Page 2 of 2
| Flashing Red Aspect 24/05/2013 at 17:29 #45109 | |
Backup
89 posts |
Of course, Gwasanaethau, not all DC is the same quality, it depends how well it's been produced. Even full-wave rectified DC can cause flickering output; especially if the smoothing capacitor is inadequate, failing, or nonexistent. So you were probably right, no matter which power supply has been used. Only a battery or a seriously high-spec rectifier set will give you something like constant voltage; and I doubt the railways use either for driving signals. There's more to it, but I feel that covers the basics. Further reading: http://en.wikipedia.org/wiki/Rectifier#Rectifier_output_smoothing Last edited: 24/05/2013 at 17:38 by Backup Reason: whoops! constant voltage, not constant current. Log in to reply |
| Flashing Red Aspect 24/05/2013 at 18:15 #45111 | |
|
Firefly
521 posts |
ok, let's not get worried about DC The only time you get 12v DC signal lamps are in very old (usually green field) sites which have 12v battery back ups in the location cabinets. Otherwise all signals are fed from the 110v AC 50hz busbar. This is then transformed down to 12v in the signal head. LED signals work directly off of the 110v AC and I have no idea what trickery goes on inside those black boxes. All things considered it appears that it's the video playing a trick on us here. Quote: It should flicker between 'in order' and 'failed' indications, as you suggest, to reflect the signal's actual state.True of a lever frame signal box, however in a modern panel you would just get a blank signal indication when the signal extinguished. If the panel indication is showing either red or green this proves that the signal is alight (Current is being drawn by the lamp). Panels will not usually have any alarm associated with this failure unless it is fed by SSI (Solid State Interlocking) in which case you'd get a critical alarm. FF Log in to reply |
| Flashing Red Aspect 24/05/2013 at 18:33 #45112 | |
|
Late Turn
699 posts |
" said:True of a lever frame signal box, however in a modern panel you would just get a blank signal indication when the signal extinguished. If the panel indication is showing either red or green this proves that the signal is alight (Current is being drawn by the lamp). Panels will not usually have any alarm associated with this failure unless it is fed by SSI (Solid State Interlocking) in which case you'd get a critical alarm. The indication should return if the signal illuminates again, though? That was what I was getting at, rather than how the failure's indicated. Log in to reply |
| Flashing Red Aspect 24/05/2013 at 18:54 #45113 | |
|
Firefly
521 posts |
Yes it would be flashing if this was a real failure. In fact it would look just like a signal that was timing having been approach locked. FF Log in to reply |
| Flashing Red Aspect 24/05/2013 at 19:08 #45114 | |
|
Danny252
1461 posts |
" said:" said:Oh lord, so he did - I mixed the order of those two words up and read it as a rather forward "It is"! Mind, the lack of a question mark does turn it into a statement.My problem was mainly that his statement was so matter of fact - not even an "I think that...".He did start by saying "Is it..." Last edited: 24/05/2013 at 19:12 by Danny252 Log in to reply |
| Flashing Red Aspect 24/05/2013 at 19:21 #45115 | |
|
arabianights
138 posts |
are you sure
Log in to reply |