Its a center positive
I wish i never started this project. Unforunately i had to because it is a part of my thesis. The other two parts are programming though
Thank you. I got a multimeter. How do i use it for this cause? The ohm-meter doesn’t it measure resistance? Why not the beeper function?
How did i ended up using these tracks? I am using jlcpcb and each board house has their won rules. Since this is my first project, i didn’t know what value to place. Forum members said about a guy that has templates for all the big board houses. I downloaded the file from github and imported his values.
Thank you very much for you schematic!
The intent of the circuit is this… All the circuit does is measure resistance. But because you can hook up , up to eight resistances the two chips below are MUX/DEMUX to select the proper one.
Actually the upper chip uses an analog circuit (i can send you if you want) that will output a square pulse in relation to the resistance. The higher the resistance, the different width of the pulse.
The pulse is fed to an arduino which uses timer interrupts to measure the width of the square pulse, in order to determine the resistance.
These pins are used by the arduino to set the MUX/DEMUX. So i guess output (from the arduino point of reference)
Thank you!
I got the traces size from a template for jlcpcb… I don’t know if this is a problem.
The arduino was supposed to be powered by the USB cable but the circuit from a barrel jack.
But since the arduino has a 5V output, i can power the board from there, this is what i will do in my next revision.
EDIT1: Ha, you are commpletely right on this one. Unfortuantely this board is big. I thought it would fit perfectly. But i used tape to insulate the resistor to make sure it does not touch.
EDIT2: This is absolutely correct! Please see my previous post for more info. The sensor is a common resistance.
EDIT3: It should be one 400pf cap, but since i couldn’t find one, i placed four in parallel. It is part of the analog circuit that will produce the square pulse analogous to the resistance of the resistor. If you want the schematic, i can post.
EDIT4: My code works fine. I already have this circuit in perfboard and breadboard. I tried to cleanse the mess with a shield. It is part of my thesis.
EDIT5: You are right on this one. I removed them completely. I routed them wrong. More info here:
https://forum.kicad.info/t/pcb-with-kicad-possible-error-in-routing-decoupling-capacitors/
EDIT6: I made sure the pins are mounted in the correct way. But that’s not to blame, because not even the RESET button is working (which is just pull GND to arduino pin)
EDIT7: My next post after this will contain a picture
Thank you!
Ubuntu 20.05
KiCAD 5.1.5
It is not hard to guess that those templates contain minimums houses can manufacture. I use board house in my city. Their minimum is 4 mils but I never tried it. Working at border of possibilities is asking for problems.
Do you know that real capacitors have their tolerances?
You should ask yourself how accurate that value have to be. If you can correct something with software than you probably could use 390pF (typically 5% so 370-410). Or if you need to believe that you have 400 you could use 390+10.
“Thank you. I got a multimeter. How do i use it for this cause?”
What do you expect @Piotr ?
Someone doing their thesis in electronics should either be able to do basic troubleshooting, or go back to the books / lectures.
I assume this is first and foremost a computer science/software engineering thesis and this Pi hat is just a side show.
Edit: Oops, Arduino shield.
Yes you are right! they have minimums. If that is the case what should i change? Only the trace width? From 5 to 10?
Yeah i know about tolerances. I have taken care about that. They are 1% and they work fine for my purpose. Thank you for mentioning it.
All right. Things got even weirder.
I hooked up the multimeter…
Everything in the button is ok. Used the beeper and two legs of the button are hooked to GND and when i press the button all the buttons are hooked to GND. It even gets transfered to the arduino pin.
About the voltages now.
The voltage at the barrel jack is 4.53V, at the op-amp chip is 4.32, at the one MUX chip is 4.48 and at the other MUX is 3.92.
Is this normal? Since it is the same channel…
Anyway, since the button at least it’s working, things are getting weird. Why it’s not “talking” with the arduino?
I can’t even read the sensors, nor does the RESET button work.
One theory could be that because the board is long it doesnt fit well and the pins do not touch the female header pins of the arduino. But i don’t think this is the case, since i pressed it firmly with my hands when testing…
What do you guys think?
Disconnect power supply and measure resistance between power and gnd.
With that much voltage sag it is likely you have a short somewhere. Or a blown micro.
Its mainly a software thing, but i also had to make this pcb.
I measured the resistance with the multimeter setting at 20KΩ and i got -> 9.71 kΩ
Then i turned the multimeter setting at 200KΩ and i got -> 62.3ΚΩ.
But then all the other times i measure i consistently got 0Ω…
I cannot understand what is going on…
If the button on the board appears to be working then the pins are probably not seating properly even though you are pushing down on the board.
The board might be pushed too far up by the Jack and USB connector. Try and “extend” the pins by plugging in a plain SIL connector strip into the arduino pins then plugging the board into the strip.
EDIT: You say the sensor is a “common resistance”. Is it just plain resistor? Or does the sensor look like a resistance?
You have shorted power and ground, of course nothing will work. You have to eliminate this issue first. And check the arduino without your board to make sure it’s still ok. Don’t connect power to your board or the arduino until you find the short and eliminate it, verify using multimeter.
ugghhh, this is painful to watch…
We have been told that this has been bread-boarded and it works, but can’t even troubleshoot a circuit with a switch to ground…
Hmmm. Can you please expand on that?
You mean that at some place these two “touch”?
If that’s the case, then how come on my measurements, when i hook up the power supply, i managed to get almost 5V between GND and Vcc?
And the button sees GND on it’s legs…
Could you please expand a little more?
Thank you very much!
Can you take a close up of the top of the board so that we can see the chips, button, traces etc?