iMac condensation issue?

Our iMacs have a large patch of condensation behind the screen. After we run them for a while, it evaporates, but it comes back after a couple of days. This has happened several times. Has anyone else had this issue? How can we stop it from happening? Thanks, Bob.

Question by memyselfand1 


Peltier coolers and condensation?

Hi there, I'm having this crazy idea of building a mini AC based on a Peltier cooler, and connect it to a PC case to introduce cold air inside of it. I have seen a lot of instructables here, but I'm worried about condensation. You know, the "electronics + power + water = Kaboom!" equation. Neither the peltier nor the "cold" heatsink will be inside the case, I'll just blow air thru the "cold" heatsink and inside the case, releasing hot air far away (maybe with a long tube?). My question is if the cold air will carry some kind of "humidity" from the condensed cold heatsink, and if it will be enough to blow things up. I can spare some 60 or 70 watts to make the peltier work, so I'll just grab a ATX power supply for the peltier and the fans. Do you think it will work? Thanks in advance, and Happy New Year. :)

Question by ethaniel   |  last reply


Help with electret microphone

Hi by checking some information and also some of the projects here, i realized that electet microphones are as good as studio condenser microphones and i was wondering if you can help me to create a condenser quality mic out of an electret element with schematics or actually a tutorial of how to do it the circuit and the pre-amp if necessary ... i got this "http://richard-mudhar.suite101.com/how-to-use-an-electret-capsule-with-p48-power-a150317"  can you check it out and tell me if it would work or give me some other ideas. thnx

Question by Markus03   |  last reply


in distilation , how is a condenser set up? Answered

after watching a video made by nurdrage and realising i could use a condenser to distill various chemicals like ammonia water, i was wondering, how is a condenser set up. now ive looked at a lot of images, and all i see is the top of the condenser where the gas enters, thenthe bottom where the gas exits as a liquid. now what i dont nderstand is the two middle middle nozzles, ive looked at many setups and theres usually nothing attached to them, or they have a hose attached to them that goes nowhere and you cant see where they end, so i must ask, what are they for, in the sense, what do they do? and what, if anything, are they attached to? whoever answers my question properly and makes sense will receive a best answer. also, i will just add, ive searched through google and wikipedia, and found zilch that made any sense to me.

Question by oldmanbeefjerky   |  last reply


Will a condenser mic work the same way as a 3.5 mm mono audio jack? Answered

I will be building an FM transmitter soon, and I wanted it to have a condenser mic with a switch that switches the input of the condenser mic, to the input of a jack that people could play music from. In other words, the user would be able to speak to the transmitter, flip a switch, and then play music through to the jack. My only question really, is whether or not it would work? Thank you for taking the time to read this, I really appreciate it. The attached picture is the schematic I am working off of.

Question by XBLmonster   |  last reply


Tall irrigated hedge to pre-cool A/C condenser? Answered

I am thinking about planting a hedge around our air conditioner condenser to increase its efficiency. This would serve as shade for the condenser and as a means to inject water to keep the plant cooling the air as it evaporates the water. When rainwater is available, an aquarium pump could "irrigate" the hedge. When not available, a switch could control a valve for a high-pressure drip irrigation system. Both could be controlled by the compressor circuit. Keep the hedge trimmed about 6 feet tall and with just enough space around the condenser for a workman to easily maintain the unit (at least 3 feet from the condenser). The hedge would have to be drought resistant and one that does not shed leaves or debris. Any thoughts about this?

Question by VirgilB6   |  last reply


How do i wire a condenser mic into my audio input of my PC/Computer? Answered

Ok, I answered it myself but I looked long and hard so hear is one option for connecting a condenser mic to a pc. This is 20 year old microphone that shipped with my family's Apple LC in 1992.  The mic works well with one of my laptops audio card... Not sure what the Zenner diode value is but its probably pretty small. I measured the voltage across the mic + to ground and it was 3.5volts. I saw another guy that only found a diode on his condenser mic so maybe newer audio cards can work without all the extra parts...

Question by hydronics   |  last reply



can i build a dual turbine which is powered by steam which is condensed and released like a water wheel. would it work?

If I build a steam turbine powered by burning waste using a pelton turbine then the steam will travel upwards. if I condense and store it, then release it past another pelton turbine to restart the cycle then will it be equally efficient. assuming the fuel source is free can this be practical in terms of electricity generation?

Question by mrgre99   |  last reply


how to change my small tractor magnet to 12 volt condenser coil?

