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Alternative SeaTalk wiring
(2023-07-30, 08:01 PM)holgerw Wrote: i would modify R22 to half or put another 3K3 on top of it.
The lower Impedance of the circuit is better against Peaks.


With R21 being 20K, that would push the on-voltage (when SEATALK_DATA is at 12V) to 0.62V instead of 1.2V. I.e. I'd be worried that the transistor doesn't fully turn on, especially if the 12V supply is on the low side, or the transistor's VBE on the upper end of its specification.

An alternative would be to leave R21 at 10K and add 3K3 in parallel with R22. That would set the voltage range at the base of the transistor to 0.3-0.9V.

To calculate the voltage at the base, I look at the voltage divider formed by R20, R21 and R22. With SEATALK_DATA high, the voltage divider is from 12V through R20+R21 and R22. With SEATALK_DATA low, it is from the
diodes anode (~2V) through R21 and R22. We want the base of the transistor swing as far above and below 0.6V as possible.

Edir: Oops. I think the second paragraph is exactly what Holger suggests!

Good news! Mine also works now with the additional resistor across R22. Unfortunately, I didn't have the correct value but did manage to get to 2k7 and its working.

I'll do some further testing but I have live data, Wind speed is responsive so that's really good and everything else appears to be there.            
Yeah. That was a surgical soldering. Really good news!

You are not using the power module but I can see only 2 wires connected instead of 3 and the black wire instead of the red wire, are you using different wiring than this one?


I’ve tried both ways, powering the board using the module and I was originally using my power supply in the photo. In that photo I had yellow seatalk data and the black wire connected to red on the seatalk network. As soon as I held the resistor across R22 the data went from nothing to receiving data. I then solder it, tested again before switching to the power module and removing usb power.
Apologies, I've been away for home / the boat for the last couple of weeks and have been unable to contribute. As I previously mentioned, I'm not sure I have the capability to add additional resisters to the board. Should I sent the board back to Spain or the US?

I've swapped the V1.1 board out with the V1 board and will be going down to the boat tomorrow to test out my N2K network.
Sailing now, better to US. Thanks!
Some ideas about the prototype MacArthur board.
Is there also an editable board design. A Gerber file o.i.d.  I noticed in the scheme that some SMA chips are hard to get.  If we can use the old fashion (DIL 16/24) chips instead of SMA it might be easier to build the board (maybe at home?).
BTW. 'm aware that the board will be bigger using DIL instead of SMA

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