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Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
make this:http://www.geocities.com/capecanaveral/lab/
5322/coildrv.htm It is simple,small,and can use a tiny mosfet instead of a 2n3055. You can vary duty cycle and frequency by a small trimmer and you can use a smaller capacitor or arger one to vary frequency range. It is what i would build.
Registered Member #105
Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
IIRC, that circuit that ArcStarter posted is a 555 driving a transistor- however that will not give the speaker an average value of 0V across the terminals. I've decided to use the SG3525 PWM chip instead. Is there any other way to vary volume besides changing the duty cycle with this chip?
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
EDY19 wrote ...
IIRC, that circuit that ArcStarter posted is a 555 driving a transistor- however that will not give the speaker an average value of 0V across the terminals. I've decided to use the SG3525 PWM chip instead. Is there any other way to vary volume besides changing the duty cycle with this chip?
Registered Member #105
Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
I have one more question- I'm trying to build an op amp bridge tied load circuit, and have it working very well when the input signal (from a 555) swings from 0-5V. However, how do I go about changing the volume? If i change the input signals amplitude (with a voltage divider perhaps) the offset values on the BTL circuit change and the center of the two output signals v(t+) and v(t-) is no longer half of each signals amplitude. How might I go about adding a volume control to a bridge tied load circuit using two op amps in a adjustable volume (gain) of 0-1? It should be easy...
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
EDY19 wrote ...
I have one more question- I'm trying to build an op amp bridge tied load circuit, and have it working very well when the input signal (from a 555) swings from 0-5V. However, how do I go about changing the volume? If i change the input signals amplitude (with a voltage divider perhaps) the offset values on the BTL circuit change and the center of the two output signals v(t+) and v(t-) is no longer half of each signals amplitude. How might I go about adding a volume control to a bridge tied load circuit using two op amps in a adjustable volume (gain) of 0-1? It should be easy...
Sorry to annoy again with the SG3525 but it can do this- it has 2 outputs, between which you can connect your speaker, this way it will be "bridge tied" and you can vary the volume with dead time...
Registered Member #105
Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
I did buy several of these- so if i used a fixed duty cycle and variable deadtime, would the frequency be fixed still? How adjustable is the dead time? I'm just having trouble seeing the waveforms that i might get with these certain parameters fixed and certain ones variable.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
EDY19 wrote ...
I did buy several of these- so if i used a fixed duty cycle and variable deadtime, would the frequency be fixed still? How adjustable is the dead time? I'm just having trouble seeing the waveforms that i might get with these certain parameters fixed and certain ones variable
Well just vary the duty cycle, this will in turn vary the dead time (these two are closely related). It can be varied from 0% to ~49% for each output, this means the "on time" for the speaker can be from 0 to 98%.
Registered Member #105
Joined: Thu Feb 09 2006, 08:54PM
Location:
Posts: 408
I think the thing I don't get is if the two outputs are just inverted from each other at all times, or if both can be low at the same time in order to deliver no power to the speaker.
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Simple Oscillator
