Is there a tool for optimal design of multiple-output voltage divider? - Page 1
Forum section: electronics / projects

author: hanakp
author_rank: Regular Contributor
timestamp: July 22, 2022, 04:05:38 pm
content: There are lots of tools that allow you to design normal (single-output) resistor voltage dividers. My favorites are tools that calculate several iterations from the existing E12-E96 series values and then you can select the closest one:https://jansson.us/resistors.htmlhttps://www.qsl.net/in3otd/parallr.htmlBut is there a similar tool (online or offline) for optimal design of multiple-output voltage divider? Specifically, I need 3-output divider (4 resistors).Now when I think about it, does anyone even make a desktop program for these basic analog electronics calculations? Something like Saturn PCB Toolkit, but for circuit design? I've seen (and used) programs for designing filters, SMPS or VCOs, but when it comes to the basic stuff, I'm still using scripts in MS Excel...

author: ataradov
author_rank: Super Contributor
timestamp: July 22, 2022, 05:13:03 pm
content: I needed this recently. I just created a Python script (attached) that just checks all possible combinations using E12 or E24 series values. It is dumb and not optimal, but who cares? It took 10 minutes to make the script, a few seconds for it to run. And I moved on with the project.The script prints a bunch of closest matches and you can pick whatever values of resistors you like the most.From that perspective Python or any other scripting language is the best tool, as it is the most flexible and you don't need to think though all the scenarios in advance, you can just code whatever you need on the spot.

author: Benta
author_rank: Super Contributor
timestamp: July 22, 2022, 06:24:21 pm
content: One problem is, that you mostly need multiple resistors per leg. This is due to the fact, that the relationship between values doesn't really change when you scale them (it's exponential).The best thing to do is an ideal-value calculation, and then select appropriate parallel resistors for the ones that are outside the E-series (using a higher value and trimming with a parallel resistor).The ideal values are trivial to find, I can do that in one minute with my trusty HP-15C.

author: ataradov
author_rank: Super Contributor
timestamp: July 22, 2022, 06:35:31 pm
content: I would not say that you "mostly" need multiple resistors. In my case, for example, I was just setting comparator levels and the standard E12 values got me much closer than I needed. And in my case I specifically preferred more common values rather than absolute accuracy.

author: Benta
author_rank: Super Contributor
timestamp: July 22, 2022, 07:42:15 pm
content: Everyone has her/his own needs. When I read multiple-level voltage dividers, I think window comparators or multiple output voltage monitoring.And the OP mentioned E96.

author: hanakp
author_rank: Regular Contributor
timestamp: July 22, 2022, 09:40:25 pm
content: Many thanks, it works beautifully! As Benta predicted, many combinations produce exactly the same results, because the E series scales geometrically. But there are also differences, because successive E values are rounded upwards or downwards from the ideal number. I was surprised that even with E24, I found a combination where all 3 output voltages were within 0,1% error.I tried putting in the E96 series to see what would happen... the script ran so slow I had to interrupt it, I estimate it would need around 30 minutes to complete.

author: Benta
author_rank: Super Contributor
timestamp: July 22, 2022, 09:53:16 pm
content: Cool, nice that you solved it.