Arduino Forum

Using Arduino => General Electronics => Topic started by: nick321 on Oct 06, 2015, 04:53 pm

Title: Arduino breadboard ADC question!!
Post by: nick321 on Oct 06, 2015, 04:53 pm
I  let my ADC reference voltage=5V

but my analog signal can't reach the 5 volts, it'll cut off the signal about 4.5 volts

but I used the arduino uno the signal  can reach the 5 volts

so  I'm very confused what's wrong with my breadboard arduino????
Title: Re: Arduino breadboard ADC question!!
Post by: septillion on Oct 06, 2015, 06:48 pm
What do you mean, can't reach the 5V? You have to supply the 5V.. Or do you mean you already have a reading of 1023 @ 4,5V? If so, with what do you supply the micro controller? Probably the voltage of that is just 4,5V
Title: Re: Arduino breadboard ADC question!!
Post by: jack wp on Oct 06, 2015, 07:08 pm
Did you use a VOM to test that voltage? Or some kind of script?
The 5v regulators may vary a bit from each other..
Put some caps on the 5v rail, and put a 0.1uf cap on the analog pin.
What are you trying to measure?
Title: Re: Arduino breadboard ADC question!!
Post by: nick321 on Oct 06, 2015, 07:27 pm
YES, I already used the VOM to measure the VDD and GND it's 5 volts

I am measure the sensor signal and I just amplify the siganl and  through the low pass filter, I'm thinking is there any possible about impedance matching..........I'm not sure
Title: Re: Arduino breadboard ADC question!!
Post by: septillion on Oct 06, 2015, 08:37 pm
Please answer all the questions...
Title: Re: Arduino breadboard ADC question!!
Post by: DVDdoug on Oct 06, 2015, 09:44 pm
Is it a problem if it won't go to 5V?    Is it supposed to go to 5V?

Quote
I am measure the sensor signal and I just amplify the siganl and  through the low pass filter, I'm thinking is there any possible about impedance matching..........I'm not sure
We need to see your schematic.

We don't know anything about your signal, your amplifier, or your low-pass filter.

If your amplifier and/or low-pass filter uses an op-amp, and the op-amp is powered from 5V, you can't usually get the full supply voltage from an op-amp.   Similarly, the output of an op-amp generally won't go the negative supply, or it won't go all the way down to ground if there's no negative supply.
Title: Re: Arduino breadboard ADC question!!
Post by: jack wp on Oct 06, 2015, 11:18 pm
What does your VOM read on the analog pin?
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 07, 2015, 05:34 am
This is nonsense.
Please state what you are measuring .
Your analog signal does NOT need to "reach" 5V . 5V is simply the FULL SCALE voltage. The ADC can measure anything from 5 mV to 5V. Obviously you have a misunderstanding about ADCs and how to use them. Start by explaining


Quote
I am measure the sensor signal and I just amplify the siganl and  through the low pass filter, I'm thinking is there any possible about impedance matching..........I'm not sure 
First of all, the only way to AMPLIFY a sensor signal is add an AMPLIFIER. The fact that you are not aware of that means you need to start at ground zero. An LPF (Low Pass Filter ) does NOT amplify. It Filters (out)  (duh) high frequencies. If it was a high pass filter it would filter (out)  low frequecies.

1- what is the sensor ?
2- do you have a clue how to make an amplifier ?
3-how much electronics experience do you have ?
Do you have a DMM (Digital Multi-Meter) (NOT VOM) ?
Title: Re: Arduino breadboard ADC question!!
Post by: nick321 on Oct 07, 2015, 09:56 am
1. it's a Piezoelectric film  sensor
2. I just used the charge amplifier+Sallen key lowpass filter=band pass
I add the DC offset 2.5V

and I already used oscilloscope to measure my analog signal

and my signal just look like a sine wave

I think I need to measure the AC signal from analog inputs
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 07, 2015, 10:02 am
We need to see the schematic of the circuit.
What charge amplifier ? What's your gain ?

