4017 sequential switching with a momentary switch

[PRR]

image

Are IC1A IC1C needed? Looks to me like the R-D-C network could go right to IC1B IC1D. If you need the other polarity, flip the network (SW to V+ etc).

[armdnrdy]

Hey Paul,

It looks like you are correct.

I try to keep voltage off of switches whenever possible. (For some reason)

This would be a good case for dual logic ICs to be manufactured in DIL-8 packages!  but there would be no money in that!

Either way...I'm stuck with a 14 pin IC.

I'll see which way makes for a more "route friendly" design.

[amptramp]

As R.G. stated...this is kind of what it is. It's not the best solution...but it is a solution. 

You have eight choices here, and depending on which channel you are at, moving up or down to a target channel only takes a few quick foot taps.

I found a few 4093s in my stash, so I'll put something more definitive up over the weekend. Maybe a video of the bread board fun.

The 4093 is a quad NAND.  The 40193 is the up / down counter.

[armdnrdy]

Hey Ron,

You might want to take a look at the last schematic revision that is posted on page 1 of this thread.

https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Multiplex%20Switcher%20IV.jpg

The circuit takes both a  4093 and a 40193.
My original drawing used a 40193 and a 40106 which is not to be confused with a 4006 or a 4010.  

[PRR]

> I'm stuck with a 14 pin IC.

I knew that. But it is fun to minimize. Mostly because as a design grows, eventually you "need one more gate" and having spare gates already on the board avoids cramming another chip in.

> I try to keep voltage off of switches whenever possible.

Power switches have voltage.

I know what you are saying. It does seem wrong for small work. But as long as there is no outside influence, and we not talking high voltage, the switch does not know the difference.

You might perhaps wish to take a trigger from some external source. Which would probably be referenced to your ground. And if you rigged it Switch/Ext, it might make sense to ground-ref the switch. But alternatively, invert the switch and then use your extra gates to not only invert the Ext signal, but buffer and clean it.

[R.G.]

At the risk of sidelining this further, if you are replacing a rotary switch to get to one of N positions, there is a simple (not a uC) solution to doing a radio-button selector. It's here: http://geofex.com/Article_Folders/fxswitchr/fxswitchr.htm

Scroll down to picture 7. If you can find a 74C373 chip, that circuit directly implements "go to this position Right Now". It needs one footswitch per position, but there's no counting up/down, just right there, right now. The C373 is getting hard to find but some other CMOS octal transparent latches can be wobbled to do the same.

[PRR]

> It needs one footswitch per position

[R.G.]

ACK!! J. S. Bach's pedalboard! 

[armdnrdy]

Mostly because as a design grows, eventually you "need one more gate" and having spare gates already on the board avoids cramming another chip in.

Noted...and a good practice.

[/i]Power switches have voltage.

I am an electrical contractor (25 years) so I have witnessed this once before. 

[armdnrdy]

At the risk of sidelining this further, if you are replacing a rotary switch to get to one of N positions, there is a simple (not a uC) solution to doing a radio-button selector. It's here: http://geofex.com/Article_Folders/fxswitchr/fxswitchr.htm

Scroll down to picture 7. If you can find a 74C373 chip, that circuit directly implements "go to this position Right Now". It needs one footswitch per position, but there's no counting up/down, just right there, right now. The C373 is getting hard to find but some other CMOS octal transparent latches can be wobbled to do the same.

Thanks R.G.
Saved to my switching folder for future use.

What I'm trying to accomplish with this switching circuit (notice I said trying) is the front end of a effect CV selector.

Many pedal designs have either a CV input or the potential to add one.
I don't see many people actually utilizing this feature.

If you have a pedal board with five effects that have a CV input, you would need five CV pedals if you wanted to be able to control whatever parameter the CV controls.

This is the tree I'm barking up.



I reposted the switcher schematic on page 1. https://dl.dropboxusercontent.com/u/53299166/DIYstompboxes/Multiplex%20Switcher%20IV.jpg
I changed C2 and C4 in the astable multivibrator sections from .47µf to .22µf for a better auto select response.

Edit:
I almost forgot to mention...I bread boarded the circuit and it works flawlessly!
I'm working on a few other things but I'll try to post a video today.

[R.G.]

Ah. I see. Good idea. And congrats on the breadboarding.

I run into a lot of gotchas in my day job where random pedals are concerned, and it makes me wary of what pedals say they do versus what they really do. That's the source of this idle speculation and question.

One thing to worry about on this is that you have to guess at what the pedals without their CV selected do when there's a plug in the socket, but no CV coming in - that is, what are the NOT selected pedals doing when they may think they're going to get a CV, but don't? Do they ignore the CV input and go back to the "no-CV-plugged-in" mode, or do they all go to the "CV is now zero" position? Or worse yet, some do and some don't, or some may go nutso on you. It depends on the actual pedal plugged into the CV selector. They'll probably do random things. Some may even be well behaved. 

Call me suspicious - or paranoid.   

[armdnrdy]

Thanks for the help and encouragement!

I've anticipated some issues with circuits I'm familiar with, (remember the trying part?  ) and have been thinking of ways to solve them.

Issues such as a TRS jack being used to disengage the internal CV voltage and introduce the external voltage.

With the CV selector plugged into the jack, you wouldn't be able to use the effect in "auto" mode.

This idea is in it's infancy....hopefully I can get a handle on it.

[armdnrdy]

Okay,

Here's the video of this switching circuit in action. Thanks again R.G. for clearing the path!