My old tractor work with magnet but i need to make it work better

Question by  


Peltier dehumidifier

I hope someone with a technical background can help me with this... I am trying to make an DIY dehumidifier. The goal is to lower the humidity of my room during the summer months (humidity is around 70% at 25C) to less than 50, preferrable 30%. I have the following setup in mind: To achieve condensation I want to use a peltier that will lower the temperature of an radiator. The condensed water will be gathered in a (plastic) box. This water will then be used to cool the hot side of the peltier, using a water block and a waterpump that was left over after using watercooling on my PC. The image depicts an simple graphic of the setup. However, I have the following questions to be answered: - How cold (relative to the ambient temperature) would the cold-side radiator have to be to get optimal condensation - How much watts of cooling power would the peltier need in order to achieve the needed temperature difference - If i lower the cold side temperature with 20C, how much heat would be generated on the hot side? (my gues: 20C, but im no genius ;) ) Thanks in advance!

Topic by pelzinga   |  last reply


How to pass sound from microphone to earphone

Hi, I need a simple way to pass sound from Condenser microphone though wire and some circuit to one or pair of earphone to be heard, live, just a simple communication tool, is there an instructable for this or please give me exact steps . Thanks .

Question by achraf52   |  last reply


dos any one know were to buy cheep laboratory equipment in The GTA or grater Toronto Area?

I need a: Hotplate, water condenser, three way adaptor,vacum adapter, claisen adaptor, three neck flask,sepparation funnel,dry tube, a flask, distilation colum,and a capillary with fine outlet.

Question by dciocoiu   |  last reply


Can convection be used to drive a passive dehumidifier?

Ok, I have a couple of radiators and a greenhouse that is too humid. In winterr can convection drive fluid from a radiator mounted low in the warm greenhouse to a second radiator mounted outside in the cold and then back to create a chilled metal radiator that will have water condense on it and drip into the soil.

Topic by drewgrey   |  last reply


How to detect audio frequencies in the ranges of 190hz, 250hz and 285hz. Thanks!? Answered

What are the advantages/disadvantage of using this LargeMouthBass' PIC processor/code over a LM567 Tone Decoder? I might use an Aruduino or another IC to command the PIC(or 567) and to output to a couple of LEDs as visual indicators...

Question by hydronics   |  last reply


Threading and pitch for Microphone mount nut or stem? Answered

Does anyone out there know the threading and pitch for a standard condenser mic stem? I lost my mounting nut and even the manufacturer won't provide the info I need. It's a Presonus M7. It should have a standard threaded stem as most universal mounts fit it. I know it's metric, Possibly an M20 or M22 with a #1 pitch. Anyone know for sure?

Question by Sparkytastic   |  last reply


How can I more efficiently use space while laser/plasma cutting? Answered

I've made a number of plans in 123d make, but there is so much empty space that becomes unusable for future projects.  Isn't there some way to "condense" a .dxf so it has a smaller footprint?  I don't care if the angle is weird or whatever, I just know that there has to be a far more efficient way to use up material.

Question by furrysalamander   |  last reply


Please help with repairing my LED light bar there are a total of 60 1w leds but 2 sets of 3 LEDs are dimmed.

I was wandering if you could give me a bit of advice on repairing my LED roof light bar, there is issue with 2 sets of 3 LEDs. there are a total of 60 3w leds and for some reason (probably condensation) 2 sets of 3 LEDs (one in the middle and one in the end) get dimmed. Any advice would be greatly appreciated.

Question by survivel82   |  last reply


Camera bag insert covering

As I didn't want to spend extra money on a new camera bag I'm using an existing bag with a divider I've made from cardboard and an old camping roll mat. My question is I want to wrap it in something so it looks a bit cleaner and add an extra layer of waterproofing. I was thinking about using the material from an old tent but was concerned about condensation build up. I live in the UK so not much chance of weather! Please share any ideas. Oh and yes I will be replacing that tape for something a little more grey.

Topic by SmilerSmiles   |  last reply


are stepper motors from electric typewriters good for cnc projects?

I have 3 old electric typewriters i got from work, one I already condensed to a steel rod and a ziplock bag of motors and gears and screws, the other, a wheelmaster 5 is next, I am going to keep the wpt-160 because its sweet. But Back to the question, are these motors generally any good for cnc machines? I think I will have about 7 or 8 stepper motors of different sizes. anybody used these before, I'm not sure of the specs yet.

Question by bramletabercrombie   |  last reply


NiChrome Power Source? Answered

So, I'm doing a project that needs to boil maybe 8-10 drops of water very quickly. I was thinking of using NiChrome wire to do this as in the included diagram (sorry low quality, MS Paint). However, I can't seem to find an appropriate power source. So, I need some easy to obtain powersource that is also relatively small. Something like batteries, a capacitor bank, or anything similar. Remember, it has to be able to boil of those 8 drops pretty fast, lest they condense in another part of the pipe before the desired pressure is reached. 

Question by LiquidLightning   |  last reply


Peltier Air Water Harvester

I was looking around at some of the air water harvesters tonight and of thinking about using a Peltier unit for one. Just started thinking and I know very little about either one of these. So my question is, could you use the cold side of a peltier to get an air current down to just below dew point causing humidity to condense on maybe a heat sink or something so it could be collected and use the hot side to create the air flow by a chimney effect? No moving parts.  Solar power it so it an be used anywhere in the world? Could be something that could supply clean water to people in need.

