Heating Element Control

[Centar]

Clacker, not pretty but functional....
Does the fan blow out or in?
It would be better if the fan blows cold air directly on that heatsink (in), it seems a bit small...you could have used a CPU heatsink/fan combo.

The input inducer may not be heavy enough to handle 1000 watts as it was designed for under 500 watts and the small power switch (can't see if it it used) is defiantly not rated for more than 10 amps (probably only 6 amps) Also the input power cord socket is only rated at 10 amps I believe.

If these components are used at 1000 watts or more they are sure to overheat and melt/die in time.

Your riding the edge at 230 VAC and 1000 watts ( a little over 4.3 amps draw)

[Centar]

All this "electronic porn" has inspired me to put up some of my own...
The following pics are of my current TRIAC based controller build (still in progress), showing how I mounted the LEDs/resister on the dimmer itself (what I talked about in previous posts), how I created an indicator light, and how I housed it all.

The housing is a common outdoor type (weather proof) enclosure box made from thick cast aluminum (good heatsink) that I added some rubber feet to.
The Indicator light is made from the lens cut off an old regular pilot light and glued into a hole drilled in the cover plate.
The TRIAC will be mounted at the bottom of the box as in the pic and the heatsinks (CPU heatsinks scrapped from video games) are mounted on the sides, making the whole unit the heatsink.

I have to get a conduit elbow for the back hole for the power cords (heavy extension cord cut in half) to complete it all.
Oh and there will be a switch mounted in the top for bypass function.

9 pics in total 5 here and 4 in next post...

[Centar]

continuation of pics from previous post....

[rad14701]

Looking good, Centar...

Are you building this controller for 120V or 240V...???

[rad14701]

Clacker, I agree with Centar regarding some of those components being borderline for the amount of power being pushed through them... Nice to see that you go the controller working, but you should probably consider replacing some of those components with higher rated ones in the near future... As far as proof of concept goes, it works...

[clacker]

Thanks for the feedback guys.

I think I need about 600-700W of heat once the initial boil is over (was always going to use straight plug for that) but I'll take onboard your suggestions and make some changes.

Fan has been reversed so blowing directly over the heatsink (Stays cool at 1000W but do have some old CPU heatsinks) and I am using the power switch shown on the back there although that is not needed so can take that out of the circuit.

It's been a very informative thread but a long time reading/tinkering so looking forward to getting back to stillin!

[Centar]

Clacker, a power diode would drop 1000 watts to 500 watts with just one part....

RAD, The design specs for my controller are for 120 VAC @ 12.5 amps = 1500 watts

The TRIAC used is a 25 amp device, the bypass switch that I will be using will be 30 amp, the rest will be rated at 15 amps.

If used at 240 VAC the available power would be 15 X 240 = 3600 watts max although it has not been tested at this voltage.

[rad14701]

Clacker, a power diode would drop 1000 watts to 500 watts with just one part....

RAD, The design specs for my controller are for 120 VAC @ 12.5 amps = 1500 watts

The TRIAC used is a 25 amp device, the bypass switch that I will be using will be 30 amp, the rest will be rated at 15 amps.

If used at 240 VAC the available power would be 15 X 240 = 3600 watts max although it has not been tested at this voltage.

For the controller I'm currently working in I'm debating on whether to use a bypass switch or to just split a standard two socket outlet to have one outlet be controlled and the other straight mains current... I've used this method before for a dimmer based soldering pencil controller that appears to have grown legs because I can't seem to lay my hands on it now...

I tossed together another pair of LED's and a resistor today and when added into my test controller box the LED's never appeared to light up regardless of whether the resistor is located between MT2 and the LED's or between the LED's and the dimmer... Considering how I got very little illumination from the smaller first pair of LED's I'm left assuming that this is related more to the style of dimmer than anything... The dimmers I use can be found for as little as $1.99USD and only contain a Pot, a Quadrac, and a Capacitor between MT1 and Gate... Not that I intend to mount the LED's where they will be visible anyway... My high power TRIAC is an NTE5685 400V 25A non-insulated stud type which is way more TRIAC than I need for this controller...

