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Self Regulating AC Phase Controller for Heater

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  • Self Regulating AC Phase Controller for Heater

    Stop here as this is not very interesting for most.....You were warned,

    So I made a self regulating AC phase controller for a heater (light bulb based) I've made for my squirrel house (or whatever)..........The Home Depot/Ace Hardware type of light dimmer rheostats (Triac dimmer) do work well enough to adjust the heat output of a given light bulb/heat source HOWEVER, they don't/can't self adjust for varying temps/loads particularly IF you use them as a heat controller as I am.

    The down fall comes when I could set it such that the light bulb gave out enough/proper heat to make it to say around 40F inside the house on one day. So on this given day, say it was around -4F out, then 2 days later it's 42F out, now it's too warm inside, I'm always chasing it from day to day seems.......no insulation per-se with a wooden box doesn't help either.

    I've considered/used the regular on to off temp dial adjustable old but, true school bi-metal type thermostats and they might work okay but, switching the bulbs from all on to all off, as they do, blows out the bulbs as I'd hit max cycle rating in a day I think.......And, they're just too big and not practical for what I'm working with.

    This thing (breadboard testing right now, I'll lay out a PCB in the next day or twelve) is pretty simple (I think, see source code link and schematic link), it still uses a Triac to control phase like the light dimmers do but, this has feedback to adjust itself accordingly........The design just monitors its own 120VAC 60Hz power source waveform, when it crosses zero (twice per cycle) a "zero crossing" circuit signals the uPC which then fires a interrupt in the code, the interrupt service routine (ISR) then grabs the desired set point temp and the actual temps and compares the two, if actual temp is less than the real temp, turn on the Triac (solid state switch) which of course, closes the AC circuit to the bulb/heater. If and when the actual temp goes higher then the set point temp, it turns off the bulb/heater, pretty simple!!........The interrupt on zero crossing keeps things in sync BTW.

    The code does this forever (while (1) loop) and fires a interrupt at the two crossing per cycle = 16.67ms/2 = 8.33ms where 1/60hz = 16.67ms. I spiced it up a bit and put a variable delay in one of the "on" routines to reduce overshoot on heat up and reduce any further filament stress there is.....Basically, I chop the "on" cycle down (from 180 degrees down to about 20 degrees)up as the real temp reaches (attack rate if you will) the set temp. I do this from a difference of 6 degrees F and less, on for full 180 degrees of the cycle for a delta greater to 6 degrees F and then down to only 20 degrees of the cycle as the delta goes to 0 F..........Seen in the scope video link, the cycles are being chopped more and less as it tracks/holds/changes temps.

    In the video, I have the set point temp at 90F with the monitoring ("actual temp") temp sensor sitting/pressed on the cup bottom as seen, the halogen is 200W (those will burn ya as you might know, feels like 700-800F seems). It holds and tracks quiet well I might add, meter scale is 0.900V = 90F, 0.905V = 90.5F etc.. Scope shows input 120VAC (top trace) relative to the bulbs input (lower trace). The microcontroller is running at 32Mhz FWIW.

    I also use a shallow'ish bird bath dish to water my back yard critters and need to use water heater (44 watt) in winter, I have to use a 120VAC inline anti freeze thermostat (pre-set bi-metal switch) that auto-magically comes on when the ambient temp is at like 28F and below but, it tends to evaporate (over heat) the water at times so fast, its dry in two days. With this however, it'll work much better set at say 35F. It'll track the water's temps waaaay better and will just warm the water enough to not freeze.......I'll just pot the sensor in some epoxy and drop it in the water weighted to the bottom.

    Why? because I can, it's like 100F outside, I'm bored, needed another project AND have a sorta sick fox squirrel. Boris (sister of Natasha and both daughter's of Rocket J) has seizures sometimes and isn't developing normally, not sure why but, beings she and her sister were both born in this house this past Feb, they both continue to live here and Boris, I'm afraid might not make it this winter.

    Part numbers are all on the schematic, the design and source code (with comments) are mine, feel free to use at your will............
    Last edited by sam am I; July 17th, 2018, 07:04 PM.

  • #2
    Sounds like your having fun. I have access to controls so I would do things different. First of all I would use some type of calrod heating element instead of light bulbs. A RTD or thermocouple to sense temperature and send to the input of a process controller and use the output of that process controller to cycle a solid state relay. You can find parts on ebay to do this. In my younger days when I had time to kill I would probably do it by breadboard like you....good luck!
    The older I get,the less I care what people think.....Central NC

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    • #3
      Oh yes, few ways to get there, forsure......


      Originally posted by bigdee View Post
      calrod heating element instead of light bulbs.
      Hmmmm, Link? How much? Definitely open to new ideas.......

