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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mictester
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Post by mictester »

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!
"Why is it humming?" "Because it doesn't know the words!"

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Post by disorder »

Hey mictester, first off thanks for sharing this. I recently spent a few casual months brushing up on my C coding skills and tried the latching relay driven by AVR micro controller but it was noisier than all hell. I'd like to give this a try...

You mentioned a few times using the fourth schmitt stage to do power-reset presumably to get it to start up in bypass on power loss. Could you give me a hint as to how this is done?

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Post by mictester »

Using a CMOS Schmitt inverter: Connect a 1µ from input to ground. Connect a 470k from input to + supply. Connect a 1N4148 diode from the input up to supply, with the anode at the input end. Apply power, and you'll see a ½s positive-going pulse at the output of the Inverter. This is your power-on reset pulse. Apply this to the "reset" inputs of any bistables you're using, and you'll guarantee their state at power-on.
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Post by mictester »

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 draw so much current that all the advantage of using this very low drain will disappear. The 40106 (or 4093) are CMOS chips, and only draw µA. The builds I've done recently have had a constant current (when "On") of just 62µA - I've increased to 150k resistor somewhat. It's still a winner - low cost, completely reliable, silent in use and takes minute current. It's actually cheaper than a crappy blue switch!
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Post by andregarcia57 »

make a switch so it would be feasible?
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tube - screamer - jfet - bypass - switch ts808.png

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Post by andregarcia57 »

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


hello how are you?
is tested the project?
grateful

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Post by galmar »

Hello people,

I built the very first circuit (post 1) using a Zettler AZ850P1-5 bistable relay, and it works fine!

But it fails to fulfill the number (4) of its advantages. That is, if I suddenly remove the power jack, the relay fails to go true bypass. I assume that the pedal power filter caps are responsible for this, since they discharge slowly and the sudden power loss is not delivered to the relay circuit - on the contrary, power is gradually lost and I assume that this is the problem.

Has anyone any quick ideas about fixing it? I am looking for a neat solution, but I wonder if anyone has already dealt with it.

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Post by mictester »

Try increasing the value of the capacitor in series with the relay coil. Just to try it, solder another similar electrolytic capacitor in parallel. I found that using more relays meant that I had to increase the capacitor - I've used pairs of relays for QPDT switching!
"Why is it humming?" "Because it doesn't know the words!"

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Post by jwpartain1 »

Here's something similar to the original posted schematic. Haven't built it, heads up.
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moment_tb_ff.PNG

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Post by mictester »

jwpartain1 wrote:Here's something similar to the original posted schematic. Haven't built it, heads up.
That seems a complicated (and not efficient) circuit. The way I did it - with two cheap transistors - works really well and adds no significant current drain to a battery-powered effect. If you want to use a momentary switch and a CMOS bistable, the easiest, cheapest, simplest and best way is to use three gates from a 40106 as I described way back in this thread. If you're concerned about the loading on the CMOS gate that's driving the transistors, you can parallel extra gates in the 40106. The circuit is well proven, reliable, cheaper than using one of the horrible "blue switches" and can be easily modified for extra features and functions.

One recent circuit that I've built for people is a clean booster with several fixed boost levels. I've used the bistable relays to select gains, and there's a "master reset" button that gives zero boost - effectively bypassed (though it's actually buffered for low impedance output to allow long cables to be driven). The logic is trivially simple, using three 40106 ICs and adding some "reset diodes" to the inputs of the bistables to give both "power-on" reset and "master reset". There are three boost levels - each with its own momentary footswitch, and the "bypass, master rest" button. Each gain selection has its own LED indicator and its own gain control. Players are finding this to be a very "musically useful" pedal.
"Why is it humming?" "Because it doesn't know the words!"

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Post by Silver Blues »

Verified vero for this circuit. Works quite nicely if I do say so myself, and it's dirt cheap to make.
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Mictester CMOS Relay.png

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Post by andregarcia57 »

Silver Blues wrote:Verified vero for this circuit. Works quite nicely if I do say so myself, and it's dirt cheap to make.
this relay will work in this circuit?

https://www.ebay.com/itm/10PCS-5V-Relay ... 54173dcd3d

thanks

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Post by electrosonic »

I don't think so - I found a data sheet for this relay

Image

You want an EA2-5SNU relay (single coil latching)

This is a EA2-5NU (Non-latch type)

Andrew.

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Post by Silver Blues »

andregarcia57 wrote:
Silver Blues wrote:Verified vero for this circuit. Works quite nicely if I do say so myself, and it's dirt cheap to make.
this relay will work in this circuit?

https://www.ebay.com/itm/10PCS-5V-Relay ... 54173dcd3d

thanks
No, and I know because I made the exact same mistake. I once ordered what I thought were EA2-5SNJ, but received EA2-5 (non-latching type). I have a few now that I have no use for. Here is my source for the Takamisawa ones, I recommend you use these. They have lots of 5, 10 or 20. Just make sure you use thin wire for the jumper, as the pins are a little on the short side.

