Rombos – A Two Resistor Series/Parallel Combination Calculator

History

- 13 March 2007 : First Edition

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Introduction

Resistors are usually manufactured according to a specific set of resistance values. Two common value sets are the E24 set of values and the E96 set of values. While it is possible to find resistors manufactured to a wider set of values, it may involve a custom order and need a longer lead time.

Placing two resistors in series or parallel using the more common set of values is one way to create a resistance value closer to the desired value.

This program can help in the selection process: by selecting the desired target value, the allowed error in percentage, and the connection type, the program lists the combinations which are within these parameters.

Features

- Series or parallel selection.

- Use E24 or E24+E96 series values.

- Adjustable error allowance 0% to 10%

- Import a list of target values for batch mode use.

- Results are listed in a scrollable window.

- Date and time and software version listed in window.

- Select for copy/paste operations supported.

- Window results can be written to a log file.

- Resistor power is listed for a given voltage.

- A single win32 executable. Does not install or require any libraries or updates.

Screenshot

Figure 1 Rombo Screenshot

Future Work

- more intelligent combination searches, especially for E96 searches. A search of a high resistance values can produce several combinations like 100000 and 10, 100000 and 12 , etc.

- for parallel mode, an open is listed as 9999999. Could be done better.

- settable decade ranges. Would be especially useful to do this for E24 and E96 separately.

- importing a custom set of available resistor values could be useful to do the search

- listing all the actual resistor values used in the program would be good practice.

- add aging and manufacturing tolerance calculations.

- a Linux version if demand is there. GUI is FLTK based.