Relay switching?

[Tdale]

I can't decide on what kind of switching to use. some say that relays can make popping sounds, especially if there is a spring reverb in the circuit.

Some say that optocouplers is the way to go, and others say analog switches should be used.

To me, relays sounds like the easiest way.. Weber even sells them mounted on a board, with diodes and all installed, just connect the 6.3V..

Any thoughts?

Tommy
Norway

[ElectronAvalanche]

Hi Tommy,

I have used 5V Relays in my 6 builds. LDRs do not make sense in a Dumble, since you do only shunt the OD input to ground. You do not want a resistance (of the LDR) in the path I think.

Switching via relay is silent, if you put a 1N4007 diode in reverse direction across the relays coil.

A couple of things to think about:

Always use a seperate small 12V or 9V transformer when using relays. Do not take the voltage from the heater winding of the preamp tubes. This will result in a hum.

I used some heavy filtering after rectification of the Relay supply in my first builds.

Then I had somebody make me some very small PCBs that have a FWB, a cap (470uF) a voltage regulator on them L7805 (5V regulator) and another cap on the output of the L7805. I thus have regulated 5V for the relays. You need a slightly higher AC voltage to feed a regulator, thus I use either 8V or 9V transformers.

Dumble has done it much easier, I think he used a small 12V transformer, a FWB, some filtering and 12V relays.

Cheers,

Electron

[Tdale]

Thanks!

What if fwb by the way?

Tommy

[pedro]

FWB = full wave bridge (rectifier)

Rgds
Pete

[Funkalicousgroove]

You can run your relays off your filament, you just have to "Float" the ground: don't ground the - side of your FWB but instead connect it to a 2W 10R connect all your Switching system grounds to the other end of the resistor and be sure to isolate your FS Jack from the chassis . It is much cleaner to just use a separate trannie IMHO.

[Bob-I]

I've used the Weber board and it works fine. No popping and no additional noise.

My latest build has relays off the heaters, using a FWB and 2 220uF caps with a 100 ohm resistor for filtering. I don't have any additional hum but I am getting a click even with the diode. The neutral is floating. I also put LEDs on the front panel that light when the relay coil is not activated. Simple, just an LED and a 220 ohm resistor across the switch.

Here's the schematic, but remember that the grounds are not to chassis, they're just connected together.

http://maximoaudio.com/forum/files/rela ... c2_916.jpg

[Tdale]

I think I might go for that.

I've seen the schematics for how to wire this...but I'm still not sure about it..

The coil gets 6.3V (or whatever voltage it needs) to open/close the relay, I get that.

Does the relay open/close when the foot switch connects the coil to ground, or lifts if from ground?

Tommy

[Bob-I]

I think I might go for that.

I've seen the schematics for how to wire this...but I'm still not sure about it..

The coil gets 6.3V (or whatever voltage it needs) to open/close the relay, I get that.

Does the relay open/close when the foot switch connects the coil to ground, or lifts if from ground?

Tommy

The relays I used activate when the switch is closed. I have the OD side on the normally open side, and the clean side on the normally closed. This way the relay coil is not active when the OD channel is on. Since the OD channel is noiser and picks up more noise I've decided to keep the relay coil not activated.

Make sure you get a non-latching relay. Latching relays need a momentary switch to flip one way, and another momentary contact switch to flip back.

[Tdale]

OK.

I have a hard time understanding what normally open/closed means....

Tommy

[Bob-I]

OK.

I have a hard time understanding what normally open/closed means....

Tommy

When there's no voltage on the coil, the contacts that are open are "normally open", the one's that are closed are "normally closed"

[Tdale]

And open, in this case, means that the signal is let through, right?

Tommy

[Bob-I]

And open, in this case, means that the signal is let through, right?

Tommy

No, just the opposite, CLOSED lets the siganl through, OPEN does not.

Take a look at this data sheet. http://www.nteinc.com/relay_web/pdf/R72.pdf

Directly under the picture of the relay is the diagram of the non-latching relay I used. Pins 1 and 12 are where you apply the 6V to activate the relay. I applied 6VDC to pin 12. The footswitch connects pin 1 to the neutral.

Pin 3 connects to the input of the power amp
Pin 5 connects to the ouput of the OD channel
Pin 6 connects to the output of the normal channel

I hope that helps.

I've also grounded the channel that's not active, see the schematics on the files page.

[Tdale]

Ok.. since you said you had the OD on the open side, and that was less nosiy because the coil is off, I thought that was what it meant..

Tommy

[Tdale]

I understand I think..

But aren't 7 and 8 used?

The way the schematics show the OD/clean switch, it should be:

3-input power
5-output OD
10-output Clean
6and7 connected
8-Input OD

Or am I awy off?

[Funkalicousgroove]

Just get your relay, 2 alligator jumpers, a 6V lamp battery, and your DMM and see how it works for yourself, that'll be the best learning experience.

It's just a DPDT switch with a magnetic coil that opens or closes the switch when you apply voltage.