Author Topic: Control Voltage Question  (Read 3055 times)

ZiggyZipgun

Control Voltage Question
« on: January 23, 2009, 12:58:30 PM »
I'm working on a little something at the moment, and the schematic has thrown me off a little, as it shows the VCC separate from the VCTL.  Is there more to this part of the circuit than it's showing? 


I haven't done a mock-up yet as I've just received a sample supply of the ICs, and if it works, I'll definitely be sharing the results here on the forum, but for the time being I've left out the rest of the schematic until I find out what legal hoops I'll have to jump through in order to use these and display the company's logo my pedals that use it.

oskar

Re: Control Voltage Question
« Reply #1 on: January 23, 2009, 01:43:51 PM »
But what IC is it? It looks like you're trying to switch between 4 caps with an analogue switch.

ZiggyZipgun

Re: Control Voltage Question
« Reply #2 on: January 23, 2009, 02:41:33 PM »
The 4-position switch configures the diodes, which step the VCTL down to the proper logic values, which are:


oskar

Re: Control Voltage Question
« Reply #3 on: January 23, 2009, 02:44:00 PM »
What is U1?

ZiggyZipgun

Re: Control Voltage Question
« Reply #4 on: January 23, 2009, 02:53:49 PM »
It's a special analog 22-pin IC, but for this control voltage question it's not important.  As I mentioned, once I've taken all the proper legal steps to use this IC I'll gladly share the build and post sound clips and everything, but for now I'm leaving that out.

tommy.genes

Re: Control Voltage Question
« Reply #5 on: January 24, 2009, 08:40:35 AM »
The term "control voltage" generally connotes a continuously-adjustable voltage that communicates an analog variable, such as a potentiometer controlling the filter cutoff in a wah effect. What you are showing is binary logic-type control; it's either on or off.

R14 and R15 form a voltage divider, and since R14 = R15, VCTL = 1/2 VCC. Assuming VCC is 9V as is typical for guitar effects, VCTL would be 4.5V. This makes sense because logic circuits typically operate at ~5V.

Note that in BYPASS, current flows from VCTRL through R1 then D2, as well as through R2 and D3, to ground, so that the inputs to CTRL1 and CTRL2 are zero. (Actually, they're about 0.7V due to the voltage drop across the diodes, but in logic switching, this is effectively zero.) By selectively switching D1 through D4, CTRL1 and CTRL2 alternate between VCTL and ground to create the four switching modes in your table.

Does this make any sense? Or did I completely misunderstand your question? I'm interested to hear more about the IC you are using when you can reveal it.

-- T. G. --
"A man works hard all week to keep his pants off all weekend." - Captain Eugene Harold "Armor Abs" Krabs

frequencycentral

  • Poster2
  • **
  • Posts: 4941
  • Total likes: 102
  • Kicking the sh!t of of your speakers since 2008
    • frequencycentral
Re: Control Voltage Question
« Reply #6 on: January 24, 2009, 09:47:44 AM »
I'm interested to hear more about the IC you are using when you can reveal it.

.........though the mystery is mystyfying!

ZiggyZipgun

Re: Control Voltage Question
« Reply #7 on: January 24, 2009, 12:07:44 PM »
I posted this in the analog section of the forum as well, which is messy, so now I have to copy & paste a bit.

You're absolutely right, Don..er, um..Tommy.  VCC can range from +5V to +12V; this is a stompbox so naturally it'll be 9VDC.  VIH can be between 2V to 5V, and VIL can be anywhere from 0V to 0.8V - so 0.7V would be fine.  I'm still waiting on an order of stuff from Small Bear that I placed yesterday morning, so it'll be a few days before she's up and running.  I have 26 of the ICs, so hopefully I won't cook or mishandle too many of 'em.

Now, I would like to set up a sequential switch to go through Modes 1, 2, & 3, which Oskar did give me some pointers on for another project, but is there any "triple" equivalent to the 4016 quad bilateral switch?  I could go back to 0, but I'd rather have true bypass (which I'll probably also need help on, as the whole thing is Stereo In/Out, including the chip). 

When it comes to digital controls, I'm new but I'm learning, much like an Eat'n'Park waitress, but user-friendliness is my goal.  For the moment, she's getting a big ol' 3-position rotary switch, which, for unknown reasons, I have a bunch of.

oskar

Re: Control Voltage Question
« Reply #8 on: January 24, 2009, 02:44:15 PM »
Edit! <------- Post 666!!!      8)     
...but is there any "triple" equivalent to the 4016 quad bilateral switch? 
Check out the 4051, 4052 and 4053... These are all analogue switches like the 4016 but I believe they also have level conversion for the control pins.
The 4053 is a tripple spdt analogue switch.
« Last Edit: January 24, 2009, 02:47:18 PM by oskar »