Hello all,

Does anyone know any tool to compute values for resistor dividers.
I have found this thread but, it seems quite old and outdated.
Resistor Circuits Calculator | All About Circuits

Thanks in advance,
Elisabeth

 

Hello,

Does this page of the text book help?
https://www.allaboutcircuits.com/textbook/direct-current/chpt-6/voltage-divider-circuits/

Bertus

 

http://sim.okawa-denshi.jp/en/teikokeisan.htm

 

If you have an Android phone, look for Electrodoc Pro in the Google Playstore.

It provides all kinds of resources, including resistors in series/parallel, Ohm's law, LED resistor and resistance value calculators. In addition, there are tables of standard resistor and capacitor values, wire resistance, connector pinouts. It's a tool I use often when designing things, answering forum questions and for quick reality checks.

I think the pro version is $5....well worth it.

 

Here's a handy site that computes the optimum standard resistor values for a given desired ratio or voltage reduction.
There are usually many combinations of standard resistor values close to the desired ratio you want, but some are closer to that desired value than others, and this site shows those so you can pick the best.

 

"Old and Outdated " software is one thing that we can thank the microsopht gang for giving us. Software does not normally "break", nor does it "wear out"!! It is forced into obsolescence by those who love to make changes for the sake of making changes, rather than actual improvements.
HOW ELSE would they force folks to replace a product that does not wear out???

 

If you have an iPhone, check out Electronic Toolbox and/or RF Toolbox. I have both apps and they are great references with all sorts of calculators for electronics and RF. They are found on the Apple app store.

kds

 

Here's a handy site that computes the optimum standard resistor values for a given desired ratio or voltage reduction.
There are usually many combinations of standard resistor values close to the desired ratio you want, but some are closer to that desired value than others, and this site shows those so you can pick the best.

That's a great calculator. It's now in my database of useful links. I'm testing it now with some 1% resistors for remote solar voltage sensor for a PIC18 ADC with a 2K source impedance spec.

 

It can be a chore to hunt for the closest nominal resistor value. A common routine of digging through marked envelopes in a shoe box.
Using software to piece together something accurate has merit. Chart shows nominal values available in variety packs.
After getting as close as possible and measuring the actual error then going beyond the standard it is necessary to add small values.
The amount and variety of small value resistors can be a limiting factor. The amount of time spent in locating the part is related to organization.
I don't know of any software that can search and help locate parts. The divider calculator and keep it simple makes sense.

 

That's a great calculator.

Many moons ago I generated a Visual Basic program to do that basic calculation for 1% resistor values, since the manual trial-and-error method for that was very tedious.
Below is a snapshot of the results for one ratio value.

I also did one that calculates the optimum standard 1% resistors for a desired resistance of two parallel resistors.

Amazingly I've transferred those programs through many versions of Windows, and they still work.

 

This is my "goto" for voltage divider calculations. Runs locally on a Windows computer.

Copy/paste the resistors.stl file where you want it. Change the .stl extension to .exe (AAC does not allow .exe files to upload). There is no installation involved; just paste it wherever and it should run directly under Windows once you change the extension.
The original "Resistors.exe" executable is on the internet, somewhere, just very hard to find!

Screenshot attached: you type in 3 of the 4 variables and the program solves for the unknown. I've used this for many years, has some quite useful features.

 

http://sim.okawa-denshi.jp/en/teikokeisan.htm
is the only one I've found that can optimise a 2-tap voltage divider.
With a little thought, you can use it to optimise any situation where you have three resistors and know the ratios, like a comparator relaxation oscillator.

 

Oh! Thank you all. Such a great community here.
The @crutschow site is exactly what I was asking for.
I have meanwhile also found wizeia.com, which I found a bit more complete and easy to use.
Regarding other options, I prefer not to download more software.
@Ian0 link was not working for me.

All the Best to you all,
Elisabeth

 

Oh! Thank you all. Such a great community here.
The @crutschow site is exactly what I was asking for.
I have meanwhile also found wizeia.com, which I found a bit more complete and easy to use.
Regarding other options, I prefer not to download more software.
@Ian0 link was not working for me.

All the Best to you all,
Elisabeth

Here it is again, just in case it didn't copy correctly:
http://sim.okawa-denshi.jp/en/

 

Here it is again, just in case it didn't copy correctly:
http://sim.okawa-denshi.jp/en/

Thanks @Ian0. The Okawa site is really good. I love the filter design page, especially when combined with https://wizeia.com/ to find the best resistor and capacitor values.