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Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
sngecko wrote ...
That's a good idea. Maybe I can work that into the instrument panel on the rack. Along with a sign that reads, "When this lamp is on, disassembly will result in a painful death."
That's what I did with mine. Well, I mean I mounted the bulb on the front panel of the power supply, but I did not post a sign like the one you were thinking of!!
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
sngecko wrote ...
That's a good idea. Maybe I can work that into the instrument panel on the rack. Along with a sign that reads, "When this lamp is on, disassembly will result in a painful death."
It's very bad practice to bring any high voltage out to front panel elements. Still worse, if the neon fails it will indicate a false 'safe' state!
Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
Proud Mary wrote ...
sngecko wrote ...
That's a good idea. Maybe I can work that into the instrument panel on the rack. Along with a sign that reads, "When this lamp is on, disassembly will result in a painful death."
It's very bad practice to bring any high voltage out to front panel elements. Still worse, if the neon fails it will indicate a false 'safe' state!
You are absolutely correct. That's why I do not trust it with my life. Before I stick my hands anywhere near the high voltage portion of the circuit, I short the caps with a low-value, high wattage resistor, and I leave it connected until I'm done working on it. If probing the circuit while it's "hot", I keep one hand in my pocket. It's a practice that I learned many years ago from an old TV repairman.
Registered Member #3429
Joined: Sun Nov 21 2010, 02:04AM
Location: Minnesota, USA
Posts: 288
Pinky's Brain wrote ...
You can bring the light to the front panel using a fiber or rod.
That's not necessary. If you get the standard NE2 lamp socket, it has a thick platic dome that screws over the lamp. So even if the lamp breaks or burns out, there is no way that someone is going to get shocked from it. If you hit the plastic dome hard enough to break it, then common sense tells you not to stick your fingers in there! If the power supply were meant as a commercial product, then sure, you would want to do something a little safer so that you won't get sued. But for a hobbyist project that will likely be under total control of the hobbyist (who hopefully understands enough about electrical safety) then there is little chance that anyone will get hurt by it. I've been using the neon lamp in series with the bleeder resistor for many years and never had a safety problem with it. I consider it a secondary alert to warn me of the presence of high voltage. My primary alert is my training and common sense!
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Xray wrote ...
That's not necessary. If you get the standard NE2 lamp socket, it has a thick platic dome that screws over the lamp. So even if the lamp breaks or burns out, there is no way that someone is going to get shocked from it. If you hit the plastic dome hard enough to break it, then common sense tells you not to stick your fingers in there! If the power supply were meant as a commercial product, then sure, you would want to do something a little safer so that you won't get sued. But for a hobbyist project that will likely be under total control of the hobbyist (who hopefully understands enough about electrical safety) then there is little chance that anyone will get hurt by it. I've been using the neon lamp in series with the bleeder resistor for many years and never had a safety problem with it. I consider it a secondary alert to warn me of the presence of high voltage. My primary alert is my training and common sense!
The idea of a 'fail safe' is that it 'fails 'safe'' (see above).
If your system fails, the capacitor remains charged.
No-one is is saying it isn't a good idea to have an 'extra reminder'.
In a thread about safety people are going to point out the weak points, as PM did with my suggestion.
I'll admit, you 'need' to know more than the basics of 'mechanical engineering' in order to be able to rely on my suggestion.
The best plan is to incorporate them all (using the fibre optic cable where required)
(Might I be so bold as to suggest that if the fibre optic light doesn't come on, on 'power off', you know something is wrong?)
EDIT: just for clarity, use a smaller value resistor, paralleled if necessary to reduce current through the neon, in conjunction with a solenoid switch, that takes, say, 5 seconds to discharge the cap, so you can watch it come on and go out.
EDIT EDIT: I'm sure someone will find fault with this
Registered Member #3447
Joined: Fri Nov 26 2010, 11:10PM
Location: North Jersey
Posts: 97
The fiber optic cable sounds pretty high speed, low drag. I can just put a 30k pot downstream of the 300M bleeder and syphon off a little voltage to a comparator that goes Hi when positive voltage is on the non-inverting input and then drive an LED that couples to the instrument panel via a fiber cable.
Of course, chicken sticks are always used to "make sure" regardless of apparent failure modes.
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Active Capacitor Discharge Bleeder Circuits
