Controlling a counter top water distiller with salvaged parts

distiller_power_off_timer

Hackaday reader [Kyle] wrote in to share a project he recently wrapped up, involving a counter top water distillation unit he uses at home.

He lives in Atlanta, and hates both the taste and contaminants in the water, so using this distiller is an absolute must in his house. The problem with this cheap unit is that it waits until it is completely dry before shutting off the heating element. According to [Kyle] this brings up two huge problems.

First, letting the unit run dry simply vaporizes all of the contaminants that he was trying to remove, allowing them to re-condense and contaminate his fresh water. Second, the heating element reaches extreme temperatures once the water is gone, which causes premature failure of the distillation unit.

He originally used a timer to remind himself to turn off the unit before it ran dry, but the process became tedious. He found that he would often forget to turn off the distiller before it ruined his newly cleaned water.

Looking for another solution, he decided to automate the process using some components left over from an Arduino-based terrarium temperature/humidity controller he built a while back. A salvaged toy clock tower was used as an input dial, which sets the distillation time on the microcontroller. The Arduino in turn manages a set of relays that controls the power supply to the distiller.

While [Kyle] only sent us this information to us via email, he has made code and pictures available online. We’re sure he would be pretty open to answering any questions you might have related to his build, so fire away in the comments section.

[Update]
After seeing that his distiller made the front page, [Kyle] directed us to a write up he prepared, detailing some more specifics on the project.

Comments

  1. Kyle says:

    There have been a few comments that recommend a wallwart timer as a solution. This brings me back to the manual timers I was using.

    I am filling vessels of varying volumes and I also wanted to independently control the fan and heating element. As the water heats up, the fan is unnecessary because the water has not yet reached boiling temperature. Also, with varying volumes of water, the time it takes to reach the boiling point varies, so the timing for the fan and the heating element needs to be altered.

    Instead of having a list of times to set each timer for the different vessels, I found my solution to be less errorful and more user-friendly to my flatmates.

    I can rotate the dial to the corresponding volume for the container I am filling. After the time it takes for that volume to begin boiling, the fan turns on. I return 25-30 minutes from that start to toss the foreshot (~50ml, first distillate that contains all the compounds that evaporate up to 100 deg C, such as many VOCs). At this point, the compounds that have a boiling point below 100 C, as well as many VOCs around 100 C, are removed, and the majority of the liquid condensing in my collection vessel is H2O. The timers turn off when the vessel is full, while leaving behind a small amount of water in the boiling tank. This prevents compounds that have a boiling point over 100 C from reaching my vessel (such as fluoride, pharmaceuticals, etc.).

  2. ColinB says:

    @Steve Cook:
    Thanks for your detailed and informative post!

    Has anyone else noticed that if you let a glass of tap water sit on the kitchen counter for a few hours, it has less of a “chlorine-ish” taste/smell than if you drank it immediately after filling the class from the tap? I notice that often bubbles form on the inner walls of the glass, and if I tap the glass, the bubbles break and a smell of chlorine can be detected over the surface of the water.

  3. t-BuLi says:

    @Hackerspacer : “So your argument is that pure almost completely non conductive DI water will corrode steel at the exact same pace as normal tap water?”

    Well no that’s not what I meant to imply because you’re right the above statement is false. Rather I wanted to show that it’s not the water itself which is doing the corroding/reacting but the electrochemistry which occurs due to ions within the water. What bothered me about your original statement was that it appeared to say the water itself was reacting instead of the dissolved ions. This is a false statement because the electrons of the water molecules are not(!) reacting; water is a stable compound. Upon second reading I realize you may have meant that sentence to refer to chlorine, which would be true, but the analogy was not accurate enough for my comfort because of the implied chemical reactions with the water itself.

    “DI water likes to react with things to pull ions out of it.”

    Water will dissolve (read: dissolve != react) ions and polar substances, but the solid metals in pipes and containers are not inherently ionic or polar. Rather it’s electrochemical reactions with ions in the water which change the metal into a dissolvable (ionic) metal salt which results in quick corrosion.

    You are right in that normally you don’t want to use DI/distilled water in metal pipes/containers but it’s because if ions do get into the water (even carbon dioxide dissolving into it from the air) there are no minerals to balance the charge and so the water is no longer neutral (think pH) and the dissolved ions can react with the container. If the water was perfectly deionized/distilled and pH neutral you would not encounter this problem.

    “My point about chlorine gas was to make an analogy that DI water was highly reactive”

    Basically, as I was getting at above, I just wanted to point out that it’s not the DI/distilled water that is reactive, but any ions that end up in it after distillation/deionization.

    “I am sorry but you have no idea what you are talking about.”

    Please keep ad hominems out of this.

    @ColinB : Yes! That happens with conventional chlorination of the water. The chlorine is put in under pressure so that more of it will dissolve into the water, when you leave it in open air (a condition of less pressure than it was previously under) the chlorine will bubble out. It’s similar to carbonation but obviously less intense else the water wouldn’t be potable.

  4. Hackerspacer says:

    “Basically, as I was getting at above, I just wanted to point out that it’s not the DI/distilled water that is reactive, but any ions that end up in it after distillation/deionization.”

    That’s fair. I am on board with that. It’s a bit more technical than I wanted to get into at the time but because water is generally not in a vacuum, it eventually becomes conductive and “less DI” the longer it sits around in a normal atmosphere. It isn’t really the water per say that is the corrosive issue but in an overly simplistic way, DI water is more “corrosive” than tap water largely in the way you have pointed out.

    We have custom built $15,000 316 stainless steel water purification systems and went through this whole song and dance about DI water and trying to balance it being conductive *enough* (and as a result, having enough dissolved ions) but not too much (almost non conductive) so that it attacks our stainless steel and seals, dramatically shortening pump and seal life.

    In short, we added an off the shelf solenoid and conductivity / TDS PID and routed it through a mixed DI resin stack to lower but not eliminate TDS.

    “Not intended as an ad hominem. Was intending to point out the perceived incorrectness of your statement based upon my interpretation of said statement: (DI/tap water are really no different in their rates of corrosion). After clarification, I think we are on the same page.

  5. mccblaise says:

    Hey where did you buy this water distiller and what model is it?

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