Lightning

[Robert Atkinson 2Participant @robertatkinson2]

And this accident involving a Do228 commuter aircraft.
http://www.aibn.no/Aviation/Reports/2007-23-eng

The thread on the rose joint end of the elevator control rod (part of a turnbuckle like adjustment) was blown out by the lightning current. The design had a bonding lead across the joint but this had not bee maintained properly.

The report gives a bit of background on the currents involved.  As I’ve said before lightning protection of aircraft and avionics is one of my professional areas of expertise. Probably the hardest protection is fuel tanks when 200,000 amps is flowing through the skin without causing sparks of more than 200 microjoules inside. This includes rivets, pipe joints etc.

Full direct effects testing is always interesting. Pin injection testing for secondary effects (basically the OP’s issue) is relatively boring particularly if there are a lot of pins with different circuits. I have seen a unit catch fire during pin injection testing but fortunately it was someone else’s test being carried out at the same test house.

Robert.

[duncan webster 1Participant @duncanwebster1]

I’ve been a bit quiet of late as I’ve been having great difficulty uploading the software to my nanos. I bought them from aliexpress described as CH340 USB input. Turns out they are not, they are FTDI but a knock off version, so windows won’t talk to them. There is a  work around by using Linux,  but something to beware of.

This could well explain my difficulty uploading to minis as well.

Not bought opto isolator yet, too many other irons in the fire

[duncan webster 1Participant @duncanwebster1]

I’ve had to send the Nanos off to my very kind volunteer as I can’t get #2 son’s Linux laptop to speak to my interweb to download the IDE, so in the meantime I’ve been trying to get my head round Robert’s suggestion of 13 June. The picture has disappeared from the entry on the forum if I look on my PC, but it still there on my phone, Weird. Anyhow, I’ve managed to retrieve it, and almost understand it. What I don’t understand is why there are 2 off 330 ohm resistors rather than just one 680 ohm, and is it likely that the CTR (current transfer ratio) is the same on each channel. As Robert suggests I can use a spare channel to calibrate the other 2 as long as this is the case.

All getting a bit complicated, but easy teaches you nothing and so is boring. Just in case others can’t see the schematic, here it is again

[Robert Atkinson 2Participant @robertatkinson2]

Hi Duncan,

Good spot! I used two 330R resistors rather than a single 680R for a couple of reasons. The first was so there is an impedance in series with the LED in the opto-coupler and it’s protective Zener for surges coming from either the 12V supply end or the track connection end. This is mostly for very fast pulses were the stray capacitance can make a difference.
Secondly it divides the voltage across and power dissipated in the two resistors making them less likely to fail.

If you want to try something across the tracks I have some new old stock 100W 47V stud mounted Zeners…

Robert.

[Author]

Posts