Problems with Optofets (H11F1 or TLP222G)

[daleykd]

I'm going insane, guys. I've tried both an H11F1 and now a TLP222G to do a mute. The H11F1 didn't work at all, and the TLP222G was able to reduce the volume, but not completely mute the signal.
I moved the TLP222G to a separate, small breadboard, and now it doesn't even reduce the volume. Am I missing something glaring? I need some help. Here's my super-simple schematic:


I've tried it with and without a CLR.  When it WAS helping reduce volume, I had no CLR. If I used a 4k7 CLR, it reduced the volume less.

[sturgeo]

Is the sleeve connected to GND at all?

[flanagan0718]

Is the sleeve connected to GND at all?

This

Also what are you testing it in. In my mission control pedal I was still getting a pop from the Delay (DBD). I still needed a pull down on the out. just saying

[daleykd]

Is the sleeve connected to GND at all?

No.  I should have been a bit more explicit.  The GND is digital GND.  But since the sleeve is hoping to shunt to the audio (by way of the MOSFET), I would think I don't need to connect the sleeve.  In fact, don't I want to keep the digital and analog GNDs separate?  Either way, I attempted to connect the two, and it had no effect.

I've added a resistor on pin 2 to GND, at a value of 470R.  This seems to at least set the recommended current of the LED to 7.5mA.

Others have suggested biasing the optoisolator (adding a pullup resistor from 5V on pin 4).  I've tried a couple different values with no luck.

One other said the TLP222G may not get me a full mute since it only takes us down to 30 ohm.  (I have confirmed that value with my DMM.)

[daleykd]

I've also done it the way Molten Voltage does it, and again, it just doesn't mute it.  It just dampens the volume.

Page 5
http://www.moltenvoltage.com/pedalsync/documentation/PedalSync_MV-57_MV-57B_Relay_Bypass_Datasheet.pdf

[daleykd]

Also what are you testing it in. In my mission control pedal I was still getting a pop from the Delay (DBD). I still needed a pull down on the out. just saying

Long story short, it's a secret until I'm ready to show it for the contest.    Right now, I'm not worried about pop until I can see if I can fully mute this.

[flanagan0718]

Also what are you testing it in. In my mission control pedal I was still getting a pop from the Delay (DBD). I still needed a pull down on the out. just saying

Long story short, it's a secret until I'm ready to show it for the contest.    Right now, I'm not worried about pop until I can see if I can fully mute this.

Ahh, Very cool. Well hopefully someone with a little more know how chimes in.

[sturgeo]

When using the 222g to mute the signal I've always connected digital and audio grounds. The only time I've kept them separate is when using the I2C bus on larger projects.

I also enable the optofet directly from the microcontroller, I originally had a resistor in series to soften the mute but found it didn't make a great deal of difference.

[daleykd]

When using the 222g to mute the signal I've always connected digital and audio grounds. The only time I've kept them separate is when using the I2C bus on larger projects.

I also enable the optofet directly from the microcontroller, I originally had a resistor in series to soften the mute but found it didn't make a great deal of difference.

I'm definitely using I2C for this project, and have like 3 or 4 devices on that bus.  I figured I'd enable it directly from the MCU, but wanted to test the resistor, first.

Here's the main question for you: if you turn on the 222G by supplying 5V, does it 100% mute your signal?

I may have the wrong expectation of the 222G.  It may not be able to fully mute the signal.

[gtr2]

None of those will fully mute your signal in that arrangement.

Use a relay in conjunction with the opto to stop the pop but still fully ground the signal.

See the arrangements that use an opto and switch or opto and relay for bypassing for arrangement of the opto and relay in your setup.

[sturgeo]

None of those will fully mute your signal in that arrangement.

Use a relay in conjunction with the opto to stop the pop but still fully ground the signal.

See the arrangements that use an opto and switch or opto and relay for bypassing for arrangement of the opto and relay in your setup.

Reading between the lines i think this is what is going on but he doesn't want to give away the full schematic which is fair enough as its for the BOTY.