Do you know the difference between ac and dc ?
If so, then what's your problem ?
If you know anything about electronics then you know you havd to tell us the frequency, amplitude, and voltage range of the ADC input signal.
Title: Re: Arduino breadboard ADC question!!
Post by: liuzengqiang on Oct 07, 2015, 04:56 pm
If you believe your signal is 5V but arduino only says 4.5V, can you use a multimeter or scope together with arduino and see if you still have the discrepancy.
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 07, 2015, 06:04 pm
Quote
If you believe your signal is 5V but arduino only says 4.5V, 
More importantly, why do you care that the voltage is only 4.5 V if it is a sensor value ? You didn't post a schematic and you didn't answer the question about how you amplified it or the gain.
Title: Re: Arduino breadboard ADC question!!
Post by: liuzengqiang on Oct 07, 2015, 06:07 pm
More importantly, why do you care that the voltage is only 4.5 V if it is a sensor value ? You didn't post a schematic and you didn't answer the question about how you amplified it or the gain.
Because OP thinks he should get 5V. If that's the issue, use both measurements and confirm it.
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 07, 2015, 06:17 pm
Quote
Because OP thinks he should get 5V. If that's the issue, use both measurements and confirm it.
I'm not suggesting he shouldn't get 5V but he hasn't explained why he thinks he should get 5V from an analog sensor. He never said it was a digital sensor and the fact that he's trying to read it with an analog input means he thinks it's analog. Have you ever run across and ANALOG sensor that outputs 5V ? Doesn't that strike you as odd ?
Title: Re: Arduino breadboard ADC question!!
Post by: liuzengqiang on Oct 07, 2015, 06:21 pm
Nothing is clear about what OP is doing so let's just hope he comes back.
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 07, 2015, 08:58 pm
Is it really necessary to spew venom on every new member?
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 07, 2015, 09:02 pm
I would hardly call that venom but I deleted the comment anyway. Jeez louise, if they can't take a little teasing ... It's not like I insulted him. This process is very simple. They post , we ask questions. (like how much electronics experience do you have?) You of all people know why we would need to know that . It saves us posting technical information that is over the OP's head. It accomplishes nothing to post a detailed technical comment if the OP has never read a datasheet. We spend our time trying to help them . The least they can do is be honest and forthcoming enough to give us a good SITREP as to their background and their project, what they have done so far in an effort to resolve their problem. If we know their background and what they've tried, we are more equipped to guide them.  Why do we have to struggle with incomplete posts that tell us nothing ? If we recommend something , we expect them to at least try it instead of telling us "I don't think it would work because blah blah blah (that coming from someone with no electronics experience)
Accusing me of spewing venom because I said "This little piggy.. " is completely unfair. A response like  "Give him a break. He's a Newbie..." or "Lighten up on the OP eh ?" would be more appropriate. Reciting children's stories is hardly spewing venom. Your response was disproportional. I have never spewed venom here on the forum. If I say something it's because I call it like I see it. It's not my problem if they can't handle the truth. We expect the truth , the whole truth and nothing but the truth from the OP and the OP should expect the truth , the whole truth and nothing but the truth from us. We aren't here to coddle them. We are experts and we should say what we think based on our experience.  I won't even get into the "have you tried google ?" thing because you know that get's old.
Read this entire thread. Virtually every reply is requesting more information (which is never supplied). The OP disappeared before I even made the comment you responded to . This whole thread was a waste of time. I think my comment was appropriate when the OP disappeared. We could have been helping someone else.
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 07, 2015, 11:57 pm
After your recent snarky posts, you are tone policing -me-?
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 08, 2015, 12:51 am
No. I wouldn't do that . I'm just saying you were too harsh on me.
Title: Re: Arduino breadboard ADC question!!
Post by: liuzengqiang on Oct 08, 2015, 03:36 am
Something in our water is making us think raschemmel is too mean! I, for one, drank said water yesterday and was told by said member that I was too sensitive. I'm going to change my brita filter tonight and try again later.
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 08, 2015, 04:14 am
ha ha ha... I get it.   ;D
Title: Re: Arduino breadboard ADC question!!
Post by: liuzengqiang on Oct 08, 2015, 05:04 pm
ha ha ha... I get it.   ;D
After changing the filter, I think I'm back to myself again ;D
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 08, 2015, 06:25 pm
No. I wouldn't do that . I'm just saying you were too harsh on me.
So... you are saying that exact choice of words matters?

 :)
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 09, 2015, 04:07 pm
If you choose words like "venom" , which suggests viciousness , yes. My posts are not "vicous" . I was polite in the sense that I didn't insult the OP directly.  Why you would choose such an inappropriate word escapes me.  Obviously the exact choice of words matters. You equate "rude" with "venom", an association that could only apply if I had insulted the OP directly in a very harsh tone. Why don't you quote whatever comment I made that you feel warrants the use of the word "venom" to support your choice of words . It appears some posts have been deleted. I think I deleted the comment the post just prior to your post but as I said before , quoting a children's story , while sarcastic,  could hardly be characterized as venomous. While "teasing" is not professional behavior, it is not "venomous".  I will admit, I should have been nicer. My bad. I feel that any issue , be it the something the OP said or didn't say or something a member said or didn't say should be addressed and sorted out for other members to gain a better understanding of how things work here. You were correct to admonish me , although I think you went overboard. I was correct to  tell the OP what he needs to tell us though it seems I went overboard. All of these issues need to be resolved for others to learn. We all make mistakes but we should learn from them and move on.
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 09, 2015, 05:16 pm
Wow. Chill. I think you are reading a lot more into this.
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 09, 2015, 05:34 pm
Hyperbole (http://dictionary.reference.com/browse/hyperbole)
Title: Re: Arduino breadboard ADC question!!
Post by: raschemmel on Oct 09, 2015, 06:07 pm
Enough said then.
Title: Re: Arduino breadboard ADC question!!
Post by: polymorph on Oct 09, 2015, 06:53 pm
 :smiley-lol: