Is the original circuit wrong?
"do what I tell you to do and just shut up, I know what I'm talking about while you don't".
I'm going to provide supply from Arduino +5V
and bias from an Arduino digital pin,
I haven't powered the circuit yet as I've done no calculation on current draw and I wish to avoid to burn out the Uno: is there anything wrong on my wiring?
ALL op amps need a split supply.
Voltage is relative, in the circuit I posted this effect of the split supply is provided by input biasing by producing a virtual ground. What is important is the minimum voltage required to drive the amplifier, in the case of the TL082 this is =/- 5V. Down doad the data sheet of this amplifier.
The other thing is how close the output can get to the rail, in the case of this amplifier it is not very good. Figure 10 in the data sheet shows you this. However it only shows this for a 30V supply ( +/- 15V ) and the output can not get within 2.5V of the rail at best with a 1K load. If the output could reach up to and down to the power supply this would be called a rail to rail amplifier.
Basically it is the wrong amplifier for the job you want it to do.
QuoteMay I ask you which IC would you suggest for my case?I would use a MCP602 it will work happily off +/- 2.5V which means you can simply power it from 5V and generate the virtual ground with resistors.
May I ask you which IC would you suggest for my case?
Biasing is the act of adding a fixed DC voltage to a signal. it applies to either inputs or outputs and there are various ways of doing it.
Quote(is it correct to say ground biasing?)No.
(is it correct to say ground biasing?)
QuoteI'm not debating your suggestions You are doing a good job at pretending to then.
I'm not debating your suggestions
Quotebecause I'm unable to apply them unless I understand themYou seem to be happy to implement the circuit you keep posting and you don't understand that.
because I'm unable to apply them unless I understand them
Quoteyou gave me a diagram for an inverting amplifier with a grounded negative supply, which I already tried and it appeared non working for a TL082.Then you must have done something else wrong then.
you gave me a diagram for an inverting amplifier with a grounded negative supply, which I already tried and it appeared non working for a TL082.
Quote from: rlogiacco on Oct 27, 2013, 12:38 amIs the original circuit wrong? The one from openmusiclabs ?
Quote from: rlogiacco on Oct 27, 2013, 12:38 am "do what I tell you to do and just shut up, I know what I'm talking about while you don't".I didn't tell you to "shut up". The part about "just doing what you're told" was in quotes, to take the sting out.You might want to consider just playing along - for the present.
Quote from: rlogiacco on Oct 27, 2013, 12:38 amand bias from an Arduino digital pin, Why? What's wrong with "+5V"?
Quote from: rlogiacco on Oct 27, 2013, 12:38 amI haven't powered the circuit yet as I've done no calculation on current draw and I wish to avoid to burn out the Uno: is there anything wrong on my wiring?Why do you have to re-render the schematic as a 2600x3300 PNG (huge)?Why can't you edit the smaller drawing, if you must change values, etc, and make it easier on everyone [everyone else]?
How will you know if the circuit works?
Are my calculations wrong?
That 10R though will produce a 500mA load on my Uno power,
Figure 10 reports 5V output for 6V supply....
but I had already bought it (5€ at the local store!)
QuoteAre my calculations wrong?Yes about as wrong as it is possible to be. It shows that you understand even less than I thought you did.
QuoteThat 10R though will produce a 500mA load on my Uno power,Only if the other end is connected to ground not the power input to an amplifier.
QuoteFigure 10 reports 5V output for 6V supply....No it does not. Not even close. Figure 10 is the output swing you will get under different values of load on the amplifier's output. This graph only applies when you have a power supply of +15 and -15 volts.
The data sheet shows that the MINIMUM supply voltage is +5V and -5V so you can not run this amplifier directly from the 5V of the arduino because that will only give you +/- 2.5V half the minimum value you need.
That circuit you posted.1) Why post an SVG file these are hard to view.2) The file again is a massive picture - you have been told about this quite a few times. Now it is verging either on stupidity or malicious.3) The circuit is total CRAP
You have to decide if :-1) You want to stick to this amplifier and power it off 12Vor2) You want to use a more modern amplifier and power it off the 5V from the arduino.
Tell me what and I will post a diagram you can use.
