I need help reading a schematic for the pedalSHIELD UNO. ?
I am bread boarding this project and am confused by the schematic? I says to connect VCC+ @ U1A #8 and U1B #8 ? how can this be possible?
page link:
https://maker.pro/projects/arduino/arduino-diy-guitar-pedal/ (https://maker.pro/projects/arduino/arduino-diy-guitar-pedal/)
thanks JL
(https://s13.postimg.org/5do5pk71v/pedalshield-uno-schematic.png) (https://postimg.org/image/5do5pk71v/)
U1A and U1B are two halves of the same chip. 8 pins total.
In other words, you only connect pin 8 once.
so connect (power supply) VCC to pin 8
what about C11?
C11 gets connected between pins 4 and 8.
Ignore the fact that your power supply pins are printed twice in that schematic.
thanks! I will give it a try...I will post you back results!! thank you...JL
+1 what EBK said. That's dead right.
Not only are the power supply pins printed twice, but they're printed once the right way up and then the other time the wrong way up! Arrgghh!
Not surprised you found it a bit confusing.
T.
my new question is about the ground ..since i am on a breadboard without a uno shield i am wondering about the ground points. are they all connected together ? thanks JL
also which is the wrong layout mentioned? 'wrong way up"
Quote from: jimitrader on February 07, 2018, 07:02:01 PM
my new question is about the ground ..since i am on a breadboard without a uno shield i am wondering about the ground points. are they all connected together ? thanks JL
Yes, they are. Anything with the same symbol should be connected together.
T.
Quote from: jimitrader on February 07, 2018, 07:03:40 PM
also which is the wrong layout mentioned? 'wrong way up"
No, it's not a "wrong layout" - it's technically correct as drawn. I just meant that I don't like the way they've used an op-amp symbol with power pins attached, so when the symbol is flipped to reverse the positions of the +ve and -ve inputs, the power pins flip too - which gives you +V at the bottom and ground at the top. Ugh.
For me, higher voltages should go at the top, and lower voltages should be lower down - logical, right? It's just a convention but it helps make stuff more readable.
Tom
What is the reason for the Virtual ground?
I am going to try and make a fritzing file image to show what i have hooked up..maybe someone could see where i went wrong...thanks JL
also in the schematic it shows led cathode to ground...if i put it that way it doesn't work? if i flip it the 'wrong way" it works...that seems strange to me...;-)
The LED cathode should go toward ground. If it only works in reverse for you then one of the following could be true:
1) You have your power supply hooked up backwards,
2) You are misidentifying the LED leads, or
3) You have some other error in your wiring.
The virtual ground is there so the op amp's input will be between its positive and negative power supply values. It gives a DC shift to your AC input.
so does the virtual ground go to ground? I think this might be my problem area...i am not to sure about that part of it. thanks for all the tips...JL
Just so I'm clear, when you say "virtual ground", are you referring to the spots labeled "2v5" in that schematic?
no i hooked that to R2 ? and then connected GND TP - TP2 to the main ground? is that wrong?
TP1 and TP2 are just labels for "test points". If you connected both to ground, then you are shorting your power supply. Only TP2 is ground. TP1 is +5V.
Quote from: EBK on February 08, 2018, 04:56:50 PM
TP1 and TP2 are just labels for "test points". If you connected both to ground, then you are shorting your power supply. Only TP2 is ground. TP1 is +5V.
I connected only tp2 to ground (where the ground symbol is) i put TP1 5v in from Arduino board then 2.5 to r2.
Quote from: jimitrader on February 08, 2018, 05:18:21 PM
Quote from: EBK on February 08, 2018, 04:56:50 PM
TP1 and TP2 are just labels for "test points". If you connected both to ground, then you are shorting your power supply. Only TP2 is ground. TP1 is +5V.
I connected only tp2 to ground (where the ground symbol is) i put TP1 5v in from Arduino board then 2.5 to r2.
then for the Arduino connectors I put digital ground -jumper-ed over to analog ground... then analog ground #2 to the breadboard ground..
I am not having any luck with fritzing
Quote from: jimitrader on February 02, 2018, 12:38:27 PM (http://www.diystompboxes.com/smfforum/index.php?topic=119625.msg1116976#msg1116976)<blockquote>
(https://s13.postimg.org/5do5pk71v/pedalshield-uno-schematic.png) (https://postimg.org/image/5do5pk71v/)
(https://s13.postimg.org/a3sdq2b03/schematic2.png) (https://postimg.org/image/a3sdq2b03/)
(https://s13.postimg.org/5do5pk71v/pedalshield-uno-schematic.png) (https://postimg.org/image/5do5pk71v/)
(https://s13.postimg.org/a3sdq2b03/schematic2.png) (https://postimg.org/image/a3sdq2b03/)
I put c11 to ground
Pin 4 to ground
5v to pin 8
for the Arduino connectors I put digital ground -jumper-ed over to analog ground... then analog ground #2 to the breadboard ground.
all other ground symbols to ground
All what you describe looks ok to me. What is the problem you are having?
jacks are mono...I talked with company yesterday :icon_biggrin:
does anyone know what the readings on the op-amp pins should be?