Question by dayfid12   |  last reply


how can i increase and rise the voice in my circuit ?

 hello  My project called " Four Tone Siren "  this is the circuit for my project .... I really need to increase the voice because it's very small you can't hear it except if you put the circuit close to you   and i only hear 3 tone and my project is 4 tone.  can you tell me please what is the reason ? my final project after 2 days please :(  this is my parts : IC UM3561 Resistance = 220 Ohms Condenser 100Mfd Transistor BC548 Battery Container 3V Switches Breadboard

Question by layal_1   |  last reply


House hold heating? Answered

Like most UK houses my thermostat is in the coldest part of the house - The entrance hall. Although I have recently fitted thermostatic valves fitted to all radiators I can't help but feel the heating would be more effective if I simply controlled the temperature in the room we spend most time in during the evening- The lounge. I guess this would mean the rest of the house would be cooler than at present but that isn't really a problems for us. Is there any reason, anyone knows, not to do this? Has anyone gone down the smart thermostat route? https://nest.com/uk/thermostat/life-with-nest-thermostat/ New high efficiency condensing boiler Thermostatic radiator valves through the house High level of insulation to walls and roof. Double glazing all round in PVC frames.

Question by rickharris   |  last reply


Big project, little parts..Need serious electrical tech help.

Well, long story short in my dumpster diving salvaging e-waste ... 2 Lorex CCTVs. One cord cut, the other intact. I disassembled the cut cord. Lr38603A PCB. Wires Identified GND 12v+ Audio Video  Analog, so USB is out of question. Acer Aspire 5100 laptop. The mommy is toasted (cause mobo sounds so geefy.) so disassembled and salvaged usable parts.I think I tossed the condenser into my "melt parts off circuit board" bin... so I need a condenser and PCB controller which leads me to something I found in my parts bin... CRT monitor, stripped and kept the  VGA PCB, unfortunately it does not have an S-Video and I think it's irrelevant here but I'm quite new to this hack n mod stuff... So, here's what I'm trying to do: Use the LCD from the laptop as a display for the analog camera, I also have several lens and such from damaged optics (hunting scopes, monocular etc) so with the lens I'll put them in a tube and craft a digital microscope. I know you can buy a cheapie USB one, but I want the pride of making something, to be able to understand the tech, and also re-use discarded electronics. I have a pretty good idea of what to do, but I've never worked on anything that involves a serious power source from an outlet and do not want to fry myself, and would like some guidelines/what to research. Google is not being helpful and nearly all the camera hacks I've came across are for USB based cameras. I have access to a solder station, voltometer and a slew of other parts from various electronics, mostly VCR's I'd like to keep the spending to a minimum, but not at the expense of safety. Can anyone help? Thanks :D

Topic by bvarious   |  last reply


Power Electronics: power converter Answered

I have been running through example questions for an exam I have coming up; the following picture is a condensed version of half a page of working. My lecturer gave us the solutions and a few steps between beginning and end to get to the solution so we could work it out. However, as you can see the picture below I got 30.6A whereas she wrote 54.2 down. The problem is to "Find the maximum values of the average" (done this bit) "and rms thyristor currents for any firing angle, alpha.". The values of R and Vs are in the diagram. Alpha is assumed to be 0 since then the thyristors will conduct for the greatest possible length of time. I think she may have got to the end then forgotten to square root of Pi before multiplying Vm/2PiR by it. Does anyone agree?

Question by Jayefuu   |  last reply


Transforming a upright freezer into a super airconditioner? Answered

 I'm getting a slightly broken, upright freezer from craigslist (only the seal is broke, so air's leaking out the door frame) and I was wondering if there is any way to make it into a slightly over sized air conditioner.  Living in Texas, it's kinda hot so I dont mind if its chilly (im the kind of guy that wears flipflops to North Carolina in the Winter on the Mountains). Im going to be putting it in a mobile home that will be internally demolished and transformed into a recording studio. It shall have its own little 'space' over in the corner. It would be great to cool down the heavy old-ish recording equipment and the computer I will house in the 'tech room'! Could I just cut a hole in the freezer and run a duct from it to the trailer? Would it put too much condensation? Thanks!  *Big, upright freezer around the size of a normal refridgerator*

Question by darkclaw42   |  last reply


EXTREMELY LOW!! flow fan/power system

 EXTREMELY LOW!! flow fan/power system   I need to find an EXTREMELY low flow air movement system (Fan?) That can be powered on almost nothing! Think 1m^3/hr maximum. I need to link this with a low power solar system. (think calculator solar cell) Weight is everything. Really need to move 10-100cm^3 air every 2-3 minutes max with minimal weight and power requirements. Much lower than cell phone fan air movement with power that can be generated from a few-gram solar cell. I am not sure this can be done mechanically, may need some kind of ion movement system. The point is to exchange air in a 50cm^3 volume enough to prevent condensation in medium humidity environments, (40% of the area is at dew point) where weight is important and no power is available beyond ambient room light. 5% royalty if product is ever brought to market.

