Does anyone have a true bypass schematic for a momentary relay setup?

[acehobojoe]

I want to put one on a board, is this possible?

[Ice-9]

Do you want a micro based around a pic/atmel processor or one using cmos gates to control the relay. all are easy to implement.

[acehobojoe]

The cmos sounds a little simpler. I was thinking just a simple switch that can control the on off for LED and the true bypass.

Controlled with a momentary switch

[R.G.]

The cmos sounds a little simpler. I was thinking just a simple switch that can control the on off for LED and the true bypass.

Controlled with a momentary switch

I realize it's easier and quicker just to give a man a fish than to teach him to fish, but I spent a lot of time writing down how to fish at geofex.com.

There are answers to your question there - and a lot of questions you're about to ask that you haven't thought of yet.

[Transmogrifox]

Here's one I cooked up if you happen to have a few pnp and npn transistors around, and if pin count is any issue:
http://www.diystompboxes.com/smfforum/index.php?topic=110084.msg1008264#msg1008264


The 2N7000 could be replaced with a standard BJT.  It came about in the process of the design looking for the best place to put the debounce capacitor.  Now it doesn't really matter any more whether that input is high impedance.

RG's CMOS version is a tried-and-true workhorse:

[knutolai]

RG's CMOS version is a tried-and-true workhorse:

Shouldn't it have the positive ends of the relay coils connected to +V? Looks weird.

[R.G.]

Shouldn't it have the positive ends of the relay coils connected to +V? Looks weird.

Looks are deceiving. They really are connected to +V. 

[acehobojoe]

Well, R.G. , I'm not opposed to reading your research! I try to do that in my spare time, I especially want to learn more about transistors as switches so I can grow in my EE knowledge.

If there are some on Geofex about the switching stuff, I'll take a gander at them!

I'm sure it will explain this latching relay driver.

I'll eventually get it to work.

[acehobojoe]

http://www.geofex.com/article_folders/cd4053/cd4053.htm

Got it!

[acehobojoe]

I would think you would be fine with a 1 uF film capacitor, but maybe you need that higher capacitance for decoupling at the switch?

[Ice-9]

The cmos sounds a little simpler. I was thinking just a simple switch that can control the on off for LED and the true bypass.

Controlled with a momentary switch

I realize it's easier and quicker just to give a man a fish than to teach him to fish, but I spent a lot of time writing down how to fish at geofex.com.

There are answers to your question there - and a lot of questions you're about to ask that you haven't thought of yet.

This is an answer I like, I have often drifted my line around the geofex info.
and guess what, it's a place where fish can be caught. talk to the man and he seems to always help.

[acehobojoe]

I grabbed a few lures, and I'm going to try out my line when the new lures come in the mail! looks like the final schematic will be interesting to try. It's a great article on technology that I didn't even know existed.

I guess there is a lot more to come.

[acehobojoe]

so what's up with coils? How do you get those and put them into design? Is it just any old coil?

[Transmogrifox]

so what's up with coils? How do you get those and put them into design? Is it just any old coil?

I'm not sure I understand the question, but I suppose you're talking about relay coils...

Usually the relay has a coil voltage rating, then if you look at the datasheet you will see also a maximum rating.  You generally want to get the highest voltage coil you can use in your circuit because the current will be less for the same switching action.  Low switching current is what you want to reduce disruptions on your power rails so you don't cause popping in your circuit.

For example, if you have a 5V rated coil, you want to be sure the absolute maximum rating is ok with 9V to drive it, or plan on putting a resistor in series with it.

[acehobojoe]

Ok, and do the mH values matter for it? I'm looking at a few on the supplier's site I use.

[knutolai]

so what's up with coils? How do you get those and put them into design? Is it just any old coil?

The coils you see in these schematics are part of the Relay chip package. For R.G. design using the 4049 check out the datasheet and pinout of a 2-coil latching relay like the Panasonic TQ2-L2-5V

[acehobojoe]

Awesome! I didn't make that connection 

[PRR]

A relay is an electromagnet which pulls a switch.

A basic electromagnet is many turns of wire around a nail.

So the schematic symbol IS the curly-line for a "coil". However in a relay we don't usually first-fret about its milliHenries and such. We consider it a "resistor" which happens to be a long wound-up wire.

Yes, it is a tricky resistor. There is a slight lag when we slap power to it (those unspecified milliHenries). There is a kick-back when we try to stop power to it (so we often want reverse-diodes or R-C networks to absorb these before they damage other things). There are relay coils wound for AC power and ones wound for DC power, not the same (but clearly specified in the data).

I don't know what you mean "momentary" relay. The classic relay, no-power gives position A of the switch, power to coil gives position B. Simple, reliable. But it burns power all the time you want position B. This is *usually* your best plan. But for pure battery use, the relay power eats the battery. So there are also "latching" relays. These work like the classic 1950s stomp switch, or a clicky ballpoint pen. Push hard, it goes A, but then you can relax. Push hard again, it goes B, but then you can relax. It only needs short bursts of power. More economical of battery. But the system to make these quick bursts isn't as simple. Actually two buttons (A and B) would do it, but sometimes two buttons is too many.

[acehobojoe]

I don't know what you mean "momentary" relay.

I actually just meant a relay that can be used with a momentary soft touch to supply that pulse it needs.

I'm not super concerned about battery, as most of my pedals I just run on 9v supply.

It looks like I'll be trying out the 4053 CMOS driven by the CD4049. I'm not sure if this is the most efficient way, but it looks simple enough.

For some reason my eagle software won't let me draw in the supply pins though, I may have to manually route pin 1 and 5 of the 4049 to supply as with the 4053.

I've also seen the "click less true bypass" by jack deville. I'm guessing his is similar to one of the transistor setups above with a TQ2-L2-5V Relay.

Kind of cool how it all works. Electromagnetism and all.

[Transmogrifox]

Kind of cool how it all works. Electromagnetism and all.

I often forget how amazing this stuff is.  I can order one of these things for $1, put it in a circuit and (hopefully) it does one of those jobs like the building maintenance guys do:  absolutely crucial but nobody notices unless it isn't doing what it's expected to do.

The scientists who brought us to a place that electromagnetism and electricity are actually useful...that's a lot to stand back and marvel about.