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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twotees
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Post by twotees »

mictester wrote: 20 Nov 2014, 19:17 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 bistable's you're using, and you'll guarantee their state at power-on.
Hello Mictester, You still out there? I very much appreciate your nifty little low powered Relay switching. Just a little unsure on the instructions you gave on the power on reset circuit to avoid out of sync on power up, which I have sometimes had a problem with, not always, but occasionally it glitches into the switch system in some builds. Please if you wouldn't mind could you do us a diagram description schematic of the "power-on reset pulse" as you previously described, This might sought my dilemmas out. Hope you can oblige. :)
Thanks, Trevor

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JimvdB
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Post by JimvdB »

Mictester, I am interested in the simpler version that your brother came up with to annoy you.

Care to share it?

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Post by twotees »

twotees wrote: 27 May 2022, 15:16
mictester wrote: 20 Nov 2014, 19:17 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 bistable's you're using, and you'll guarantee their state at power-on.
Hello Mictester, You still out there? I very much appreciate your nifty little low powered Relay switching. Just a little unsure on the instructions you gave on the power on reset circuit to avoid out of sync on power up, which I have sometimes had a problem with, not always, but occasionally it glitches into the switch system in some builds. Please if you wouldn't mind could you do us a diagram description schematic of the "power-on reset pulse" as you previously described, This might sought my dilemmas out. Hope you can oblige. :)
Thanks, Trevor
Its okay mictester, figured it out with some help on another forum. Go's something like the following schematic attachment. Works well also, Gets the FX reset to FX on at power up, and when power is pulled or brown out, reverts to true bypass every time. Cheers
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mictester
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Post by mictester »

bubstance wrote: 18 May 2012, 22:36 Just so it's there, here's a combination of mictester's circuit and a debounced bistable flip-flop using a 555.

**EDIT** I think the numbering on the relay is bunged up, but the concept is there.
Hi. The circuit idea is a good one, but the 555 will draw more current than the whole of the rest of your circuit! It's a very current-hungry device. If you're going to use this approach, spend a little more on the CMOS version of the 555 - it's called the 7555, and sips current! Your battery consumption with the conventional 555 will be tens of milliamps, with the 7555, it will be down in the microamps!
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Post by mictester »

twotees wrote: 14 Jun 2022, 14:28 Its okay mictester, figured it out with some help on another forum. Go's something like the following schematic attachment. Works well also, Gets the FX reset to FX on at power up, and when power is pulled or brown out, reverts to true bypass every time. Cheers
I've been away for a while, but will be contributing again shortly.
"Why is it humming?" "Because it doesn't know the words!"

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MattG
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Post by MattG »

twotees wrote: 14 Jun 2022, 14:28 Its okay mictester, figured it out with some help on another forum. Go's something like the following schematic attachment. Works well also, Gets the FX reset to FX on at power up, and when power is pulled or brown out, reverts to true bypass every time. Cheers
@twotees, did you ever build and test that circuit as drawn? I did, and when power is applied, it immediately goes into the active state. When power is removed, it does go back to bypass. But the switch doesn't work. In other words, once power is applied, it's permanently on, and stays on until power is removed.

I understand how that first inverter should have a pulse to set the initial relay state. But once that 1uF is charged, it seems like that first inverter (IC1C) will always see positive potential, i.e. a "1", right? And therefore, cause the last inverter (IC1B) to output a "0", which will turn on the PNP (Q1). How does the momentary switching "overcome" the always-0 output of IC1C?

Edit: Upon further testing, plus help on another forum, the circuit won't work as drawn. Indeed, once cap C5 charges, that first inverter sees a constant "1", and the actual switching mechanism becomes ineffective. Completely removing that first inverter from the circuit makes it work as a basic on-off switch, although the power on and power off states are not deterministic.

To fix the circuit, the suggestion was to move C1 such that, instead of being from IC1C pin6 to ground, it is in series from pin6 to pin1 of the next inverter (i.e. the junction of pin1, R1, and switch pin1). But I have not yet tested this.

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Post by twotees »

Hi MattG, As for that circuit shown earlier in the previous post back a little, I only just took a part of that to add to an existing circuit that I were working on, I needed it to determine the startup position for the switch in a predetermined way with a power on reset pulse to achieve as much.
The final schematic I settled with is over on the Diystompboxes website at -

https://www.diystompboxes.com/smfforum/ ... c=118021.0

Where I see you did find it over there and had successfully built the finished circuit I put together.
I just got to read your inbox message to me over there, and replied to it today.
So Cheers, Trevor

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Post by bubstance »

mictester wrote: 28 Jul 2022, 11:46
bubstance wrote: 18 May 2012, 22:36 I wrote something a long time ago
Hi. The circuit idea is a good one, but the 555 will draw more current than the whole of the rest of your circuit! It's a very current-hungry device. If you're going to use this approach, spend a little more on the CMOS version of the 555 - it's called the 7555, and sips current! Your battery consumption with the conventional 555 will be tens of milliamps, with the 7555, it will be down in the microamps!
Hey, I know I'm way late to seeing your reply to my dumb original idea, but thank you for taking the time to add some input on how to make my hodgepodge of ideas a bit better.

Cheers,
-bubs
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Post by J4mes »

So, after leaving this for a little while, I've come back to it and seen one issue. The Pin 7 of the 40106 should be connected to ground and not the to of the 100n capacitor.

Image

Image corrected, and ready to print. It's probably best if the admin deletes the last post, as I can no longer edit it for updates.



Have fun.
J

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