D7. https://www.raspberrypi.org/documentati ... educed.pdf
I'm planning on using a LM2596T-5 this time, with a BIG heatsink, and a fan.... That way, in combination with the 12v regulator next to it (I'll run them in parallel this time, input is 15.6V from a laptop power supply), so yes, switched rather than linear this time.davidcoton wrote: ↑Wed Apr 03, 2019 3:59 pmWhile redesigning your PSU, you should add a polyfuse (same type as D7) to the output if you need to power the Pi through the GPIO header.
Is there a reason for trying to use a linear regulator? 12V in, 5V out gives about 33% efficiency -- wasting twice as much power as the Pi uses (that's when it doesn't overheat and burn out). Better to use one of the many switch mode regulator modules that are readily available. You still need an extra polyfuse or equivalent if you need to power the Pi through the GPIO header.
If the damaged Pi works with D7 removed, replace it before returning it to regular service. Without D7 it certainly will not survive another 12V attack.
OTOH, lower voltage means higher current means either thicker wires and/or more voltage/power lost.
The protection diode is not like a normal diode. I believe it is bi-directional and shouldn't conduct in either direction until the voltage hits 6.0V (in this case). It's a bit like two Zener diodes connected back to back.
I sit corrected. I should have checked instead of relying on faulty memory.davidcoton wrote: ↑Fri Apr 05, 2019 9:49 am
There are TWO versions of the SMBJ5.0.
1) The SMBJ5.0A is uni-directional, and will act to clamp reverse voltage at a low value. This is the part specified for Pi computers, AFAICT.
2) The SMBJ5.0CA is bi-directional, and would provide no protection against reverse polarity supply. While some models had a perfect diode to block reverse polarity, the Pi3B+ does not. So this is not suitable for use on a a Pi3B+ (or Pi3A+, I suspect).
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I had to call the doctors as soon as I got up this morning. The receptionist asked my date of birth... it took me a good fifteen seconds to remember it! And then I wondered momentarily if I was right.
I try to avoid doing anything until the 2nd coffeeI blame morning caffeine deficiency.