Question by sipfle   |  last reply


Op-Amp Help

Hi- So, I made the circuit below to make sound-reactive blinky LEDs for a halloween costume (the round thing on the left is a condenser mic). I think I just got lucky that it worked, because I'm no genius when it comes to op-amp usage or design. Now I want to adapt it to control something else that needs a slightly higher voltage than the LEDs. Basically, I'd like the output to swing as high as V+ when the mic input is "loud" (a relative and possibly adjustable level). I've messed around with various resistor values as well as adding or removing resistors in places it seemed like it would help (according to the LM741 datasheet). All to no avail. Anyone out there who might know what to do? Again, I want the mic input to cause the output to go as hight as V+ (9V in this case) when it's loud, and be more or less at 0V when it's "quiet." Thanks in advance, _mykle

Topic by deadbilly   |  last reply


Looking for a thermostat

I am a science teacher and need help finding a thermostat to fix the department's water distiller. It looks very similar to the "Waterwise 9000 contemporary distiller" but is slightly different in appearance. The basic operation is you fill the reservoir and turn it on, the water boils and is then condensed and drips into the bottle that slides into the front of the device. When the heater reaches a certain temperature a thermostat turns on the cooling fan, when the device cools to below that temperature the cooling fan turns off. There are lots of warnings about running it without the fan because it will burn out the heater. I have tested the heater and it works fine, I can bypass the thermostat and the fan works fine, but the thermostat no longer switches on the fan. If I can find a replacement thermostat that should fix the entire distiller but it seems to be a custom order only for the manufacturer who wants you to buy a whole new distiller. Can anyone suggest an appropriate substitute? The code on the side of the thermostat is:  36tme02 22471 f150-15f p185-97 a0615 I found a similar image on the emerson site for a 36T thermodisc thermostat http://www.thermodisc.com/en-US/Products/Bimetal/Pages/36T.aspx Does anyone know how to figure out the switching temperature from the code from the side of the thermostat? Any suggestions are appreciated!

Topic by CitizenScientist   |  last reply


How do I use an Arduino to write say 2.1 volts? Hobo dataloggers accept 0-2.5vdc inputs. Arduino outputs PWM.. thanks!? Answered

I'm working with a university and they love their Hobo's and I don't blame them... they're pretty straight forward to use...  I'd like to write to the Hobo... here's the hobo analog inputs: 0 to 2.5 Vdc; 0 to 5 Vdc; 0 to 10 Vdc; 4-20 mA Hobo stats: http://www.onsetcomp.com/products/data-loggers/u12-006 Analog channels: 0 to 2.5 Vdc; 0 to 5 Vdc; 0 to 10 Vdc; 4-20 mA Accuracy (logger only): ± 2 mV ± 2.5% of absolute reading; ± 2 mV ± 1% of reading for logger-powered sensors Resolution: 0.6 mV Sample Rate: 1 second to 18 hours, user selectable Time accuracy: ± 1 minute per month at 25°C (77°F), see Plot A Operating range: -20 to 70°C (-4° to 158°F) Operating temperature: Logging: -20° to 70°C (-4° to 158°F) Launch/readout: 0° to 50°C (32° to 122°F), per USB specification Humidity range: 0 to 95% RH, non-condensing

Question by hydronics   |  last reply


Portable usb power supply for turtle beach X12 headset. Answered

I recently acquired a pair of X12's and they require usb power to run, I would love to be able to use them for applications outside sitting at my computer. I very little real experience with electrical power supplies, but I am almost sure that  most of the portable usb batteries that I have found put out too much for them too handle. Here are the full specs for them; Headset 50mm diameter speakers with neodymium magnets Speaker Frequency Response: 20Hz - 20kHz, >120dB SPL @ 1kHz Condenser Microphone Frequency Response: 50Hz - 15kHz Cable length: 16 ft. (4.87m) Weight: 6.4 oz (233g)        In-line Amplifier Headphone Amplifier: Stereo DC-coupled, 35mW/ch, THD <1%, Frequency Response: DC - 30kHz Bass Boost: Variable up to +12dB@150Hz Mic mute switch Maximum analog input level with volume control on maximum setting: 2Vpp (700mV rms) 3.5mm plug for line input 3.5mm plug for mic output 2.5mm XBOX 360® controller input jack USB connector for power (5VDC @ <60mA max) Dimensions: Height .5in (1.27cm), Width 2in (5.08cm), Depth .75in (1.905cm)

