Go Down

Topic: Wemos A0 does not read voltage (Read 840 times) previous topic - next topic

westfw

Quote
I also thought I remembered seeing rt9013 regulators on Wemos mini schematics.
Aren't the WeMos boards about as heavily cloned as Arduino Nanos ?  The official schematics could easily say one thing, while random clones have some other regulator that the vendor just happened to have on hand...

PaulRB

Quote
So the situation where im in now is not ok? Using a 100k resistor between the + and the A0.
100K is good. I use 180K which gives a slightly higher range of voltages that can be read.  But 100K should work well. If the ADC on the chip is working, perhaps the voltage divider or the PCB tracks are faulty on the Wemos board.

Did you try that pot yet?

PaulRB

#17
May 21, 2018, 08:13 am Last Edit: May 21, 2018, 08:17 am by PaulRB
Aren't the WeMos boards about as heavily cloned as Arduino Nanos ? 
True. Certainly for the Mini. I've not heard reports of clones of the Mini Pro, but I guess there probably are.

@srozemuller, can you post the link where you purchased the mini Pro? The only place I know for sure you can get genuine Wemos is the Wemos shop on AliExpress. There is a link to that on the Wemos site.

srozemuller

#18
May 21, 2018, 08:25 am Last Edit: May 21, 2018, 04:40 pm by srozemuller
Hello Paul, no i dont have a pot to test with.
I've purchased the Wemos at Ali indeed.

link to wemos

PaulRB


wvmarle

I don't think they ever used ams1117, unless that was the D1 or D1R2 (the Uno size boards).

Maybe you were thinking of the nodeMcu boards?
No, had a quick look at some forums, maybe mixed up the different types of WeMOS boards.
NodeMCU indeed also uses the AMS1117, great advantage being that you can supply it with 12V. The RT9013 can't handle that voltage.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

srozemuller

So i have to calculate +1.1 v at the vcc?

PaulRB

Hello Paul, no i dont have a pot to test with.
Then just use two resistors of the same value. One from A0 to GND and the other from A0 to 3.3V. You should get a reading of around 500 from analogRead().

I've purchased the Wemos at Ali indeed.
Ali is a market place, like eBay or Amazon. Many vendors sell similar items and many of them are clones. Your link is to an item that is not in the Wemos shop, so it could be a clone. To find the genuine Wemos parts, you should go to the page for the Pro Mini on Wemos' website and click the "Buy" button. The Wemos shop is called "LO_LIN". Your link has a different vendor name.


PaulRB

#23
May 21, 2018, 08:23 pm Last Edit: May 21, 2018, 08:27 pm by PaulRB
AMS1117, great advantage being that you can supply it with 12V. The RT9013 can't handle that voltage.
True, but the ams1117 has a droput voltage of 1.1V and quiescent current of 5mA, making it a lousy choice for small battery powered circuits. By comparison, the Wemos' me6211 regulator had a dropout of only 0.25V and a quiescent of only 40uA.

PaulRB


srozemuller

Well, because of the different regulators on the wemos and the droputs. Can i make the conclusion my Wemos is using the old ams1117 with a droput of 1.1V?

wvmarle

The built-in measurement will measure Vcc, not the actual battery voltage. The two are not necessarily the same - and generally are not when there's a regulator in play.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

srozemuller

After some investigation on the forum this thread came on the radar.

there i found this part

Quote
You are measuring the output of the 3.3V regulator on the Wemos, so you get answer of 3.3V. Use the A0 pin with a 180K resistor connected to the 5V pin. The Wemos has a voltage divider on the board which allows voltages up to around 3.3V to be measured. The 180K will extend this to around 4.7V.
it seems i have a mistake in the wiring. Instead of connecting the 100k resistor directly to the battery it have to be connected on the 5v on the Wemos. For now i did some quick test and voila there where some 1024 results. So it seems the A0 is working properly.

Now doing some solder work, will keep you posted.

PaulRB

Quote
Instead of connecting the 100k resistor directly to the battery it have to be connected on the 5v on the Wemos. For now i did some quick test and voila there where some 1024 results. So it seems the A0 is working properly.
I can't understand what you mean, and it doesn't sound like the reason for the problem to me. Can you post a schematic showing how you had the 100K connected before, and a schematic showing how you have it connected now?

wvmarle

To get a reading of 1023 (you shouldn't see 1024 at all) you can also connect the A0 directly to the 3.3V.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

Go Up