# Parallel Resistor Calculator - the other way round...

#### hotheatsink

Joined Sep 22, 2011
3
Hi, I've made a tool which I thought might be useful for people who play with, work with, or generally mess around with electronics.

Basically, it works out combinations of two resistors which, when in parallel, give any resistance you specify (or as close as possible to it). You can specify which E Series the resistors may be selected from too. The table of results also includes the current through each of the two resistors, if you choose to specify the total current.

I used to need to work out this sort of thing at work, and found the tool pretty useful. Have a play, and see if you have a use for it...

Here it is: http://tools.hothotfire.com/parallel_calculator

Enjoy.

#### SgtWookie

Joined Jul 17, 2007
22,230
That's useful - how about adding series resistor calculations to it as well?

#### hotheatsink

Joined Sep 22, 2011
3
Thanks, I could look at adding a similar series version. I hadn't really considered it before though as, firstly, it is generally a lot easier to visualise and calculate series combinations mentally (I find). And secondly, series combinations don't lend themselves to hitting target values so well.

I guess the nature of the PCBs I used to work on also meant that parallel combinations were a preferable option. In that when working with surface mount components, it's really easy to piggy-back two resistors, whereas adding a second in series would often mean cutting tracks etc.

I'll look into it though, it can only be simpler than the parallel version...

#### SgtWookie

Joined Jul 17, 2007
22,230
Have a look at this one:
http://www.qsl.net/in3otd/parallr.html

I'd been using it for awhile, but noted that it was missing a number of combinations.

So, I threw together a more brute-force approach in a Basic program, just to keep it simple.

#### hotheatsink

Joined Sep 22, 2011
3
Ah, yes, I see - it combines both serial and parallel in the same results set. Yes, I could easily incorporate something like that.

I remember I tried searching for something like it before I made it, but couldn't find anything really. I think that might just be because it's difficult to know what to search for though - obviously "parallel resistor calculator" just swamps you with the "normal" kind.

Brute force is the order of the day here too, currently. The algorithm isn't very intelligent! (Hence the rather long processing times on higher series! haha)