Rp2040 pin names quandry

[EleriLove]

as stated above. thank you for repeating me.

[mykepredko]

A few things to untangle here.

@EleriLove

a capacitor used in this way will cause a higher voltage. making a sensor less accurate, avoiding this would be VERY VERY nice in this situation.

No. Not possible in this situation.

@EleriLove

furthermore the cables in this run are… about a foot in a half long already? this is very likely already measuring up to 0.1 uF of capacitance already. I don’t have tools here to measure this at the moment. but I’ve seen enough experimentation of similar “cable” capacitors before, even at low voltages such as these. the air gap is too low to not induct a capacitance, and more than long enough to make a capacitance of this distance.

A pair of wires will have a capacitance nowhere close to 0.1μF. I just did a quick check on a capacitance calculator (Wire Pair Capacitance) and it comes back with the reasonable value:

@EleriLove

though it doesn’t look like the capacitor is well defined in the image above we can… probably assume it’s about 4 uF (sorry I don’t know the alt code for miro or pico) … and now I learn that my keyboard for some reason doesn’t work with alt codes… yey…. worthless keyboard.

It’s 4.7μF. Do a Google search on “Greek Alphabet” and you can just copy and paste the character. You can also use the “Character Map” in Windows, but Googling it is easier.

@EleriLove

oh I forgot to mention that I plan on measuring the capacitance that I actually need by making a 555 timer signal in about the right specifications and do a capacitor testing suite to it with my o-scope, I don’t know much about filter caps. but I think I know how to make a test circuit to learn enough, or at least test enough. to know enough!

What are you expecting to get here?

Honestly, this is wasted effort as you’re making as assumption as to the cause of the problem without verifying that it is the case.

@EleriLove

I will be getting my new thermistor, a creality 100k thermistor which I won’t have to manually calibrate myself later.

Before doing anything else, could you do the experiments I asked you to do previously? I’m setting them out explicitly below:

Get a 47k resistor:

• Experiment 1. Put the 47k resistor at the “Thermistor” location shown in the diagram above as close to the Raspberry Pi Pico pins as possible, restart Klipper and record the temperature waveform. The purpose of this experiment is to see if the RP2040’s ADC will return a consistent results. If there is a problem with the RP2040’s ADC you will see the same waveform as you posted above, stop here and post the temperature waveforms so we can discuss.
• Experiment 2 if the waveform in Experiment 1. is clean. Put the 47k resistor at the end of the wires where the thermistor was previously, restart Klipper and record the temperature waveform. The purpose of this experiment is to see if the length of wires are picking up noise. If you see the same waveform as you posted above, stop here and post the temperature waveforms so we can discuss.
• Experiment 2 if the waveform in Experiment 2. is clean. Keep the 47k resistor at the end of the wires where the thermistor was previously, restart Klipper, SET THE EXTRUDER TO 200C and record the temperature waveform. The purpose of this experiment is to see if there is an induced current caused by the current flowing through the heater wires. Post the temperature waveforms so we can discuss.

This series of experiments, which should be fast to do will give us an idea of what’s happening.

If the waveform is a straight line in all three, then the most likely cause of your problem is your thermistor.

[EleriLove]

@mykepredko

What are you expecting to get here?

Honestly, this is wasted effort as you’re making as assumption as to the cause of the problem without verifying that it is the case.

I literally have a thermistor in the mail being delivered in less than half an hour. how am I possibly making assumptions without verifying cause?

futhermore, self learning and self education is never wasted effort. this entire community is based on what you’d consider “wasted effort” if it was. we do things not because it makes sense to others, but because they make sense to us.

this is how I learn best, I know I don’t understand filter capacitors as much as I’d like to. I have 555’s coming out of my tear ducts, the circuit is piss cheap, and my oscope is always ready, this would literally take me 10 minutes to settup a test to test it and learn for myself. just because you learn best by googling… doesn’t mean everyone does. is it more effort? for me no. no it’s not. it’s far far less. and gets me way better results in understanding which I can then use to read the documentation on the subject and compare with my experiences.

as for the experiments, I already stated previously that I was going to.

