Resistor Network Finder

Help

How to use

The basic use of this tool is really simple. You list the resistors that you have in the "extra" field (green), and the values that you need in the "target" field. Then press "Search" button to see the suggested networks (you may have to wait a few seconds).

In case if your stock is based on particular series, such as E12, you can specify the series and boundaries, and then (optionally) mention your missing and extra values.

If you can't figure something out, let me know. I'll be glad to help.

Limitations of networking resistors

Usually you can use this tool to design a perfect network for your target resistance, easily getting error of 0.1% or smaller. However this does not guarantee that you'll get the same error when you build the physical network, because the actual resistors you stock may have much larger error.

Limitations of this tool

Network size. This tool finds networks of at most 6 resistors currently.

Number of networks. This tool tries up to 20 million networks per single search, if the server is not under much load. (Under load the number is smaller).

Additional values. This tool can find the most useful additional (non-stocked) resistor, depending on your target and search options. Ideally you'd like to search for an optimal set of multiple additional values, but for now the tool finds only only single such value. Also, with additional values the maximum network size is 4 resistors (currently).

Defaults

If you omit the target list, the default list of E192 values will be used as target.

If you omit the stock, the default stock of E6 values from 1 Ohm to 1 MOhm will be assumed.

If you specify the series, but not the range ("From" and "To" fields), it assumes 1 Ohm to 1 MOhm range.

FAQ

Q: What is E3, E6, etc?
A: These correspond to series of standard values. E3 includes 1, 2.2, 4.7, 10, 22, 47, 100, etc. In other words, it spans each decade in 3 steps. The other series are similar, but have way more values in each decade. Read more in Wikipedia.

Q: What is "bases"?
A: The values that you have in each decade, in other words, multiplied by 10N for a range of N.

Q: E6 resistors have 20% tolerance. How on Earth can I build any remotely accurate network out of them?
A: You probably can't (at least not easily). However you can use resistors with E6 nominal values and 1% tolerance (or even 0.1%). Such resistors are available and popular. Historically the E series were defined to have particular tolerances (E6: 20% error, E12: 10% error, etc). Nowadays however the meaning of E series is usually limited to just nominal values, and the tolerance is mentioned explicitly, when necessary.

Also note that this tool assumes ideal spot-on accurate resistors, while finding the best network. When you build the physical version of such network, its accuracy will depend on tolarances of the actual resistors you used (and luck). It's up to you to choose appropriately accurate resistors for your network, and to measure the network before using it.

Q: I specified maximum network size of 6, but the tool only searched until size 3. Why?
A1: Perhaps the tool already found close enough approximations for all your targets. The meaning of "close enough" is specified by you in the "Target error" field of the search form. If you'd like the tool to keep searching, set "Target error" to 0.
A2: The tool realized that the number of possible networks is getting too large, and decided to stop there. If you're sure that you need an enormous search, contact me. We can discuss it and may be try it offline.
A3: May be the server is busy (in this case there will be a warning at the top of the page). In this case you can simply try again later.

Q: The tool searched till network size 5, but shows only 2-resistor network for my target. I know a closer match with larger network - why is it not shown?
A: The tool shows the simplest network that meets the target error spec. Try setting target error to 0 in order to find the closest network possible.

Q: <100 | 1k - 220 - 1k | 100> - what the heck is this network?
A: It's a bridge. You can click on it to see the schematic.