A Switching Scheme  [documentation]

Original effects with schematics, layouts and instructions, freely contributed by members or found in publications. Cannot be used for commercial purposes without the consent of the owners of the copyright.
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stole59
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Post by stole59 »

Hello guys. I have two really important questions:

- I made few double side boards using layout mmolteratx provided. It works great but my CD40106 overheats. Did anyone experience similar problem? Does anyone know what could cause this?

- I experience some problems when I use 9v batteries. Effect will turn on for few times and then stop turning on, only LED diode turns on while effect stays in bypass mode. If I disconnect battery, wait for few minutes and connect it again effect will turn on fine for few times like in the beginning and stop turning on after few minutes. What could cause this?

Thanks in advance

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mictester
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Post by mictester »

What relay are you using? Also, what value of LED current limiting resistor are you using? Measure the current drawn by the circuit - in the "bypass" state it should be almost nothing (just a few µA) and in the "on" state the current drawn should be just the LED current - a few mA.
"Why is it humming?" "Because it doesn't know the words!"

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stole59
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Post by stole59 »

I use takamisawa AL5WN-K and I usually use 10k or larger value resistor.

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mictester
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Post by mictester »

You must have a connection fault then. The 40106 doesn't get warm if correctly connected!
"Why is it humming?" "Because it doesn't know the words!"

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stole59
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Post by stole59 »

I'm not really sure what happened. This happened on more than one pedal so it couldn't be my fault. Only thing I noticed is that pins 8-13 on 40106 are grounded, on some other layouts they were not connected to anything.
This is the layout I've been using while having these problems
Image

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stole59
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Post by stole59 »

I solved the problem. Pins 8-13 on 40106 are not suppose be grounded like it was done in this layout. Somehow this causes 40106 to overheat and to drain batteries so quickly. Thanks anyway mictester, hope this helps someone in the future

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nr372
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Post by nr372 »

I've been pondering this circuit more lately, and have a question about the bistable switch:

Using the 40106 circuit as initially drawn, the output always comes up high when power is applied (LED lit, effect engaged).
Am I correct in thinking that removing the 100nF capacitor to ground from the first inverter will cause the output to always come up low instead?
This modification seems to work fine in my testing, but I'm not sure if I've interpreted the circuit's function correctly.

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Silver Blues
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Post by Silver Blues »

Interesting. I have all the unused pins connected to ground on the one I have built and I don't have any of the issues described below, however the default state is "on" as nr372 describes. (Not really an issue as much as a minor annoyance.)

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nr372
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Post by nr372 »

Unused CMOS inputs should be tied to VCC or GND to prevent oscillation. Any unused outputs should be left floating; tying them to GND can cause problems, as we've seen in this thread.

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pedalpimps
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Post by pedalpimps »

moosapotamus wrote:I made PCB/perf layouts for both versions...

Latching SPDT Footswitch
[ Image ]
[ Image ]

Momentary SPDT Footswitch
[ Image ]
[ Image ]

I tried to make them as small and compact as possible while still having a single-sided layout for easy DIY etching. The component numbering follows the schematic that mmolteratx posted here...
viewtopic.php?f=13&t=13295&start=120#p215994

Here it is, for those that do not have Eagle...
[ Image ]

Footprint for the relay in both layouts is setup to ground the circuit input (SND) when bypassed. The momentary switch version is verified by me. The latching switch version should be good too, since it was just copied/pasted.

Thanks, mictester!

~ Charlie
is this gonna work with panasonic TQ2-5v?

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gsb
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Post by gsb »

Hi!
I have build 40106 circuit and work very good. But have 3 inputs unused .I will try to use optofet TLP222G from Toshiba as Mute.I need only signal -pulse wenn buton is presed for about 30-40ms to mute output.How to use unused gates to make a short puls for optofet ? There is one version but with microcontroler -http://stompville.co.uk/?p=423,

Thanks gsb

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Post by spacecowboy »

Hello!

I like to build the "simple" version with the two Darlington Transistors (if I understand it correctly)
with the 2N3904 and 2N3906, Capacitor 100uF, R1=47, Diode=1N4148 like it is designed for 9V
I also want to use the RY5W-K relay and a latching switch.
When I want to use the circuit at 5V power supply:
R2 15K -> 8,2K and R3 150K -> 82K - will this work or have I to change more?