With no input, the input stage is biased to that 2.5V virtual ground, so it should be at 2.5V. With no input, the output of that op-amp should be the same as the input, so that pin and the -ve input should both be 2.5V too.
Same logic applies for the output stage - with no input signal, you should get a midpoint voltage from the PWM, so 2.5V. That stage is set up as a voltage follower, so the output and the -ve input are both 2.5V too.
Please someone step in and correct me if you spot something wrong in this line of reasoning, but it looks to me like you should have 0V and 5V on the power pins and 2.5V everywhere else.
Which op-amp are you using? Not everything will cope with a 5V supply.
Tom
Pin readouts:
1 1.08
2. 1.10
3. 1.00
4. 0.00
5. 2.57
6. 2.80
7. 2.77
8. 5.54
I am using the TL972 op-am ic
any thoughts? thanks JL
The output op-amp is about right, but the input op-amp is terrible. The input is way low. That's where you need to look.
T.
Quote from: ElectricDruid on February 11, 2018, 06:24:52 PM
The output op-amp is about right, but the input op-amp is terrible. The input is way low. That's where you need to look.
Isn't it the other way around? According to the schematic posted pins 1,2,3 are the output opamp and pins 5,6,7 the input one.
Pins 1,2,3 are way too low. On the other hand... how is the output opamp biased?
Quote from: potul on February 12, 2018, 04:32:57 AM
Quote from: ElectricDruid on February 11, 2018, 06:24:52 PM
The output op-amp is about right, but the input op-amp is terrible. The input is way low. That's where you need to look.
Isn't it the other way around? According to the schematic posted pins 1,2,3 are the output opamp and pins 5,6,7 the input one.
Yes, it is. Sorry, my mistake. It's the output one which is wrong. I replied quickly and didn't check the schematic again.
Quote
Pins 1,2,3 are way too low. On the other hand... how is the output opamp biased?
It's fed a 0-5V signal from the PWM output - that's directly DC coupled, so the bias is included on the PWM output.
That suggests that perhaps the Arduino is not outputting the PWM that it should. Perhaps the circuit is ok and this is a firmware issue?
Tom
what could cause the pins 1,2,3 to be so low? i re made it 3 times and am really sure i have it all connected right...double checked the code and tried with different uno...still nothing..hmmm
I would check the software to verify that the PWM output is working as expected.
Try to modify the code to send a fixed value through the PWM and verify what you get out of the Arduino
Do you have a scope?
Quote from: potul on February 15, 2018, 05:44:20 AM
I would check the software to verify that the PWM output is working as expected.
Try to modify the code to send a fixed value through the PWM and verify what you get out of the Arduino
Do you have a scope?
No I don't have one(scope)...I have used the board for other testing and i know that it is ok...when you say software are you talking about the code? thanks JL
yes, I mean the code
Quote from: jimitrader on February 14, 2018, 03:50:17 PM
what could cause the pins 1,2,3 to be so low? i re made it 3 times and am really sure i have it all connected right...double checked the code and tried with different uno...still nothing..hmmm
Aside from the code, the only thing I can see is that one of those two capacitors to ground could be faulty. It's pretty easy to "overcook" them when soldering, especially if they are film caps. I've frazzled a few like that, and then you can get shorts inside the cap itself.
HTH,
Tom
I am trying to build on breadboard...no soldering yet...I will double check the caps...and the code...thanks JL
I would definitively do some code debugging. If the PWM is not working, you will probably get low voltages there.
Try to code a tone generator that simply outputs a sine wave or similar.
Quote from: potul on February 19, 2018, 12:10:44 PM
I would definitively do some code debugging. If the PWM is not working, you will probably get low voltages there.
Try to code a tone generator that simply outputs a sine wave or similar.
the volts from my usb ports are 6.8v and out of the Arduino about 6.12? seems kinda high shouldn't it be 5 on both?
what would cause that?
maybe that is part of the problem?
Solved!!
I was using the wrong code!! Thanks potul!!after reviewing the site again I noticed the code i was using was the sample code..after finding the real codes everything is sounding good now...Thanks for all the tips...JL
Good to know you could solve it. Once you have something interesting coded, show us the result!