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.
User avatar
roseblood11
Tube Twister
Information
Posts: 1886
Joined: 23 Aug 2008, 14:21
Has thanked: 366 times
Been thanked: 313 times

Post by roseblood11 »

Maybe this is the answer?
julessouren wrote: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.

User avatar
KillerBerthier
Information
Posts: 2
Joined: 07 Jun 2016, 15:13

Post by KillerBerthier »

roseblood11 wrote:Maybe this is the answer?
julessouren wrote: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.
I’m not sure… Actually I have a circuit using only the flip-flop part of this system (with a 40106) to drive other stuffs and it is subject to the same issue.

User avatar
robinbowes
Breadboard Brother
Information
Posts: 146
Joined: 06 Jan 2011, 14:07
Location: York, UK
Has thanked: 17 times
Been thanked: 6 times

Post by robinbowes »

mmolteratx wrote:Here's a drop in PCB that uses a momentary switch. Haven't yet built it, but all looks good. 1.1375" x 1.0500".

[ Image ]

.brd - http://dl.dropbox.com/u/8021347/Relay.brd
.sch - http://dl.dropbox.com/u/8021347/Relay.sch
I don't suppose anyone happens to have these files? The dropbox links are dead.

Related: did anyone manufacture any of these boards?

Thanks,

R.

User avatar
mictester
Old Solderhand
Information
Posts: 2921
Joined: 11 Sep 2008, 20:29
my favorite amplifier: Mesa Boogie, Roost Sessionmaster, AC30
Completed builds: Hundreds! Mostly originals, a few clones and lots of modifications.
Location: Somewhat closer to Amsterdam than before!
Has thanked: 32 times
Been thanked: 841 times
Contact:

Post by mictester »

julessouren wrote:Can anyone (calling out mictester) comment on why no coil suppression is employed here?
Hi. If you look at the original circuit, you'll see that the relay coil is fed with a series electrolytic capacitor. The current flow through the coil is in one direction during "set" and the other during "reset". It's obviously not possible to connect the usual reverse-biased diode across the coil, and it's completely unnecessary as the current rush through the electrolytic capacitor is much bigger than the reverse spike caused by the collapse of the magnetic field when the drive current stops flowing. Since the relay coil is (effectively) AC-coupled, there's no problem.

The origin of the circuit was my desire to use up a whole heap of old "Carling" brand SPDT switches that I'd liberated from wah pedals when upgrading them to true bypass. I came by the 5V bistable relays at a very low price, and the rest is history. I've used the original two-transistor circuit in literally hundreds of pedals over the last few years. I've had no failures (of the switching) whatsoever, and I've nearly run out of the SPDT switches now!

I had a run of switching PCBs made, and spent several evenings soldering the parts into them. I made (as I recall) about 220 of the boards. I know that I've got more of the PCBs - somewhere - but they've been buried amongst a lot of other, more deserving projects when I moved house!

Just to annoy me, my brother came up with a simpler circuit, using a DPDT switch and a non-polarised electrolytic, but - as I pointed out to him - his non-polarised electrolytic cost more than the whole of my circuit!
"Why is it humming?" "Because it doesn't know the words!"

User avatar
robinbowes
Breadboard Brother
Information
Posts: 146
Joined: 06 Jan 2011, 14:07
Location: York, UK
Has thanked: 17 times
Been thanked: 6 times

Post by robinbowes »

mictester wrote:I had a run of switching PCBs made, and spent several evenings soldering the parts into them. I made (as I recall) about 220 of the boards. I know that I've got more of the PCBs - somewhere - but they've been buried amongst a lot of other, more deserving projects when I moved house!
If you did happen to find them, I might be interested in about 5 :)

R.

User avatar
sanga94
Information
Posts: 1
Joined: 20 Aug 2016, 22:26

Post by sanga94 »

Hi! This is my first post, because I usually only read.
I'm trying to desing a schematic for a unlatch switch bypass, but not sure how to try it. My idea is to implement an analog version of coda effects https://www.coda-effects.com/2017/02/re ... -code.html.

So I thought to modify the schematic of geofex as I do in the picture attatch.
So the first three inverter are identical to the original desing. The inverter d, has a 100k resistor to ground as the input, at opposite of inverter e that has a 100k to power supply. This should provide a pulse to the set transistor when the led is on and a pulse to reset transistor when the led is tourn off.
Now, the f inverter pilot the optocompulator, I set the input with 2 100k resistor, one to PS and one to GND with a bigger capacitor.

As far as I understand of Mickey Mouse logic this should provide a pulse both when the led is switching on and switching off of about 22ms, that activate the opto, that short the output effects to ground forthat time. The transistor should take about 5ms to tourn on due to RC timing circuit formed with 50k R and 100n C. So the effect result short to ground during all the time the relay is switching.

