I created this attiny85 battery tester but it is showing the wrong voltage on new batteries. It should show 1.5V but it is showing over 2.5V. The battery tester has an OLED and and RGB LED to display the voltages. The main issue is the OLED display showing the wrong voltage. Here is the code #i…

Which core are you compiling with? Which physical pin # are you connecting the battery to on the ATtiny85?

Are the Nano and the Attiny getting the same VCC? e.g. if you power the Attiny85 from a lower voltage the analogread will show a higher value.

The attiny85 is powered by a 3V battery, pin4 is ground and pin 8 is VCC. The arduino is connected to the computer. Is this the part of the code that needs changing? voltage = 0.0048*analogValue;

voltage = 0.0048*analogValue; can also be written as voltage = 5.0 * analogValue / 1023.0; // (or 1024.0 depending on your POV) The 5.0 is for 5V operation. For 3.3V operation the equation should be voltage = 3.3 * analogValue / 1023.0; // (or 1024.0 depending on your POV)

[image] hmeijdam: from a lower voltage the analogread will show a higher value. Is the use of Vref a valid way to avoid this?

Yes, as long as you can ensure that the voltage to be measured is below the 2.56 Volt of the internal voltage reference. The internal voltage reference requires a VCC of minimum 3 volts. So your 3Volt battery is the absolute minimum. [image] O, and you still need to adjust the calculation like @v…

1.1volt Aref is a safer option. Then 3volt VCC is not a problem any more. When using 1.1volt Aref, battery voltage that you measure must then be reduced to ~1volt with a voltage divider. Say 10k from pin to ground and 4k7 between pin and (for a 1.5volt) battery. That is not a bad thing, because yo…

I measured 3.3V of NANO by PC-connected NANO and have found 3.3V on the Serial Monitor. I have measured the 3.3V of NANO using PC-connected Digispark ATtiny85 Dev Board, and I have found 3.1V -3.2V on the OLED Monitor. If yo are are operating ATtiny85 by VCC = 3V, then you have to make a two-point…

Changing the voltage from 3.3V to 2.38V worked! voltage = 2.38 * analogValue / 1024.0; This comes to within 0.01-0.04V accuracy in 1.5V batteries. Is there a way to change the code for it to read 3.0V and 9V batteries? This code reads a new 3.0V battery as 2.37V. It also reads a 9V battery as 2…

[image] spiderman288888: Is there a way to change the code for it to read 3.0V and 9V batteries? Voltage dividers on the battery are needed when battery voltage exceeds Aref. If you don't, then the A/D will just peg at it's highest value of 1023, which will display 2.37volt with your current …

Attiny85 battery tester shows wrong reading

Projects Programming

Topic		Replies	Views
ATTiny85 reference voltage changing with Vcc? 3rd Party Boards	19	1418	July 24, 2024
atTiny85 internal Vcc analog voltage reference 3rd Party Boards	28	604	January 24, 2026
getting a reading from OLED on attiny85 Programming	5	1548	February 13, 2021
Attiny85 Battery Tester General Guidance	68	2367	June 14, 2023
Secret attiny 84 voltmeter General Guidance	26	610	October 22, 2024

Attiny85 battery tester shows wrong reading

Related topics