Current set resistor, 3.5k substitution options?

[Rotax91]

Hello CNC'ers

I have a question regarding the current set resistor which is supposed to be 3.5k for my Keling 381oz motors. Good luck finding a 3.5k resistor at Radio Shack. So I bought a combination of resistors today. Some 3.3k, 220ohm & 100ohm. I twisted a 3.3k & 220ohm together as a test and it came out to almost 3.46k.

How crucial is it that it it be 3.5k on the nut? Would I experience any performance loss with 3.46k?

Thanks for the help.

/tim

[jalessi]

Tim,

Using a 3.46K resistor in place of the 3.5K will cost you slightly over 1% of the total torque produced by the stepper.

Nothing to lose any sleep over.

Jeff...

[Mariss Freimanis]

The same goes for a much more readily available 3.3K 5% resistor. The low-speed torque 'hit' is 5.7%, a pretty meaningless loss if the motor has to turn faster than 300 RPM or so because this 'hit' only happens at very low speeds or while the motor is stopped.

It makes little difference that a 380 in-oz motor can develop only 358 in-oz at 30 RPM when that same motor moves a mechanism at 600 RPM where the motor may have less than 100 in-oz available.

Mariss

[lovebugjunkie]

Ordered these last week for use on my G540. May be of use to you.

EZ-G540

[Rotax91]

Thank you for the repsonse. I'll just leave it with the 3.3k & 220ohm (3.46k). Just for my own knowledge, what is the calculation you guys used to come up with the % values?

Mariss, thanks for the example. As a matter of fact, I'm using those 380oz. motors. Got them from Keling.