Hi all
I'd like to have a periodic dimmer for some LEDs I have, for lounge lighting effect. I have them arranged in containers lighting coloured glass beads, it looks quite nice, and I'd like to have the bulbs periodically change from low to high luminosity and back again. I'm thinking a very slow transition, say, from once every five minutes to once or twice in one minute, that is roughly, 0.003Hz to 3 Hz. (I hope I worked that out properly).
The bulbs are 12V car lamp bulbs, with 120 SMD diodes on each 'corncob' and a T10 plug. They draw 200mA from 12V (and are quite bright!) . I'd run them from a 12V plug pack, with individual controls for cycle times.
I don't think that LEDs vary much under changing voltage, or just vary rather abruptly. My thinking was to have a PWM circuit for each bulb, with a cyclic (and controllable) pulse width.
That's as far as I got. I have some PWM circuits for controlling 12V fans in computers, but they are all using a pot to vary the duty cycle. I guess the FETs in the designs I have will get hot, I've already grabbed some IRF530N FETs for that, the rest is just a 555 and its timing components, plus ... ? A very low frequency variable voltage source? I'm really displaying my ignorance so I'll stop before I hurt myself.
Could anyone suggest how to do build something like this ?
I'd like to have a periodic dimmer for some LEDs I have, for lounge lighting effect. I have them arranged in containers lighting coloured glass beads, it looks quite nice, and I'd like to have the bulbs periodically change from low to high luminosity and back again. I'm thinking a very slow transition, say, from once every five minutes to once or twice in one minute, that is roughly, 0.003Hz to 3 Hz. (I hope I worked that out properly).
The bulbs are 12V car lamp bulbs, with 120 SMD diodes on each 'corncob' and a T10 plug. They draw 200mA from 12V (and are quite bright!) . I'd run them from a 12V plug pack, with individual controls for cycle times.
I don't think that LEDs vary much under changing voltage, or just vary rather abruptly. My thinking was to have a PWM circuit for each bulb, with a cyclic (and controllable) pulse width.
That's as far as I got. I have some PWM circuits for controlling 12V fans in computers, but they are all using a pot to vary the duty cycle. I guess the FETs in the designs I have will get hot, I've already grabbed some IRF530N FETs for that, the rest is just a 555 and its timing components, plus ... ? A very low frequency variable voltage source? I'm really displaying my ignorance so I'll stop before I hurt myself.
Could anyone suggest how to do build something like this ?
