Help with audio modulating
Njubster, Mon Oct 20 2014, 06:51PMI bought a lovely little pwm controller called SG3524N in a local shop, cause they had no TL494s, I followed the datasheet and I came up with attached circuit. It's working pretty fine for 12V, but I'm having trouble making it sing. I tried few things like applying audio signal to current limit comparator, or feeding audio signal to the base of external transistor, and then feeding the emitter current to the shutdown transistor base, but none of those worked.
I'm just a hobbyist, so I do have some huge gaps in knowledge, but it would be awesome if anyone could just give me an idea how could I achieve what I want :)
The schematic:
Re: Help with audio modulating
Sigurthr, Tue Oct 21 2014, 12:37AM
I've never used that chip but I am experienced with the SG3525, its brother. I capacitively couple line level audio into pin 6, the Rt timing resistor, to achieve audio modulation.
I was going to post a schematic I use for the 3525, but the pinouts are too dissimilar to be of much use to you, I think.
Sigurthr, Tue Oct 21 2014, 12:37AM
I've never used that chip but I am experienced with the SG3525, its brother. I capacitively couple line level audio into pin 6, the Rt timing resistor, to achieve audio modulation.
I was going to post a schematic I use for the 3525, but the pinouts are too dissimilar to be of much use to you, I think.
Re: Help with audio modulating
Njubster, Tue Oct 21 2014, 03:10AM
Thanks for your reply. I saw some people using that technique with TL494, but I had no luck in making it sing like that.
Is the capacitor value critical?
Njubster, Tue Oct 21 2014, 03:10AM
Thanks for your reply. I saw some people using that technique with TL494, but I had no luck in making it sing like that.
Is the capacitor value critical?
Re: Help with audio modulating
Wolfram, Tue Oct 21 2014, 05:57PM
Try something like this.
Wolfram, Tue Oct 21 2014, 05:57PM
Try something like this.
Re: Help with audio modulating
Njubster, Tue Oct 21 2014, 06:08PM
Dude, I didn't even notice the mistake with voltage divider... Thank you... I will try it now :)
Njubster, Tue Oct 21 2014, 06:08PM
Dude, I didn't even notice the mistake with voltage divider... Thank you... I will try it now :)
Re: Help with audio modulating
Njubster, Fri Oct 24 2014, 09:52PM
Finally managed to get some audio output by connecting the audio out to Rt pin, but my phone starts to mess things up when it's connected, how could I fix this?
Njubster, Fri Oct 24 2014, 09:52PM
Finally managed to get some audio output by connecting the audio out to Rt pin, but my phone starts to mess things up when it's connected, how could I fix this?
Re: Help with audio modulating
Sigurthr, Sat Oct 25 2014, 01:43AM
Make sure you capacitively couple the audio in, don't DC couple it. (Use a series nonpolar 2-10uF cap, or polar with positive towards the Rt pin). DC coupling leads to all kinds of problems.
Sigurthr, Sat Oct 25 2014, 01:43AM
Make sure you capacitively couple the audio in, don't DC couple it. (Use a series nonpolar 2-10uF cap, or polar with positive towards the Rt pin). DC coupling leads to all kinds of problems.
Re: Help with audio modulating
Njubster, Sat Oct 25 2014, 06:41PM
Hey, thanks a lot, 2u2 electrolytic and it works :) Still needs a bit tweaking though.
Njubster, Sat Oct 25 2014, 06:41PM
Hey, thanks a lot, 2u2 electrolytic and it works :) Still needs a bit tweaking though.
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