Basic question about capacitors

[Stickman]

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!

 

[Rich Grise]

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