The Case of the Frequency Generator:
The frequency generator is coupled to an amplifier. And it is a whole setup. Even if one wants to use the frequency generator, the amplifier also needs to be switched on; though the knobs are kept at zero.
Usually this frequency generator is used to modulate lighting of halogen lamps: Sine wave modulated and in the offset of 2.5 V. If the offset is reduced there is very less (than even one half cycle) ON period. The amplitude is always set somewhere in the range of 5-7V. There is a trade-off between the amplitude and the offset that can be set. This relationship is as given as below
x + |y| = 10 where ‘y’ is offset and ‘x’ is the amplitude
(All these information are hands on and first.)
EXPERIMENT and PROBLEM:
I tried modulating a 70W 220V LED lamp. It did modulate, but there is NO off state. To put it in other words, the off state is: a constant less intensity glow. Even when the offset is set to zero the lamp glows. No below-zero offset can be achieved. No matter how low (negative) the offset can be taken the lamp continues to glow (don’t forget the trade-off I mentioned above).
I have been looking into possibilities that might be the cause for it.
ACTIONS and OBSERVATION:
1. The output of the function generator (and amplifier) was connected to multimeter leads. With no output, it gives out a 70V (±5) output (RMS multimeter).
2. On connecting a CRO: initially I viewed 50Hz AC which was moving up and down like a skipping rope whip. On zooming out we could see the wave become a line and then act accordingly as I modulate and set offsets.
QUESTION:
How to modulate the LED source with a proper negative half cycle (OFF STATE EXISTING)?
The frequency generator is coupled to an amplifier. And it is a whole setup. Even if one wants to use the frequency generator, the amplifier also needs to be switched on; though the knobs are kept at zero.
Usually this frequency generator is used to modulate lighting of halogen lamps: Sine wave modulated and in the offset of 2.5 V. If the offset is reduced there is very less (than even one half cycle) ON period. The amplitude is always set somewhere in the range of 5-7V. There is a trade-off between the amplitude and the offset that can be set. This relationship is as given as below
x + |y| = 10 where ‘y’ is offset and ‘x’ is the amplitude
(All these information are hands on and first.)
EXPERIMENT and PROBLEM:
I tried modulating a 70W 220V LED lamp. It did modulate, but there is NO off state. To put it in other words, the off state is: a constant less intensity glow. Even when the offset is set to zero the lamp glows. No below-zero offset can be achieved. No matter how low (negative) the offset can be taken the lamp continues to glow (don’t forget the trade-off I mentioned above).
I have been looking into possibilities that might be the cause for it.
ACTIONS and OBSERVATION:
1. The output of the function generator (and amplifier) was connected to multimeter leads. With no output, it gives out a 70V (±5) output (RMS multimeter).
2. On connecting a CRO: initially I viewed 50Hz AC which was moving up and down like a skipping rope whip. On zooming out we could see the wave become a line and then act accordingly as I modulate and set offsets.
QUESTION:
How to modulate the LED source with a proper negative half cycle (OFF STATE EXISTING)?