      Here's my current heat box..........I wanted (and ran last winter) it to be more or less safe as safe could be. Didn't want red hot anything...The bulb filament is of course in glass tube, the bulb body is mounted on ceramic seat and has a ceramic cover (bowl over the top), then placed a heater box that is lined top to bottom with hardback with a piece of hard back directly over the top of the works angled such to deflect/direct the heat up into the copper heat pipe, that as it enters into the house, is perforated and is copper capped off at the top. Don't want bedding to be in heat box.

      Originally posted by bigdee View Post
      A RTD or thermocouple
      Considered, extra part$ with either tho. LM34 off the self cheap, +/- 1 degree F over temp range I need, plug and play too RTD's and T couples are nice tho, agreed

      Originally posted by bigdee View Post
      use the output of that process controller to cycle a solid state relay.
      Yes, I have some BUT, I'll take more if you have extra just laying around .......SSR's are just Triac's or FET's with opto front end's, I'm cheap, made my own.


      Originally posted by bigdee View Post
      In my younger days when I had time to kill I would probably do it by breadboard like you....good luck!
      You're never too old, gotta make the time
      Last edited by sam am I; July 17th, 2018, 08:33 PM.

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      • #4
        Hey, I bought halogen bulbs for street light because of so much fog near by our home and also accidental prone area so I was thinking something helpful for passer by controlling the brightness of light, I saw your post today and being a newbie to this area, I google out this AC light Dimmer and was thinking to buy and you have any experience in this kind of products can suggest me, will it be helpful to control the lightning of halogen lights through this AC light Dimmer ?
        AC Light Dimmer 2-Channel x 750W This high-power 2-Channel Pulsar series AC light dimmer offers 256 levels of computer-controlled brightness with lighting e

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        • #5
          Originally posted by sam am I View Post
          Oh yes, few ways to get there, forsure......

          Originally posted by bigdee View Post
          calrod heating element instead of light bulbs.
          Hmmmm, Link? How much? Definitely open to new ideas.......
          Several ideas: old toaster over, electric stove burner element, resistance wire element out of old space heater or toaster.....you could cut to length to get the wattage you desire. Also a 240 volt halogen lamp would last a very long time if cycled with 120 vac. You could also use standard light bulbs and series 2 or 3 of them together(probably cheapest option). I believe a cyclic method would be a better way to control temperature than analog. In your case a simple on/off approach via a thermostat would work. If you are serious about accurate/consistent control you would need a PID process.
          The older I get,the less I care what people think.....Central NC

          Comment


          • #6
            Originally posted by bigdee View Post

            Several ideas: old toaster over, electric stove burner element, resistance wire element out of old space heater or toaster.....you could cut to length to get the wattage you desire. Also a 240 volt halogen lamp would last a very long time if cycled with 120 vac. You could also use standard light bulbs and series 2 or 3 of them together(probably cheapest option). I believe a cyclic method would be a better way to control temperature than analog. In your case a simple on/off approach via a thermostat would work. If you are serious about accurate/consistent control you would need a PID process.

            Ahhhh, okay, Nichrome

            thx Bigdee.......

            Comment


            • #7
              Ah, I see....edit spoke too soon
              '47 18' CC Utility "Knock On Wood"
              Various Evinrude powered Pontoons all named "Floosy"

              Comment


              • #8
                bi-metalic thermostat chord (old but bullet proof tech) and a self-adhesive oil pan warming pad (no flashing lights, designed to be turned on and off)

                now go fishing.
                Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                Past Boats
                1970 Wooster Hellion - Merc 9.8
                2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                What’s behind you doesn’t matter.Enzo Ferrari

                Comment


                • #9
                  Originally posted by Scott Danforth View Post
                  bi-metalic thermostat chord

                  now go fishing.
                  Heat tape(nichrome wire) with bi-metal stat? Very safe, easy yes, on/off yes, like it BUT, not enough heat/area if so.....Heat box sits underneath, it's same W x L as house but, is perhaps 18" deep

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                  Not sure what this beast is, gotta link?

                  and just was
                  Last edited by sam am I; July 18th, 2018, 05:22 PM.

