pratyush.j
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Value of Inductors used on MMU 2 Control Board.

Nov 27, 2018 4:13 pm

Hello folks,
I was building the Prusa MMU2 Control Board for myself as it was too expensive for me in my country.
I already converted the 4 layer board to 2 layer by rerouting manually and sent it for manufacture by a cheap Chinese PCB fabricator.
So, while I was ordering the parts for the board, I noticed that the SMD 0603 Inductors (L1 to L22) are without any value in the BOM. It only shows 'FB' for their value. Also, FB stands for Ferrite Bead. I wanted to know what their value is in uH(micro Henry) so that I can order the parts.
I am attaching link to the BOM:
http://htmlpreview.github.io/?https://g ... e-BOM.html

Image

Also, thanks to Prusa for making it opensource. :)

And, thanks for reading my thread.
Attachments
BOM.png
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michael.m148
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Re: Value of Inductors used on MMU 2 Control Board.

Nov 27, 2018 6:35 pm

Though these are available in various specifications (usually a dc resistance and a impedance at 100 mhz), you shouldn't replace with something that is intended as a more conventional inductor. Ferrite beads are intended to have low Q and be especially lossy at VHF frequencies.

pratyush.j
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Re: Value of Inductors used on MMU 2 Control Board.

Nov 27, 2018 6:41 pm

michael.m148 wrote: Though these are available in various specifications (usually a dc resistance and a impedance at 100 mhz), you shouldn't replace with something that is intended as a more conventional inductor. Ferrite beads are intended to have low Q and be especially lossy at VHF frequencies.
Thanks for the info. I do not intend to use a different value. But the schematic says only 'FB'. So I want to know the actual value which is used in the board.

michael.m148
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Re: Value of Inductors used on MMU 2 Control Board.

Nov 27, 2018 7:57 pm

pratyush.j wrote:
Nov 27, 2018 6:41 pm
michael.m148 wrote: Though these are available in various specifications (usually a dc resistance and a impedance at 100 mhz), you shouldn't replace with something that is intended as a more conventional inductor. Ferrite beads are intended to have low Q and be especially lossy at VHF frequencies.
Thanks for the info. I do not intend to use a different value. But the schematic says only 'FB'. So I want to know the actual value which is used in the board.
As long as you pick ones that fit the SMT footprint and have a sufficiently high current rating (looks like some are on the output terminals?), it shouldn't matter much, except maybe for how much RF interference is emitted from the board. My main reason for deterring you from using other types of inductors is that they could have unwanted self-resonance that might affect circuit operation, but the lossy nature of ferrite beads is usually less trouble.

pratyush.j
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Re: Value of Inductors used on MMU 2 Control Board.

Nov 28, 2018 7:53 pm

michael.m148 wrote: As long as you pick ones that fit the SMT footprint and have a sufficiently high current rating (looks like some are on the output terminals?), it shouldn't matter much, except maybe for how much RF interference is emitted from the board. My main reason for deterring you from using other types of inductors is that they could have unwanted self-resonance that might affect circuit operation, but the lossy nature of ferrite beads is usually less trouble.
Thanks. I picked out two kinds.
2.5Amps for motor outputs. See link https://lcsc.com/product-detail/Ferrite ... 88988.html

2Amps for all other. See link https://lcsc.com/product-detail/Ferrite ... 14709.html

michael.m148
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Re: Value of Inductors used on MMU 2 Control Board.

Nov 29, 2018 3:46 am

That sounds reasonable.

david.t28
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Re: Value of Inductors used on MMU 2 Control Board.

Dec 26, 2018 7:13 pm

Thanks for posting, this will be great information to use when you have a board that stops working. Prusa is great at supporting their products. This past weekend the Online Chat diagnosed my MMU problem to be the MMU control board.
Once I get the RMA part I can use your information to troubleshoot and repair the board as a spare as I don't think they will want the part back.

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