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Why are 250 ohm resistors for bread boards so hard to find?

urlonz wrote:Why are 250 ohm resistors for bread boards so hard to find?

Because resistors are nearly always manufactured to fit into a standard series of resistor values by range. These ranges are known as E6, E12, E24, E48, E96 and E192. 250 Ohms doesn't exist in any of these standard ranges.

See the table at the link below and select the nearest standard value...

http://www.logwell.com/tech/components/ ... alues.html

Unless the resistor is being used as part of a precision reference chain for some reason, its exact resistance probably isn't going to matter a great deal within 10% either way. Very loosely speaking, the lower the range you can select from, the cheaper it will be.

I have some, but they are chunky 1 watt jobbies. Can't remember ever having seen a 1/4W one.

If you need 250 ohm then do a bit of 1/r1 + 1/r2 and solder a couple in parallel.

A 270Ω resistor would be the nearest preferred value. It's only 8% higher than 250Ω . A properly designed circuit won't be upset by than small a change in values.

PeterO