Question by aerinthaare   |  last reply


Mounting Lenses On Your Microscope

I found a broken cell phone with it’s camera and wondered if the lens could be used as a microscope objective. Image A shows the lens and it’s mounting with the CCD. The back of the lens is shown. The lens is about 4 to 5 mm in diameter. The starters from florescent lights make good lens holders. Image B shows a starter along with my modifications to hold the cell camera lens. The starter tube has 4 slits along the length so it can be compressed to fit the turret of the microscope. Image C shows it mounted on the turret. Image D shows the resulting view of a feather. It’s quite bad. Image E shows, for comparison, the view through an ordinary 20x objective (.40 NA). Here are some more lenses that I tried: Lens from a discarded flatbed scanner..... Very good! Lens from a 8mm movie camera...... Fair. Lens from the laser pickup of a discarded CD player..... Almost worthless. To take pictures through the microscope, I used eyepiece projection with a wide angle eyepiece. The lens on the camera was set to wide angle and maximum aperture, with a remote used to trigger the shutter. The camera’s LCD was used to focus and adjust the image. The camera’s autofocus handles the rest. For even illumination, be sure to center the objective lens over the substage condenser.

Topic by ShutterBugger   |  last reply


Bonding hydrogen and oxygen to make water? Answered

Ok, so I got how to get water, but how do I condense it without losing much, and would it be at least a semi-efficient and/or fast way of obtaining around a cup of water? So, I have another question. I know, I've been posting a new question at least once a week for a while now and you're all probably like "Dark Master87, Y u no shut up and stop trying to do impossible things?? w(O;O)w" Most people on here probably know about electrolysis and seperating water into hydrogen and oxygen with electricity, but it's simple and I don't currently have a use for it. But does anyone know how to bond hydrogen and oxygen to create water? I'm expecting there to be heating or cooling involved, probably more likely heating. Would you light the two gases on fire? Or would they just automatically bond with each other at the point of contact? More importantly, would this be possible to acheive on the limited budget of a 14 year old hobbyist who *may* have access to *some* lab equipment, but probably not? Thanks for paying attention, if it's not feasible/possible, I won't mind if you nag about me never doing any reasonable projects. And also, how hard would it be to get the hydrogen and oxygen from electrolysis with losing too much of it? 

Question by ALogan97   |  last reply


Is it a good idea to wire an ELECTRET mic in parallel? What are the advantages and disadvantages? Answered

I already made a prototype of a low-noise desktop microphone (with an internal 5 stage transistor preamp). It only had one ECM capsule inside. A few days later I found a couple of pictures of a certain microphone with two ECM capsules wired up in parallel. It made me wonder, will it increase the sensitivity of the mic while reducing noise or will do the exact opposite? Is is a bad idea to hook six of these in parallel? Sorry, I'm not an expert when it comes to microphones. Before I post a guide, I wanted to make sure of what I'm saying.  The Reason: If you are familiar with the Blue Snowball USB microphone, you'll be surprised on what's in it. I recently discovered that it has two "Electret Condenser Mic Capsules" soldered in parallel. I thought there was something special about the Snowball since the reviews went crazy (4 1/2 stars on amazon)! I was expecting a huge diaphragm, but no, it only had two tiny ECM mics soldered on a Preamp + USB DAC. Lesson learned! Never underestimate an ECM mic.  ______________________ The picture is my prototype, it's working great right now. Luckily, the 5 stage preamp is giving zero noise. I'm planning to add a USB D.A.C. and an ECM array on my final version.

