Help with remote relay switching

[neurino]

I have some Omron G6H-2-DC5 non-latching relays laying around so I'm planning building a stereo bypass looper.

These relays do not allow silent switching (despite what advertised) and I tried some circuits to minimize ticking.

I'm planning of using this to drive relays:



I found adding C1 ticking is reduced to a level I can live with.

If anyone has any advice to cut off ticking even more I'd be grateful.

Besides that my problem is that, working this way, a SPDT is needed for switching while I'd like to add a classic MONO remote footswitch IN, that bypasses onboard footswitch, to remote control the looper with a classic SPST operated footswitch/controller.

Cheers

[R.G.]

Read geofex.

[neurino]

Hi R.G.

I read about everything on Geofex... also I guess the schematic above comes from something I read there.

If you can be more specific at least on which topic I should read better (suppress ticking or replacind the SPDT with a SPST) I'd be grateful

Edit:

I also add I tried adding a 100uF cap across the coil or a NP cap between transistor drain and gate with no audible reduction in ticking.

[Gurner]

Have you established if your ticking comes solely from the circuit driving the coil, or perhaps some noise permeating within the relay itself? eg you could rig a battery & a series resistor and try energising the coil that way ....if you get a tick, then it's the relay or perhaps dc sitting on the the poles that causing a pop when the relay contact gets made. Unless you know where the tick is coming from, it's gonna be difficult to cure it.

[neurino]

Hi Gurner,

I think the noise comes from the relay itself upon swithcing.

With the schematic above if, after connecting 1 to 3 (+5V) with a jumper you simply disconnect it, without putting to ground, the relay keeps engaged (and the led slightly turns off) for some seconds while C1 discharges.

Then a click is heard upon switching.

Also I add I already used those relays without driver but simply with a switch connecting coil to power and experienced ticking. Then adding a 100uF cap across reduced the pop to an acceptable tick.

[Gurner]

Can you physically get access to the relay contacts to switch them manually (this will tell you whether your click is related to residual dc on the contacts vs something permeating into the signal from the coil being energised)

[neurino]

Unfortunately no, the relay is sealed:

[Gurner]

ok, so what happens if you just short the relay contact pins with a link of wire (ie to simulate them being closed)....do you get a click then?

[neurino]

I have not the breadboard here now but today moving jumpers around, for example grounding RETURN to act as a mute, I didn't get the tick, maybe some other noise coming from handling wires but I'm quite sure not that tick.

I precise testing the circuit I simply connect guitar to IN, amp to OUT and connect SEND to RETURN with a jumper.

[R.G.]

Relays pop from a couple of different causes. One is that the fast, sharp edge of the coil drive voltage is coupled through stray capacitance to the signal lines. This gets worse as the impedances connected to the signal lines go up. With guitar signals, you're stuck at about 1M for the impedances for a bare guitar and amp input. So you can
reduce the voltage (lower voltage relay coil) or slow down the edges. A particular relay fixes the stray capacitances. Other relays might be better.

Or worse. 

Another cause is sudden change of currents in ground or power supply. If the relay coil makes a transient in either power or ground, this is amplified by whatever is on the ground/power lines.

Try running your relays from a different power supply that's not running your pedals and NOT connecting the relay coil ground to the signal ground, or only connecting them together with a 1K to 100K resistor depending on whether you get hum or not.

[neurino]

so you can reduce the voltage (lower voltage relay coil)
...
Try running your relays from a different power supply that's not running your pedals and NOT connecting the relay coil ground to the signal ground, or only connecting them together with a 1K to 100K resistor depending on whether you get hum or not.

I tried powering with 2.6V instead of 5V or separating power ground from signal ground.
Nothing changed, except getting hum in latter.

Does anybody got these Omron relays to switch silently?

[R.G.]

- does it pop when the relay contacts and releases, or only when it releases?
- what gate-drain capacitance did you try?
- if you substitute in a mechanical switch for the relay, does it still pop? Could be that there is a problem with what is being switched
- try putting a 220K to ground on both signal sides of the relay; this is not a permanent fix, but may help with the diagnosis

[neurino]

- does it pop when the relay contacts and releases, or only when it releases?

it ticks in both contact and release

- what gate-drain capacitance did you try?

0.1uF and 0.47uF.

The first is the value I thought to remember I saw on some schematic, probably on geofex, the latter is the biggest NP cap I have.

- if you substitute in a mechanical switch for the relay, does it still pop? Could be that there is a problem with what is being switched

I wonder why I didn't tried this already

I substituted the relay with a DPDT toggle and it pops anyway.

Not the same sound, toggle tick has more basses and maybe is a little louder. Relay tick is shorter, higher in pitch.

Maybe I could have tried with a DPDT pushbutton too but had no time

- try putting a 220K to ground on both signal sides of the relay; this is not a permanent fix, but may help with the diagnosis

I had not 220k in stock so I went with 330k.

It seems to me there has been a little reduction in tick volume but not a sensible change.

For testing I simply connect SEND with RETURN relay pins with a jumper



I had no substantial changes in tick volume changing connected amp or guitar or leaving IN unconnected.



Thanks for your time, also I'll be grateful to whom will give me some advice on adding/converting a/to SPST switching.

[R.G.]

I substituted the relay with a DPDT toggle and it pops anyway.

Not the same sound, toggle tick has more basses and maybe is a little louder. Relay tick is shorter, higher in pitch

This indicates that it's not the relay, or at least not entirely the relay. A relay is a magnet-actuated switch. The voltages and leakages from the magnet can cause pops, but if the switch contacts themselves cause clicks, at least some of the problem is outside the switch.

Until it's quiet with a mechanical switch, it can't be quiet with a relay.

[neurino]

Until it's quiet with a mechanical switch, it can't be quiet with a relay.

It makes perfect sense...

[neurino]

Ok, given the switching tick is not coming from the relay nor from the driver this is what I finally came out, after some tweaking:



Adding R4 and R5, adjust to taste, commutation gets slower and tick pitch is lower in a way I find less annoying.

Also I lowered C1 from 10uF to 4.7uF to keep switching latency in a range of a 1/10 of second or two.

Now I ask you advice about my second question: how do I turn switching from SPDT to SPST?

[DavenPaget]

Using the two outer lugs , for most switches .
and i can't see your schematic .

[R.G.]

Now I ask you advice about my second question: how do I turn switching from SPDT to SPST?

Make R1 22K. Make R5 infinity (i.e., remove it entirely).

[neurino]

Thanks R.G.,

this is the updated schematic, I tweaked R1 and R4 to find my sweet spot of low ticking and delay.



Thanks again for helping.