In this case, the speed of the Triac is dwarfed by the speed of the lamp itself. Incandescent lamps take a non-trivial time to warm up enough to give off light. How long they take depends on the filament design and bulb. This is one of the reasons that phase control dimming works, because you can get rid of half of each half wave of AC and not notice any flickering - it takes too long for the filament to cool down (and warm up) to lower the light level and bring it back up noticably. This is also why there's little reason to transmit light brightness updates more than 40 times per second (as is done in DMX-512). So, depending on the incandescent bulb, IMO, it could certianly take an incandescent bulb 40mS to achieve 80% brightness, regardless of whether you used a triac or any other switching device to turn it on. Please note that I haven't measured this. You can see the difference by looking at a car which has LED brake lights versus one with regular bulbs. You can perceive that the LEDs appear instantaneously, whereas the bulbs definitely have a warm up time. -Adam John Pearson wrote: >I should get straight to the point, while all the info is very helpfull too. > >What would be the longest possible time it would take to turn on an >incandecsent 150 watt bulb with a triac controlling 110 volt 60Hz current. >Somehow I figured it could be as long as .040 secs. This is assumming a >perfect light bulb, that would illuminate instantly and a perfect triac, >that would turn on instantly. > >Thanks > >John >----- Original Message ----- >From: "Michael Reid" >To: >Sent: Thursday, April 24, 2003 8:38 AM >Subject: Re: [EE]: Triacs, turn on characteristics > > > > >>there are some great TRIAC tutorials on the teccor web site, on ST's web >>site, as well as other manufactures of TRIAC's. Most TRIAC's are 3 >> >> >quadrant > > >>devices. Teccor also has sensitive gate TRIAC's that can be triggered >>directly from I/O's of some microcontrollers, using an inexpensive diac >> >> >vs. > > >>opto isolator. >> >> >> >> >>On Thursday 24 April 2003 08:13 am, John Pearson wrote: >> >> >>>How fast are generic Radio Shack triacs for switching 110v 60Hz >>>current to...say...a 150Watt incandecsent light bulb. >>> >>> >> >> >>>When the triac is enabled, where on the AC wave form will it turn >>>on? Anywhere? >>> >>> >>You don't "enable" a triac, you turn it on. And it turns on within a >>very short time (a few usec) of turning on the trigger current. >> >> >> >>>How about turning off, as I recall, the AC needs to cross zero for >>>a triac to turn off? >>> >>>Thanks for any help. I am in a real pickle here. Got caught BSing >>>on a forum and need to do some damage control. ; ) >>> >>> >>-- >>Ned Konz >>http://bike-nomad.com >>GPG key ID: BEEA7EFE >> >>-- >>http://www.piclist.com hint: The PICList is archived three different >>ways. See http://www.piclist.com/#archives for details. >> >>-- >>http://www.piclist.com hint: The PICList is archived three different >>ways. See http://www.piclist.com/#archives for details. >> >> > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. > > > > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.