RE: [OT]? Lighting Controllers

Both ideas seem intriguing. But what size/rating of resistor is "safe" enough for use on a PIC????

Also, I have seen "programmable" resistors (can't remember who or part #) that you could hook up to a PIC and just program the resistance (I think, haven't tried).

John Mullan

-----Original Message-----
From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Michael Rigby-Jones
Sent: Tuesday, December 07, 1999 7:54 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [OT]? Lighting Controllers

look for light dependant resistor optoisolator...........an l.e.d and a
resistor in the same package.....................
firing the led from the pic in pwm style produces a full range of resistor
output values...........then connect the
resistor in to say a triac circuit to control the ac voltave...........ac
light dimmer............for just an idea..........
you can make you're own if you cant find one.........green led........and a
small cds photocell................
use black 1/2 inch diameter heat shrink and wall........la..........an
ldr...........just a thought.........tim

You certainly enjoy using the period key don't you Tim :o)

You don't actually need to use an optoisolator, there have been several dimmer circuits that have run directly from the mains with no isolation at all. The mains voltage is fed directly to a PIC input via a current limiting resistor to detect zero crossing points. However, if the dimmer is going to be wired to someones PC for control then obviously this little scheme has it's drawbacks. (like electrocution).

Mike

-----Original Message-----
From: Mark Boyce <mark@INTERHOUSE.REDBUS.CO.UK>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Tuesday, December 07, 1999 5:00 AM
Subject: [OT]? Lighting Controllers

>Hi all,
>
>Hope this isn't too off topic for people :-)
>
>I need to be able to switch/dim some lighting from a pic
>controlled system.
>
>The actual target lighting will be pairs of 12v halogen spots
>such as you find in most low-voltage desk lamps or alike.
>
>The circuit I'm after should produce either 0<->12v or
>0 <-> 240v on the output and take something I can connect
>to a pic on the other side.
>
>Software is my game with a little bit of 'plug the black boxes
>together' digital electronics so I'm out of my depth here :-)
>
>Does anyone have any pointers/urls/circuits/tips/etc that might
>help ?
>
>Cheers,
>
>Mark
>
>--
>"What contemptible scoundrel stole the cork from my lunch ?"
> - W. C. Fields