Quotebut I had already bought it (5€ at the local store!)Sorry but you have been totally ripped off.
With regard to the Instructables - he's using two batteries (a TRUE split/double-ended supply); it is different.
The 10? resistor, with the "preferred" circuit, is part of a filter.I don't want to debate its merit/s, but if you were to omit it the world would not end.
With regard to SPICE etc: - on a certain level, "an op-amp is an op-amp is an op-amp."
In any event, please understand that the op-amp's output (level) cannot be greater than its supply.With a 5V supply there's no risk of overloading anything.If you had/have a "non-Arduino" 5V source/supply, you could relax [a little (: ].
For "true gain", if I may call it that, I would use a pot/rheostat in place of the "100K" between the output and the non-inv input)If we stay, basically, with the "preferred" circuit, the only modification I would make would be with regard to the output (lose the pot and place there a diode with its anode to Gnd - that may seem backward but it is "dc restoration").
If you had an oscilloscope then we could all breathe again. (:[/b}
Quote from: Runaway Pancake on Oct 27, 2013, 02:13 amWith regard to the Instructables - he's using two batteries (a TRUE split/double-ended supply); it is different.Ok.... I don't get why though... Can you point me to something that explains why using two separate batteries is different from using a single supply with a voltage divider?
problem is I can't operate a TL082 from Arduino's voltage supply as it appears Mike and me have finally agreed.
1) What's hard to view in an SVG file? Double click and it opens up in the browser.
Quote from: Grumpy_Mike on Today at 09:30:05 amQuoteAre my calculations wrong?Yes about as wrong as it is possible to be. It shows that you understand even less than I thought you did.And in which way this should help me understand where I was wrong?
I admitted my ignorance on op-amps.
but I'm here to learn and understand.
Is it possible we are looking at two different datasheets?
As promised here is a diagram of what you need. It contains nothing you have not been told about before but it puts it into one diagram.
Could you please go back to your original post and Modify it to include the "design objective"?I'm sorry, but after so many posts, I think we've nearly lost the plot (that's not an indictment or a nasty aside - it's in the interest of clarity).
Mike,Is that diode between "A0" and Gnd the right way round?
Things you have to know are1) Ohms law2) How currents flow through circuits3) Basic electricityNow you might think you know these things but you don't. And you never will if you persist with your attitude.QuoteI admitted my ignorance on op-amps.And basic electricity. The things you are misunderstanding are not specific to op-amps but apply to the whole of electronics.
Quotebut I'm here to learn and understand.If only that were true we would all have a happier time. What you want is for some one to explain exactly why you have these ideas in your head that we are all saying are wrong. You want to know exactly why they are wrong - but in order to do this we need to be a mind reader or to be able to find out and understand the whole of your internal model for electronics. And then correct that. Sorry that is not going to happen it is just impossible.The way to learn is to look at and study correct circuits. If there is something you don't understand about these correct circuits then you can ask and it will be explained to you.
I have no idea why you thought that by connecting a 10R resistor in series with your OP- amp's would give you a 500mA load on your arduino. It is so far divorced from reality as to be totally incomprehensible. Therefore I can't explain what you are doing wrong except to say everything. Or would you like me to speculate on the three thousand you could have miscomprehended?
QuoteIs it possible we are looking at two different datasheets? Yes we were. I was looking at the one:- SNOSBW5C -APRIL 1998-REVISED APRIL 2013No idea what one you were looking at because the link you provided did not point to a data sheet but just to the TI web site, therefore there is no way of knowing what one you were looking at.
How much do I get for the electronics basics test?
1) I = V/R
V = I*Z
2) Current always flows through the easiest path:
3) Like the atom structure,
Source was basic Ohm's law: 5V through a 10R resistor imply a 500mA current.
f the op-amp impedence was going to be very low
Doesn't it say the TL082 will not work with less than +/-4V?
when I got complaints about attachments of a few hundred KB.
1) diodes D0 and D1 are there to protect arduino against inverse voltage, right?
2) what is the purpose of C2?
3) The op amp is biased at 6V
thus it's output will swing between 0-10V (considering the datasheet), right?
4) C1 is there to smooth the input line,
is C4 there to smooth the output?
5) is C4 R6 an high pass filter?
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