Relay true bypass power Consumption

[antonis]

As Rob said above, you use BC549 as a "switch" (Saturated - Cut-off) so you only need plenty of Base current (ON) and lack of it (OFF).
The later is easily obtainable but the former needs a conservative design (involving h_FE worst case scenario, coil intial current, LED current and lowest "wasted" current..)
All the above result into an appreciably undersized Base resistor..

P.S.
Is there any possibility to feed relay switcing configuration from an independent source (like another PS or battery..), to see if click/pop persists..??

[amptramp]

A couple of thoughts:

1. The NE555 itself is known for its current spikes when switching between high and low states.  You might need more bypassing right at the IC to limit the noise from the current spike.  There is a CMOS version of this device that could drive a Darlington transistor or small power MOSFET to reduce the required output current.

2. The noise from the coil itself is due to the rate at which the current rises and falls.  A capacitor to ground at the switching transistor base may reduce the inductive kick when the coil turns off and the current ramp when the coil turns on.  Splitting the base resistor into two equal series resistors and placing the cap to ground from their junction may let you get away with a smaller capacitor.

[antonis]

A capacitor to ground at the switching transistor base may reduce the inductive kick when the coil turns off and the current ramp when the coil turns on.  Splitting the base resistor into two equal series resistors and placing the cap to ground from their junction may let you get away with a smaller capacitor.

+1 

[jackwithoneye]

Thanks for all your feedbacks!
here are the results :

-Putting a 1M Resistor to ground on the FXIN doesn't change anything (for the popping)

- I had adjusted the R2 (transistor driver resistor to a lower value 10K)

- i tried to use 2 differents (basics) power supply to feed the FX circuit and the relay bypass circuit. Still popping at high level of output volume setting on the FX (but only during silence or low level playing, maybe the pop is hidden/masked when i play louder, but i don't hear it)

A couple of thoughts:

1. The NE555 itself is known for its current spikes when switching between high and low states.  You might need more bypassing right at the IC to limit the noise from the current spike.  There is a CMOS version of this device that could drive a Darlington transistor or small power MOSFET to reduce the required output current.

2. The noise from the coil itself is due to the rate at which the current rises and falls.  A capacitor to ground at the switching transistor base may reduce the inductive kick when the coil turns off and the current ramp when the coil turns on.  Splitting the base resistor into two equal series resistors and placing the cap to ground from their junction may let you get away with a smaller capacitor.

1/ you mean the ICM7555, LMC555 or TLC555 i think, interesting, too bad i have 25x NE555, i should order few ICM7555 to try

2/ what kind of cap are you thinking of? I tried with a 100nF film, that does not affect the popping thing

[antonis]

Try to wrap relay in grounded aluminum foil..
(99% it shouldn't work but we aim to 1%..)

[jackwithoneye]

Try to wrap relay in grounded aluminum foil..
(99% it shouldn't work but we aim to 1%..)

if i wrap myself in aluminium, it helps?

[antonis]

A Faraday cage should be more economical..

[Rob Strand]

i tried to use 2 differents (basics) power supply to feed the FX circuit and the relay bypass circuit. Still popping at high level of output volume setting on the FX (but only during silence or low level playing, maybe the pop is hidden/masked when i play louder, but i don't hear it)

So are you basically saying it is better than before?

Also, is the click still happening on both changes in state ie. effect off to on and effect on to off.

If so then the supply filtering might be on the right track.

Ideally the switching circuit (the whole thing) should have its own ground which is run back to the supply input.  Lookup star grounding.  Its possible to get glitches on the grounds.  I only 50%/50% on this as a cause though.

Quote from: amptramp on Today at 08:11:30 AM

    A couple of thoughts:

    1. The NE555 itself is known for its current spikes when switching between high and low states.  You might need more bypassing right at the IC to limit the noise from the current spike.  There is a CMOS version of this device that could drive a Darlington transistor or small power MOSFET to reduce the required output current.

    2. The noise from the coil itself is due to the rate at which the current rises and falls.  A capacitor to ground at the switching transistor base may reduce the inductive kick when the coil turns off and the current ramp when the coil turns on.  Splitting the base resistor into two equal series resistors and placing the cap to ground from their junction may let you get away with a smaller capacitor.


1/ you mean the ICM7555, LMC555 or TLC555 i think, interesting, too bad i have 25x NE555, i should order few ICM7555 to try

2/ what kind of cap are you thinking of? I tried with a 100nF film, that does not affect the popping thing

The idea behind filtering the switching circuit is it would also filter the NE555 circuit.
(A 100nF cap is good for the NE555.)

As an ultimate isolation experiment, don't use your existing circuit at all.  Get a battery and power the relay coil on its own.  Leave the relay diode in and the relay series resistor.  Just watch out about getting the supply around the correct way otherwise you might fry the diode.  That will completely remove any artifacts from the power supply and the NE555.  If it were my circuit I would doing this test.   You need to get it to work with this simple set-up before you can continue.

[Rob Strand]

Here's an idea which might help stop the glitches from the switching circuit getting into the audio *via* the relay.  Given you can't shield the contacts from the relay structure the next best thing is to slow down the signals which switch the relay.   You can see the addition of a 100nF cap (C2) across the collector and base of the relay transistor:




RG's circuit has the same idea (although for a different type of relay),

[jackwithoneye]

i tried to use 2 differents (basics) power supply to feed the FX circuit and the relay bypass circuit. Still popping at high level of output volume setting on the FX (but only during silence or low level playing, maybe the pop is hidden/masked when i play louder, but i don't hear it)

So are you basically saying it is better than before?

Also, is the click still happening on both changes in state ie. effect off to on and effect on to off.

If so then the supply filtering might be on the right track.

Ideally the switching circuit (the whole thing) should have its own ground which is run back to the supply input.  Lookup star grounding.  Its possible to get glitches on the grounds.  I only 50%/50% on this as a cause though.

No, sorry, it's not better with seperated power supplies
the click happen during both changes, on and off.

Quote from: amptramp on Today at 08:11:30 AM

    A couple of thoughts:

    1. The NE555 itself is known for its current spikes when switching between high and low states.  You might need more bypassing right at the IC to limit the noise from the current spike.  There is a CMOS version of this device that could drive a Darlington transistor or small power MOSFET to reduce the required output current.

    2. The noise from the coil itself is due to the rate at which the current rises and falls.  A capacitor to ground at the switching transistor base may reduce the inductive kick when the coil turns off and the current ramp when the coil turns on.  Splitting the base resistor into two equal series resistors and placing the cap to ground from their junction may let you get away with a smaller capacitor.


1/ you mean the ICM7555, LMC555 or TLC555 i think, interesting, too bad i have 25x NE555, i should order few ICM7555 to try

2/ what kind of cap are you thinking of? I tried with a 100nF film, that does not affect the popping thing

The idea behind filtering the switching circuit is it would also filter the NE555 circuit.
(A 100nF cap is good for the NE555.)

As an ultimate isolation experiment, don't use your existing circuit at all.  Get a battery and power the relay coil on its own.  Leave the relay diode in and the relay series resistor.  Just watch out about getting the supply around the correct way otherwise you might fry the diode.  That will completely remove any artifacts from the power supply and the NE555.  If it were my circuit I would doing this test.   You need to get it to work with this simple set-up before you can continue.

Here's an idea which might help stop the glitches from the switching circuit getting into the audio *via* the relay.  Given you can't shield the contacts from the relay structure the next best thing is to slow down the signals which switch the relay.   You can see the addition of a 100nF cap (C2) across the collector and base of the relay transistor:




RG's circuit has the same idea (although for a different type of relay),

I think you've got something there!
I tried with
- a 100nF, then a 470nf => still the same pop
- 1uF => It clearly removes the trebly part of the pop.

I used an alternative routing for the cap which gave me better results :




I then tried with an electrolitic 10uF cap, it even better, the pop is has "almost" disapeared !


At the end, with a 47uF electrolitic, there a 0.5second release whistle, that's defenitly the limit you dont want to reach.

The 10uF electro cap win the popping race!
As it's still not perfectly silent, the switching pop is now really acceptable, far from the "click" it was!
Great tip Rob, thanks a lot!

Still have to work on the seperate ground trace for the switching circuit i guess?

[Rob Strand]

I then tried with an electrolitic 10uF cap, it even better, the pop is has "almost" disapeared !


At the end, with a 47uF electrolitic, there a 0.5second release whistle, that's defenitly the limit you dont want to reach.

The 10uF electro cap win the popping race!
As it's still not perfectly silent, the switching pop is now really acceptable, far from the "click" it was!
Great tip Rob, thanks a lot!

Wow they are very large caps which will result in very slow switch times (as you have seen).

Still have to work on the seperate ground trace for the switching circuit i guess?

Quite possible this could still be the cause.