[cardoc]

Cable capacitance is between your sensor and the ADC input pin. A filter capacitor goes between the ADC input and ground.

Not the same thing.

[EleriLove]

that’s literally not how that works. the capacitance is between the two leads of the sensor. on both sides of the sensor. between the sensor and adc input pin is just just a copper cable, how is there capacitance when there’s continuity? a capacitor is literally the exact opposite of continuity.

you’re thinking of an inductor.

[cardoc]

@EleriLove

furthermore the cables in this run are… about a foot in a half long already? this is very likely already measuring up to 0.1 uF of capacitance already.

Isn’t this your post concerning cable capacitance?

[EleriLove]

most of the people in this thread seem bent on starting a fight over misunderstandings and poor communication instead of actually understanding electrical theory or… more acurate to the purpose of the thread, answering the question, which was answered a LONG LONG time ago, so i’m going to leave the solution here for those trying to wade through the internet debauchery with a simple summation and will leave the bickering to those trying to call a single wire a capacitor.

the answer above was that I was a dumbass and needed to supply a pullup resistor to a 3.3 source,

@mykepredko

Here’s how I would recommend that you wire in your thermistor:

Now, you can use GPIO26 or GPIO27 - it doesn’t matter.

this was the solution I chose to test first, after doing so the output agreed with my well calibrated bed thermistor as to what the room temperature was, and seemed to make sense for higher teperatures as well.

@EleriLove

we then discovered what many have discovered and that when using a RP2040 adc pin we get a noisy signal,

2 solutions to this situation were given, both very good suggestions.

small filter cap somewhere between .5μF - 10 μF (I will be doing a test later to better determine what would best filter this out, the results of which I will no longer be sharing because of the aforementioned debauchery)

the second suggestion was a potentially poor thermistor. also very likely as this is the original thermistor that came with the Davinci 1.0 pro 3in1 printer which were “custom” and poorly documented, but also seemed to fail a lot easier than other thermistors.

to test this I ordered a new thermistor and am waiting for it in the mail (they failed to put in the apartment number in the buzzer to be allowed into the apartment building… yey)

the first order of testing is to try a new thermistor.
if that doesn’t work, try plugging it in directly to the rp2040 to eliminate multiple junctions in the wiring.

if that doesn’t work I will test with a 100K resistor stack at the rp2040 to finally rule out if the adc is just crap or not. if it is the adc I will add an additional filter cap. there is already one on the vref line. I doubt this will be the solution. I am far more likely to believe the issue is a failed connection, the wiring in this thing has been a gremlin. I will not be replying further to this thread, I hope this helps you all solve your own issues in the future, and genuine kudos to MyKepredko.

(instead of the 47k one suggested by mykepredko (cheers mate, you’re awesome, really good work on schematics and understanding the circuits. not to mention being very good at troubleshooting))

[mykepredko]

@EleriLove

this is how I learn best, I know I don’t understand filter capacitors as much as I’d like to. I have 555’s coming out of my tear ducts, the circuit is piss cheap, and my oscope is always ready, this would literally take me 10 minutes to settup a test to test it and learn for myself. just because you learn best by googling… doesn’t mean everyone does. is it more effort? for me no. no it’s not. it’s far far less. and gets me way better results in understanding which I can then use to read the documentation on the subject and compare with my experiences.

The reason why I’m questioning this is because it won’t teach you anything about filters.

What it sounds like you’re doing is setting up an RC network on the output of a 555 timer which doesn’t make any sense to me because a 555 timer uses an RC network to specify the delay. So, if you want to use a 555 timer to learn about RC networks and the delay they cause

Here’s a pretty good site explaining 555 timers and how resistors and capacitors are used to set up the chip’s oscillation period:

https://www.electronics-tutorials.ws/waveforms/555_timer.html

@EleriLove

futhermore, self learning and self education is never wasted effort. this entire community is based on what you’d consider “wasted effort” if it was. we do things not because it makes sense to others, but because they make sense to us.

I’m trying to lend my experience and knowledge to a) help you get a working printer and b) help guide you to better understanding the topics you want to learn about by trying to steer you away from going in the wrong direction.