Do you know if inverter f produce the pulse responce that I aspect? do you know a method to test this circuit without an oscilloscope? Do you know where I can simulate the schematic?
Attachments
bypass.jpg

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

Hey, Thanks Mictester, Like your work.
I have built a few of the Mictester relay switch circuits using the Panasonic TQ2-L-5V Relays.
$2AUD Each at Aliexpress - Cheap as Chips
https://www.aliexpress.com/item/3227359 ... 4c4dzgapkg
Pretty much identical to the TAKAMISAWA AL5WN-K
Check the pinout, possible only difference.
Used a 2N5087 PNP and a BC169 NPN and they work perfect.

Must say I am quite impressed at their efficiency and very low power consumption.
Only question I pose now - How do I connect and power up the same relay switching circuit to run on a Dual +/- 9V Voltage supply with a centre 0 Volt - (Ground)???

Please help. all contributions gratefully accepted. :)

User avatar
bmxguitarsbmx
Cap Cooler
Information
Posts: 510
Joined: 25 Mar 2010, 21:15
Has thanked: 700 times
Been thanked: 216 times

Post by bmxguitarsbmx »

twotees wrote: 20 Nov 2020, 05:36 Hey, Thanks Mictester, Like your work.
I have built a few of the Mictester relay switch circuits using the Panasonic TQ2-L-5V Relays.
$2AUD Each at Aliexpress - Cheap as Chips
https://www.aliexpress.com/item/3227359 ... 4c4dzgapkg
Pretty much identical to the TAKAMISAWA AL5WN-K
Check the pinout, possible only difference.
Used a 2N5087 PNP and a BC169 NPN and they work perfect.

Must say I am quite impressed at their efficiency and very low power consumption.
Only question I pose now - How do I connect and power up the same relay switching circuit to run on a Dual +/- 9V Voltage supply with a centre 0 Volt - (Ground)???

Please help. all contributions gratefully accepted. :)
Just ignore the -9V. Connect your circuit between Ground and +9v as normal. Simple as that.

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

mictester wrote: 14 Aug 2014, 23:15
JFace wrote:Is there any advantage of using a 14 pin logic chip (40106, 4093) over using a 555 timer? It seems as though having a smaller footprint would be ideal if the functionality is the same.
The 555 will take about 20 times the standby current of the CMOS Schmitt ICs. You have to bear in mind that the circuit was designed for minimum current draw - I didn't want it to kill batteries. It was also designed to avoid switching pops and (mostly) to use up a load of SPDT footswitches that I'd collected over the years when doing "True bypass" mods to Cry Baby pedals! I bought a few hundred of the Takamisawa relays and have used them in everything!
One thing I don't understand is that you say the CMOS schmitt trigger runs at very low current draw, and the 40106 datasheet confirms that it should, with a rating of DDmax Quiescent device current = 2uA max at 10 volt Vdd
and yet I am running my 40106 at 9 volt Vdd and its drawing 0.93mA at idle, Quiescent.
Why such a difference from rated power consumption to actual??
The 0.93mA seems a bit excessive when the idea for the switch circuit is low power.

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

Here s a revision on the Mictester Low Power relay switch, it uses a CD40106 CMOS as the Schmitt Trigger for momentary push button switching, Alternatively can be used with a latching type footswitch. see schematic.
While I like Mictesters design and effectiveness on this switch along with the low power consumption, it is a pretty good deal for relay switching without having to go the MCU software route. However I were a little miffed at the fact there was a noticeable thump like noise on activation, its mainly due the relay points making contact and some noise coming through from there.

This is usually muted out through software means using a MCU chip. So to try and emulate as much without going the software route, I added a new feature being the addition of the temporary mute circuit R14, R5 and Q1 with the trigger from C1 on Pin 10 + on the relay also triggering a temporary opening on Q1 between Drain and Source, shorting momentarily the output signal at J2 Relay pin 8. This is just enough temporary mute to very much simulate a software MCU approach to silent switching. I have tested it and find no interference with the audio output compared to without the added circuitry. It also was significantly quieter than without the Mute circuit, where there was experiencing a thump thwat sound when relay contacts were making. Hope this might help some out there. Cheers
Attachments
LPRELAYSw_with Mute.jpg

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

Update, Re: Previous Post
Some troubleshooting!

Revision on the Mictester Low Power relay switch, using a CD40106 CMOS as the Schmitt Trigger for momentary push button switching, can be used alternatively with a latching type footswitch. see schematic.
While I like Mictesters design and effectiveness on this switch along with the low power consumption, it is a pretty good deal for relay switching without having to go the MCU software route. However I were a little miffed at the fact there was a noticeable thwack like noise on switch activation, its mainly due the relay points making contact and some noise coming through from there.

