Everyone

Frank Schoofs

Froyo

You need a non-common E-series resistor like e.g. 1.55 Ohms? Connect 2 resistors parallel or in series!
The "Resistor" app displays a list of suitable combinations consisting of matching R1 R2 pairs.

Choose e.g. the pair that provides a resulting value closest to your chosen target value. Or choose the pair with the lowest difference between R1 and R2. This helps to balance the current through the resistors which results in warmth balance as well.

Select a different pool of resistor candiates from different E-series, such as E6, E12, E24, E48, E96 and E192.

Decrease the output list of matching resistor pairs by setting filters:
- Max ratio R2 / R1: R2 must not be larger than ratio * R1.
- Maximum error: a resistor pair is added to the output list if its resulting impedance is equal to or lower than the specified maximum error (with respect to the target resistor).
- Multiple solutions: just show ONE solution per resistor and inhibit multiple solutions per resistor. Example: the target resistor (here: E24 series) is chosen as 1.25 Ohm. Matching parallel combinations are e.g. R1=1.3 Ohm and R2 = 3 Ohm (the error to target resistor is 0.06%), as well as R1 = 1.3 Ohm and R2 = 16 Ohm (the error to target resistor is -3.82%). Both pairs have the same R1 of 1.3 Ohm. If this filter is active, it suppresses the solution with the error of -3.82 %. So per resistor value, just the best match (i.e. lowest error) is added to the output list.

Sort the output list by different columns, namely R1, R2, R1 || R2 (or R1 + R2), error and delta(R1, R2). The latter item sorts by difference between R1 and R2. This could be useful if e.g. a somewhat large current through a sense resistor is expected. A small difference between R1 and R2 allows to use the same resistor package while keeping the thermal behavior more or less the same.

Enjoy!


Series/Parallel Resistor

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