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Cable lenght between board+Module


#1

Hello

ye, it’s me again -.-
And my question is again veeery basic…
it’s about the Cable lenth between a Hydra and Modules like Joystick/buttons and 16xRelay modules.

Can I for example make a extension with 2 Breakout modules and connect pin1-pin1 etc. and add a 1m or even 1.5m Cable between? or do I need for every Module that is a bit more far away from the mainboard a PowerExtender?

friendly greetings evul


#2

You can’t really just extend the signals and expect everything to work - it might, but it might not.

“it depends”.

If you were doing this in a remote location with no electrical interference and no other chance of signal integrity change, you might be ok. If you were doing it anywhere else, you may have problems.

You will likely need to think more about signal integrity than power losses; the relay however is a special case and you really need to deal with power separately.

Can you articulate what you really are trying to achieve here ? General questions will get general responses, and if you’re a little more specific you might get some more targeted strategies for improving the chance this works. You should be very explicit about how (un)reliable you can handle this being


#3

Ye.

For basics… it was a very general question and I expected a general answer ^.^

Well, I’m working on a Exo-suit-armor (Movie: Edge of Tomorrow) and i want to implement some funktions… so that it’s not only a costume.

I have on the right side a joystick, button and a character display and a x1relay for a power LED.
No problem there so far… it’s very compact and works with the longest aviable cables from GHI.
Now I wanted to add a x16 relay module for various frunktions with motors and LEDs… but since there is no space on the arm I wanna put it on my back.

So, I either need a long cable for the 16xRelayModule and maybe a rotary unit… or I put the Hydra on my back too and extend: joystick,button and caracter display :confused:

What about a 1.5m shielded cable to ground between the 16xRelayModule and teh Hydra… could that eventually work?

pls don’t mind my poorly drawn overview >.>

greetings evul


#4

cool project. Can’t wait to see the video :slight_smile:

I assume you’re referring to the ISOx16 module https://www.ghielectronics.com/catalog/product/391 ? it uses a Y socket, so is using standard IO pins, in a pseudo-SPI form. You can possibly get away with using a custom wiring using shielded cables, but you’re pretty much on your own if you do so. Given it’s only you in the exoskeleton, you’re probably going to be taking all the risks yourself anyhow right ? :slight_smile:

If you look at the ISOx16 module schematic, you can see it only uses HC595 logic chips, so they will be somewhat more prone to spurious bits affecting the port outputs, so I would suggest trying the other side first, run long cables for the joystick and display. The display may also be affected by the signal length, but at least that doesn’t turn motors on or off at inappropriate times :slight_smile:

If this becomes more than tinkering in the back yard, you might want to think about industrial standards, like RS-485, that protect signal integrity, but that’s likely to imply you will start adding separate processors for these separate functions.


#5

@ evul - depending on budget, you could add another Gadgeteer mainboard in back and use something along the lines of RS232, RS485 wiring, or your favorite radio device bluetooth, WiFi, … The extra processor might come in handy for other things…


#6

Speed is generally the enemy when you run long cables. If your data rate is slow you can always just add capacitors to create a low pass filter to get rid of any noise. If you can run your SPI slow enough you should be able to make it work.

For high current stuff you need to think about the voltage drop across the cable.


#7

well. made a bigger order now including some breakout modules.
I’ll try to extend the cable for the 16xRelayModul to about 1,2m with a shielded cable and try to stay away as far as possible from the Motor^^

If I get funny actions on the module I can still use the same cable for the display module and put the mainboard near the 16xRelayModule and extend the joystick and button too^^