Problems connecting a CX101BG

[jimmym]

I just bought 2 of these LCD panel meters. CX101BG (For common ground). They're BOTH wildly inaccurate.
I have the inputs connected per this post. https://www.edaboard.com/threads/123247/ Post #4 (I've attached the schematic from that post)

I have mine configured using a divide by 10 divider (1M & 100K). 1.86Vin (before divider) = .171V (after)(tolerances, etc) at the CX101 inputs. Voltage measurements taken with a Fluke 189. I have the decimal point in the first position so the display should read 1.710V. But I can't get anywhere near that. It reads 1.008V. Even if I turn the trim pot on the back of the CX101, it doesn't even get close. Am I missing something?

 

[kak111]

You should try wiring like this......................



https://www.circuitspecialists.com/images/cx101bg.pdf

KAK

 

[jimmym]

You should try wiring like this......................

**broken link removed**

https://www.circuitspecialists.com/images/cx101bg.pdf

KAK

OK. I dialed back the pot on my board to get .172V and the display now shows 1.722V Muuuch better.
Let me mess around with a divider now.

---------- Post added at 11:40 ---------- Previous post was at 10:55 ----------

OK. Now I have a divide by 10 divider grouded at pin 6 (INLO) and the meter displays as expected.
Thanks.

 

[iface]

OK. Now I have a divide by 10 divider grouded at pin 6 (INLO) and the meter displays as expected.
Thanks.

Greetings,

I'm a very newbie with electronics, trying to learn, still confused with some concepts ;-)

I'm trying to work with almost the same Led Display (mine CX101B), and thanks to this thread I could connect a Temperature sensor TMP36gz to it. Thanks!!

Now it shows a number, that is more less stable, and increases/decreases with the temperature rise/descend in the tmp36. Cool, exciting stuff :smile:

My problem is that division, how to get the right temperature value in the display. If I don't put any resistor in the circuit, I get a value of around 1090, when my temperature sensor is at around 0.71V (around 21°C). If I put a couple of resistors, like they show in the display datasheet*, I get a value of 33, which is quite close to what I want, but does not seem to work because the value is way too stable: it does not change at all when I heat or cool the tmp36. I tried with different resistor values and combinations, but the result is more less the same.

Could anyone help me? I'm a bit lost now... :roll:

* Datasheets
display: https://www.mpja.com/download/cx101b.pdf
tmp36: https://www.ladyada.net/learn/sensors/tmp36.html

 

[Riser]

My problem is that division, how to get the right temperature value in the display. If I don't put any resistor in the circuit, I get a value of around 1090, when my temperature sensor is at around 0.71V (around 21°C). If I put a couple of resistors, like they show in the display datasheet*, I get a value of 33, which is quite close to what I want, but does not seem to work because the value is way too stable: it does not change at all when I heat or cool the tmp36. I tried with different resistor values and combinations, but the result is more less the same.

You really have to look at 2 different issues. The panel is limited to 200mV so you need to insert a divider (10 is a very convenient number) so that the panel can display the range you need. You can build that as decribed above, test it and set it aside. Look at the datasheet for the TMP36: (https://www.analog.com/static/imported-files/data_sheets/TMP35_36_37.pdf), you'll see that the TMP36 outputs 750mV at 25C. This means that there is an offset of .5V that you need to take care of.
In other words to get your temperature from the reading:
Temp in °C = [(Vout in mV) - 500] / 10

As per the datasheet you should also include a bypass capacitor otherwise you might get wrong readings.