Sensing resistor and L298

[brentonw2004]

Hello all. I am working on a basic stepper motor controller using L297/L298. In the datasheet of the L298 it says that the sense resistors must not be wire wound. However, I am having a lot of trouble finding resistors to meet my requirements (0.5ohm, >=2W) that are not wire wound. Am I looking at this wrong? Any suggestions as to where to find these? Thanks!

-Brent

 

[Bob Scott]

Probably they presumed that wirewound resistors are inductive because they are wound like a coil. This inductance can also cause real distortion problems if they are used as emitter resistors in audio amplifiers with current limiting.

Can you obtain non-inductive wirewounds? They will probably work, but not as readily available as the regular ones. Call an application engineer at the IC manufacturer and confirm. You can usually email them too. The non-inductive type wirewounds usually have "NI" in the part number or some other identifier.

Bob

 

[brentonw2004]

Do you have any idea where I could find such a resistor? I've had no luck finding anything that is non wirewound/non-inductive.

 

[KMoffett]

You didn't say what accuracy or tempco you wanted, but for this application I would guess 10% is OK. Four 2.2Ω-1/2W carbon composition resistors in parallel would work...0.55Ω-2W.
https://www.mouser.com/Search/Refin...lKeyword=carbon+resistor&Ntk=Mouser_Wildcards

Ken

 

[Megazzeth]

Hello Everyone
I am using an atmega 16 and l298 to control a sanyo 103h7121-1311 stepper motor. i have connected the current sensing pins of the l298 to gnd.
i am using a 15 vss, but what i am getting as output is only 5 v. Is it because of the absence of any sensing resistors, if so please advice about which ones shoud i use. I tested the circuit without connecting the motor and found that the output voltage is not going beyond 5 v.
The functioning seems to be fine since the outputs are changing according to the programming. Please advise.
Thank you

 

[nickelflippr]

For the OP look for current sense resistors, like http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=13FR100E-ND

 

[Megazzeth]

Hi again
well i connected a .5 ohm resistor to the current sensing pins of the l298. I am still not getting the output in the range of my vss all i am getting is a 0 v to 5 v output. I am using a simple power adapter which is set to give 15 v but its current is limited to 500 mA as written on it, could this be the cause of the low range(voltage) output. I have also not tried to connect the motor to it yet since iam not getting a decent voltage. I am an IT engineer actually so i really dont understand a lot about this stuff so please dont mind my silly questions.
Thank you