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SD not working due to length of cable

Posted by kd6hq 
SD not working due to length of cable
November 16, 2018 09:33AM
I've run into an interesting problem.
RAMPS 1.4, Firmware : Marlin 2.0
I recently built a new machine.
From what I can tell due to the length of ribbon cable for the display the SD support fails.
If I change the cables back to the original it works fine.
I will continue to experiment with it but has any one had this problem before?
Does anyone know if this is true?

Thanks
VDX
Re: SD not working due to length of cable
November 16, 2018 09:46AM
... this is common for EMI (Electro-Magnetic-Interferencing) problems - either shield the single data lines or use higher voltage levels --> 5V bettter than 3.3V, 12V better than 5V ... industry uses 24V ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
Re: SD not working due to length of cable
November 16, 2018 09:55AM
Yes this is a very common issue

ribbon cables are dreadful for longer distances (anything over about 30cm...)

You will need to make up some sort of shielded cable
Re: SD not working due to length of cable
November 16, 2018 10:42AM
Ok thanks. Then I guess I'm lucky that my 177cm cables work at all. Only thing not working is the SD. Everything else seems fine. Guess I can live with out SD.
thanks again
Re: SD not working due to length of cable
November 16, 2018 10:48AM
I've run into the same problem. Does one end of the shield get terminated to ground?
VDX
Re: SD not working due to length of cable
November 16, 2018 01:07PM
... yes, if shielded, then one end should be grounded.

In past we've arranged GND lines between data lines and/or inserted a resistor of around 20 to 50 Ohms into the data lines to reduce ringing ...


Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org]
Call for the project "garbage-free seas" - [reprap.org]
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