Author Topic: Help RE: stupid grounding question(s)  (Read 434 times)

Help RE: stupid grounding question(s)
« on: January 24, 2021, 01:53:21 PM »
Hi friends,

So, I am pretty new to diy electronics and even newer to building effect pedals, so please pardon my ignorance on probably SOOOO many things.... that being said, there are two things that I am trying to make sure that I am doing correctly and could use any help I can get... as a sanity check, at the very least... and so I don’t screw up all my work on the other extreme.

1) I’ve been putting together this Earthquakes Disaster Transport Jr. from the layout (the original one, not the “tails” one) provided here: http://tagboardeffects.blogspot.com/2017/12/earthquaker-disaster-transport-jr.html?m=1
I have the whole board assembled and am nearly finished the off board wiring, for which I used the following as a guide: http://beavisaudio.com/techpages/stompboxwiring/
My first question is this (and I apologize if this is a really dumb question)... for the main circuit layout shown on tagboardeffects.blogspot.com for the pedal, there is one ground wire coming out of the board on the bottom left, there. On the off board wiring diagram, though, it shows the placeholder circuit for whatever you’re wiring up as having two different “ground” wires/connections.... My initial thought was that I just connect everything labeled ground together.... so the sleeve of the output, the sleeve of the input and the middle left contact of the stomp button would all feed into that one ground wire from the circuit board layout. Would that work? Or am I going about it/thinking about it wrong?

Then, thinking about all of that got me thinking about effect pedal grounding in general. I’ve read so many posts about it, but I feel like I still don’t fully grasp it.... I always thought that all grounds in an audio effect pedal connected to each other and went back to the negative of the power source. Is there more to it than that with effect pedals? Or am I completely wrong in thinking that? I am new to all of this and just trying to wrap my old man brain around it.

Thank you all for your continuing support, education, kindness and overall helpful dispositions. You’re all the best!




andy-h-h

Re: Help RE: stupid grounding question(s)
« Reply #1 on: January 24, 2021, 03:08:27 PM »
You are right - everything marked as ground connects together, including the negative pin on the power supply.   I can see how that diagram could throw you - two grounds with different colour leads....   

Good luck with the build and welcome to the rabbit hole that is pedal building.   :)

GibsonGM

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Re: Help RE: stupid grounding question(s)
« Reply #2 on: January 24, 2021, 03:19:53 PM »
Welcome, Peter. Your 'concern' about how to do this is actually right.  In higher voltage or more noise-sensitive circuits, how you ground CAN make a difference.  Overall we try to do 'star grounding', which you can find out more about on the net, and it's good reading as you learn more.

For most things, tho, it's like Andy said.    In the switch wiring diagram, pretend the 'left ground' has a little wire under the board going to the 'right ground'.   It wouldn't matter if you grounded that output jack at the power jack " - ", or the ring of the input jack, or on the board itself.  Some people leave it off and let the enclosure ground that jack body - but if it ever comes looks it makes horrid noise, so that's what the wire is for. 

I think they just drew it that way for neatness. 
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antonis

Re: Help RE: stupid grounding question(s)
« Reply #3 on: January 24, 2021, 03:56:18 PM »
This happens inside board, if it helps..  :icon_wink:

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Re: Help RE: stupid grounding question(s)
« Reply #4 on: January 24, 2021, 09:26:20 PM »
Thank you guys all so much for your quick, thorough, and helpful responses. It’s VERY much appreciated. While looking over the rest of the circuit, I noticed something else weird that I was wondering if you guys might have some input on.... if you look at the layout diagram that I used for the main circuit posted above (here it is again: https://2.bp.blogspot.com/-M_hQJs1CGGk/WrqsN0YAcTI/AAAAAAAACCw/Wncel1o4q6whghLgv9xDujCS9Ys5D8EegCLcBGAs/s1600/EQD%2BDisaster%2BTransport%2BJr.png ), if you look at the 78L05 one the far left, it has an “i” at the top, an “o” at the bottom and with the “flat side” of it on the right side.... when I look at the datasheet for the 78L05 that is supposed to go there, it basically says the opposite.... so the question is do I place the 78L05 in a way that corresponds to the letters on the layout that I linked or do I place it in following the shape of the component shown on the layout? Or do the “i” and “o” NOT mean input and output? Or am I missing something else entirely?

P.S. also, I could not get an exact 78L05, so I am using an “L78L05CZ” that I got from Mouser (which also has the same pin layout as the regular 78L05), but it was my understanding that the one I got would work just as well... would you guys agree? Thanks again for everything!

