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We all do.
In this case the combination of resistors and capacitors are the parts that define the filter frequency. The transistor(s) provides gain to offset the losses in the filter.
In general, the passive components (capacitors and/or inductors typically combined with resistors) set the frequencies and amplification is added to buffer impedances or to provide gain (or less loss).
thanks that is very helpful
one question....how do you figure out the frequency
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thats perfect ,but can you wire other leds to different frequencies on it
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The channel has not been tested, and can only run one frequency at a time. I presumed that a low-pass filter would be best as bass would be the first thing wanted.
Of course the frequency of cut-off can be changed, and if you built one and it worked OK you could build some more and use logic gates to get the lights bouncing around a bit.
I'd say test it first and see to it that it meets your needs, and think about more channels and logic after that.
Of course the frequency of cut-off can be changed, and if you built one and it worked OK you could build some more and use logic gates to get the lights bouncing around a bit.
I'd say test it first and see to it that it meets your needs, and think about more channels and logic after that.
Oooh hoo, there might indeed be an issue there... what a lot of work to correct it! I guess it's been too long away from the bench for me.
Let's say all circuits need breadboarding and testing, lest blind thinking prevail!
Thanks for that Duke!
PS
I suppose my eyes must have boggled, and boggled back, but right now it looks like a functioning 6dB/octave filter to me. Is someone else able to give an opinion?
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Poor mystic
I wondered about the DC conditions of the first amp. I would put a fat capacitor on the input and a high value resistor to the centre reference point to set the mean running voltage. The 5k6 resistor should go across the 1u cap to set the DC negative feedback.
I have never used a state variable filter but it looks as if you can get three for the price of three. You would need three of poor mystics rectifiers and output circuits.
I wondered about the DC conditions of the first amp. I would put a fat capacitor on the input and a high value resistor to the centre reference point to set the mean running voltage. The 5k6 resistor should go across the 1u cap to set the DC negative feedback.
I have never used a state variable filter but it looks as if you can get three for the price of three. You would need three of poor mystics rectifiers and output circuits.
Thanks Duke
of course you've noticed the artificial voltage rail (maintained by the last op-amp) to which the signal and op-amp are working?
It looks to me like the 5k6 from the - input of the 1st op-amp should keep the whole arrangement centred on that artificial 3V rail. Or is there something else that I have missed?
of course you've noticed the artificial voltage rail (maintained by the last op-amp) to which the signal and op-amp are working?
It looks to me like the 5k6 from the - input of the 1st op-amp should keep the whole arrangement centred on that artificial 3V rail. Or is there something else that I have missed?
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Also, Duke
if we don't use some kind of detector (could be a schottky), and following output circuits, what do we use? I can certainly see the value in the state-variable filter in this application, but I don't see how it helps trigger the lamps.
PS: Perhaps it is a good idea to include a high-value resistance (100k?) across that op-amp1 feedback cap.
if we don't use some kind of detector (could be a schottky), and following output circuits, what do we use? I can certainly see the value in the state-variable filter in this application, but I don't see how it helps trigger the lamps.
PS: Perhaps it is a good idea to include a high-value resistance (100k?) across that op-amp1 feedback cap.
The rail voltage should go to the + input and the - input should have a connection to the output to bring the two inputs close to one another. See A on diagram. I have included a capacitor in the input since I do not know what the input signal is like.
B on diagram shows a unity gain two pole low pass filter [*]
C on diagram shows an inverting LPF with gain [*]
[*] Electronic Filter Design Handbook Arthur B. Williams
B on diagram shows a unity gain two pole low pass filter [*]
C on diagram shows an inverting LPF with gain [*]
[*] Electronic Filter Design Handbook Arthur B. Williams
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that i can work off ............that can probably fit in to my experiment thanks ....................
...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................i knew i joined this for something
...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................i knew i joined this for something
It will be necessary to use one of poor mystic's rectifier and output for each filter output. Better to start wih one and perhaps work up from there if required.
Poor mystic, what do you think about eliminating the zener and placing another led in the emitter of the BC348? Would this do the same job but give double the light?
Poor mystic, what do you think about eliminating the zener and placing another led in the emitter of the BC348? Would this do the same job but give double the light?
Darn right it would, duke37!
Actually I had hoped conductor3 might eventually use opto-couplers which is what the output stage is all about, but you've got a good notion there.
Actually I had hoped conductor3 might eventually use opto-couplers which is what the output stage is all about, but you've got a good notion there.