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                  • #10
                    just google tank heater pads or oil pan heater. they are 150 watt, about a foot square. will keep a 6B Cummins warm in -30F temps

                    about 2 dozen companies sell them, however phillips and Temro (zero start) is probably the best.

                    https://www.google.com/search?q=self...firefox-b-1-ab

                    they are used on large hydraulic reservoirs, motors, etc.
                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                    Past Boats
                    1970 Wooster Hellion - Merc 9.8
                    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                    What’s behind you doesn’t matter.Enzo Ferrari

                    Comment


                    • #11
                      Originally posted by Scott Danforth View Post
                      just google tank heater pads or oil pan heater. they are 150 watt, about a foot square. will keep a 6B Cummins warm in -30F temps

                      about 2 dozen companies sell them, however phillips and Temro (zero start) is probably the best.

                      https://www.google.com/search?q=self...firefox-b-1-ab

                      they are used on large hydraulic reservoirs, motors, etc.
                      Ahhhh, same as my bird bath water heater, yes saw those, silicone coated nichrome heating pads.....Very nice, made for on/off.

                      Pad on outside bottom but issue with blocking floor vent holes (sorta required) and the bi-metal adjustable temp inline stat then lives in the house with the chewies.....Would need to conceal it internally somehow, might need to mod the house to do this, those stats are pretty big.......It has a false roof, if small enough stat, could do this and sense the house heat from the false roof but, camera self heats a bit....Hmmm

                      Or, could use a remote sense capillary type bi-metal adjustable stat, probe end could poke in the house and be covered with a bit of something like I was going to do with the LM34....


                      I like it, but the floor would rot (i used cedar, so slowly rot) and blocking vents would not allow the floor works and critters to breath so well.

                      What isn't shown, that the inside floor bottom is false too. The bedding is suspended (bedding falls in and plugs the drilled floor holes) and laying above the wood through-hole vented floor by about 1/2" on a framed alum screen.....i.e., there's a 1/2" air gap between the inside drilled vented wood floor bottom and the bedding.

                      I know, I know, some people shoot them/eat them........Well, some people eat dogs too!!
                      Last edited by sam am I; July 18th, 2018, 06:28 PM.

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                      • #12
                        Put in a false floor with the pad on botyom and t-stat on top. set the temp for 55-65 degrees...

                        Critters would have warm floor ( like hydronic heat im my buddys garage) nothing for critters to chew on. Access panel on bottom and you dont disturb them.

                        Add burlap curtains....for that homie feeling
                        Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                        Past Boats
                        1970 Wooster Hellion - Merc 9.8
                        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                        What’s behind you doesn’t matter.Enzo Ferrari

                        Comment


                        • #13
                          Originally posted by Scott Danforth View Post
                          Put in a false floor with the pad on botyom and t-stat on top. set the temp for 55-65 degrees...

                          Critters would have warm floor ( like hydronic heat im my buddys garage) nothing for critters to chew on. Access panel on bottom and you dont disturb them.

                          Add burlap curtains....for that homie feeling
                          Ya know..........I'll just put the pad IN the heat box!! Not rolled up but, curved a bit up on one edge!!

                          200W is 200W regardless if its a bulb or silicone covered nichrome or carbon, nor does it matter, in this case, if its stuck on something (the wood) or not. 200W of radiating heat of whatever origin in the heat box has to go somewhere and that's up, mostly, the way the heat box is designed, it will.....Safer than the bulb too!! I like that...

                          I will still drive it (along with the bird bath heater, both are same difference) with my circuit for two reasons 1) The stat (heat sensor) is tiny as a tic-tac 2) Much evener heat (analogous to cooking on gas burner verse electric burner)

                          Very cool indeed, thx....

                          Thinking aroma therapy over the burlap though...

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                          Last edited by sam am I; July 19th, 2018, 06:23 AM.

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                          • #14
                            my only concern on electronic vs a simple bi-metalic switch is that many animals are susceptible to various frequencies..... it may drive them nuts.
                            Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                            Past Boats
                            1970 Wooster Hellion - Merc 9.8
                            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                            What’s behind you doesn’t matter.Enzo Ferrari

                            Comment


                            • #15
                              Sign up today
                              Hmmmm, good point and very true about critters abilities to hear things we do/don't and it can mess with their heads.........Thinking that because I'm not switching (PWM'ing) at some high freq for example but, actually I'm either just turning off the/or part of the 60hz cycle by cycle. I'm in fact then, when the heater is on in any given cycle, I'm not adding components by just turning more off of what is already there, I'm actually taking away more by shutting it off more often.

                              However, there could be the possibility of a low amplitude side band artifact/harmonic created from the fast turn on rise times. Soooooo, I will run a FFT at a few given chopping points, will look at a 100K spectrum of what's there. TYVM for bring that up.

                              And in addition and as seen, the house has a web camera (also event driven web based temp monitors/alarms and UL/CSA thermal cutoffs) and I have many years and pretty solid baseline of their free will habits coming and going from their/this house. I'll be observing them closely when I remotely energize their house heater, watch for any adverse actions/reactions, both short term and long, if any.
                              Last edited by sam am I; July 19th, 2018, 02:23 PM.

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