Assuming you want to just vary the voltage to the lamp (and can put up with the inefficiency of a linear circuit), I'd just use a dual or quad op-amp. One section would be an inverting integrator (non-inverting input grounded, input resistor to inverting input, capacitor output to inverting input). Another section would be a non-inverting schmitt trigger (wired just like an inverting amplifier, but use the non-inverting input for the "feedback"). The output of the integrator will linearly ramp up and down. It could drive an emitter follower driving the lamp. For higher efficiency, another pair of op-amps could make another triangle wave generator, only at high frequency, and a final op-amp would serve as a comparator between the high and low frequency integrators. The output would be a PWM signal to drive the lamp. Back on PICs, the ShoeBox dimmer at http://www.dovesystems.com uses a 16c74b and includes this ramping function (in software). If the channel select switch is set to 701, there's a 1 second fade up of channel 1, then a 1 second fade down of channel 1 as channel 2 fades up. This repeats for channels 2, 3, and 4, then back to 1. The second two digits set the fade time in seconds (701 is 1 second, 799 is 99 seconds). Harold Harold Hallikainen harold@hallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm On Tue, 27 Jul 1999 19:23:42 -0400 Ralph Landry writes: >Hi all, >I'm looking for suggestions on a chip that can do a triangle wave >generation. I have an application where I want to ramp up and down a >6 >to 12v lamp. ie slowly on to full bright, and then back down in an >endless loop. I'd like to do it with minimal parts, I've seen some >circuits that use opamps but geez you need a trunk full of external >parts. The simpler the better and this will be it's only function. > >-Ralph >rlandry@haywood.main.nc.us >"If they call it Tourist Season why can't we shoot 'em?" >ICQ# 19545315 ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.