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KiCad 8 is just now out. I d/l it today. I should spend some time working with it. It does have an importer for Eagle although the one schematic I tried crashed it, haha.

wow, it must have JUST come out. interesting... I'll have to download and test.

and an eagle import feature? I'm listening, but skeptical (especially after your test there, hehe). I'm thinking of redoing a dual tremolo I self-etched a LONG time ago, so maybe that'll be my test.

Unless y'all made a dual LFO tap tempo tremolo pedal (e.g. 2 separate audio lines sharing one LFO - I made mine with the tapLFO v2 chip and a homemade VACTROL with 2 LEDs and 1 photoresistor)... DID you make a dual LFO tap tempo tremolo pedal? LOL... I'm getting off topic here...

Either way, Kicad wasn't TOO bad once I knew that Eagle was no longer an option, and now I might kinda prefer it. I always jump WAY into the deep end and start with a huge project, but maybe revisit a past project and start small (this advice for the OP and others - pretty sure Brian's got a lock on PCB layout at this point, hehe). That video helped a lot. I really like the 3D viewer, too.

Thought I'd quickly throw out that I knew I wasn't going to able to lay out my latest project in Eagle - it was too long and I knew I was going to have to design some parts myself, so I jumped back into kicad and... I might be a convert!

Here's the insanity I'm working through:



That's a very long bus for some LEDs going into a switch (bottom), and then some smaller ones that I'm cutting out and mcguyver-ing onto some momentary switches (top).

I watched this tutorial which made kicad make sense a little better: https://www.youtube.com/watch?v=3FGNw28xBr0&t=54s

Now: it's not without its quirks - and WOW is there a learning curve to those... for example; it has an align and spacing tool, but you could have selected one PAD of a part instead of the whole thing, and then things go haywire. Another thing that's probably a setting change, but I couldn't find it, was that once your route a trace, it doesn't move with the part, should you need to nudge or flip things around.

But - the align/spacing tool and how easy it was to make any part that I needed made this a worthy transition. It also seemingly has more parts, so I only had to make a couple parts, which that tutorial made pretty easy. Eagle may be in my rear view mirror by choice now...

As with anything, ymmv! I'm just doing a double sided pcb without any real bells and whistles - its not complex like some folks may be doing, it's just physically big. Either way... Good luck!

Nice!  It's good to see it really coming along.

yes! And thank you for the logic NOT gate advice - it worked great for the single coil relays, which I've since replaced with dual coils because of a misunderstanding, but will definitely be designing the PCB for both (not that I'll be selling these things - It took me 9 years to build ONE, lol - but it's good to have options should something happen down the road - JLC has order minimums, after all).

I tried the mains wiring per that video above - the Arduino parts did NOT like it, hehe... but the relays did! Whisper quiet in the audio signal, so It's looking like I'll power the Arduino straight from 9v, the LCD and LEDs from 9v (via 5v converter) and the relays from 9v to mains to 5v converter.

Awesome help from you all - this is why I love the internet sometimes, hehe... Thank you all!

Awesome!
I has kind of going through my troubleshooting concepts, but putting them into exhaustive words isn't always easy
By headless, I meant no screen. Just Incase there was some super noisey rectification stage on it's pcb. Due to the nature of the world's economics, very few things are built to the best of their ability anymore and instead to the cheapest of their ability. That can result in noisy single stage rectifiers where proper octavirus could be implemented for just a few cents more. This is extremely common in LED lighting.
Cheap LED bulbs scream interference like banshees at times.

Got it - yes, I think there's some remnant *very very very* faint noise from LEDs or the Arduino itself - I think the Arduino is built well, but the LEDs are neopixels and probably use the... ummm... less good components in exchange for proper scale (the documentation on their site is actually for 2 separate, but similar, products, so... I like their functionality, but feel like they may be accounting for some noise, hehe).

It appears that you have the room, so I would consider, if I were you, placing both a mains filter on an IEC cable connect coming into the unit as well as a dedicated power supply. Control what you can control and in terms of powerline noise, that gives you a lot of control for very minimal financial investment.
Emi and RFI are weird but those two things will give you some safeguards moving forward for various environments.

I found this (looks to be a good friend of the forum, and I'm pretty sure I've purchased an EQ board from them) and will incorporate:

https://www.youtube.com/watch?v=julbbj4R3Ko

I have no 470u caps, but I do have a lot of 220uf - perhaps I run them in parallel and can get close? Trying to avoid another order and use up what I've got - pedal building can be so wasteful! hehe. I'll call this the mains circuit

Right now, separating all the component areas into chunks, I have the Arduino (9v), the relays (5v), the neopixels/LEDs (5v) and the LCD (5v). I think it would make sense to add the mains circuit going into 1a) the Arduino (9v) and 1b) a 7805 circuit (5v) that would power the neopixels and LCD (100u > .1u > 7805 > .22u > 100u). I would add ANOTHER mains circuit into 2) 7805 circuit for just the relays. Maybe overkill? But also... does it hurt?

