Today on my Breadboard....

[gasboss775]

Just had to repost this:

You know, I've always had a thing about authority, and I really resent the fact that in order to post something, I must 'submit'.

- Nelson Baboon.

[gasboss775]

A couple of Lunetta type oscillators....I'm planning on building a little CMOS synth with these and a few other simple circuits.

The Schmitt NAND gate can be 1/4 of either a 4093 or 74hc132

[gasboss775]

I found this to be a better version of the previously posted circuit above.

[gasboss775]

The next Schmitt oscillator isn't really a VCO as such however it does permit a degree of modulation of both frequency and pulse width which is very much dependent on the setting of the main tuning control VR2 as well as that of the actual modulation depth control VR1.

With VR1 fully clockwise and VR2 at maximum resistance it is possible to get around an entire octave of frequency modulation, however with VR2 at minimum resistance the maximum frequency modulation is equivalent to about a major 3RD going by ear.
The CV input was at VDD which in the experiment was equal to 10.04 Volts.
These results were obtained using 1/4 of a TI CD4093B.

The relationship of frequency to CV is neither linear or 1V per octave but given its simplicity
I think this is OK!

[gasboss775]

This one is a square noise generator, basically it outputs random 1s & 0s. This can be fed into shift registers to produce random gates or random voltages ( using a DAC such as an R2R network )

The low pass output is just more slowly changing, effectively it gives an alternative random output.

[gasboss775]

A very simple VCO using a Schmitt trigger oscillator controlled by a Vactrol. Note this VCO isn't linear OR 1V per octave! Is very simple though, good for Lunettas!

[whoop_john]

Just had to repost this:

You know, I've always had a thing about authority, and I really resent the fact that in order to post something, I must 'submit'.

- Nelson Baboon.

I have been involved with website design for the BBC here in the UK for some years and the official guidelines have always said never to use a submit button or a quit button, they are negative terms.

[gasboss775]

Just had to repost this:

You know, I've always had a thing about authority, and I really resent the fact that in order to post something, I must 'submit'.

- Nelson Baboon.

I have been involved with website design for the BBC here in the UK for some years and the official guidelines have always said never to use a submit button or a quit button, they are negative terms.

Somehow it doesn't surprise me that the BBC are this pedantic, it took them over 10 years to decide on which analogue colour TV system to choose. In saying that the PAL system is now generally regarded as having been superior to the alternative NTSC system, so there might be some merit in their level of pedantry.

[gasboss775]

Seasons Greetings Fellow Wigglers!!!



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Today's Serving A 2 input logic module with OR, XOR & NAND Outputs using hex inverter and diodes and resistors.

[gasboss775]

An interesting VCF can be made using a bridged T circuit and an FET optocoupler like H11F1, it is a bit like a vactrol but with a light sensitive FET rather than an LDR.

2 distinct factors make the behaviour of this device and hence that of this VCF different.
The first is speed, this device can be modulated by an audio frequency control signal, the other distinguishing characteristic is non linearity. For low level signals 200mV or less the photo FET behaves much like a variable resistance but at higher levels more like a current source this causes the signal to be distorted with interesting effects.

I powered the circuit with + / - 15 V supplies but it should work ok with + / - 12 V supplies also.

I included the 10K input level pot so that you can control to what extent the filter is driven into the distorted region, there is a range of sounds that are possible using varying degrees of drive.

[gasboss775]

Another H11F1 FET optocoupler circuit, this time a VCA....

I feel that I should point out that as with other circuits using FETs as the control element, that the relationship between control voltage and gain is neither linear or exponential but something in between. Perhaps some of the more learned Wigglers could provide a more detailed analysis of this situation.

[/i]

[gasboss775]

I recently made a passive lowpass filter

The cut off frequency is selected with a rotary switch ( The diagram shows only a 2 way switch due to not having a rotary switch symbol ) My circuit had 6 frequencies but with more switches and capacitors more frequencies could be selected. The pot varies the resonance, which is highest at minimum resistance.

The 4 Henry inductor was made from the primary winding of a mains transformer, the secondary is just left unconnected.

INPUT IS AT BLUE OUTPUT IS AT GREEN

[whoop_john]

deleted as I'd previously responded, apologies

[Splinter(UA)]

Hey! Very good stuff. Please tell me how it works with an audio signal? I'm trying to do something similar, but until I figure out which transformer is best. Tnx

I recently made a passive lowpass filter

The cut off frequency is selected with a rotary switch ( The diagram shows only a 2 way switch due to not having a rotary switch symbol ) My circuit had 6 frequencies but with more switches and capacitors more frequencies could be selected. The pot varies the resonance, which is highest at minimum resistance.

The 4 Henry inductor was made from the primary winding of a mains transformer, the secondary is just left unconnected.

INPUT IS AT BLUE OUTPUT IS AT GREEN

[gasboss775]

Hey! Very good stuff. Please tell me how it works with an audio signal? I'm trying to do something similar, but until I figure out which transformer is best. Tnx

I recently made a passive lowpass filter

The cut off frequency is selected with a rotary switch ( The diagram shows only a 2 way switch due to not having a rotary switch symbol ) My circuit had 6 frequencies but with more switches and capacitors more frequencies could be selected. The pot varies the resonance, which is highest at minimum resistance.

The 4 Henry inductor was made from the primary winding of a mains transformer, the secondary is just left unconnected.

INPUT IS AT BLUE OUTPUT IS AT GREEN

Sorry for not replying sooner, I don't visit here so much now.


The circuit is a lowpass filter. Uses inductor to reduce higher frequencies and a capacitor to shunt the higher frequencies to ground, creating a steeper cutoff. However at the point of resonance when the inductor and capacitor are equal in impedance there is a peak in the response the resistance in series with the inductor will effect the size of this peak, lower resistance = bigger peak, higher resistance = smaller peak.

The transformer is being used as an inductor, I used the primary winding (220-240VAC) of a small mains transformer (6VA it was rated ) The secondary windings can just be ignored