As for whistle.   That could also be an indication of yet another problem.   I was actually going to add this to my previous post but I held off in order to keep the post simple.  However, the fact you mentioned whistle means you have this issue to some degree.   What the switch time is slow the relay will take longer to close.  This means the effect input is open circuit for a short time which then promotes oscillation in high gain circuits.

If you look at this schematic,

http://www.generalguitargadgets.com/pdf/ggg_bmp_tri_sc.pdf

You can see the equivalent of your FXIN line has a 100pF cap (C15) to ground.   This helps prevent oscillation/whistle.  So it might be wise to try adding it.   A value of 47pF to 1nF is often used.   It needs to be large enough to stop the oscillation but not so large as to affect the tone.  Maybe try 220pF to 470pF.

You might want to check this cap value by making sure there is no whistle in your 47uF case.   After that see if you can use a smaller cap to reduce the click (just in case the oscillation is causing the click, which is possible).

FYI, when you get obscure problems like this it's pretty normal to have to dig deeply into the problem.   Sometimes that makes you rethink what is actually fixing the problem.   There's a lot of reasons under the hood for this stuff and they aren't so easy to explain.    Fortunately tracking down the problem can be helped by some experiments and perseverance.

I used an alternative routing for the cap which gave me better results

You might be better off connecting the cap to ground instead of back to the switch input.
What this is doing is slowing down the signal to the relay - it could even be doing more than that!

Still have to work on the seperate ground trace for the switching circuit i guess?

It's possible.   At the moment the fix can hide many sources of the problem.  I'm not exactly sure what
that source is yet.

[Rob Strand]

Quote

    Still have to work on the seperate ground trace for the switching circuit i guess?

It's possible.   At the moment the fix can hide many sources of the problem.  I'm not exactly sure what
that source is yet.

I guess what I should add is, supposed the click is due to the ground layout.  Then while the things you have tried seem like they they are moving in the right direction we are actually solving the wrong problem.  We are just reducing the true problem using indirect means.

[antonis]

I used an alternative routing for the cap which gave me better results :

I'm not sure if NE555 would like a 10μF, with no series resistor, on its output..

[amptramp]

With your alternative routing, you may need to use a non-polar cap because the voltage across it changes polarity.  If you used a cap from coil to ground, you do not run into this problem.

[anotherjim]

Could you not just feed the relay coil +supply via an RC filter?

The R of the filter sets the hold voltage with the coil DCR when the relay needs to be on.
The C of the filter sets the duration of the relay pick pulse It will charge to the full +supply voltage when the relay is off.
The hold voltage can be lower than the relay pick voltage. 5v relay might hold as low as 3v. Hold current can be lower.
The momentarily higher +supply voltage than the coil rating when picking is probably harmless as it's only of short duration.
The current stored in the C provides the peak current to pick the relay, not the + supply.
When turned off, the C charges up again for the next pick, the R slows the charge rate avoiding a pulse of current.

[jackwithoneye]

Again, thanks for the brainstorming guys!

Rob, i'm sorry, i may have not explained correctly the whistle, i was talking about wasn't really a whistle, more like a Starwars light saber switch off (zzeeeewwww), maybe the discharging cap with the led struggling slowly.

I now understand that this glitch solution is not really healthy, and not sal problem source.

It's really hard for me to understand the concept of seperate ground traces, as the connect together at a point, and even if it's at the DC power connector, i don't understand how it wouldn't go to the audio Jack connectors ground. I don't get the layout technique/workflow to optimise this.

With your alternative routing, you may need to use a non-polar cap because the voltage across it changes polarity.  If you used a cap from coil to ground, you do not run into this problem.

putting a C14 10uf electro cap to ground like on the below picture helps a bit on the SWITCHING OFF popping.



to do list : 
-try using a low current LED
-try using a ICM7555IPAZ instead of the NE555, to avoid the well known NE555's current peak spike when switching state.
-use a 3PDT 

Could you not just feed the relay coil +supply via an RC filter?

The R of the filter sets the hold voltage with the coil DCR when the relay needs to be on.
The C of the filter sets the duration of the relay pick pulse It will charge to the full +supply voltage when the relay is off.
The hold voltage can be lower than the relay pick voltage. 5v relay might hold as low as 3v. Hold current can be lower.
The momentarily higher +supply voltage than the coil rating when picking is probably harmless as it's only of short duration.
The current stored in the C provides the peak current to pick the relay, not the + supply.
When turned off, the C charges up again for the next pick, the R slows the charge rate avoiding a pulse of current.

i think rob was speaking about working on the power supply part too, i have to dig into it too

NB: After testing at loud Volume and analysing, i can affirm that as soon as you got a signal in the audio path, there is no popping when switching(not even hidden in the audio signal)

[antonis]

After testing at loud Volume and analysing, i can affirm that as soon as you got a signal in the audio path, there is no popping when switching(not even hidden in the audio signal)

If so, you need a make-before-brake switch..
(for signal continuously present on contact lugs)

[Rob Strand]

Quote from: anotherjim on Today at 08:26:31 AM
    Could you not just feed the relay coil +supply via an RC filter?

i think rob was speaking about working on the power supply part too, i have to dig into it too

You should be able to get Jim's idea to work as well.   The idea behind using caps around the transistor is it requires smaller caps to achieve the same job, more or less.