Question by ASCAS   |  last reply


Technology Makes Cheap Drinking Water from Air

INTRODUCTION:   How can we best apply basic technology to help the underprivileged and/or disaster-hit countries like Haiti? Daily hygiene and nourishment are among the top needs for disaster ridden regions!  Simply put, no water means no hygiene. The Romans understood that over two millennia ago and created their complexly beautiful aqueduct networks for handling both fresh and wastewater! Other ingenious water systems like “air wells” have been found in the city of Theodosia (cf: discovered in 1900 by Zibold, see Zibold’s Collectors/Dehumidifiers) dating back to Greco-Roman times during the Byzantine Empire. These were strictly passive systems that naturally dehumidified air, collecting its potable water in underground basins. All air, even in relatively dry desert regions, will precipitate or release its natural water content (initially in the form of vapor) through condensation when it hits its dew-point temperature and below. That means you “chill” it to an appropriate level that is anywhere from 5F to 50F below its current air temperature, depending upon how much water content (relative humidity) it has locally absorbed. The condensation of the water vapor releases its internal latent heat (reheating the cooled air) which must be constantly dissipated (absorbed by something) in order for water formation to steadily continue. So how do we dissipate this resultant vapor-heat and chill our air without any infrastructure or electricity, in an underprivileged or disaster-ridden region? We simply bury a long cast-iron or any metallic drain-pipe sufficiently underground where the temperature of the earth is naturally held to a constant at around 45F to 55F. That’s our “free” chiller gift from nature. One end of the pipe, Figure-1,  sticks out of the ground to suck-in local outside hot air, and the other end dumps cooled dry air and water into an underground cistern where it gets collected and is piped to the surface to both exhaust the cooled dry air and connect to a water pump. We need a hand operated water pump to lift up the water above ground, and we need an electric fan to constantly pump air through the ground-chilled piping system. We can even force the cooled piped air to exhaust into a tent-like structure where it provides air conditioning as an added bonus, but this adds the penalty of both power and the increased fan size necessary to drive our required airflow further into an enclosure! While this concept is not “passive” (requiring electricity to work) like those clever Byzantine air-wells, it will produce much more potable water and within a smaller volume than those elegantly passive historic devices. The electricity for our fan power requirements can be produced by any one of four ways using either “active” or “passive” techniques: 1) An active playground or bike-pedaling-person or oxen-driven mechanism-generator, 2) A passive windmill generator, 3) A passive solar energy collection system that directly generates electricity, or 4) A passive thermo-electric system that directly generates electricity using the Peltier effect, operating solely on temperature differences between the cell’s top and bottom surface (we jury-rig the cool pipe and hot ambient air to contact separate sides of the cell). Depending upon how much water is needed, the required air volume plus pipe length and diameter, together with the fan will be sized accordingly. We can also configure groups of parallel fan-driven air pipes that are radially fed into the cistern. The sizing of this underground network depends upon the ambient air’s local average temperature and relative humidity (how much water gets absorbed into the air) plus buried pipe depth and effective underground temperatures achieved. The basic concept is one where we “wring” water from air at some given humidity content. The higher its relative humidity the more water is recovered from the air. The air-wringing process simply chills the air as it scrubs along the cooled internal pipe surface until it starts to rain inside the pipe from condensation onto its surface. The condensation is like the dew that forms on car windows, grass or any cooled surface in the early morning, before the sun comes out and evaporates the dew back into the heating air. A further bonus is that our dew-formed water is naturally distilled and very clean. It is potable water ready to drink without the need for additional sterilizing agents. Of course, we must make sure that the interior piping and cistern network is biologically cleansed before burying it underground. The hand pump with its 10 to 15 foot extended piping to reach the underground cistern must also be cleansed. The beauty of this constantly replenishable water supply is its convenient underground installation anywhere! After the in-ground installation, we have a virtual, partially passive, no moving parts, non-breakdown system containing above ground total access to all moving parts that could breakdown, namely the water pump and electric fan. Also, it is easily maintained, with few moving parts (water hand-pump and electric fan) and basically lacking any technical complexity which makes it ideal for technologically backward regions. The example below uses a relatively small industrial fan moving air at 1500 CFM (Cubic Feet per Minute) with a DC motor rated at 1kW. This fan together with our underground piping system will conservatively generate 12 GPH (Gallons Per Hour) of potable drinking water without need for any purification chemistry. Based on an average electrical cost of 14-cents per kWh (kilo-Watt hour), the typical commercial distillation of one gallon of drinking water costs roughly 35-cents as compared to our cost of only 1.2-cents. Furthermore, if we decide to go green and use solar energy for generating our water, it would effectively cost us nothing beyond the initial installation! USING A PSYCHROMETRIC CHART TO SIZE OUR WATER SUPPLY: The following gets a little technical and is only provided for those die-hards who are truly interested in how the science works. Those non-technically schooled may skip this part and not miss the basic concept. Figure-2 shows a Psychrometric Chart for air. This chart summarizes some of the basic thermodynamic properties of air throughout its typical range of operating temperature. The chart uses six basic air properties that defines the physical chemistry of water evaporation into air:  (1) the enthalpy or total energy contained within a unit of air which is a combination of its internal and external energy, expressed as the amount of BTU-energy per unit mass of reference dry-air, (2) the specific volume or the ratio of a unit volume of local air to its mass of reference dry-air, (3) the humidity ratio or the amount (mass) of moisture in a local unit of air divided by its reference mass of dry-air, (4) the percent relative humidity per unit of local air, or the mass ratio (expressed in percentage form) of the partial pressure of water vapor in the air-water mixture to the saturated vapor pressure of water at those conditions (the relative humidity depends not only on air temperature but also on the pressure of the system of interest),  (5) the dry-bulb temperature or the locally measured air temperature, and (6) the wet-bulb temperature or saturation temperature which is the local air temperature experienced during constant water evaporation (a wet-bulb thermometer is typically used:   a thermometer that measures resultant temperature while wrapped in a water wet-gauze and spun to generate local air movement and max-evaporation)  1.0   The Process and A Sample Calculation Our Psychrometric Chart uses six thermodynamic properties that help to determine the amount of water available for extraction from the local ambient air as a function of its temperature, pressure and relative humidity.  Let’s assume the following local ambient conditions for the region we plan to construct our water system at:  (1) Typical daily air temperature Td = 106F and one atmosphere pressure assumed at sea-level, (2) Relative Humidity, RH = 55%, and (3) Typical underground temperature down at six feet is measured at Tu=55F (at 12ft. it drops to ~45F). This yields the following calculated results for obtaining a steady-state supply (changes at night) of water to fill the cistern:      1)      In our example, the “local” air (dry-bulb) temperature is Td=106F, at a relative humidity of RH= 55%.  Fig-2 indicates that the resultant Humidity Ratio is HR= 0.0253 Lbs-water/Lb-Dry-Air (intersection of Td=106F line and RH=55% line, then horizontal to HR value).  We then determine the “gulp” of air volume containing the HR Lbs-water which corresponds to the point of intersection of Td and RH. Interpolating on specific volume “mv” yields mv=14.7 ft3/Lb-Dry-Air (this value sets the optimum unit airflow for our given ambient conditions, and creates a ballpark pipe length to diameter ratio needed later). It represents the basic unit of air volume that will enter our underground pipe per given time, and ultimately defines the size of our fan and piping network. For increased water creation, multiples of this unit volume will scale up the additional amounts of water that can be collected. 2)      As the inlet air cools down to a temperature of Tu=55F, from contact with the relatively cold underground pipe, we follow the constant enthalpy line (red upward left-diagonal) from the intersection of Td and RH to its saturated air temperature condition of Ts= ~88F, which is its dew-point temperature where the corresponding local RH=100%.  At this temperature or under, the air precipitates and releases its moisture content, resulting in water condensation onto the pipe walls.  Since our air will chill to a final pipe temperature of Tu=~55F, we follow the RH=100% saturated curve (green) down to yield an HR=~0.009 Lbs-water/Lb-Dry-Air. This is how much water is left in the air when it gets to 55F.  Therefore for every pound of local outside air that enters the pipe, mw=0.0253 – 0.009 = 0.0163 pounds of absolute pure, distilled potable water precipitates onto the inside pipe wall (per pound of dry air that is cooled and dehydrated) to gravity-flow out the pipe exit and into the cistern. 3)      We now convert pounds of air per unit time into a unitized volumetric airflow that yields gallons of hygienically pure potable water production per unit time. For every Va=100 ft3 of local volumetric air movement per minute (CFM) through the pipe, which translates into ma=Va/mv= 100/14.7 = 6.8 lbs. of dry air per minute or 6.8 * 60 = 408 lbs. per hour (PPH), to yield a water-flow of mwf=ma * mw = 408 * 0.0163 = 6.65 PPH or 6.65/8.345 = 0.8 GPH of water.  An industrial fan rated at 1kW DC will typically move 1500 CFM at a pressure of 8-iwc, to continuously produce 15 * 0.8 = 12 GPH of pristine potable water. 4)      Not shown here are the design details of sizing our pipe, fan and solar collection system for electric power requirements using heat transfer principles coupled with a thermodynamic heat balance, and aerodynamic fan performance assessment. These details help to size the electric power generation requirements plus margin used to properly size a solar collector containing further margins for overcast days. The engineering involved here is straight forward but beyond the scope of the current project.

