Someone on a forum asked me what size heating elements I intended to use in my brewery. My answer was simple – but then I decided to try to do some math…
My batch size is going to be 10 gallons. I am planning on using a 4500 watt element for my HLT and a 5500 watt element for my BK. These numbers are based purely on random guesses. But… I’ve been wanting to know too. So let’s figure it out.
I just found this info on Wikipedia:
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A BTU is the energy required to raise one pound of water by one degree Fahrenheit. A U.S. gallon of water weighs 8.3 pounds. So, to raise a 40-gallon tank of 55 °F (13 °C) water up to 105 °F (41 °C) would require (40 × 8.3 × (105 − 55) / 100,000) BTU, or approximately 0.17 CCF, at 100% efficiency. A 40,000 BTU/h heater would take 25 minutes to do this, at 100% efficiency.
In comparison, a typical electric water heater has a 4500 watt heating element, which if 100% efficient results in a heating time of about 1.1 hours.
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Okay, so based on that info and the Wiki entry for BTU we find that the formula for calculating power required to heat water is: BTUs = (GALLONS * 8.3 * (FINISH_TEMP – START_TEMP))
And based on random crap I found around the Internet we know that heating elements (and heat sources in general) are measured in BTUs per hour or Watt hours. i.e. how many BTUs they put out in an hour or how many watts they put out in an hour.
So now we just have to figure out the two formulas based on time.
So, using my case of a HERMS system let’s say I want to know how long it will take to raise 15 gallons of 55 degree water to my 170 strike temperature. That’s:
(15 * 8.3 * (170 – 55)) = 14317 BTUs
If I use a 4.5kW element I am creating (4.5 kW * 3414 BTUs per kW) = 15363 BTUs per hour
So my time to heat my water is 60 minutes / 15363 BTUs * 14317 BTUs = 55 minutes!
That was actually much less difficult than I expected
Based on that info, I think that I will put a 5500 in my HLT and the 4500 in my BK. The big difference here is the temperature difference. To go from tap water to sparge water it’s a 115 degree difference but to go from mashed wort at 156 to boiling it’s only 56 degrees – so it will make more sense to have the bigger heater in the MLT. It will save me about 10 minutes in heating my mash and sparge water.
Now, getting back to your original question – RIMS seems more difficult to calculate because the water is moving past the heating element. I’d need to think about it more but maybe that doesn’t matter. If water is always in contact with the element and water is constantly being moved through the tube maybe that’s the same as being in contact with all the water at once. You end up applying more BTUs to less water, so maybe it averages out. Let’s assume it does.
If you wanted to ramp 20 gallons 1 degree in one minute it’s:
(20 * 8.3 * 1) = 166 BTU hours * 60 minutes = 9960 BTU minutes / 3414 BTUs per kW = 2.9 kW. So, it seems like with a 100% efficient system you could use a 3kW element to get your steps. I think the real problems will be trying to get 20 gallons of wort past the element in 1 minute. It looks like my March 809 pumps are a max of 6 gallons per minute, so you’d need at least 3.3 minutes to get all the wort past the element.
I guess another option would be to oversize the element to decrease the amount of wort that needs to flow past it. If it will take 3.3 minutes to move your wort past the element, what if instead you use 3x the heat? If you use 3x the heat you would only heat 1/3 of your kettle but the wort would come out of the RIMS much hotter and would increase the total temperature of the wort.
So, there’s my attempt I am sure someone who knew anything about thermodynamics would just read this, laugh and walk away, but it’s probably better than guessing!
It’s probably time I start posting about my brewery.
I’m building an all electric Heat Exchanger Recirculating Mash System (HERMS) brewery that will live in my garage. The brewery is intended to fix all the problems I had when I was brewing in Kansas and make brewing enjoyable instead of a horrible chore.
The basic gist of the system will be 3 20 gallons pots, the Hot Liquor Tun (HLT), the Mash Lauter Tun (MLT) and the Boil Kettle (BK). The HLT will contain a large coil of stainless steel tubing that wort will circulate through to change the temperature of the liquid in the MLT. This is the HERMS. The system will use two pumps to move all the liquids around and several (10, perhaps?) solenoid valves to make on the fly plumbing changes. The goal is that the system will require no manual plumbing changes and (ideally) could run almost 100% automatically.