This is usually muted out through software means using a MCU chip. So to try and emulate as much without going the software route, I added the feature of a temporary mute circuit R14, R5 and Q1 with the trigger from C1 on Pin 10 + on the relay also triggering a temporary opening on Q1 between Drain and Source, shorting momentarily the output signal at J2 Relay pin 8. This is just enough temporary mute to very much simulate a software MCU approach to silent switching. Tested it and find no interference with the audio signal output .

The temporary mute function is significantly quieter and effective with the switching on the way in when engaging FX, however on the way out back to true bypass there is still a noticeable thwack sound when relay contacts are making, this is due the transistor can only be triggered one way with the FX switching in and not effective with the switching out. If anyone can assist with how to get a triggered transistor response to mute the output signal when switching back to true bypass then please I would be happy to hear from you. It basically needs a second switching transistor with a trigger somehow from existing circuit to mute when switched out the same as what works as when switching in. This might help some out
Last edited by twotees on 01 Jun 2021, 07:36, edited 1 time in total.

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

twotees wrote: 01 Jun 2021, 07:25 Update, Re: Previous Post
Some troubleshooting!

Revision on the Mictester Low Power relay switch, using a CD40106 CMOS as the Schmitt Trigger for momentary push button switching, can be used alternatively with a latching type footswitch. see schematic.
While I like Mictesters design and effectiveness on this switch along with the low power consumption, it is a pretty good deal for relay switching without having to go the MCU software route. However I were a little miffed at the fact there was a noticeable thwack like noise on switch activation, its mainly due the relay points making contact and some noise coming through from there.

This is usually muted out through software means using a MCU chip. So to try and emulate as much without going the software route, I added the feature of a temporary mute circuit R14, R5 and Q1 with the trigger from C1 on Pin 10 + on the relay also triggering a temporary opening on Q1 between Drain and Source, shorting momentarily the output signal at J2 Relay pin 8. This is just enough temporary mute to very much simulate a software MCU approach to silent switching. Tested it and find no interference with the audio signal output .

The temporary mute function is significantly quieter and effective with the switching on the way in when engaging FX, however on the way out back to true bypass there is still a noticeable thwack sound when relay contacts are making, this is due the transistor can only be triggered one way with the FX switching in and not effective with the switching out. If anyone can assist with how to get a triggered transistor response to mute the output signal when switching back to true bypass then please I would be happy to hear from you. It basically needs a second switching transistor with a trigger somehow from existing circuit to mute when switched out the same as what works as when switching in. This might help some out
Just a follow up on previous mute de thump circuit, the way I have it working now is it eliminates well and truly the relay switch thwack when going from bypass to Effect in,, every bit as good as the PIC MCU chips will do, as far as what I have experienced, and reviews as much on those. The fact is the worst noise was associated with the switching in to effect mode, and really the switch noise on returning to bypass is very negligible even if you don't bother going any extra yards to quieten it on that side of the switch. The reason I said previous there was noticeable noise on the return to bypass , was because It was concerning a variant circuit switching 2 relays simultaneously, I have since found a way to eliminate as good as MCU on return to bypass as good as going into effect, so problem solved for me on that end.

However the single relay circuit isn't quite as noisy on the switch in to bypass , so really only needs muting on the switch to effect for my liking, unless you feel the need to go with some extra parts to mute both sides of the switch effect in and effect out.
So whoever said you can't do it without a programmed MCU, I believe I've de bunked that theory with what's worked out here, thanks to mictester and others and some perseverance to get a better result

The switch time can be lengthened or shortened simply by adjusting the value of the 100 ohm resistor, for a longer mute time you might like to go all the way to a 1k resistor and this usually gets past all the switch noise without being excessively too long, but for the most part the 100 ohm is pretty sufficient.

I also note that RG Keen, says that using a single mosfet for a mute switch has inherent problems with reverse current being opened up when mosfet is closed, leaving the mosfet internal diode hanging on your audio signal, and thus causing distortion. However I have tested the circuit above with no anomalies found by any means of any interference , distortion or otherwise on the signal path, just straight clean audio. my test circuit has been the Boss FA-1, and you would certainly notice any unwanted distortion on that effect if it were present.

So works for me, and might help some others.
Sure you can easy likely go the MCU route, but I just didn't have the inclination at present to learn the coding etc. to get it done, plus this circuit runs on straight 9v supply , where you don't need bother with step down voltages.
Cheers. Trevor

User avatar
CheapPedalCollector
Resistor Ronker
Information
Posts: 399
Joined: 19 Oct 2020, 15:15
Has thanked: 452 times
Been thanked: 147 times

Post by CheapPedalCollector »

Can you use just a J113 FET or so instead of the MOSFET?