Congrats on getting working and quiet and rocking.
You could absolutely use the other pole of those relays for led indicators by the way.
Great work!

The relays are using both poles now - one for sending to the effect, the other for receiving from the effect. However, the Arduino handles the LEDs, and the neopixels are cool for that because they only use one pin for many LEDs, and I can control the colors through code.

wicked cool!

Thanks! I'll be pumped once it's actually in the box and working, but for now I'm taking the wins! hehe.

The issue is seemingly resolved. I have a 220uf electro cap and .1u box cap along the power rail for the relays. I also wired up a socket for powering the Arduino, so everything is now on the same ground, and the noise is quite minimal.

I just redid the demo altogether - the guitar is live the whole time and I never hear it in the recording. It's working pretty nicely: https://youtu.be/S_nsFbjlikU?si=gU5EaoL_g21BBZqA

I think it's safe to hit up PCB design and move to the next phase... WOO! 

FWIW, I still use Eagle, and I still hate it - such clunky software. I tried Kicad a while back, and I think my biggest issue was finding part libraries - not that it's a walk in the park for Eagle, but there's at least legacy stuff and similar alternates for getting a design together.

I also hate the size constraint in Eagle, but I'm typically able to work within the confines.

I must've missed the news - Eagle is going away in 2026?

It's possible the noise will go away once it's PCB built and everything is shielded in an enclosure. Also, stick a couple 470uF caps and a 100n film cap in parallel to decouple the main power supply if you haven't already.

470u?! I think the largest I've ever had on hand is 220u... would that work? I also have a LOT of 100u.

Everything is powered from 9v into two 5v converters (l7805s - one powers the LEDs, the other powers the relays). Typical setup for those - 100u, 100n, 7805, 220n, 100u. I separated the LEDs cause they were originally making a LOT of noise. Realizing this may be due to the grounding issue where I separated audio ground from the system - Once I connected audio/system ground, a lot of the noise went away, but there's still a faint high pitch...

The arduino is so far powered by USB, so that could have implications - I'm just not sure how to connect actual power since I think it's center positive.

I'll make another video this morning, the noise is far better once I connected audio ground to the system ground.

That looks like a huge and awesome project.

What does perturb me is that as you Arduino cycles, the noise changes. That leads.me to believe either it or its supply are the source.
That being said, start with adequate filtering there. ¿Maybe? even a ferrite bead if you want to get fancy.

Also, on Brian's coattails, any change with all pedals bypassed vs all bypassed and all powered off? If so, try to narrow down which one.

Could also tin foil hat the Arduino and see if that depletes it. If you find that's the origin and filtering/changing supply doesn't remedy it, you may have to try a different model or find a shielding solution. Oh, also, run it headless(no screen) if able.

Really want to see how this comes together as it's freakin awesome!

First off, thank you - when I started it YEARS ago, not many folks had used this method with an Arduino - it was sort of a hacked instructable that I happened upon. Now it looks like others have tried similar to varying degrees of success. I have a good feeling about this one, though - Some folks at the Arduino forum really ran with it and insisted I use better code, then helped get it beyond where I thought it would land, so I'm excited.

I think filtering is the key here - perhaps specifically along where the relays are powered. You also mentioned tinfoil hat-ting the arduino, which means I should probably figure out the center positive supply. I have an adapter, I just need to wire it correctly.

I did try disconnecting and reconnecting the pedals, as well as just bypassing them all - same noise, but again the ground issue resolved a lot (But not all) of the noise.

Not sure what you mean by headless/no screen? I'm running pins right into an arduino mega, so there's no screens attached yet.

I'll post the completed project here; realistically, probably March - I've had the enclosure for years, and it'll be super custom (tuner, tap, master bypass, etc.), so I gotta be realistic - but it needs to get done and the parts out of my closet drawer. I still have to layout and order the PCBs; probably through JLC, even though I'll get more than I need. Annoyingly, I had single coil relays that worked fine on the breadboard, but through a misunderstanding on the Arduino forum about how they were triggered, I ordered dual coils. Turns out they essentially work the same way in this context, but I think I can account for that in the design of the PCB and either version can be used. Guess I'll have an extra, hehe...

More to follow... will employ some of these notes this morning...

Quick update - I realized that I never connected audio ground to the rest of the system - once I did that, the noise is almost totally gone - though it's still a bit faint.

If there's some kind of high frequency filtering or something I should attempt, I'm all ears.

This is turning out pretty cool!

Hi everyone! Forgive if this is the wrong spot for this (and I'm happy to move it), but hopefully someone can help...

Because I made so many madbean pedals (not joking - like 80%+ of my board originated here in some fashion), I needed a switcher... 9 years after starting, I'm finally finishing it up.