I'll be very apreciated for your help!

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Post by josh777 »

Resurrecting old threads.....

Sorry if this is a silly question but what advantages do the transistors give? Is it just for increased discharge current?

Why is this better than a spdt switching between +9v and ground, connected to the capacitor and relay (with maybe a current limiting resistor?) This would give no quiescent current!

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mictester
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Post by mictester »

I did that to start with, when I got my first bistable relay. I found that the untamed rush of current wasn't good around high gain circuits - loud pops and bangs are not what I wanted to achieve! I messed with current limiting resistors and suppression capacitors, and inspiration struck when I tried using a transistor to switch a resistor to discharge the capacitor..... The next step was to add the diode (originally part of the noise suppression) and that suggested the use of a PNP transistor to switch the NPN transistor.... allowing the use of a single switch pole! This was the generic solution that I was looking for - minuscule current, low switching transients and the option to indicate "On" with a really low current LED - all done with a single switch contact.

The beauty of the circuit is that it costs next to nothing, gives the "true copper bypass" so beloved of guitarists, and allows the use of battery power. I found a company that had massively overstocked on the original relay, and bought just under 18000 of them for a few pence each! I sold most of them at a large mark-up (we had a good couple of holidays that year) and kept a few strips for my own use. I only build a few pedals these days - for friends mostly - so I don't need a large stock. I've now officially retired, so I'll spend more time in the workshop and occasionally supplement my pension by selling a few electronic gems at very high prices!
"Why is it humming?" "Because it doesn't know the words!"

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Post by Boba7 »

Just came to say thanks a lot for the great project!! I just built one with the 1st vero layout and it works flawlessly. Thanks so much!!
(I hate 3pdts :D)

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Post by lakesidepark »

I use the cheapest method, a 4013 flip flop and 4066 dpdt, no noise, no pop, cost with pcb and momentary switch USD 3.

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Post by lupita22 »

lakesidepark wrote:I use the cheapest method, a 4013 flip flop and 4066 dpdt, no noise, no pop, cost with pcb and momentary switch USD 3.
Would you mind explaining how you have the 4013 hooked up? Better yet, a schematic :lol:
Thanks

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Post by julessouren »

Can anyone (calling out mictester) comment on why no coil suppression is employed here? I know a simple diode doesn't work for this type of coil, but I feel as if its omitted just to keep the parts count low... I don't have a scope to check how high the voltage spikes go for this circuit. Not sure how the cap likes those spikes.

Also, if I want to use the triple inverter latching circuit, but with IC's rated only for a 5V supply, would I to hook the output of the last inverter to the gate of a logic level mosfet, and hook up the the source to 9V and drain to the diode, something like that?

Lastly, I remember someone who wanted to use the unused inverters to drive an opto-fet to mute the circuit before the relay switches, and unmute after the switching. With a microcontroller this is peanuts to do, but can anyone comment on how to do it without a micro?

Loving this circuit by the way, has some great miniaturization potential :)

Edit: changed gate to drain

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plush
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Post by plush »

julessouren wrote: can anyone comment on how to do it without a micro?
You simply don't waste your time on it. Trust me, it's reaaaaaaally not worth the effort.
Go buy a cheap pickit clone from aliexpress, bunch of pic controllers and devote some time to learning C.

I've discovered a whole new world of pedal diy, such as programmable, fully analog (or not) modulations, delays, distortions and other bullcrap, with automatic midi sync and other bells and whistles, which you simply can't achieve w/o micros.

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Post by KillerBerthier »

I built several latching versions of this system (AL5WN-K with 40106), using either two and three inverters. They worked wonderfully, however after a few months of regular use, it became difficult to switch in one direction. More exactly, the falling edge at the first inverter input (directly connected to the footswitch) wasn’t going low enough to change its state. I found that powering everything lower (around 6V) improved the situation. Another simpler solution I adopted was connecting a moderately large resistor (330kΩ–470kΩ) between the first inverter input and the ground. I had this problem on every circuit I built, so I think this is not caused by a faulty part. Note that it always occurred after a long time, at first it worked very well.

Anyone else encountered this issue? What could cause this? Is the 40106 subject to early aging? Or is it something with the caps (I use MLCC caps, not the cheapest ones)?

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