After several weeks of making 36 LED display panels, and delivering them on time ( with a million headaches on the way ) I connected one set of 6 up to the decoder and power supply, to show them how it works.
I was so pleased to have this monkey off my back.
Saturday morning I get a call to say that they had connected another 6 up, and the magic smoke was let out from all the chips, just to make sure, they connected another panel, and sure enough, the magic smoke again.
I went to the factory, and sure enough, they had connected the it up and it hadn't worked because they had the shift reg in plug going to the socket that says out and vice versa - which is perfectly harmeless.
Because it didnt come on, the guy thought that perhaps I had the red and black wires to the DC power supply mixed up, so he swapped them over ..................
So now I have to find 35 TPIC6B595s , and an ATmega 328, in a hurry before his boss kills him !
At university I had many students mainly of forigin extraction wire up our home made lab supplies wrong. They had red and black terminals but some one had labled them as 0 dash 12. The dash was perceived by some as a negitave sign so the red terminal was wired up as the negitave. I thought it interesting that the culture of our home grown students had red and black so in trenches in their minds it stopped them making that mistake but it was absent in some of the forigin ones, especially the middle east ones.
Unfortunately I am running the 12v psu at 13.8 ( flat out ) to get the 18mA through the LEDs, I cant afford the Vf drop. ( and there was no time to get another 6 power supplies )
But saying that, these Meanwell PSUs have an excellent trip cct, I left one on all night with a dead short on the DC plug, and it was fine in the morning, hardly warm, so perhaps I can put a diode accross the input on the PCB.
If its consumer struff, I try and make it idiot proof, but these guys make and wire up lightboxes all the time !
Next batch I will fit a plug and socket for connecting the DC, but I dont like to have more contacts if I can help it.
Kill figuratively speaking 8). I'm living in a country where even child molesters and murderers are allowed to run free after 15 years off jail. So even though killing is cheap (in jail time); it is socially not acceptable to even consider doing it (we don't even kill murderers).
As far as I understand South Africa is a different story.
What I mean is "Do you want to run the risk this happens with your next batch?"
Yes => live on happy ever after 8) (I wish I could live this way)
No=> do something or have someone else do something.
As you stated "hurry before his boss kills him"
I would go for "Let his boss do something by timing my actions appropriately".
This is off course assuming that your expression "his boss kills him" is also figuratively.
In other words "I don' want blood on your/my hands but a good lesson seems a good idea. As his boss is willing to teach one, why would you avoid it?"
I dont think he will do it again, and as I say, I can make a plan, either with a polarised connector , or better still an enclosed ( to avoid corrosion in the tropics ) relay to only connect with the right Polarity.
I will fix up the units, and the guy will owe me BIG time, and his boss will be grateful to me, so what the heck, I dont want to get all grumpy about it
The trouble is, how idiot proof must I go ? Should I then have a different connector on the mains supply to the psu, etc etc.
I want to avoid connectors as the equipment is going to the tropics, and I like to spray everything with clear laquer to waterproof it.
These guys that swapped the red and black over , wire up light boxes and high voltage neon lights, its a big signage company that connects up LED strips etc !!!
I did say just to see how they manage to to hook that up backwards.
That's because on two occasions I can remember, it was done! Mind you, cutters were used.
I know Murphy well enough to know there's no such thing as idiot-proof.
The big surprise for me is how the number of idiots has steadily increased the past 40 years.
Had the same problem with my early prop designs. I spent so much time making the case bulletproof, and securing wires so they couldn't be pulled out or broken (these things are going to be in the middle of a simulated war, after-all), only to have the customer plug the battery in backwards (I used a AA battery holder with a 9v snap connector on it). It didn't power on at first, so he tried connecting it backwards. My props are really simple, so he was only out a LM7805, and it was easy enough for me to add a diode to my design. Never underestimate the ability of people to find ways to break your system.
The big surprise for me is how the number of idiots has steadily increased the past 40 years.
I refuse to be drawn into discussions about the South African Government
The US writer Mark Twain (real name Samuel Clemmens) wrote in his biography:
Suppose you were an idiot. And suppose you were a member of Congress. But I repeat myself.
I suspect it is common around the world to think government (and business) leaders are idiots.
I've heard it said, that amount of intelligence throughout the universe is constant, but the population is growing...
Never underestimate the ability of people to find ways to break your system.
My son makes a living doing that. After years of breaking my stuff, he is now a test engineer and breaks other peoples stuff for money.
He says his greatest skills are inventing new ways of abusing stuff, things that the developers would never think of doing.
that amount of intelligence throughout the universe is constant,
Favorite quote from a Monty Python song:-
Pray that there is intelligent life somewhere out in space, because there's bugger all down here on Earth.