[clacker]

Clacker, a power diode would drop 1000 watts to 500 watts with just one part....

Are you talking about a bridge rectifier?

That's what I've been using the last year in my pot still as the element is 2200W and the pot only contained about 10L of wash.

I tried that with my new CM head but the condensor tube is smaller than the half inch worm of my pot so I had to drop lower.

[still crazy]

Now for a question completely different

If I install a 240V 1500W element in my keg
And wire it 240V direct
AND 120V direct
Will it be in essence a 750W element when using the 120V

[rad14701]

Now for a question completely different

If I install a 240V 1500W element in my keg
And wire it 240V direct
AND 120V direct
Will it be in essence a 750W element when using the 120V

375W @ 120V

[still crazy]

So cutting voltage by 50% drops wattage by 75%?
Why so in simple terms

[rad14701]

So cutting voltage by 50% drops wattage by 75%?
Why so in simple terms

http://www.allaboutcircuits.com/vol_1/chpt_2/1.html" onclick="window.open(this.href);return false;" rel="nofollow

HINT - Resistance...

[squidd]

Clacker, a power diode would drop 1000 watts to 500 watts with just one part....

Are you talking about a bridge rectifier?

Just a single diode.
It will eliminate one half of an AC wave and so reduce power by 50%.

squidd

[Centar]

Still crazy: Power is simply voltage times current
and ohms law sates E=I*R or voltage = current * resistance

So...if you half the voltage across a resistance (the heating element) what happens?
FUll power 1500=240x ? = 6.25 amps
and 240=6.25x ? = 38.4 ohms resistance for the element
SO at 120volts we get 120=? x 38.4 =3.125 half of the current and power=current(3.125) times voltage(120)=375 watts

Simply stated: halving the voltage across a fixed resistance cuts the power dissipation by a factor of 1/4 (25% not 75%)

((This is called "logarithmic" and many things in nature respond this way including your hearing! (thus "log" pots for audio gear as opposed to "liner" pots say for a voltage control)))

RAD: The NTE5685's datasheet states that the min gate current to trigger it is 100ma, LEDs are typically 20 ma max.
It appears that you are blowing the LEDs shorting them out effectively removing them from the circuit! It is not the fault of the dimmer as that is only acting as a switch in the circuit.

Not only is this TRIAC overkill for the circuit but also the source of your troubles with the "LED" circuit which was designed for Regular TRIACs and POWER TRIACS of the microwave oven variety which have a much more sensitive gate.

[clacker]

Just a single diode.
It will eliminate one half of an AC wave and so reduce power by 50%.

squidd

Ahh yes, should have realised that as I am only using half of my bridge rectifier.

[Filby]

Hi

First time post!

Been doing a lot of reading (all 44 pages of this thread) and Im looking forward to getting stuck into making a still. The heating control side seems to be my only real hurdle. Can someone tell me if these two components that are available locally (Australia) will work with Odessit's circuit? ( http://homedistiller.org/forum/viewtopi ... 0#p6841975 )

http://www.jaycar.com.au/productView.as ... rm=KEYWORD

http://www.jaycar.com.au/productView.as ... rm=KEYWORD

I only want to run a 1500w element. Also this is 240v 50hz Aussie power.

Cheers

Fil

[Centar]

Clacker - actually a full wave (4 connections) bridge rectifier is 4 diodes. You only need to use 1/4 of it.
If it is a half wave (3 connections) you will need half of it...

You can turn a full wave into a half wave and double its current capacity by connecting the 2 AC connections together.

(of course assuming that were are talking single phase AC here)

[rad14701]

Well, against my better judgment, I removed the two LED's from my controller and ran directly through a 1200 Ohm resistor from MT2 to the dimmer... My TRIAC shorted as soon as I got to full voltage and tried backing down to 50% power... By the time I got down to ~80 volts the TRIAC had shorted... This thing has been a real workhorse and worked perfectly right up until I removed the LED's, which still work by the way... I guess they weren't shorted after all...

