Tiny XU4 isolated I/O board for CON11

Post Reply
User avatar
mctom
Posts: 736
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polish
ODROIDs: N2+, Game Advance, a few XU4
Location: Gdansk, Poland
Has thanked: 74 times
Been thanked: 93 times
Contact:

Tiny XU4 isolated I/O board for CON11

Post by mctom »

I was terribly hungover today, so I occupied myself with something easier and more generic.

I designed this little I/O board for often ignored CON11. I've got other plans for CON10. 8-)

The board offers two isolated digital inputs and outputs. This means it can sense and drive digital signals even in devices powered from different power supply, maintaining galvanic isolation. No ground loops!
Outputs may work in one of three modes, selectable by resistor placement:
- True isolated output, that can pull external logic either high or low
- 5V TTL-compatible inverted output (related to local ground)
- 5V non-inverted.

Inputs can work with any logic level above 1.5V (input resistors need adjustments).
Inputs also tolerate down to -5V.

The board is smaller than 17x17mm, which is about a diameter of US dime.
Of course 2.54mm pin headers are completely optional - personally I'll just solder wires right into it.

When I get any better, I'll push it to github.
2021-11-20-213233_1711x1065_scrot.png
2021-11-20-213233_1711x1065_scrot.png (146.69 KiB) Viewed 31 times
2021-11-20-210859_912x870_scrot.png
2021-11-20-210859_912x870_scrot.png (103.31 KiB) Viewed 31 times
2021-11-20-210828_1016x862_scrot.png
2021-11-20-210828_1016x862_scrot.png (94.17 KiB) Viewed 31 times
These users thanked the author mctom for the post (total 3):
L67GS (Sun Nov 21, 2021 2:45 pm) • joerg (Sun Nov 21, 2021 7:30 pm) • odroid (Mon Nov 22, 2021 9:37 am)
Punk ain't no religious cult, punk means thinking for yourself!

Maintainer of PiStackMon

User avatar
rooted
Posts: 8853
Joined: Fri Dec 19, 2014 9:12 am
languages_spoken: english
Location: Gulf of Mexico, US
Has thanked: 743 times
Been thanked: 402 times
Contact:

Re: Tiny XU4 isolated I/O board for CON11

Post by rooted »

Nice use of your time. What would you use this for?

User avatar
joerg
Posts: 1418
Joined: Tue Apr 01, 2014 2:14 am
languages_spoken: german, english, español
ODROIDs: C1, C1+, C2, N1, N2, C4
Location: Germany
Has thanked: 100 times
Been thanked: 227 times
Contact:

Re: Tiny XU4 isolated I/O board for CON11

Post by joerg »

Nice to see someone else is tinkering around like me. :)
When I last time made some small board and let them manufacturing in CN, I made a mistake. Thought I order a batch, but not, I ordered single and got only 5 instead of 30. So next time I will copy as much as possible on a 100 x 100 pcb order as single board and cut them by myself.

User avatar
mctom
Posts: 736
Joined: Wed Nov 11, 2020 4:44 am
languages_spoken: english, polish
ODROIDs: N2+, Game Advance, a few XU4
Location: Gdansk, Poland
Has thanked: 74 times
Been thanked: 93 times
Contact:

Re: Tiny XU4 isolated I/O board for CON11

Post by mctom »

rooted wrote:
Sun Nov 21, 2021 12:50 pm
Nice use of your time. What would you use this for?
One output to mute audio amp when not in use - in this case isolation is crucial to avoid ground loops.
Another output to control radiator valve in the room. Hence a small space left blank on my board - there was supposed to be a temperature sensor in SOT-23-6, but couldn't find any that talks 1.8V directly.

I don't plan to use inputs at this point, but figured it could be more useful this way than just 4 isolated outputs.
Anyway, the inputs accept virtually any logic levels, so the whole board could be used as a level shifter.
In many simple setups, this could work instead of the shifter shield.
joerg wrote:
Sun Nov 21, 2021 7:30 pm
ordered single and got only 5 instead of 30. So next time I will copy as much as possible on a 100 x 100 pcb order as single board and cut them by myself.
I think they'll reject such order, especially if you include rows of holes to snap individual boards off more easily. ;)
Because in that case, well, I could fit 30 boards like this on one 100x100mm sheet. And with minimal order of 5, I'd end up with 150 pieces. A bit more than I need.
Also, I just checked: If I simply ordered 150 pieces instead of 5, I'd pay $15 instead of $5. Not that great difference after all, and all boards are neatly finished without me spending a day cutting them.

I guess this is how I ended up ordering 30 PiStackMon PCBs, it was just too cheap not to. ;P Now I include bare PCBs to anyone who buys an assembled unit. :roll:

However I often compile a few projects on a single stencil to cut the costs. :)

EDIT: Here's one cool idea I just figured out. Optically isolated output could be used to change feedback resistance of the switching converter. To lower voltage of fans or LED lights, for example.
Isolated outputs also can drive high side switches (pnp, pfet) pretty much directly, with one pull up resistor or so.
Punk ain't no religious cult, punk means thinking for yourself!

Maintainer of PiStackMon

Post Reply

Return to “Hardware and peripherals”

Who is online

Users browsing this forum: No registered users and 2 guests