I just got through (with the help of the Arduino Forum) coding and breadboarding this monster 16 effect, 9-bank pedal loop/switcher. Here's a demo off the breadboard:

https://www.youtube.com/watch?v=0g-en5EuvsM (please excuse the messy practice area, hehe)

It functions great, but there's definitely some digital noise bleeding into the signal. I put the LEDs (neopixels) onto their own 5v supply, and the audio doesn't share a ground or anything with the Arduino or other 5v supply needs... but I also have no filtering on the audio signal at all. Not sure if that's what's needed, and if so, what that looks like? Would love some advice...

My next step is getting a few PCBs made for it, so I have my work cut out for me...

I'll add tap tempo, tuner and master bypass to it once I get it into the enclosure. Overall, I'm seeing a finish line, but just need to fix that pesky high pitch noise!

Here's what worked for me...

I tried this exactly as you have it, and it was the same as my own - the readings were only like .15v different when triggered and I had to reduce the resistor to get the voltage right across the pins. These TQ2 relays are oddballs.

I also checked the transistor datasheet, which seems to have a 1500mA on the collector pin, so 50mA shouldn't be an issue for it... though 50mA feels high, but I think the relay pulls 40mA (which is why I didn't want to run it directly from the Arduino when I'll have so many) - if you have a minute to explain the math there, I'm all ears (not saying I came up with anything different - I've just never had to measure it before, lol. A quick google search has a lot of multimeters and whole home circuit panels, which may not apply one-to-one against this need).

Thank you thank you thank you again - I would not have gotten to something that works without your help, so I really appreciate it!

Breakthrough! I replaced the 10k resistor from +5v with 100r, and it's working!

When the relay is triggered, it measures 4.25v to one side of the relay, and between .1 and .3v on the other. (I think it needs at least 75% of 5v to work, or 3.75v, and 200r got me 3.3v, so 100r gives me a good buffer to work from depending on the power supply)

When both optos are on, voltage is .1v each side of the relay.

When I measure the transistor pins - collector matches the relay pins - base is .7v when optos are on, and when they're off it reads -1.1v and grows slowly up toward -1.6v (I imagine it would keep moving up if I left it in that state - but I think the optos are always on except when triggered in the code).

So I guess my last question on this thread then would be: Is there a danger to the transistor using only 100r with the NOT gate circuit, given the above numbers?

If you have any info, I'd love it!

Here's the diagram as it stands now.

I have LEDs in series with the optos for testing only - but I should be able to turn one off, leave the other on, then reverse that, and it should "click" - but it doesn't.

I did a pin readout - on the 5v pin, I read 5.8v with direct power, but only .14v with the NOT gate.

Measuring direct from the collector, it's 5.8v when opto is triggered, 0v when otherwise.

I just don't get it...

Using a 555 would probably work, but all it's doing there is being a voltage controlled switch.  Which is the same as a transistor or mosfet really.  Not sure it will get you anything different to what you've already tried?

You are probably right, and that 555 circuit doesn't work anyway. But I just can't get the other inverter circuits to work with this relay - like I said, I'm able to invert the voltage with a logic NOT gate, but once I connect each to the coil pins, the voltage drops and nothing happens when I trigger the coil, as if it's just connecting the 2 NOT gate circuits to one another through the coil instead of .

I just did a quick test using NOT gate with the s8050 - one of the NOT gates on one side of the relay coil at 0v, and direct 5v (straight from power source) on the other side of the relay coil. This setup snaps the relay when I swap the pins, so the relay works, and I know that at least the NOT gate at 0v will work. 

I then did the same test with one of the NOT gates at 5v, the other at 0v. Doesn't work when I swap the pins.

Am I missing a diode(s) between the NOT gates and the relay pins that would keep the voltage from going back to the collectors? I can't figure it out...

Furthering the 555 timer, it seems like I could do something like this: https://www.eeweb.com/voltage-controlled-switch-using-555-timer/ - that appears to be a bistable mode, but there are so many variations of this I can't quite figure it out.

I'd need 2 555s, but I've got plenty and they're cheap - if I have both always set at 0v by the , I can pulse one 555 to activate it (pin 1 5v, then 0v), and the other 555 to deactivate (pin 2 5v, then 0v) it... at least that's what I'm thinking.

I mocked it up quickly in illustrator over lunch. Any thoughts on this one?

I'll see if I have time to breadboard something tomorrow for you.  Hopefully I've got a spare relay sitting around somewhere. 

I think what you need is two pins from the Arduino, connected through a transistor or mosfet each as a buffer, and then switch one pin high, other low.  Then reverse the high and low to switch back the other way. 

I think that diagram you've been looking at is a non latching relay?  That might be why it's not quite working.

I do appreciate it, so thank you in advance if you take that step!

In the meantime, I'm seeing folks on the internets using 555 timers to create/operate latching relays - and have a ton of those on-hand.

There's this video: https://www.youtube.com/watch?v=dzcgETRXbOM and also this: https://www.youtube.com/watch?v=f8O44E9RlsY

I know those aren't 1:1 what I'm doing, per se, but it seems like a similar logic may be able to be employed to trigger the relay. I'll do a little sleuthing - 555 timers have always confused me and I have little experience with them, lol, yet somehow I have 16 on-hand!