guskenny83
- Jul 29, 2009
- 46
- Joined
- Jul 29, 2009
- Messages
- 46
Hi.
Im playing around with 555 timers trying to learn how they work.
I built a circuit very similar to the one here:
https://encrypted-tbn3.gstatic.com/...AU87g7llTWJMHiOtBb1GbvFdqO_6r1LDFZI6uu-IhlyaB
With the intent to just make a simple square wave oscillator, with the frequency controlled by a pot at R2, so i can try out different resistor and capacitor values to see what changing them does to the frequency ranges.
When i hooked a speaker up to pin 3 (output) and pin 1 (ground), i got no sound. But when i hooked it up to my cheap oscilloscope, it seemed to be putting out a nice square wave, and at a good frequency range, i just couldnt hear it through the speaker.
When i accidentally ungrounded the speaker, i got a very faint sound through it, and then when i touched the end of the speaker wire with my finger, it got louder.
So i experimented with touching the ground speaker wire to various parts of the circuit, and when i touched it to pin 5 (control) it worked great with a nice loud square wave sound coming from the speaker.
My question is, why did this happen? And should it? My understanding is that pin 5 is there to allow the frequency to be controlled by an external voltage, and is not normally used for anything in these simple circuits. So why does it suddenly make my speaker work when it is connected to it?
Is it because the speaker shouldn't be connected directly to ground and there should be a resistor or something in between, and connecting it to pin 5 is allowing the speaker to ground through some resistance? Im probably completely off the mark with my reasoning, but that's the only thing i could think of.
Any help understanding this would be greatly appreciated.
Sorry if it is a very simple question, im just trying to learn about all this stuff..
Thanks
Im playing around with 555 timers trying to learn how they work.
I built a circuit very similar to the one here:
https://encrypted-tbn3.gstatic.com/...AU87g7llTWJMHiOtBb1GbvFdqO_6r1LDFZI6uu-IhlyaB
With the intent to just make a simple square wave oscillator, with the frequency controlled by a pot at R2, so i can try out different resistor and capacitor values to see what changing them does to the frequency ranges.
When i hooked a speaker up to pin 3 (output) and pin 1 (ground), i got no sound. But when i hooked it up to my cheap oscilloscope, it seemed to be putting out a nice square wave, and at a good frequency range, i just couldnt hear it through the speaker.
When i accidentally ungrounded the speaker, i got a very faint sound through it, and then when i touched the end of the speaker wire with my finger, it got louder.
So i experimented with touching the ground speaker wire to various parts of the circuit, and when i touched it to pin 5 (control) it worked great with a nice loud square wave sound coming from the speaker.
My question is, why did this happen? And should it? My understanding is that pin 5 is there to allow the frequency to be controlled by an external voltage, and is not normally used for anything in these simple circuits. So why does it suddenly make my speaker work when it is connected to it?
Is it because the speaker shouldn't be connected directly to ground and there should be a resistor or something in between, and connecting it to pin 5 is allowing the speaker to ground through some resistance? Im probably completely off the mark with my reasoning, but that's the only thing i could think of.
Any help understanding this would be greatly appreciated.
Sorry if it is a very simple question, im just trying to learn about all this stuff..
Thanks