tiberio (11/30/82)
I saw a device like the bulb saver in a small electronics hobby book i got at radio shark years ago (~1970). They called it a cheapo light dimmer. Basicly its just a half wave rectifier that turns 120 vac into approx 80vdc (smooth out the pulses and that what you get). Not very efficient.
ark (11/30/82)
I am assuming that a "bulb saver" is one of those little button-like devices I have seen advertised that go in the base of a light bulb socket. While I have never seen one in person, I cannot think of anything but a rectifier that would go in one of those. What would be the effect of a rectifier in a light bulb socket? Much the same as switching the bulb off during the negative half of each cycle. Since half the power comes from the positive half and half from the negative half, the effect would be to reduce the power used by the light bulb by a factor of two. Thus a 100 watt bulb would use 50 watts, etc. At least this would be so if light bulbs were linear. They aren't. There are two things I can think of, and I do not know how to predict accurately the results of either of them. First is the fact that the efficiency of a light bulb depends on its operating temperature. By "efficiency" here I mean the fraction of the electrical energy that is emitted as visible light. For incandenscent light bulbs, this number is small -- a few percent if I recall right. A bulb receiving less than the power input it was designed for will have a cooler filament, and I would therefore expectit to emit less light and relatively more heat than normally. In other words, I would expect more light out of a 50 watt bulb than out of a 100 watt bulb running at half power. Second is that the resistence of a filament is temperature dependent. I am not exactly sure of the dependence, but I think that resistance goes down as temperature goes down. Thus your 100 watt bulb running through a rectifier should use more than 50 watts. It is now unclear whether it will emit more light than a 50 watt bulb or less. Summary: I would expect a rectifier in a lamp circuit to decrease the amount of electrical power used by the lamp, and also to decrease the amount of light emitted by the lamp. I would expect the light output to decrease more than the power input -- in other words, the efficiency would go down. I think you would get more light for less electricity by using a 50- or 60- watt bulb than by using a 100-watt bulb through a rectifier. The only thing I think would be a real gain would be the increase in bulb life. I would expect this to be fairly unimportant unless the bulbs are in locations that are hard to get at. If you want bulbs that last a long time, scrounge hardware stores until you find bulbs rated at 130 volts -- these last for years. If you really want to minimize your electricity costs, get flourescents.
phr (12/01/82)
As I understand it, bulb savers are negative-coefficient thermistors which reduce the shock to the filament after the light is turned on. They do not appreciably reduce the amount of light produced (or power used) by the bulb, after they've warmed up for a fraction of a second.