Arduino Tutorial: Using external voltage reference

This tutorial describes how to use an external precision voltage reference (LM431) for the ADC on the Arduino to increase accuracy of analog readings.

[hansdegroot]

thank you very much for this very clearly explained video in English! i havethe parts but never knew how to use it.

[Tirdad]

Thank you so much for sharing this. It is absolutely helpful.

[bigheat]

thank you so much. had some struggle with this topic (because you cant change the analogReference voltage MULTIPLE TIMES within the code, without doing some IMHO dirty tricks).

[snnwstt]

Nice, EXCEPT for the computation of the values for the resistance... those are magic numbers: "That makes 90 ohms, but for R1, we generally took 1k... " and for R2, it is even more dramatic " It is a minimum of 1 mA, ... and here it is 2.5 V, so... for R1 I used 1K and 2.2K for R2". That is NOT a computation.

But for the other parts of the video, felicitations. I assume that you used some reference to an external 9V battery (in your computation) just for demo, since you could use the 5V (+/-) from the Arduino board to supply a voltage to the TL431, in practice, without any modification in the code... is it not.

[johnSmith-zren]

Has anyone here successfully got the LM431 working for what Ashutosh was showing in his video? He says (and I believe him) he has connected a battery to the circuit and its battery voltage is showing on the serial monitor (which shows clearly in the video) but it's a mystery to me as to how he's connecting the battery unless I'm missing something real obvious. He's not showing a schematics to show how its hooked up? And if you look at his so called schematics (which he admits is bad) in the video and wire it up accordingly, it displays the numbers 2516 and 1023 on the video monitor regardless if the the wire coming off the the cathode going to pin A0 is connected or NOT. I don't understand what's going on. Can anyone here explain to me how this works? I would really appreciate any help anyone can provide.
Thanks
jessey

[WoodmanFFM]

What you're saying about incorrect reading is true if and only if the Arduino is NOT fed from the same source as the rest of the circuit.
And even then, it would make more sense to derive the AREF voltage directly from the Vcc of the external circuit - because who knows if your external circuit's Vcc might droop under load like the regulator on the Arduino does?

I.e. if you feed your Arduino and your circuit from an external 5V source there is no need for a voltage reference.
Also if your external circuit is fed from the Arduino board there is no need for an external voltage reference either.

Please be more accurate in describing the exact setting in which using a voltage reference makes sense.
You make people think they just need to use a voltage reference and will then receive correct analog readings - and this is simply not true.

[hacker]

it would be better if you show stability for a minute.

[suryavoid]

If the Rs is 90 ohm why are we using 1kohm which is very great than what we got

[PaulWheelerjr]

Arduino noob here, so If I want to measure 0-10V or 0-5V on A0 would the AREF voltage need to be 10 or 5V ? or does it not matter as long as its constant?

[mubashirshafie]

after all you used a maped function....this is campared function not a measuring method
sir..

[AmitIka]

Why is the voltage reading alternating between ~1300 and ~500?