Post by thread:AC power control with 12C671

I would like to control how much power is delivered to some Christmas lights, using a PIC12C671. Initially, I was going to detect AC zero crossings, wait for my desired phase delay, then fire an SCR (phase control, repeat every half cycle). The only problem with this is that I am a PIC newbie and would rather find a method with simpler programming. My question is are there simpler ways to control the power to my christmas lights with a PIC? The reason I ask, is that in our lab there is a very simple device to vary the power delivered to a AC motor (universal vacuum type motor). It consists only of a potentiometer (100k, to select voltage), a red disc capacitor marked V130LA10A, a orange capacitor inductor looking thing marked .22-200 DC, a small resistor looking thing (diode maybe?), and a triac (SK3659 or MAC15-8). I don't know how this works, but whatever it does, must not require the timing that I would need for phase-control. Toby Stensland spam_OUTtobyTakeThisOuTstensland.com http://www.stensland.com

Toby Stensland wrote, without linefeeds: > in our lab there is a very simple device to vary the power delivered > to a AC motor (universal vacuum type motor). It consists only of a > potentiometer (100k, to select voltage), a red disc capacitor marked > V130LA10A, MOV = Metal Oxide Varistor = surge supressor. > a orange capacitor ... marked .22-200 DC, a small resistor looking > thing (diode maybe?), Likely a Diac - trigger device with threshold somewhere in the 8 to 30V range. > and a triac (SK3659 or MAC15-8). Standard light dimmer circuit. -- Cheers, Paul B.

On Thu, 10 Dec 1998 12:37:21 -0700, Toby Stensland wrote: >My question is are there simpler ways to control the power to my christmas ligh ts with a PIC? The reason I ask, is that in our lab there is a very simple device to vary the power delivered to a AC motor (uni versal vacuum type motor). It consists only of a potentiometer (100k, to select voltage), a red disc capacitor marked V130LA10A, a orange capacitor inductor looking thing marked .22-200 DC, a small resistor looking thing (diode maybe?), and a triac (S K3659 or MAC15-8). I don't know how this works, but whatever it does, must not require the timing that I would need for p hase-control. That's basically an analog version of what you want to do with the PIC. You wil l probally find that the capacitor is tied to the gate of the triac and charges through the pot. When the cap reaches Vg of the triac, it discharges and turns on the triac. Repeat cycle. I don't know if it will be any eaiser code wise but you might look into zero cro ssing power control. Basically instead of turning the ac on at a particular phase point you turn the AC off for x cycles and then on f or x cycles. Also has the advantage that it does not generate any EMI since all the switching is done at the zero cross. -- Richard A. Smith Bitworks, Inc. .....rsmithKILLspam@spam@bitworks.com 501.521.3908 Sr. Design Engineer http://www.bitworks.com

Toby Stensland wrote: <snip> > It consists only of a potentiometer (100k, to select voltage), a red disc capa citor marked V130LA10A,<snip> The V130LA10A is a MOV (Metal Oxide Varistor). It is a transient voltage surge supressor and is usually used across an AC power line. It has a nominal breakdown voltage of 130 AC (RMS) or 175VDC. It handles about 38 joules of energy. The 10A at the end is supposed to be an a mperage rating, but I could never make it fit the specs. Anyway, a 10A handles approximately half the current of a 20A, etc. Michael ************************************************************************* When the way of the Tao is forgotten, kindness and ethics must be taught. Men must learn to pretend to be wise and good. -- Lao Tzu *************************************************************************

On Thu, 10 Dec 1998 12:37:21 -0700, Toby Stensland <tobyKILLspamSTENSLAND.COM> wrote: >I would like to control how much power is delivered to some Christmas lights, using a PIC12C671. Initially, I was going to detect AC zero crossings, wait for my desired phase delay, then fire an SCR (phase control, repeat every half cycle). The only problem with this is that I am a PIC newbie and would rather find a method with simpler programming. > >My question is are there simpler ways to control the power to my christmas lights with a PIC? The reason I ask, is that in our lab there is a very simple device to vary the power delivered to a AC motor (universal vacuum type motor). It consists only of a potentiometer (100k, to select voltage), a red disc capacitor marked V130LA10A, a orange capacitor inductor looking thing marked .22-200 DC, a small resistor looking thing (diode maybe?), and a triac (SK3659 or MAC15-8). I don't know how this works, but whatever it does, must not require the timing that I would need for phase-control. Nope, sorry to disappoint. But it DOES use the timing you would need for your project. The diode thing is really a DIAC which is really kind of a voltage controlled switch. Above a certain voltage it turns on. It's also bi-directional. The DIAC will behave the same regardless of which way you supply the voltage. The circuit is setup so that as the voltage from the AC rises, it eventually hits a point where the DIAC is triggered on. This in turn fires the TRIAC for the rest of the cycle, after which point the Triac turns itself off, and the whole thing starts over on the opposite edge of the cycle. The variable resistor is used to change the voltage across the DIAC so that a higher or lower line voltage is needed to trigger the DIAC. This in turn cause the DIAC to trigger later to earlier in the cycle, for a dimmer to brighter light. So the timing is all built in, using the level of the AC cycle as the trigger point/timing -- everything happens 120 times a second. Capacitors and inductors are thrown in to keep the whole unit from acting too much like a wide band AM noise generator. (Just try using an AM radio near one of these things!) -Zonn <><><><><><><><><><><><><><><><><><><><><><><><><><><>< ------ ___ Member of A.A.C.S.: |---- | ( ) Association for Artistically / / ( () ) Challenged Signatures / / //\\ // (__) / ---/ // \\ //\\ // zonn @ zonn . com -------| // \\/

On Fri, 11 Dec 1998 06:55:13 +1000 "Paul B. Webster VK2BZC" <.....paulbKILLspam.....midcoast.com.au> writes: > > Standard light dimmer circuit. The standard light dimmer circuit, of course, is doing phase control timing using an RC network. Although it'd be terribly nonlinear and probably vary unit to unit, it seems that one could "remote" a hardware store light dimmer by using an opto coupler that has a CDS opto-resistor as the output device. Substitute it for the pot in the timing circuit, then vary the LED current (possibly using the PWM output of a PIC). In our light dimmer products (at http://www.dovesystems.com), we use the PIC to drive an opto triac at the appropriate point in the AC cycle (using the capture compare register to generate an interrupt at the appropriate time), or have a PIC do DMX to analog conversion, then drive analog comparators that are comparing the analog with a negative going ramp synced with the AC line. Harold Harold Hallikainen EraseMEharoldspam_OUTTakeThisOuThallikainen.com Hallikainen & Friends, Inc. See the FCC Rules at http://hallikainen.com/FccRules and comments filed in LPFM proceeding at http://hallikainen.com/lpfm ___________________________________________________________________ You don't need to buy Internet access to use free Internet e-mail. Get completely free e-mail from Juno at http://www.juno.com/getjuno.html or call Juno at (800) 654-JUNO [654-5866]