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watertrade

Help with mains electrical project 240v big amps!

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I know as a general rule, that by having to ask the question I probably shouldn't be doing it... But I really want too!

Could someone with the knowledge help be out?

I am looking to control the power output of a 1800 watt electric water heating element. I would like to use a micro controller to vary the output from 0 -> 100%

I intend to do this by switching a relay on/off for different periods of time with the micro controller (arduino) I would like to do this as safely as possible and without too much electromagnetic interference.

Is it as 'easy' as using a zero crossing solid state relay, something's like 50 amps with a big heatsink and possibly a fan, putting it in a nice safe box?...And wearing rubber thongs?

Thanks

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Do you need really need varied output? How much water are you heating? There is really no need to have a modulated output for doing water, just adds cost (ie keep the heater on at 47%)

I personally would use a bog standard solid state relay controlled by a PID, be it a standalone pid control (easy), or arduino (more control, but more fiddling). I would also put a heat sink on it, something like this, add a fan if it gets to hot to touch. Ive never had any trouble with EM with on/off SSR, triacs are a different and noise is an issue (can couple with the thermocouple wire), as you have zero crossing signals and really chopping the wave form up.

PS. SS Relays are almost easier to use than mechanical ones. Just use proper termination techniques, using eyelet/ U terminals, rated wire, solid connection. AND GROUND!

post-15518-0-46990800-1419374389_thumb.j

Edited by smokeliss
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Hey mate,

I looked into this a while ago but never started the project. There are some good SSRs on ebay for cheap that apparently safe and will do the job.

Google "keg element controller" or "keg element wiring diagram" to get lots of ideas. Also lots of discussion on distilling forums like Aussie distiller, but be prepared to be abused when you ask about home wiring lol. Lots of arseholes on that forum.

I wouldn't have it switching too fast as it can wear out the element faster, apparently. Could always just buy a variac but a home made SSR circuit is much, much cheaper. Get a decent heatsink and fan.

I have also seen ready made thermostat units for home brew temp control for a reasonable price, but I don't think these can handle high current for boiling.

Please let us know what you decide. I hopefully will be doing this myself one day so very keen to hear how it all goes.

Good luck and don't burn your house down.

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Thank you both.

If you hadn't already guessed this is for controlling an alcohol still when i visit new Zealand where it is legal to do so.

The need for variable control is so i can add a known amount of power and make rough calculations about the rate of heating of a alcohol/water mix and the volume of vapor produced.

I need to keep switching fairly fast (< 2 seconds I've heard) to keep the volume of vapor constant and the still column 'balanced'.

Alice, i used to visit the distillers forum. :) I was active there for a while but as you said, there are too many pricks there. I got frustrated with people trying to tell me i was doing the wrong thing when they had no idea what they were taking about. >:)

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In that case I recommend a nice big triac setup. The heater is always on so dont have to worry about cycles. This is what Im playing with at the moment, using an interrupt for the zero crossing signal. This setup causes a little noise if you run the thermocoulpe wires near the triac output, but that's just 240v.

post-15518-0-12555800-1419382155_thumb.p

Edited by smokeliss

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Thanks smokeliss, i will try and figure it out from your schematic. May i ask what your project is?

Edited by watertrade

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well, i like your project but your massively massively over complicating things.

if you have the correct element for the volume (matched so it won't scorch the mash) then you don't really control its temp, its on or off...

the temperature in the reflux distil head, is determined by the water rate.

for an automatic setup, the water temp coming out is the important thing to monitor (and the actual head temp), as if its flow is slow and water is very very hot your still can malfunction and real liquids will spew out instead of your 96% ethanol (more like 95%)

And you should never ever alter the heat of the mash, as it disrupts the quality of the end product.

Once you turn it on, you do not adjust the heat until your finished, and turn it off.

Edited by C_T
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Its a prototype vaporizer logic board, powering a halogen light for heat source.

There is quiet a few different styles of traic control floating around the arduino world, this is just made from bits and pieces. The triac control is 1 input - zero crossing, 1 output - traic trigger, using a teensy 3.x uController. All that you would need in the top left bits, rest are prototyping I/O ports and temperature sensors (2x max31855).

Edited by smokeliss

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well, i like your project but your massively massively over complicating things.

if you have the correct element for the volume (matched so it won't scorch the mash) then you don't really control its temp, its on or off...

the temperature in the reflux distil head, is determined by the water rate.

for an automatic setup, the water temp coming out is the important thing to monitor (and the actual head temp), as if its flow is slow and water is very very hot your still can malfunction and real liquids will spew out instead of your 96% ethanol (more like 95%)

And you should never ever alter the heat of the mash, as it disrupts the quality of the end product.

Once you turn it on, you do not adjust the heat until your finished, and turn it off.

To clarify, it's a vapour management reflux still.