Topic by RT-101   |  last reply


Spring thaw drainage dc pump

Every year we get large puddles around our property in low lying areas. Our front sidewalk also dips down at our steps and gets a huge pool. I could shopvac the puddles but the problem is they REFILL slowly but consistently until the grass dries out during the spring thaw. This is a big problem because in the morning these large puddles are ICE and are slippery as anything. Then they thaw during the day and the cycle repeats - for a month or so.So I took an old cheap craftsman tool box and put in a 12v5A battery and a 12v5A pump. The pump uses 3/8" clear hose that you'd see coming from a condensate pump. I put in a 20 mesh filter reservoir thing to keep out small particles from the pump.I ran it and WOW - not only did it work perfectly but even my wife thinks it is "cool". The pump works at about 1 gallon a minute. I purposely did NOT want a high capacity pump. I wanted to move the water slowly and allow it to drain back in. Also if you move water slowly you have way less problem with sucking in leaves, etc. It just quietly does its thing and in about 1/2 hour the puddle is gone. The problem is - overnight the puddle comes back.So I'm going to wire in a dial to slow the rate of flow down.I'd also like to make a water sensor switch. The water has very little salt in it so no electrolytes to make good current. I tried zip tying two wires to the mouth of the intake and wiring them between the battery and pump positive side. No dice.Does anyone know how to make a water activated switch that would work here? If I could get that done I'd have both flow rate and auto on/off. Sweeeeet.

Question by SumG1   |  last reply


Question on using a Peltier/TEC device for air temperature control - Help please.