I’ve been designing, drawing, dreaming and buying stuff for a month or so now. I made a giant shopping list and have been trying to buy the stuff needed to get a single kettle up and running and then go from there. This weekend I finally had most of that stuff together so I got to work. I wanted to build the HLT first since that would be the most complex. The first step was to fabricate the HERMS coil as the size of that would determine the positioning of many things. I picked up 50′ of 1/2″ OD stainless tubing McMaster and when it arrived it was in a 24″ diameter coil. Unfortunately I needed a 12″ coil. So, after doing some reading and asking questions I filled the whole thing with nice, dry sand (which was a pain in the ass) and very slowly and painfully coiled it around an old 12″ diameter pot I had laying around. This worked pretty well but it was HARD work! My coil turned out to be 12″ in diameter and about 8″ high when compressed.
Side note: When the project is done I will post a spreadsheet with prices and sources of all the parts. I don’t feel like putting them all in these posts as I go along.
That was Saturday. Sunday I measured everything, draw some dots and set out to drill some holes in my Boilermaker. This was fairly difficult but I think it was my own fear of drilling in the expensive pots more than anything. I drilled a 1/8″ pilot hole using lots of cutting oil and plenty of pressure with my hand drill and then widened each hole to 13/16 with a large Unibit. Lots of pressure, cutting oil and some good hearing and eye protection and it wasn’t really that bad. I drilled two holes on the left side of the pot. One at 5″ from the bottom and one at 13″ from the bottom. These are the entry and exit holes for the HERMS coil. I would have liked the coil to sit a little lower but I needed room for the heating element which will be at 3″ from the bottom. The holes needed to be slightly larger than 13/16″ so I cleaned them up just a little bit with a sanding wheel in my Dremel.
The next step was mounting the coil. I had intended to use a pair of weldless bulkheads, two 90 degree elbows and just run the coil right into the elbows. This turned out to not really work. Because of the angles involved the coil would rest against the side of the kettle. I tried using a coupler to move the whole assembly further into the pot but that made it go too far to one side and hit again. When I had really wanted to do from the beginning was have the coil terminate in two straight pieces from a 90 degree bend so it could go straight into compression fittings through the kettle wall. Unfortunately I had had some trouble doing 90 degree bends in the stainless tubing. Since this ended up being necessary I got to work on that.
To get my 90 degree bends in the tubing I first straightened about 16″ of tubing at the top of the coil. I did this by slipping a plumbing spring over the coil then straightening it about an inch at a time in my vice. This worked really nicely. Once it was straight I put it back in the vice around where I wanted my 90″ bend and started pulling on it. I would bend a few degrees and then move it in the vice a quarter inch or so and then repeat. This was hard work but it got the job done. The only problem is that the resulting bend has a very slight kink to it. I don’t think it will cause too much restriction but only time will tell. I tried to reshape the kink in the vise a little and had moderate success.
That’s where I finished on Sunday. I have another 90 degree bend to make and then I should be able to mount the coil. I am thinking I might pick up a tube bender from Harbor Freight and try that. They sell one for $30 that looks like it might be capable.
So, tonight I’ll try to make the other bend, mount the coil and test it all out for water tightness. After that it’s on to installing the first heating element. I bought a 1.25″ chassis punch that should make that a lot easier but it’s not here yet. Should be here soon. I’ll also be receiving a bunch of control panel parts tomorrow that I can start laying out and seeing what works.
Also, I should mention I built and am selling a custom display for the BrewTroller brewery controller I am using. Check it out!
And finally this is a quick rundown of the specs and major components of the brewery I am building:
All electric HERMs brewing system. 240v, 50A input.
3 20 gallon Boilermaker kettles.
240v 4500 watt HLT and 5500 watt BK.
Control provided by a BrewTroller v3.3 w/ 16 relay output board and BrewTroller software 1.2.
3 Custom PID temperature displays.
2 March 809-HS pumps for fluid movement.
7-10 stainless steel 12v solenoid valves for fluid routing.
Plate style stainless steel wort chiller with 20 plates.
Silicone tubing plumbing to start, stainless hard plumbing eventually.
Custom stainless brewing stand. I’ll be welding this once my TIG skills are a little better.