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

Hello, Yeah I would imagine a standard jfet would work the same, I did try it with a BJT transistor and got similar results.
Cheers, Trevor

User avatar
electrosonic
Breadboard Brother
Information
Posts: 130
Joined: 28 Nov 2008, 16:53
Location: Vancouver, BC
Has thanked: 27 times
Been thanked: 19 times

Post by electrosonic »

Won't the intrinsic diode in the mosfet potentially clip the unbypassed signal?

Andrew.

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

I also note that RG Keen, says that using a single mosfet for a mute switch has inherent problems with reverse current being opened up when mosfet is closed, leaving the mosfet internal diode hanging on your audio signal, and thus causing distortion. However I have tested the circuit above with no anomalies found by any means of any noticeable distortion interference on the signal path, just straight clean audio. my test circuit has been the Boss FA-1, and you would certainly notice any unwanted distortion on that effect if it were present.

Have also since found an equally efficient similar mosfet mute function circuit for the switch back to bypass that uses a momentary footswitch through the 40106. Thus giving quite FX in and FX out switching very similar and effectively compared to that of a micro processor. All it takes is a second momentary trigger pulse for when the effect is switched back to truebypass, this can be done utulizing the CD40106 on an alternating schmitt trigger output to the one that switches the effect in.

Someday I hope to go the MCU route with a bit more time for learning the coding, but for now, these temporary mute switches do a fair comparison albeit without having the extra bells and whistles plus convenience of the MCU. But by all means beat hands down the old clunkyness of the 3PDT switches.
Last edited by twotees on 04 Sep 2021, 11:41, edited 1 time in total.

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

Alternatively, if you were real concerned over the mosfet internal diode hanging off your audio signal, then you could likely use a PhoteFET TLP222A or similar to allow a momentary pulse coming from the relay coil when effect switched in to trigger the PhotoFET LED, and allow the temporary output signal ground mute to block the switch click. See Coda-Effects for more detail

https://www.coda-effects.com/2016/08/re ... ystem.html

Alternatively you could also try a standard bjt transistor or standard jfet for same type result I expect.

This I believe would alleviate any concerns for unwanted hanging diode potential clipping. if such a thing really exists? :)

User avatar
electrosonic
Breadboard Brother
Information
Posts: 130
Joined: 28 Nov 2008, 16:53
Location: Vancouver, BC
Has thanked: 27 times
Been thanked: 19 times

Post by electrosonic »

Looking at your schematic, when the mosfet is off it will clip any signal that is larger than 1.4 volts peak to peak. This may or not be an issue depending on the pedal, however the mosfet is always in the circuit even in bypass, so the pedal could potentially clip the guitar signal when bypassed.

I have used TLP222As successfully in pedals in the past, but I prefer to use a jfet because it uses less current to activate and the turn on/off times can be slowed to avoid any pops.

User avatar
Manfred
Tube Twister
Information
Posts: 1936
Joined: 04 Apr 2009, 23:42
Has thanked: 1668 times
Been thanked: 1344 times

Post by Manfred »

I generated the flowchart with the Code Visual to Flowchart software for the CODA source code, there can see the sequential flow well.
CODA_Flowchart.pdf
(40.42 KiB) Downloaded 174 times

User avatar
twotees
Information
Posts: 39
Joined: 26 Jan 2013, 06:24
Has thanked: 2 times
Been thanked: 6 times

Post by twotees »

electrosonic wrote: 04 Sep 2021, 22:29 Looking at your schematic, when the mosfet is off it will clip any signal that is larger than 1.4 volts peak to peak. This may or not be an issue depending on the pedal, however the mosfet is always in the circuit even in bypass, so the pedal could potentially clip the guitar signal when bypassed.

I have used TLP222As successfully in pedals in the past, but I prefer to use a jfet because it uses less current to activate and the turn on/off times can be slowed to avoid any pops.
Yeah I can see the concern for potential clipping from the mosfet internal diode, But after a lot of testing at various levels using the Boss FA-1 which is a relative clean type preamp at lower levels, there proved to my ears no noticeable apparent clipping produced. If a clean Preamp at low volumes stays clean then I find it workable. And yeah the mosfet diode is still there in bypass, but still no noticeable clipping to my ears.
I tried a bjt transistor as a substitute for the Mosfet, and while the temp mute worked just fine same as for the mosfet, it actually rendered the relay inactive, not sure why, so bjt doesn't work, lest there be some further circuit mods required, also tested a jfet and that shut down the relay as well, those type trannies may still work with some circuit tweaking, I don't know?.

As for the TLP222A well they still have diodes in them, hanging on the output signal, but I think I read somewhere something from RG Keen, that said the 2 internal diodes within the PhotoFET cancel out any potential clipping. might therefore be a better more foolproof system than standard Mosfet muting, will have to delve deeper.
As for using a jfet for the temp mute function, would be glad for you to share the circuit for that if you didn't mind.
Cheers.

Post Reply