I measure the vapour temperature at the top of the still and not the condenser water output. As long at the vapour is all condensed it doesn't matter what the water temp is. I also collect before the reflux condenser. The temperature at the top (vapour) can't be controlled. The temperature is dependant on the component mixture of liquids/vapours. 96% ethanol can't get hotter than around 78degrees C at sea level.

It Is good advice not to adjust the heat to the boiler under normal operation, but under automatic operation the amount of heat adjusts the volume of vapour produced and therefore the reflux/theoretical plates. adding more energy wont change the temperature of the mash. It can't get hotter than the boiling temperature of the liquids boiling temp. Some where between higher than ethanol alcohols and pure water ---> 100 C

In my still the warm up stage is at high power, the pre ethanol stage (heads) will be at one power, the ethanol and tails at another. And then off at finish. As long as the still is allowed to balance out at each stage (heads only in practise) changing the power input won't effect quality.

CT I think you are refering to what people call a cooling management still. (?)

Ps. If i can control the power i would probably go for a bigger element too.

Edited by watertrade

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problem with adjusting your heat element, is it may scorch the mash thats in direct contact to the element (even tho the entire liquid isnt that hot)

to decrease pre-heating, boil your jug and put that hot water in with the mash, drastically cuts heat up times, and doesn't affect the mash.

Edited by C_T

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the 'mash' i use isn't thick like a whiskey mash. I only really use stripped sugar wash ~ 40% I said mash above but it should have been wash. ~ terminology ;)

there are no solids, just a crude mix of alcohols.

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Cool project smokeliss, report back if you want to share. I think people here would be interested.

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just get a relay to run your load and use the load of the thermostat to power the relay i do it with 3kva fans

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just get a relay to run your load and use the load of the thermostat to power the relay i do it with 3kva fans

So would this essentially be a zero crossing SSR? -I want to switch the power on/off pretty quick. But can't use a thermostat as there is no set temp I'm aiming for.

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.

Edited by Alice

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Thanks ct,i actually have a few stills which are similar to that one but (in my opinion) are much better.

I also use a woven copper mesh for the packing. It has a much higher surface area and lower volume than the ceramic raschig rings.

Making this new still wasn't just to make alcohol. But to build on the successes of my previous stills and tie them all together in an automatic highly customisable still.

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then you should know changing heat once distillation starts, will affect the fractions. you'll get some surging.

i just don't see any positive, you need to turn the tap on/off, you need to re-fill the vessel.

its just not an automatic job. unless you know something i dont?

and if you use my tips, re add 50/50 boiling water from the kettle, distil takes no time at all, i can get it happening in 8 minutes.

edit: you can use my tips or ignore them, i don't see anyone else offering tips!!!

Edited by C_T

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I appreciate the effort you have put in to replying CT, indeed this discussion is mainly us talking.

When i read back over this thread it looks to me like I'm just trying to argue with everything you have said, this isn't my intension. I think I have just failed to fully explain what I'm doing.

With adjusting the energy input. You are right adjusting the power up can throw out the balanced column. But consider this...

High power to heat up.

One power to balance column, take heads and ethanol. ( + Different output rates)

Then a change to take tails (quick.) and a final change to turn off.

Any problems there?

I'm not just making this up as I go along, it has been done by lots of amateur distillers and is covered in the books The Compleat Distiller - by Nixon and McCaw and Designing and Building Automatic Stills - by Riku. Both published by the amphora society, NZ.

When this is built I'm sure a lot of experienced distillers would think its a waste of time and money. But i want a still that runs automatically from start to finish. Of course I will still need to turn on the power and fill the boiler. (No refilling of vessel needed) But nothing else until clean up.

If you think this is over engineered, i should show you my all grain home brewery.! ;)

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do what i do for my kilns. use a PID controller (type for ssr) with solid state relay with thermocouple. it's only 1800 watts, why use a massive 50 amp relay? that system wont even pull 8 amps.. not much. these things can be set up cheap and easy and can switch power on and off like 50 times a second or so. also, they can be set up to give whatever % of full load using built in PWM. I cant see any other way to have the system so simple, effective, and with full temp ramp controll =) I build crazy reactors and machines all the time to run on 240v, have done since i was 5yo.

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there is a PID library for Arduino ghosty. without knowing it at the moment I think that is what I would have been using with a SSR. as for the 50 amp relay, as far as I know there are not any issues with using an overrated relay. I just thought the redundancy would be good and i had a particular one in mind. I now have a smaller model in mind.

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youll find with producing 95% you dont really get heads and tails like a pot still

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youll find with producing 95% you dont really get heads and tails like a pot still

Here i go again :)

How do you manage that? When i have done this previously (manually) i always get heads. By heads i mean the higher alcohols which are more volatile than ethanol and distil off at lower temperatures than ethanol. And the ethanol contaminated by the 'higher' alcohols.

All alcoholic fermentations produce them, even the cleanest most controlled fermentations done in fancy labs.

Edited by watertrade

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