I want to have some control over the temperature inside the Orchidium I'm designing and I thought it might be cool :) to use a Peltier Device (device aka module) (Peltier aka TEC or Thermoelectric Cooler). I find I need a lot of help! (Please!) Alright, this isn't a completed Instructable, it's a plea for help, and maybe if the subjects lie in some of your fields of knowledge then we can all enjoy and learn from it. So, the Orchidium I'm designing is an acrylic case 24"W x 18"D x 30"High. It's to grow species orchids indoors in a microclimate, with LED grow lights, proper humidity, air movement and temperature control. (Of course, other critters would like the case, too: poison dart frogs, newts, carniverous plants, etc.. But I'm going to call it the Orchidium.) I've got it all pretty well planned out so that it can be built for a very reasonable price (yes, including the LEDs) and still be aesthetically pleasing and real purdy, too. All planned out EXCEPT FOR THE TEMPERATURE CONTROL. I was looking for some way to cool my case and I stumbled across Peltier devices in eBay. They are CHEAP, costing about $5 or more, depending on the Wattage, etc. The eBay sellers intimated that all you have to do is plug them in and the device gets ice cold. Later, with diligent web-study I learned that actually ONE SIDE of the peltier gets cold, while the other side gets hot. Also, you MUST attach a heat sink and fan to both (?) sides of the peltier. Also, that these devices are not ready to be plugged in; you must attach a DC power supply to them. Oh, another trick that these miraculous devices do is reverse their hot & cold sides when you reverse the polarity of their juice. Ideally, I would like a Peltier device with heatsinks, fans, a thermostat and a DC wall transformer attached... the Peltier/heatsinks/fans would measure about 2" x 2" x 6" and would be mounted in the sidewall of the Orchidium. When the temperature is 65-85F degrees the orchids are happy and the device is Off. But when the thermostat senses the internal temp going over 85F it turns on the Peltier, cold side inside, and so the inside of the case doesn't go up to 90-95F like mine does now; it cools the case a little. Conversely, for someone with chilly orchids or sneezing newts the thermostat would switch the Peltier to hot-side-in to heat the Orchidium a bit. The retail cost for us to buy a Peltier device, 2 heatsinks w/fans and a DC transformer is cheap... roughly $30. The thermostat might be cheap, but I don't know enough about what's needed. If it's too expensive then the Orchidium can do without it. I was hoping I could find an off-the-shelf Orchidium cooler/heater. No such luck. These miraculous Peltier devices are still practically undiscovered -- relatively speaking. People want to use them to cool their computer chips but are hampered by condensation; my orchids welcome condensation. Pathetically, it seems the most common use for Peltiers now is to cool/heat the little boxes on your car seat... they plug into your cigarette lighter and keep your 6-pack cold. Come on! You folks at Instructables can surely help me figure out how to best make an Orchidium cooler with this barely-discovered and poorly-utilized device. I started out a few weeks ago writing to many of the Peltier manufacturers around the world in hopes they might help me in choosing which of their modules I might purchase for my Orchidium. None of them was any help. They wanted to know how many million Orchidiums I planned per year. They told me my basic plan was hopeless or inefficient cost-wise. A Swedish company wanted $800. An American company wanted $500. Some other company wanted $5,000 to $8,000. I wrote back and said I could get a Peltier on eBay for five bucks. The Swedes snottily claimed that their Peltiers were very high quality. No. No way is any svensker Peltier $795 better than ANY other Peltier in the known universe. They both get cold and grow ice crystals on one side. I just need to cool the case A LITTLE BIT, like from 90 to 80 degrees Fahrenheit. I am not trying to make a refrigerator or freezer. The case (Orchidium) is large, at about 7.5 cubic feet, and there is practically no insulation. Acrylic provides a little insulation, that's all. The temp of the interior of the case is derived from the ambient room temperature of your house... and the lights... which is why I designed it with LEDs. There is a constantly-operating muffin fan inside the case to provide air movement for the plants, but it does not provide any evaporative cooling since it's a closed case. So, first off what size Peltier do you recommend... do you think a 40 Watt would be enough, or what? Next, the placement. I envision the Peltier device mounted vertically through a hole in the side of the case. It might be a plan to mount it in the ceiling, but remember that the LEDs take up most of the ceiling. Next, the heatsinks. I confess I'm not totally clear on this, but I "think" that 2 heatsinks-with-fans may be needed, with one sticking out the outside and the other inside the case. I went ahead and got 2 heatsink/fans from Newegg for supercheap ($1 after rebate), but they aren't really what I want. They're actually shaped to fit some AMD chip. What I think I need is a copper heatsink with a flat bottom a little bigger than the Peltier, and fins... and a heatsink fan attached... and some way to attach it to the Peltier, and through the case to the other heatsink. See? Simple... well it should be but I can find nothing. Next, the power supply. I know it has to be DC, but I don't know which brick to get. I did find a bunch of DC or AC Wall Transformers for sale at alltronics... around $10 or so. All that stuff would be enough... at least to test the cooling power. But if we want to go whole hog then the icing on the cake would be thermostatic control of the Peltier. Well, I throw that out in case one of you is sharp in that field.

Topic by Knuten   |  last reply