Link to the L78L05CZ that I got: https://www.mouser.com/ProductDetail/STMicroelectronics/L78L05CZ/?qs=%2Fha2pyFadugURvrY14htz6LUO0grzImWFDydd49K8iU%3D






DIY Bass

Re: Help RE: stupid grounding question(s)
« Reply #5 on: January 24, 2021, 10:34:53 PM »
For your regulator, the pinouts are more important than which way the flat faces.  Make sure you match o to o, i to i and gnd to gnd.

PRR

Re: Help RE: stupid grounding question(s)
« Reply #6 on: January 24, 2021, 11:22:22 PM »
For your regulator, the pinouts are more important than which way the flat faces. .....

True; but on TO-92 you can't tell which is which without the flat.

It IS confusing. The chip data shows the bottom of the TO-92. The perfboard drawing shows the top of the TO-92. Also turned 90 deg. Here's my scribble/cheat-sheet, but do not trust me, work it out yourself.

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andy-h-h

Re: Help RE: stupid grounding question(s)
« Reply #7 on: January 25, 2021, 12:37:20 AM »
Thank you guys all so much for your quick, thorough, and helpful responses. It’s VERY much appreciated. While looking over the rest of the circuit, I noticed something else weird that I was wondering if you guys might have some input on.... if you look at the layout diagram that I used for the main circuit posted above (here it is again: https://2.bp.blogspot.com/-M_hQJs1CGGk/WrqsN0YAcTI/AAAAAAAACCw/Wncel1o4q6whghLgv9xDujCS9Ys5D8EegCLcBGAs/s1600/EQD%2BDisaster%2BTransport%2BJr.png ), if you look at the 78L05 one the far left, it has an “i” at the top, an “o” at the bottom and with the “flat side” of it on the right side.... when I look at the datasheet for the 78L05 that is supposed to go there, it basically says the opposite.... so the question is do I place the 78L05 in a way that corresponds to the letters on the layout that I linked or do I place it in following the shape of the component shown on the layout? Or do the “i” and “o” NOT mean input and output? Or am I missing something else entirely?

P.S. also, I could not get an exact 78L05, so I am using an “L78L05CZ” that I got from Mouser (which also has the same pin layout as the regular 78L05), but it was my understanding that the one I got would work just as well... would you guys agree? Thanks again for everything!

Link to the L78L05CZ that I got: https://www.mouser.com/ProductDetail/STMicroelectronics/L78L05CZ/?qs=%2Fha2pyFadugURvrY14htz6LUO0grzImWFDydd49K8iU%3D






On layouts, components are always shown from the top.  When in doubt, google the part with the word pinout, and you will usually get a result that's easy to follow if the data sheet isn't.   Usually the person who created the layout will go to the effort to check and make sure it's the right way around to start with. 

The part you bought will be fine to BTW.   

I've built the Disaster Transport using that layout - stick with it, it sounds great.  It does get very cramped in parts (especially next to the voltage regulator), so be careful with your soldering and part placement.   



Re: Help RE: stupid grounding question(s)
« Reply #8 on: January 25, 2021, 02:21:29 AM »
Awesome, I think I got it. Thank you guys so much for all of your help.... it’s VERY much appreciated!

All the best,

Peter W.

nocentelli

Re: Help RE: stupid grounding question(s)
« Reply #9 on: January 25, 2021, 02:24:19 AM »

I have the whole board assembled and am nearly finished the off board wiring, for which I used the following as a guide: http://beavisaudio.com/techpages/stompboxwiring/
My first question is this (and I apologize if this is a really dumb question)... for the main circuit layout shown on tagboardeffects.blogspot.com for the pedal, there is one ground wire coming out of the board on the bottom left, there. On the off board wiring diagram, though, it shows the placeholder circuit for whatever you’re wiring up as having two different “ground” wires/connections....

I don't think this bit has been addressed in replies yet: The Beavis off-board wiring correctly shows how ground is "switched on and off" by inserting or removing the input plug of the guitar cord: The black wire carries "power ground" / "power supply negative terminal" from either battery or dc adaptor plug, but the input socket is stereo, and uses the fact that a mono guitar plug will bridge the power ground (sleeve connection, black wire) to the "power ground" rail on the circuit board (ring connection, blue wire). This means that a battery powered effect will not drain the battery in a matter of hours, since the power connection n can be disabled by simply removing the input jack plug from the input socket.
« Last Edit: January 25, 2021, 02:28:20 AM by nocentelli »
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