0,36",5 Digit DC 0-33.000V Digital Voltmeter Panel Meter

[0xFFF0]

0,36" 5 Digit DC 0-33.000V Digital Voltmeter Panel Meter

https://www.ebay.de/itm/132474589055

Does anyone know if you can change the voltage divider? Found two resistors: 330k and 20k. The division ratio is a bit strange.

[coromonadalix]

not sure if the firmware in them is settled as a maximum of 33volts ...    even if you change the divider  you may get stuck

you have the 3 1/2 digits with intersil 7106 or 7107   lcd  or led  display    1,999 19.99, 199.9 

you have the 4 1/2 digits based on intersil 7135 ddm chipsets,  you can change the decimal point and add a divider  .... 

they display 1,9999, 19.999  199.99  .....

around 20 usd  when i've bought them ... be careful,  you have fakes on ALI ....    it's a dip  ic   not a surface mount in the picture(s)
smd do exist   

but the most i've seen are based on some (top sanded / unknown)   mcu's

[0xFFF0]

All these modules are ST MCU based.

[coromonadalix]

not all of them  if you search and choose wisely ...

took me a while to find the 4 1/2 ones with real dmm ic's

https://www.china-purchaser.com/goods/item/detail/id/21678871866

https://www.china-purchaser.com/goods/item/detail/id/21678871866

or build your self one with arduino like this : https://www.digikey.com/en/maker/projects/how-to-make-a-simple-digital-voltmeter-with-an-arduino/082dff9d725549aea8bf84a7e302c1b2 

and you can adjust the range to your needs ...  an arduino mini / pro  etc ...  well placed behind an 16x1  lcd or serial led display  etc..

[Kleinstein]

There could be other similar modules for different ranges. It would need a change in the divider and the code / cal constants to really show the right result.
AFAIK many of those modules use a MCP3421 ADC with internal ref. and a STM8 µC.
Without an extra buffer it is tricky to use a 10 M divider like with most DMMs. The lower resistance is still OK for power supplies and similar projects.

[floobydust]

There are a few different varieties of these 5 digit panel meters. Usually using either of two types of ADC, check which one you have.
I dislike the sluggish averaging firmware they use to cover up all other cheapness.

[0xFFF0]

There could be other similar modules for different ranges. It would need a change in the divider and the code / cal constants to really show the right result.
AFAIK many of those modules use a MCP3421 ADC with internal ref. and a STM8 µC.
Without an extra buffer it is tricky to use a 10 M divider like with most DMMs. The lower resistance is still OK for power supplies and similar projects.

As a matter of fact. It's an MCP3421. Unfortunately, the differential input Vin- has been connected to digital ground. R1=330k, R2=20k, full range 30.000 equals to 1.7142V

[Vovk_Z]

Does anyone know if you can change the voltage divider? Found two resistors: 330k and 20k. The division ratio is a bit strange.

Yes, you can add several MOhms in series with an input to get e.g. 330.00 V limit. I have done it, just not remember exact additional resistance value at the  moment.
And I cut wire and added additional mosfet (2n7000) to move a decimal point.

[mariush]

Either way, you're limited by the linear regulator used, with maximum voltage of 35v

The one in the ebay link uses MST5333B ... datasheet attached.

The resistors make sense if they use that microchip adc with 2.048v reference.

If you want higher voltage, either change the linear regulator or replace with a switching (buck) regulator and separate from the adc input / voltage divider

[Vovk_Z]

Either way, you're limited by the linear regulator used, with maximum voltage of 35v

Those precision voltmeters usually have separate power input, so power supply voltage range is not connected with measured voltage.