Mounting screw through inductor - Page 1
Forum section: electronics / beginners

author: pmbrunelle
author_rank: Regular Contributor
timestamp: March 18, 2014, 02:49:22 am
content: I have a 2.2 mH inductor, thru-hole.Datasheet:www.bourns.com/data/global/pdfs/1140_series.pdfIt has a hole through the middle to allow for a screw to secure the inductor to the PCB.Can I use a normal steel screw? Will it do anything weird? I could find nylon screws.The inductance value is not critical; this is for power supply ripple reduction.

author: kizzap
author_rank: Unknown
timestamp: March 18, 2014, 04:51:45 am
content: the only thing that comes to mind is to be careful to not make a loop around the inductor core (turning it into a pseudo transformer.)I don't see why you couldn't do what you suggest, but surely it would be easier to use some form of goop on them to stop any vibration?If you are still determined to use a screw, consider maybe using a nylon screw?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 18, 2014, 06:07:47 am
content: I'd use a brass screw just in case, but yes, it's okay.The "transformer" direction is solenoidal (wrapping around the axis), not axial (lengthwise), so you don't have to worry about clamping stuff down around it. But do keep wide metal objects away, especially from the corners (where the field is most strongly concentrated).Is this a DC filter choke, or big switching, or..?Tim

author: pickle9000
author_rank: Super Contributor
timestamp: March 18, 2014, 06:42:00 am
content: Nylon would give you more freedom with the pcb layout.

author: johansen
author_rank: Super Contributor
timestamp: March 18, 2014, 06:44:45 am
content: depends on the frequency and ripple current.either the steel screw will increase the inductance, or it will get warm, or both.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 18, 2014, 05:09:09 pm
content: Layout doesn't have much for options as-is; the faces are probably somewhat conductive (bare ferrite) so you should avoid traces and vias on the component side within the footprint. The screw (if metal, or the ferrite touching the pad, if any) can be grounded to the circuit if you like, or simply left floating.Tim

author: Zero999
author_rank: Super Contributor
timestamp: March 18, 2014, 08:01:23 pm
content: Quote from: T3sl4co1l on March 18, 2014, 06:07:47 amBrass will reduce the inductance, if anything.

author: pmbrunelle
author_rank: Regular Contributor
timestamp: March 18, 2014, 08:10:55 pm
content: Quote from: T3sl4co1l on March 18, 2014, 06:07:47 amIt's a DC filter choke. It makes a pi filter with two large capacitors. The DC output of this filter is used to excite load cells. There may be some small 2x line frequency ripple, and also noise from a nearby brushed DC motor I want to remove. I'm not sure about the effect of a non-ferrite core with higher frequencies.Quote from: kizzap on March 18, 2014, 04:51:45 amSince you mentioned goop, I will use hot melt glue if I can't find a nylon screw.I only realized I needed to consider a method of securing the inductor after I etched the PCB (it's a one-off). By chance, there happened to be no traces within a 0.2" radius of the mounting hole...