I'm still big on the dual time constant sensitive TRIAC controlling the high power controller so that's what I'll be using once I get more TRIAC's... Don't have a local source for them so I'll have to place an order for components to build several different types of controllers... Here is the one I have been using on and off for several years in various projects... The small .8A TRIAC has been replaced due to a connection error on my part when I was in a rush to migrate it from one project to another... I usually run a 75 Ohm 25 Watt ceramic resistor between MT2 and this circuit which then feeds the Gate of a high power TRIAC... This circuit came out of a 1500W Northman ceramic heater that still resides in its original box in the closet that I've had for about 20 years...

I've also been contemplating building an LM555 and an Opto-Triac circuit as well... Can't tinker with electronics too much... Unfortunately, I never get to stick with it long enough to remember from project to project without doing research... All we need is another concept to throw more twists and turns into an already convoluted topic...

[Centar]

Rad: The whole concept of my circuit is to modify a regular household light dimmer, not sure of the kind your using there....
Practice the "KISS" principal and just use a regular dimmer and a half way normal power TRIAC and the LED circuit will work fine.
It is as straight forward as it can get.

It has crossed my mind to make available the prototype that I am building as a production unit for a affordable price to members here on this forum.

[rad14701]

Rad: The whole concept of my circuit is to modify a regular household light dimmer, not sure of the kind your using there....
Practice the "KISS" principal and just use a regular dimmer and a half way normal power TRIAC and the LED circuit will work fine.
It is as straight forward as it can get.

It has crossed my mind to make available the prototype that I am building as a production unit for a affordable price to members here on this forum.

Mine is a regular household dimmer that I buy them from several sources and they all contain the same components...

I build all kinds of small power supplies for different projects... I have quite a few different low power control circuits for nichrome wire foam cutters from back when I needed just one for cutting model airplane wing cores and ultralight airplane wing ribs... To me "normal" is a relative term...

If you are looking to market controllers I think 240V units would provide a bigger market than 120V...

[clacker]

http://www.jaycar.com.au/productView.as ... rm=KEYWORD

http://www.jaycar.com.au/productView.as ... rm=KEYWORD

I only want to run a 1500w element. Also this is 240v 50hz Aussie power.

Cheers

Fil

Hi Filby,

They are the exact two parts I used for mine...no dramas.

Just be careful as the 400V 15A SC151 Triac is non-isolated so your heatsink will be "live". Having said that, that was the part I ordered under and it ended up being a different Triac model with same specs but was isolated.

I also added a 1M OHM resistor across the pot like Odessit mentioned to increase the range.

[Filby]

Thanks for that Clacker!

So with the 'live' triac I should have the heatsink in a plastic case (with ventilation) so its electrically isolated?

Also, I'm struggling to find a heater element which uses the threaded coupling. What did you end up using for your setup?

Cheers

Fil

[Centar]

Filby: The NON isolated TRIAC means that its mounting (the case) is actually connected to the T2 or T1 leg, it will make anything it is bolted onto electrically "live"
You need to mount it with a insulator between it and the heatsink as well as use insulated mounting hardware (screws, nuts) OR you need to insulate (electrically) the heatsink from everything else with plastic stand-offs, etc

This is why isolated devices are much more desirable. Much easier to design with and mount to heatsinks (just bolt em on)
They make NON isolated devices because they have a lower thermal resistance and can dissipate more power than the isolated versions.

[Centar]

RAD: I'm most confused by your experience with removing the LEDs from you controller....

#1 the LEDs have at best a 2 volt drop across them and can handle up to 20 ma current, so if they were not lighting up there was much less than 10 ma going through them and removing them would make NO practical difference to the circuit.

#2 If your TRIAC "shorted" how were you able to get it back down to 80% before it shorted again....unless I am misreading your post.....

Sounds like you need to do a test: Get a 100 ohms (aprox) resister and a 1 to 5 K pot and connect it all in series and try your dimmer at different resistance settings, try to set the pot for its lowest setting that #1 doesn't heat up the 100 ohm 1/4 watt resister and #2 provides proper operation, then unhook it (the pot and resister) and measure its total resistance, that value (aprox) should be used with the LEDs in your dimmer.

and your right....I should never use the word "normal" to describe something technical......

[clacker]

Thanks for that Clacker!

So with the 'live' triac I should have the heatsink in a plastic case (with ventilation) so its electrically isolated?