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Post by rullywowr »

mictester wrote:
jwpartain1 wrote:Here's something similar to the original posted schematic. Haven't built it, heads up.
That seems a complicated (and not efficient) circuit. The way I did it - with two cheap transistors - works really well and adds no significant current drain to a battery-powered effect. If you want to use a momentary switch and a CMOS bistable, the easiest, cheapest, simplest and best way is to use three gates from a 40106 as I described way back in this thread. If you're concerned about the loading on the CMOS gate that's driving the transistors, you can parallel extra gates in the 40106. The circuit is well proven, reliable, cheaper than using one of the horrible "blue switches" and can be easily modified for extra features and functions.

One recent circuit that I've built for people is a clean booster with several fixed boost levels. I've used the bistable relays to select gains, and there's a "master reset" button that gives zero boost - effectively bypassed (though it's actually buffered for low impedance output to allow long cables to be driven). The logic is trivially simple, using three 40106 ICs and adding some "reset diodes" to the inputs of the bistables to give both "power-on" reset and "master reset". There are three boost levels - each with its own momentary footswitch, and the "bypass, master rest" button. Each gain selection has its own LED indicator and its own gain control. Players are finding this to be a very "musically useful" pedal.
Mictester, I really appreciate you sharing this switching....it's totally awesome. I was wondering if you could elaborate on the "master reset" diodes tied to the input of the bistables? If using a latching switch, is there a way to ensure the relay goes into bypass if the power is disconnected?
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Post by mictester »

There are several approaches - mine is to use 4013 bistables with the two transistor circuit for each relay. I tie the not-Q output back to the D input, ground the S input and feed all the R inputs through diodes from a power-on reset circuit. The great thing about the CMOS logic is that it draws minute current. I'll scribble up some circuit diagrams and add them to this thread tomorrow.
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Post by andregarcia57 »

A recent circuit I built, seems to work well so far. Anyone use this?
40106 & 4066
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40106 & 4066.jpg

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Post by mictester »

The 40106 and 4066 circuit is well known, and was widely used in cheap Japanese effects as long ago as the 1970s. The only problems are:

1. Breakthrough of high gain effects - the CMOS switches aren't perfect, and it's quite possible to get signals "bleeding through" where you don't want them to.

2. The 4066 is susceptible to static damage. Maxon had a whole production run of an effect ruined by static. The 4066 needs to be buffered from the Outside World - I used simple emitter-follower transistor buffers (sacrilege for the "golden-eared"!). The problem is then that you're using more board Real Estate and extra parts.

3. The 4066 (and its brothers) have an "on" resistance of about 60R and the "off" resistance is just guesswork (dependant on applied supplies and the frequencies of applied signals).

The 4053 is a more appropriate part than the 4066 because it has changeover switches and has extra control lines that can be put to good use, but it still suffers from the same problems as above.

The bistable relay solution is cheap, completely reliable, noise-free and provides a "solid copper path" in bypass. It's actually very hard to beat!
"Why is it humming?" "Because it doesn't know the words!"

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Post by andregarcia57 »

mictester wrote:The 40106 and 4066 circuit is well known, and was widely used in cheap Japanese effects as long ago as the 1970s. The only problems are:

1. Breakthrough of high gain effects - the CMOS switches aren't perfect, and it's quite possible to get signals "bleeding through" where you don't want them to.

2. The 4066 is susceptible to static damage. Maxon had a whole production run of an effect ruined by static. The 4066 needs to be buffered from the Outside World - I used simple emitter-follower transistor buffers (sacrilege for the "golden-eared"!). The problem is then that you're using more board Real Estate and extra parts.

3. The 4066 (and its brothers) have an "on" resistance of about 60R and the "off" resistance is just guesswork (dependant on applied supplies and the frequencies of applied signals).

The 4053 is a more appropriate part than the 4066 because it has changeover switches and has extra control lines that can be put to good use, but it still suffers from the same problems as above.

The bistable relay solution is cheap, completely reliable, noise-free and provides a "solid copper path" in bypass. It's actually very hard to beat!
ok thanks for the explanation. I've ridden here with some 4066/40106, and really to GT2 with greater volume than 7 there was noise. More on SHO booster worked well.

I'll try to buy these Takamisawa al5wn-k. This store seems reliable.


https://www.ebay.com/itm/5pcs-TAKAMISAW ... 4ae70a1840

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Post by andregarcia57 »

I ended up getting into with 40106 and 4066 switch. works up well,
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10250218_551053401702451_7061674062383105090_n.jpg
11149247_551356358338822_8261327606290808633_n.jpg

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