Just to summarize the likely causes:
- changes in current from the relay causing glitches on the power
- change in current from the relay causing glitches on the ground
- the change in voltage on the relay coil coupling through to the contacts (inside the relay)

Slowing down the drive to the relay tends to reduce all of those but it doesn't tell you the cause.

I guess my beef is *if* the problem is noise through the ground we are solving the wrong problem.  We would be putting in a heap of filtering to slow things down when really moving a few ground wires will improve things by a factor of 10 or 100.  Moving the ground wires might still not be enough but it will certainly reduces the amount of filtering required.

It's really hard for me to understand the concept of seperate ground traces, as the connect together at a point, and even if it's at the DC power connector, i don't understand how it wouldn't go to the audio Jack connectors ground. I don't get the layout technique/workflow to optimise this.

Before doing that, in order to workout if it's noise on the ground or glitches through the relay itself the best way forward is to power the whole switching circuit and relay from a separate power supply.   You don't want any connections between the ground or power rails of the "new" power supply and the existing effects power.   The only wires that connect between the two are the relay *contacts*.   This way the switching and switch power are completely out of the picture.  If you get glitches then it must be coupling in inside the relay from the coil to the contacts.

The next step would be to keep this configuration and run a single ground wire between the ground of the switch circuit and the ground of the audio circuit.    No current should flow down the ground wire.  What this test can do is make the coupling between the relay and audio worse (and easier to detect) but it does this without glitches on the power and ground.

If either of these tests show glitches then the coupling is inside the relay and the only hope to remove the ticks is to slow down the signals to the relay.

Continuing on, the next step is to power the switching circuit from the same supply as the audio.  This is where is can get complicated because I don't know how you have your power set up.
- Can your pedal be powered from battery and external power?, or does it just have an external power jack?
- Does your input socket (or output socket) switch the effects power off?

The aim of this step is to make sure we don't make the glitch worse.  We want to make sure glitches on the power and/or glitches on the ground don't change or increase the glitch.   That would point to multiple causes.

Rob, i'm sorry, i may have not explained correctly the whistle, i was talking about wasn't really a whistle, more like a Starwars light saber switch off (zzeeeewwww), maybe the discharging cap with the led struggling slowly.

OK got it.  Sometime later it occurred to me it could be that.   Relays do that when the current sits around the on/off point too long.

[jackwithoneye]

thanks for this great recap, it helps a lot, and my understanding is getting better 

One thing i may have be clear about,...again...my fault..., is that my FX circuit is breadboarded, and the switching circuit is half-breadboarded (the relay itself is breadboarded, connected with wires to a pcb i made for the 5V relay, which has different footprint). It will be easy to power up the 2 circuit with different power supplies, i've done it, by i may have missed a thing, since the audio was trash when i did that, so i was not able to really test anything. I'll redo it more carefully.
I will fully breadboard the switching circuit for the rest of the experiments.

Since i'll have no time for the next 2 days, i'll get back to you asap, with new datas!
Thanks again.

NB; Ive boxed the pcb i've done with the

[R.G.]

The constant current draw is going to be an issue for any single-action relay. It's the problem that made me go down the path of latching relays. These are pulsed on and pulsed off, and can be made to draw no current between changes. They still have the problems associated with clicks in the circuit like single action relays do unless you go tricky. In my case, tricky meant filling a 100uF cap through a resistor to supply the pulse for on and off, and being really careful to not let any of the current in the path from cap to coil to transistor and back to cap circulate in the circuit power or ground traces. The resistor-cap isolation trick and double coil relay pretty much solves the issues with constant on-current.
The tricky part also needs a circuit to pulse the "on" and "off" driver transistors. There is an earlier version of this circuit on geofex, but today I'd use an 8-pin microcontroller. Pulse on/off relays also offer some relief on the relay voltage issue. A 5V relay can be used with a 9V pulse that goes off in a short time because they don't have time to heat up.