Soft Switching

[DFX]

I'm looking at adding soft switching with a relay bypass, i don't want to go down the micro controller route, I wanted to ask, has anyone used the NE555? i can see the advantages to this being low cost but are there any down sides i should be aware of?

[electrosonic]

I have used uCs in the past (Attiny13A), they work well and it is only a few lines of code. I don't want a uC in every pedal, so I have laid out a relay switching board using a NE555 and a P-channel JFet for muting. I'm waiting for them to arrive from OSH Park to verify...

I have read that the 555 timers can create current surges when switching which can be pretty noisy, I was pretty careful with the ground currents in my layout. Hopefully it won't be an issue.

Andrew.

[287m]

i hate 555 because much current. I know isn't problem since always use PSU. But some friend here is battery die hard. So move on to cheap solution, like this. Easy to etch or perf. And NEC relay is cheap and available everywhere, compare to panasonic.

and thanks for remind me that layout, must try that. Hunt for fujitsu!

[mjg]

What about using a CD4013 flip-flop? 

See the data sheet: http://www.ti.com/lit/ds/symlink/cd4013b.pdf    -  Section 8.2 I think shows the basic idea.  Connect D to !Q, and then each time you apply high voltage to the Clock pin, it changes the Q pin between high to low (or back again).  Use the Q pin to turn on your relay.  It would need to be a non-latching relay. 

Of course, this might be a terrible idea.    I've not used it in exactly this way before, but I've used a 4013 for similar stuff. 

[electrosonic]

I've considered using a CD4013 for a flip flop, but it would need an additional transistor to drive the relay and it is a larger IC -14pins vs the 555 timers 8 pins.  I don't use batteries for my pedal board so the quiescent current of the 555 is not an issue.

Andrew.

[aion]

I've attempted several versions of non-microcontroller relay switching and they all have issues that made them unsuitable for use in my opinion.

The main issue is that the relay needs as short of a pulse as possible (usually 6-10ms) - enough to trigger the relay and no more. If the pulse is too long then the relay coils introduce switch pop on the contacts.

Only a microcontroller can give you an extremely short and predictable amount of pulse, so that's why all commercial implementations of relay bypass use one. It's of course much simpler to use a CMOS setup if you can (no programming needed, and it's cheaper, especially in manufacturing) but it just doesn't cut it.

Here are some of my adventures from a couple years ago:
https://www.diystompboxes.com/smfforum/index.php?topic=118109

[WormBoy]

The main issue is that the relay needs as short of a pulse as possible (usually 6-10ms) - enough to trigger the relay and no more. If the pulse is too long then the relay coils introduce switch pop on the contacts.

However, at GeoFex, RG advices to slow down the voltage across the relay coil as it is the fast changes that lead to pops ... Wouldn't the short pulses of the micro-controller actually cause popping? Source: http://www.geofex.com/article_folders/rmtswtch/rmtsw.htm.

I must admit that I have experimented only very little with relay switching. However, I built a switching system myself, based on the work at GeoFex, and it works beautifully and without popping. On the other hand, I have tried a few store-bought bypass PCBs with micro-controllers and they either popped or had an annoying mute (and in one case both  ).

[aion]

You got anything exciting coming out this year dude?

Lots! New baby in a couple days (you didn't say effect-related ), new kits in a few weeks, new website in a few months, and at least 10 brand new circuits - original traces - before the end of the year along with a bunch more less-original releases.

My activity schedule goes in waves... there was a ton of stuff from January through March, then it's been quieter the past few months while preparing for a noisier back half of the year. But 2019 is just getting started!

[sarde]

I've used the nope relay from TH Customs for a micro controller less relay. http://diy.thcustom.com/shop/nope-relay-true-bypass-kit/
It looks like it uses an CD40107 for its operation.

There is also a good article on TH Customs about micro controller less relay based switching worth reading. http://diy.thcustom.com/switching-relay-true-bypass-circuits-not-using-a-microcontroller/

Cheers,
Sarde

[gordo]

Bugg steps it up a notch with a few cool twists.  I like the Coda and use it a LOT (especially with the cheap relay) but there's a few cool tricks to this one.

Sarde, that's a cool avatar.  Looks a bit like ES-125 with the butterbean tuners and no binding.  Sweet.