Disregard the busy bread board. There are two other circuits on it. The switching circuit is spread out from the active LEDs back.

Is this what you were looking for Rob? (Sorry I stole your thread  )

[PRR]

> this switching circuit in action.

Cool!!

>> Power switches have voltage.
> I am an electrical contractor (25 years) so I have witnessed this once before.

Ah. In that world, switches are "always" on the "live" side.

Interesting why we favor different approaches at different power levels.

A key question is: what happens when someone drives a nail through our switch lead into a water-pipe? Or loose wires inside the box? (Or breadboard!)

The Live-Resistor-Switch-Ground approach tends to burn-up the resistor. However the gate input is very-very low current, the resistor can be low current, the "burn-up" can be tolerated forever with a 2-cent part. Power-wise this is very inefficient. In practice we do not care.

Now switch a large lamp or heater. If we leak power through a resistor, and switch-short the load to kill it, we have large voltage-drop when load is on and massive power waste when load is off. So we break all power with a series-switch, very efficient.

If the switch is in the groundy (White) wire, when that nail hits it the lamp goes on. For a lamp this may be only annoying. A heater or power saw could be dangerous.

If we switch the "live" (black) wire, and nail the switch-leg to ground, infinite current flows. You may have pulled-out a blob that used to be a switch. However this happens often enough that we have fuses (breakers) which "should" (most often do) trip-out before the fire starts. (Also quickly flipping the switch Off breaks the excess current.) So a switch in the "live" lead does require over-current against ground-faults, but we need over-current for so many other reasons that this is reasonable. And more-safe than a switch in the groundy lead which might leave loads energized uncontrollably.

So yeah. Pull-up switches exposed to ground-faults perhaps should have current limiting. At logic-input powers, this could be a few hundred ohms resistance. Compromise between reliable pull-up and how much spare power and resistor-bulk you care to pay for. 1K should still pull-up, the 5mA fault typically won't blow your power or resistor budget.

Side-point.... since I am reading a 1970s book on logic.... TTL inputs need significant pull-down but teensy pull-up. So you might tend to use the metal switch to pull down, the resistor to pull-up. However nobody uses genuine TTL any more. L and LS TTL have the same thing but much lower currents, resistor pull-down is practical if not best. CMOS is all about stray capacitance and how fast you need to pull-up/down, and for finger-input you often want slower not faster (to mask contact bounce).

Far side point: I just got Big Red Paddle switches for power-saw and gas burner. Both are 2-pole, so I'll break *both* white and black. (Legal to break white IF black is surely broken simultaneously.) The power-saw switch is also a magnetic contactor: if power fails and comes back, the saw stays off. (The old burner never had a drop-out; the new one has a CPU which does a POST before re-starting and I'd rather not have to re-start the burner on power-fails.)

[armdnrdy]

Good read Paul.

If I remember correctly, I recall a semi recent post by you talking about working on site somewhere.

Are you in the trade?

[PRR]

> Are you in the trade?

No. I worked around the fringe for decades in audio, computers, and networking. "Wire guy", but not licensed or unioned. (I paid dues for a while but because it was a non-technical organization I was in a Clerical union.)

More to this point:

My first house was built in 1830, wired in the 1920s, then again 1940s 1960s and 1970s. Mostly by home-owners or their nephews who were very nice but very non-technical. I found some frightening things. Heavy cable spliced in the secret attic with no splice-box. Two "circuits" cross-wired on *two* breakers so no single breaker would kill the power. When I found the north wing was "wired" with 1950s lamp-cord dropped inside sawdust-filled stud cavities, I went berserk with WireMold and a distribution panel.

This house was homeowner built, with local trees, and local labor, perhaps paid in beer. And added-on a few times with more beer. Nowhere near as bad as the last house, but getting there. I spent a couple dozen hours in the fusebox and many dozen hours in the cellar trying to figure out which wire went where. Some wires I never did find until we tore-out the kitchen ceiling and found hidden splices (at least they were in good boxes). There was one loose cable (I saved it) someone had written "I don't know where this wire goes". BTW, there's a ground-rod driven 2 feet and sawed-off, then never connected. We are fixing-up and making-nice, so along the way I've re-strung or new-strung about half the wire in the house. This summer project is the burner, I know where much of its circuit is, and I can't get to it; so it's getting abandoned and new circuits (burner and humidifier/misc) run in plain sight.

I have copies of NEC from 1908 to a few years ago (when they get cheap on Amazon; I think I'm near 2009). My town runs a couple years behind, I run a couple years behind the town, but often I am facing issues that were dubious in 1972 or 1982, so it's catch-up.

My table-saw's off button is real darn hard to find, so I wanted a Big Red Paddle. Power lock-out is a bonus.

Burners should have switch at the burner and "outside" the burner room. Traditionally at the top of the cellar stair (not outside but near-enuff). Several times someone coming up the stairs has turned off the burner instead of the light. I got a bigger red plate and a switch-guard to make this harder, but a Big Red Paddle makes a lot of sense to me. Doesn't look like, or work like, a light switch, yet is reasonably obvious in a panic.

[deadastronaut]

@larry, that's it...brilliant, i,m away from home at the mo, so can,t tinker with anything, but that looks great, nice work man, .

[deadastronaut]

hi larry, i'm back home now, do you have a schemo for the switching in your vid?...

oops, is it the one in reply 29?

[armdnrdy]

Hey Rob,

That would be the one.

Sounds like you had a good road trip.

I need a vacation from my vacation!

[deadastronaut]

cheers man,

yeah had a goodun..

i'll order those chips up...