I am ordering parts and would like to order an inductor in order to build a circuit like the one shown on Grumpy Mike's decoupling page at the bottom.
Grumpy Mike mentions that an inductance value of a few tens of milli-henry would be sufficient.
I would like to try the attached circuit with a mosfet to drive a relatively small motor (about 5 amps). Here is the inductor that I would like to order.
According to those specifications provided in the link, the inductance is 47mH. The problem would appear to be the maximum DC current of 38mA. Is that DC current value important? I don't even see a 47mH inductor rated anywhere near 5A. Could someone please explain why this value is or is not important?
The DC current rating is vital - go much above that and the choke will cease to do anything
useful as its magnetically saturated - you have a very expensive low-value resistor in fact!
You want a choke (ungapped), not a gapped inductor, since the precise inductance is irrelevant, but
the current carrying capacity is important. Ungapped cores have the highest inductance for a given
winding (ie the shortest winding for a given inductance). Gaps stabilize inductance value but reduce it
a lot.
For 5A a choke would likely be wound on a ferrite toroid in thick copper wire.
But do you need a choke? They are bulky and expensive and if electrolytic decoupling capacitors are
enough for the job its simpler just to use them.
Possibly I will be fine with the decoupling capacitors. At the moment I am using very small motors with my arduino and sensors both powered by 6 ~1.5V NiMH batteries. In order to reduce noise from the motors, I would like to know if the decoupling that Grumpy Mike describes would be enough or should I use two separate power supplies? I will rephrase this question and post it to another thread.
