ESD protection?!

[DL3MHT]

Hi!

I am just wondering did anybody add ESD protection diodes to their (tr)uSDX or has any recommendations which ones to pick/use?

I mean the inputs/outputs go directly to the Atmega. One healthy zap and it's time for the hot air station again. So I was wondering if soldering a few onto the backside of the 3.5mm connectors might be a good idea.

-Tobias

[Ohwenzelph]

I agree it seems logical.

What do you think of these at mouser? 652-CG0603MLU-05E

[Ohwenzelph]

Or possibly these
241-PJGBLC05CR100001

I saw some that looked like they might be good but they were like 201 size or smaller and there was no way I could get something that small reliably soldered anywhere. Also, not sure what the ideal parameters would be.

[dl6sez]

Hello OMs,

yes there is no protection circuit elsewhere, but every Arduino, Raspberry or ESP32 does not have one
do you really think it is necessary?
I also have three QCX and yes, they also have nowhere a protection circuit.
We are using about 5W and it does make sense to protect every input of a QRP trx?
Maybe an overvoltage protection on Antenna connector would be useful, but i would not do more.
All my small transceivers are still alive and used from time to time without damage

73 de Chris DL6SEZ

[Ohwenzelph]

Where I live, at least in winter, it is cool and dry and just sliding in and out of bed there are audible visible palpable sparks. Some of the trusdx's have behaved strangely, some have stopped working and some have been revived or repaired by replacing the processor. Having the right materials and equipment the process of replacing can be done but the processors are a bit scarce lately. An experimental or hobby device with out esd protection is acceptable and cost constraints may force some compromises. Usually I don't fry my radio with reverse polarity but I have done it! and will be adding at least a diode for that. For those of us who would like to have the processor keep working correctly, some discussion of esd protection is reasonable. It's not free and you certainly do not have to do it but I am considering it and would be interested in what might be best, and also in what might be bad.
73

[N6YWU]

I always grab an audio cable by the metal part of the connector and then touch the side of the same hand to the radio's or Arduino's ground before plugging anything in. The impedance across one's hand should help dissipate static charge before the plug connects to the non-ESD protected pins.

[DL3MHT]

Thanks for the suggestion for the two types of diodes Ohwenzelph!

My two cents is it would be good engineering practice to add a few ESD / TVS diodes.
We are talking about a few cents extra cost and a huge headache avoided swapping out components.
At least i am known to throw 1cm long sparks in Winter touching metal bits when moving around the house .

My knowledge about ESD protection diodes is non existing. I see there are unidirectional and bidirectional types. There are also types that go to VCC and GND with a "middle" connection between two diodes. I have to smarten up which type to use when and where.

That's why i asked for suggestions here.

-Tobias

[Ohwenzelph]

IMG_0687.jpeg (142.93 KiB) Viewed 826 times

(more)Debounce for encoder and 8v reg for display with Schottkey for 5v via usb power, too soon to know any results or to recommend, just flailing around ( the inductors are kinda random ) and sharing. Key to follow in next post.

[Ohwenzelph]

IMG_0653top.jpeg (218.15 KiB) Viewed 822 times

Main board top

[Ohwenzelph]

IMG-0653bot2.jpeg (162.19 KiB) Viewed 822 times

Main board bottom

Parts
C2 47uF 16v 20% x5r
Tp (C4, C14) 47uF 10v 20% tant polymer
TVS bidirectional 14v pre fuse
F Fuse 0.75 amp resettable (1.5 amp trip)
S schottkey diode, post fuse, to U2. No reverse polarity can get thru but… runs with a voltage drop
PF post fuse 12v unidirectional TVS diode, shorts reverse polarity so blowing resettable fuse protecting power supply.
V post fuse 14 volt varister, belt and suspenders protection
0.1 uF NPO 50 v 1% so non-microphonic C22 & C29
TCXO tcxo on thinnest PCB osh park does
1n 1nF(1000pF) NPO 25 v 1%
10 0402 size 10uF 20% 10v x5r, parallel with 0.1uF to ground at C6, C15, C21
0.01 0.01uF film cap 16v 2%
31.6k ohm 1%
c cut
5 bidirectional 5 v TVS
24 bidirectional 24 v TVS
Schottkey diode for usb power at 5 v