Electronics > Beginners
Something to see my signals with?
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Gyro:
I'd avoid using the microphone input on your laptop. If you did have an accident, it would probably screw it forever and you'd loose it for skype or whatever. It doesn't sound as if there's much chance of you replacing the laptop at the moment.

A USB soundcard would be an option, depending on what you can turn up in the neighborhood. There's always a small risk of damaging things by putting high currents into the USB ground but it wouldn't be any more risk than using the Arduino. As rstofer said, checking with a DMM first should keep you safe.

Don't give up on using the Arduino as a 'scope' though - there must be loads of projects on the web.
Zero999:

--- Quote from: Cody Turner OKC on August 28, 2018, 06:05:04 pm ---Okay cool I see, great! It is analog signals and I think 5khz would be plenty like I said I just want to see for fun because it would be kind of like owning a oscilloscope in a way! I will look through those links , I don't know anything about the Arduino yet so I will have a lot of research to do I suppose and dang that "shield" would be awesome! I unfortunately can't order stuff online or buy stuff except what I can find in local stores within walking distance,  but thank you guys so much it gives me something to work off of!

--- End quote ---
Note that 5kHz would be the highest harmonic visible to the oscilloscope. If you're looking at a square wave, the maximum usable frequency will be much lower, as a square wave is full of harmonics.
Cody Turner OKC:

--- Quote from: Mr. Scram on August 29, 2018, 10:09:28 pm ---Hey Cody, did you ever get that multimeter going?

--- End quote ---



Hi Mr. Scram, I actually did! when i got it going the next day my parents stole my laptop and sold it to a pawn shop to get money for something bad (im guessing....) They said they havent seen it but no one enters the house and it has never left the house and I am very clean and organized kid.

I told my teacher since my homework was on it and she felt reallybad and a few days ago gave me her old laptop and a locking chain thing! Very nice, so thankful, but when i came back to the forum and got logged back in finally I couldnt find my post anywhere or figure out how to get to it, I am missing something in plain sight i bet!

Anyway, i used a razor blade and cut the 4 legs of the smd bridge diode and it works perfect now!! I have been looking through stored junk PCBs i have scavanged for a new bridge rectifier but no luck yet unfortunatly, so I havent ussed current measurment since for saftey as advised on the posts except for initial test to confirm that it worked!
Cody Turner OKC:
Rstofer, thanks a lot for that link! I didnt know I could do that, but my new laptop, well new to me at least is a old model is is running windows Vista still and quite slow, it does great for me to research and stuff but as Gyro said below, I better not use my laptop as it is the most valuable thing I havee and I really dont want to mess it up!
JS:
  Too bad to hear that man! Pay attention to Dave's giveaways, he sometimes does one pick based on a story and you can probably qualify for it! Same thing can happen in other places, you could get a nice gift someday. Keep your projects well organized to show people, like the meter repair, or this project, they can help you at some point, it's important for people to see what you've done. This forum can be a good place, just don't loose track of your posts.

  Here's your old post, so you can upload your results there. For the diodes, there's probably enough space there to fit a few diodes to protect the inputs, but you could also use external resistors to measure current.
  You could get 1% resistors or even better, a broken meter could give you what you could need. If you prefer to work a bit more, you can use ten 10Ω resistors, measure them in series and note the value, then connect them in parallel and you will get an 1Ω resistor with 1/100th the value you measured in series with better tolerance than the components have. And you will be getting your toes wet in metrology, the 100Ω is easier to measure. For the 0.01Ω get's trickier but having the known 1Ω resistor you are half way to it.
https://www.eevblog.com/forum/repair/fluke-87iii-broken-current-input/

  Coming back to the Arduino to look at signals, if you don't want to get to your computer you will need some sort of display, other option, you might be able to find a cheap wifi module, those ESP8622 are everywhere now. From there you could pick the signal from the computer without any risk for the computer, and if you run from batteries or even a power bank you will have a floating scope which is great! Be careful with it. Also, you will have much more memory, like a few MB and the sampling freq is likely to be higher.
  If you go back to the computer idea, or the arduino to the computer, there are ways to protect the channels pretty well, a fuse, a few resistors and diodes can get you a very long way there. A well protected circuit for the computer isn't unreasonable, the thing is you need to protect not only the signal input but the common, using a low current fuse, a 1k resistor or something and a pair of diodes to ground would do a pretty decent job. For the signal you want a high value resistor, at least 1M, if you can get a ~5V zener diode great, or a few in series. That after the resistor will limit any signal going to the next stage, the resistor would only let pass 100µA at 100V, so hard to damage anything. After that, an attenuator, which could be a 100k or greater potentiometer.

  I have to tell you, when I started, 15 years ago or something, I wouldn't even dream in getting an scope, arduinos weren't available and I was far from using pic or getting a programmer for it, I think it could be done with parallel ports back then though. Long story short, I only got my scope a few month ago, now I work and can justify expending real money on it, so far I was getting away without seeing the signals, which can teach you a lot on how to know what's going on without looking at it. It's much harder but you can do a lot of things without one, don't hurry into it, as I mostly did audio, a small amplifier did the trick, also should be protected but damaging the power stage of a scavenged radio isn't a big deal, and hearing can tell you a lot from the signal, like if there is just noise or has some oscillation, if there is signal still present in the path or you loose it in the previous stage, etc. If you can build something would be great and really useful, but don't think that till you don't have it you can't do anything with electronics.

JS
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