NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Everything Else » Need Quiet Switch Now

September 28, 2010
by norby31
norby31's Avatar

Hey folks. I've made a circuit that has an output of digital high or low, and I want it to open and close a switch that audio will pass through. I've tried a few different circuits for the switch but all of them have some "pop" to them. The digital may switch pretty quickly, 5-10 Hz. I've tried usual stuff like adding caps to ground on output, putting cap Vcc to GND. Tried a 4066 analog switch and a JFET switch.

September 28, 2010
by mongo
mongo's Avatar

Sounds like you need an analog switch that ramps up rather than just simply snapping on and off. It can be done with a voltage follower circuit where the signal can come up from a ground state to its full output state smoothly.

I'll see what I can come up with and get a sketch posted shortly.

October 01, 2010
by norby31
norby31's Avatar

Ok, cool Mongo. Could be like a VCA? Or a cap charging up to modulate a programmable op-amp?

October 01, 2010
by mongo
mongo's Avatar

Similar. I haven't had much time to think on it but essentially, it's a simple circuit that just brings up the supply and gain between two circuits. They can be parallel circuits and switched in and out to a common output or separate outputs. I'll try to get some time later tonight.

October 01, 2010
by rajabalu21
rajabalu21's Avatar

May be this could help.

-Raja

October 01, 2010
by mongo
mongo's Avatar

Raja, Great set there. Yeah, something like that. I was thinking along the lines of NPN transistors but FET's work niicely too.

October 01, 2010
by norby31
norby31's Avatar

I constructed the second circuit on that page (thanks Raja) a few days ago and I still get some popping...confused.

October 01, 2010
by mongo
mongo's Avatar

The schematics will all probably give a little pop while switching.

The circuit that uses the 4016 chip would be the best but one minor alteration might help.

On the gate input to the segment, add a 1M resistor in front of it and at the input, add a small capacitor to give a slight delay in the signal so it gently goes online instead of abruptly.

October 02, 2010
by norby31
norby31's Avatar

Gate??? I don't see a FET in the 4016 circuits. Which schematic?

October 02, 2010
by mongo
mongo's Avatar

The "gate" on a 4016 is the control input. Pins 5,6,12 and 13

October 03, 2010
by norby31
norby31's Avatar

Ok, cool I'll try it...I don't have a 4016 lying around but I'll buy one on Monday. So 1M from pin 13 to the node below it? Thanks...will report on it.

December 02, 2010
by norby31
norby31's Avatar

Thanks for your help, I appreciate it, but I need to know which of the multiple schematics on that page that you are referring to when you speak of adding components to a gate :)

December 02, 2010
by BobaMosfet
BobaMosfet's Avatar

I would recommend using a BJT for this, which eliminates a physical disconnect- and is an analog component itself. Beyond that, if you have an issue, consider adding a filter circuit.

BM

December 03, 2010
by mongo
mongo's Avatar

It has been a while so I will have to review the thread to see where it left off.

Post a Reply

Please log in to post a reply.

Did you know that NerdKits make a great gift? Learn more...