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Sci.Electronics.Basics -> Basic question about capacitors
There are 2 messages in this thread.
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Author: StickmanDate: 03:20 10-04-08
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Hi all.
I'm assembling a stepper motor control circuit using the L298 (http://
www.pminmo.com/l297-8/L297_8schematic.pdf), and don't have the proper
capacitors on hand.
The circuit calls for a 0.1uF caps between 5V & ground, another 0.1uF
cap between the 24V motor power and ground, and a 100uF cap to absorb
voltage spikes coming back from the motor.
Am I correct in thinking that for these purposes, the capacitor values
are not critical, as long as the capacitance is greater than that
specified? I have no 0.1uF caps on hand, but a pile of 22uF caps.
Can i use these instead?
Thanks for the help!
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Author: Rich GriseDate: 14:49 10-04-08
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On Thu, 10 Apr 2008 00:20:24 -0700, Stickman wrote:
> Hi all.
>
> I'm assembling a stepper motor control circuit using the L298 (http://
> www.pminmo.com/l297-8/L297_8schematic.pdf), and don't have the proper
> capacitors on hand.
> The circuit calls for a 0.1uF caps between 5V & ground, another 0.1uF
> cap between the 24V motor power and ground, and a 100uF cap to absorb
> voltage spikes coming back from the motor.
>
> Am I correct in thinking that for these purposes, the capacitor values
> are not critical, as long as the capacitance is greater than that
> specified? I have no 0.1uF caps on hand, but a pile of 22uF caps.
> Can i use these instead?
>
> Thanks for the help!
When it calls out 0.1 uF, I wouldn't recommend substituting a 22 uF,
because of the different capacitive reactance at the higher frequencies
where the switching noise is at.
Just go ahead and order a pile of 0.1 ceramics - here's an example:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=490-3873-ND
100 of them is $5.90. ($0.059 each :-) )
Cheers!
Rich
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