Is the schematic for the relay & muting portion as shown here? : http://stompville.co.uk/?p=423 (about half way down the page)

OK, if you're using the I2C bus then yes keep AGND & DGND seperate and if neccessary join them only at 1 place, i tend to put 2 pads next to each other so i can easily pop a jumper on if needs be, i'd also suggest adding plenty of filtering in close proximity to try and keep the noise levels down.

The 222G appears to fully mute the signal when switching as i don't get any pops and the switch is more noticeable as there is a percieved silence, i'll confirm this tomorrow by editing my code and putting a much larger delay in.

[daleykd]

None of those will fully mute your signal in that arrangement.

I think I just needed someone to confirm this.

Use a relay in conjunction with the opto to stop the pop but still fully ground the signal.

This is what I think I'm going to do.

Reading between the lines i think this is what is going on but he doesn't want to give away the full schematic which is fair enough as its for the BOTY.

It's not THAT hush, hush.  Some know about it.  And until I saw the BOTY post, I wasn't keeping it as close to my vest.  FWIW, I do plan on making this open source and offering a kit.

Is the schematic for the relay & muting portion as shown here? : http://stompville.co.uk/?p=423 (about half way down the page)

His post, along with the back and forth with R.G. in DIYSB, is what I used as a basis.  I just had to learn more about the technical details of these things than I ever have before.

OK, if you're using the I2C bus then yes keep AGND & DGND seperate and if neccessary join them only at 1 place, i tend to put 2 pads next to each other so i can easily pop a jumper on if needs be, i'd also suggest adding plenty of filtering in close proximity to try and keep the noise levels down.

Yeah, I thought about doing that!

The 222G appears to fully mute the signal when switching as i don't get any pops and the switch is more noticeable as there is a percieved silence, i'll confirm this tomorrow by editing my code and putting a much larger delay in.

Yeah, like 5 seconds!

[gtr2]

As a side note.  I suggest looking into digital vs analog return currents.  It will improve your PCB design and you won't stress sharing a ground plane etc.  There are a lot of misconceptions out there.

[sturgeo]

I can confirm that the TLP222G can completely mute the signal when used in conjunction with relay switching as described on the stompville site.

My effect on code is as below, i set the "MUTEONDELAY" & "MUTEOFFDELAY" variables to 5000ms, when clicking the switch the led turned on, signal muted, a 5 second delay, hear the relay switch, another 5 second delay and then the guitar signal was unmuted.

{
  digitalWrite(LED, LOW);   // turn LED on
  digitalWrite(MUTE, HIGH); // enable optomute
  delay(MUTEONDELAY); // pre switch mute
  digitalWrite(RELAY1, HIGH);  // switch relay to on position
  delay(RELAYDELAY);  // wait for relay to switch
  digitalWrite(RELAY1, LOW);  // turn coil off
  delay(MUTEOFFDELAY); // post switch mute
  digitalWrite(MUTE, LOW); // disable optomute
  state = ON;
}

Edit: I'll also add that as this is a single attiny, its all on a single ground plane.

[daleykd]

As a side note.  I suggest looking into digital vs analog return currents.  It will improve your PCB design and you won't stress sharing a ground plane etc.  There are a lot of misconceptions out there.

I'll dig into that at some point.  I'm redesigning my PCB for the third time to keep digital and analog even further apart than I did last time.  I'm also doing my best to keep ground planes super small.

I can confirm that the TLP222G can completely mute the signal when used in conjunction with relay switching as described on the stompville site.

This weekend I was able to 99% mute the signal when using a 10k series resistor on the audio path.  That was achieved by using a relay to mute the signal.  I wonder if this is all because of a breadboard.  When the 10k series resistor was used with the TLP222G, I got about an 80% mute.

Very curious indeed.

Now, to be fair, I did a couple things:
1. Turned my amp (Blues Jr) up to max master volume and max volume.  (Talk about a bunch of 'noise.')
2. Tested with my Epi Les Paul.
3. Tested with a Ditto looper at max volume.

I'm not 100% pleased; perhaps I'm 90%.