Quote:
Originally Posted by Robsradio
So near, and good recall, they are 5v 0.09A. I assume they went for 5v to allow for the volt drop within the flasher circuit, I guess the static lamp's bulbs were slightly overdriven.
I seem to remember that torches that ran on 2 D cells had a 2.5v bulb, so maybe that was the practice to slightly overdrive them, maybe for a whiter light?
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Yes, most of these road lights used a 5 volt 0.09 amp bulb, miniature centre contact type.
Under a modest load the battery voltage would probably average about 5.5 volts, which together with a little voltage drop in the transistor would run the lamp at about 5 volts.
Various version of flasher circuit existed, many were potted in ordinary candle wax, this being much cheaper than proper potting compound and still fairly effective for a low cost product.
Perhaps surprisingly these bulbs are still available. Apart from the intended use, they are useful whenever a long running light is needed from a 4 cell dry battery. The bulb life is fairly short, but that is actually preferable since it improves the efficiency and gives the most light from the limited and very expensive energy in dry cells.
A single zinc carbon 996 lantern battery should give 100 hours service. Most useful before the LED age.