Circuitbenders Forum

Circuitbenders Forum => Circuitbending discussion => DIY Synths => Topic started by: Spann on April 12, 2010, 12:06:38 AM

Title: Control Voltage
Post by: Spann on April 12, 2010, 12:06:38 AM

So, over the weekend I built my first 555 based synth circuit.

Now, I want to add a control voltage at some point (was thinking about one of those Maplin Sequencers), but was planning on using a jack socket and cable to connect the two. Where would I wire the ground to?

Or, should I just use something like an RCA?

Title: Re: Control Voltage
Post by: Gordonjcp on April 12, 2010, 02:57:38 PM

Use any kind of socket you like.  Wire the ground to... ground!

Since the 555 oscillator circuit has its frequency controlled by a resistor rather than any sort of voltage control, you'll need to come up with some sort of converter.  Probably a transistor to ground somewhere would do it.

Title: Re: Control Voltage
Post by: Spann on April 12, 2010, 04:10:09 PM

Ground would make sense, wouldn't it?

As you may be able to tell, I was a little bit tired when I posted this last night!

I'd been reading this:

Quote

By applying a voltage to the CONTROL VOLTAGE input, pin 5, you can alter the timing characteristics of the device. In the astable mode, the control voltage can be varied from 1.7 V to the power supply voltage, producing an output frequency which can be higher or lower than the frequency set by the R1, R2, C timing network.

and figured it'd work.

I might just experiment with a control voltage as-is, see what happens.

Below is the schematic for it (Minus a few teeny changes that don't make a difference), nicked from the Maplin site.

(http://img.photobucket.com/albums/v730/spann/synth.jpg)

Maybe I'll stick a video up (Of this and the other stuff I've built) soon.

Further question: Could anybody suggest a simple circuit to build in order to experiment with the output?