Also, I'm struggling to find a heater element which uses the threaded coupling. What did you end up using for your setup?

Cheers

Fil

Happy to help, it's a great forum to be a part of!

I'd ring your local Jaycar to see if they have the same stock I got.. BTA code on the TRIAC indicates isolated (Pretty certain but I'd check the datasheet anyway).

I had preps ready to isolate heatsink (as I was expecting non-iso) but it was much easier after I got the iso package. Seems much safer to me as well.


I've gone off the shelf parts which isn't ideal but I'm using a 19L BIGW stockpot and 2200W kettle element from BIGW kettle

I've since learned that kettle elements aren't as robust but my one has done 20 x 2 hour runs so far so I'll monitor it's life vs cost.

[rad14701]

UPDATE

Now, this is a first for me... Yesterday I posted about how my NTE5695 (400V 40A) TRIAC, previously stated as being a 5685 (400V 25A), had shorted out... Well today I did some simple testing to see if it was actually the dimmer switch that had shorted and it was fine... The TRIAC still fired up at full power even with the dimmer control circuit disconnected from the Gate terminal...

Then I noticed it... At some point I had managed to have some of my soldering flux paste drip down onto the top of the TRIAC... Hmmm, I thought... I grabbed a Q-Tip, dipped it in some alcohol, and cleaned off the top of the TRIAC... Presto...!!! Now the TRIAC didn't power up without signal to the Gate terminal... All of this from a very very thin layer of solder flux paste that was barely visible with the naked eye... I reconnected the dimmer control circuit to the Gate terminal and did some extended testing and everything is back to normal... The TRIAC is functioning perfectly... To be honest, I never would have expected such a tiny amount of flux paste to cause the triggering of a high power TRIAC...

Just thought I'd make mention of this on the off chance that it might help someone else should they ever run into a similar circumstance...

[MuleKicker]

So the flux was acting as a conductor? I have some flux that appears to have solder dust in it. Could that be it?

[Centar]

Conducting flux (rosin) is unheard of......there must have been some contamination in it like solder or a VERY thin piece of wire or something....Just goes to show my point that the BIG gate resister isn't needed, TRIACs usually have a quite sensitive gate. BUT I gotta say RAD that is a new one on me too and I have been repairing electronic gear for 30 yrs and have NEVER seen rosin cause a problem like that......are you absolutely sure is was ROSIN CORE solder? Because acid core would explain it all...

[rad14701]

Conducting flux (rosin) is unheard of......there must have been some contamination in it like solder or a VERY thin piece of wire or something....Just goes to show my point that the BIG gate resister isn't needed, TRIACs usually have a quite sensitive gate. BUT I gotta say RAD that is a new one on me too and I have been repairing electronic gear for 30 yrs and have NEVER seen rosin cause a problem like that......are you absolutely sure is was ROSIN CORE solder? Because acid core would explain it all...

Surprised me as well... I've been working with electronics for 40+ years and have never encountered anything like this... I got my first electronics kit, soldering pencil, and soldering gun when I was just 8 years old... I keep getting lured back into tinkering with electronics every so often and then put it on the back burner for weeks, months, or even years at a time... I still have PCB direct etching dry transfers that are at least 25 - 30 years old... I even used to make my own computer components back in the early to mid-80's...

Archer 64-005 60/40 Rosin Core Solder straight from Radio Shack... One thing I had done recently was to clean the tip of the soldering pencil with Berzomatic Petroleum Based Plumbing Flux (Lead Free), but that was all wiped off with a damp sponge prior to soldering...

I duplicated the "phenomenon" again after my last post... I re-soldered the TRIAC wiring and the rosin core flux vapor once again shorted the TRIAC... I cleaned it off again using a Q-Tip and alcohol and it worked as expected... The controller is working so well that I've actually screwed the cover back on - something I almost never do with my projects... I'm not playing with this one again... I'll order up some more parts in the near future and have another go at one of several designs... I know I can build dimmer based controllers so I'll probably build a few dual time constant circuits next, or an LM555 + Opto-Triac circuit because they are easily adapted between 120V and 240V...