circuit might not work at all. I call that bad design !
There are better projects to spend your time on.
answered Sep 3, 2015 at 7:33
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\$\begingroup\$ By the way,after looking at many projects like this (on instructables) involving electronics,I am starting to think that most of them have the same quality as this one.What do you think? \$\endgroup\$ Sep 3, 2015 at 7:55
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\$\begingroup\$ Somewhere in the comments to the instructable it mentions using the delays in the comparators - it basically oscillates at whatever speed the comparators can react to feedback. Still kind of sucks, and the true frequency may change depending on the exact flavor of 555. On top of that, pushing the audio into the output of the 555 just gives me the willies. \$\endgroup\$– JRESep 3, 2015 at 8:05
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\$\begingroup\$ @DanielTork I'm afraid you might be correct. I have not looked at many of those projects as they are indeed very basic in level. Fun to play with but not much more. The many Arduino based projects might be Ok though, not much that can go wrong when you're just switching things on and off. But then, I would not call that electronics as you can build up an Arduino project without having the slightest idea of how to use a transistor. \$\endgroup\$ Sep 3, 2015 at 8:39
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\$\begingroup\$ @FakeMoustache I will be honest,I didn't look at many,I looked up just a few but I had this feeling that they're not really that much.Anyway,I think we should appreciate that the posters did their best,putting at least some work into those projects. \$\endgroup\$ Sep 6, 2015 at 5:17
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Yeah, it'd work but not well.
a 555 can run at 1MHz, which is the middle of the AM band,
There's no capacitor, but the parasitic capacitance between the parts and ground is enough for it to run.
if you build it you'll have a low power output AM transmitter that drifts like a balloon and spams several harmonic frequencies. and is illegal to use as a transmitter almost everywhere
answered Sep 3, 2015 at 9:17
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\$\begingroup\$ Some manufacturers 555s will run faster than others, but point well received. \$\endgroup\$– RYSSep 3, 2015 at 10:33