Considered reply.
In the olden days when dynamo's were used as starter motors you'd have been OK.. and then we moved to alternators with reg boxes....Not so clever but still with luck on your side........ then we got really clever with 25acr's with the whole shebang on the back of the alternator......I used to use the argument that if the juice isn't wanting to flow through it leave the alternator (usually a 3 phase) connected in circuit (via the battery).....However with the advent of can-bus (and are you talking of transistors when mentioning NPN as opposed to PNP? they latch with even the tiny current from your personal static..let alone induced current) Do you understand the ability to send instructions to various components down a single wire? Why aren't they optically isolated instead....it would save the instant dismissal for the welder not disconnecting the battery at the repair shop...What about the cheap TIG welder that can turn a laptop off at 15'? I see no evidence of "industrial hardening" on motorcycles.......You are correct on your assumption of a little knowledge is dangerous....Hopefully you'll be the one bearing the cost of your misguidedness.......I'd wager my electronics diploma on it not being a pleasant experience for you to guarantor your advice!
Little knowledge indeed......Stupidity is free....grab as much as you can get!
No, I do not think it is misguidedness, it is just the sheer robustness of modern electronics as currently developed for industry.
Going back around 35 years ago, when alternators first appeared on British cars, they were made by Lucas. No greater abortion has ever been foisted upon a sceptical public.
Bad battery connection, using jumpleads, welding on vehicle, in fact, doing nearly anything to the vehicle resulted in failure. At that time, a service exchange on a dynamos (note, no apostrophe) usually cost around 10 pounds. an alternator cost around 90 pounds for a service exchange. I left in a faulty one, and it took Lucas 3 goes to provide me with a working service exchange unit. (Wages at that time averaged under 20 pounds per week)
These disaster areas were the reason why people developed such a fear of welding on vehicles.
I mentioned the NPN configuration on canbus equipped vehicles. All inputs are opto-isolated, and powered via a resistor (never checked exact value - probably circa 10k) from the 12v vehicle system to keep them high. All switches on the bike ground them to take them low.
I had the misfortune to buy a 2 off "Autoswitch" units around 2 years ago.
For use with HID lights. The first one did not work properly, so I bought another. It did not work properly either, so I started to investigate. I found that they were suffering from harmonics generated by some HID ballasts.
I tried every form of supression to overcome this problem. None were successful.
During these tests, I discovered the sheer robustness of the Canbus based processor systems fitted to these bikes. It is totally immune to all external interference I could generate.
It was mentioned that computers are very suspect when welding near them. Yes I agree, but only because the computers are not designed for such an environment.
This week, I was working on a grinding system for polishing the inside of a hydraulic cylinder 4 metres long & around 200mm I.D. There was a deep groove around 2 metres into the cylinder. The company made up a Mig welder gun assembly on rollers, and fitted a computer camera to the end of it , along with a light. Rolled it up into the cylinder, inspected damage, and proceeded to weld it at 2 metres distance from operator. For some reason, the computer screen goes black every time the arc is struck! Recovers instantly when arc stops.
Modern industrial electronics are very robust. Around 15 years ago, I acidentally put 110v AC onto the 24v inputs of a PLC. I presumed it would be scrap. No damage.
Around 6 years ago, on another site, a wiring error put 230v onto the 24v rail of of a PLC. Once again, no damage.
Last week, went to a PLC which was seen to be smoking in the transistorised output area. Disconnected the offending output. & system started to work again. I was amazed.
I have been welding on vehicles for over 30 years without disconnectiing anything. I have never suffered a failure, but, as mentioned, I am ultra careful of the earth path.
Myke