Custom control panel with On/Auto/Off controls for pumps, heaters and all valves. Also includes 3 of my BrewTroller PID Displays, the BrewTroller LCD and rotary encoder for input.
All stainless pipe fittings.
Inline oxygen injection during pump to fermenters.
Constant recirculation of MLT and HLT to avoid temperature stratification.
Man, I never post any more. It makes me kinda sad. I like posting! But I am so damn busy doing shit that I never feel like I have to time to write up a proper post about all the stuff I did and it just piles up.
The last few weeks have been kinda crazy. For a few months now we’ve had a lot of travel planned for May and then at the last minute I added another one. My brother has been threatening to put a supercharger on his 2005 Lotus Elise for a while now and he finally decided to do it. I had expressed some interest in helping with the install, so when he ordered the kit I booked a flight to Kansas City. It was a short trip but lots of fun. I got in Friday afternoon and spent the evening hanging out with friends at Barley’s, then we got up for an early start on the supercharger Saturday morning. We were expecting around 12 hours of work, and it ended up taking more like 20 but man it was worth it. We worked from 8am till about 7pm on Saturday and ended with the supercharger stuck about halfway in. We had skipped a step involving moving the alternator early on and we ended up having to go back and do it the next morning.
So, bright and early Sunday morning we got up, moved the alternator and it was pretty smooth sailing the rest of the way. Minus one pipe that we had to modify more than recommended the install went pretty smooth the whole way. Not to say it was easy: It wasn’t. I had bruises and cuts and sore muscles for a week afterward.
I wrapped up my KC trip at Gengis Kahn with a few friends, then got up at 3am and flew back to Seattle. Short, but long trip 🙂
Next up was New Jersey. My step-dad Fred has been dating a lovely lady named Dori for quite a while now and last year they decided to marry. After getting the invite we planned a trip out for the wedding and for Courtney to get a chance to see where I grew up and meet some family. It was also a short but action packed trip. The wedding was very nice, and I got to spend lots of time with family I seldom see. Courtney got to meet quite a bit of my family. We also managed trips to Dippy’s, Sals and Steak Out for traditional NJ grub and we visited my old house in Sewell, and in Mantua.
We also took a trip out to the cemetery where my Dad is buried so that I could see his grave. The day of the funeral his marker had already been placed and it had snowed the night before so I couldn’t see it and didn’t know where it was. That part of the trip was pretty painful, but much needed.
Finally, we took a drive past von Nieda park in Camden since I had not been there in years. It seemed like a really great place to get killed so I took a picture of the sign and we got the hell out of there. Off to the airport and back to Seattle!
Next up was the Bay Area Maker Faire in San Mateo, which we just got back from Sunday. I don’t have a whole lot to say about it this year. There were some cool exhibits but most of it I had seen last year. Maker Faire seems to be very geared towards kids and families, which I think is awesome but it’s not awesome for me. I am really glad this exists for kids to get excited about science and hacking and DIY but I found myself kinda bored this time around. The exhibits that stuck out in my mind were the Mondo Spider which is a huge, hulking, ridable metal spider and the big POV sphere in the middle of the Tesla coil hall. On the downside, I am pretty worn out by “art” exhibits that aren’t much more than a propane tank and a source of ignition. I guess that stuff is is awesome when you are tripping your ass off at Burning Man and it’s dark out but I just don’t see a lot of value in blowing off a bunch of fossil fuels to make pretty flames.
Also: Get off of my damn lawn!
Anyway, we hit Maker Faire Saturday morning and stayed till about 4, then again Sunday morning and stayed till about 2 when I had a massive allergy attack. After getting back to the car so I could take some medicine we decided we were done and headed out to see a little bit of California before we had to fly again. We ended up kinda randomly on the coast and cruising down Highway 1 which was really a lot of fun. Absolutely beautiful everywhere you looked. It really deserved to be driven in a convertible. We ended up at the Pigeon Point lighthouse before turning around and that was really pretty. Courtney took lots of pics with our new Olympus EP-1 which takes really great pictures. After that: more driving, more flying and back in Seattle again! Our dogs are starting to think we only live here about 50% of the time now.
Our last trip is this weekend to Denver to see John and Aoi right before they are with baby, and to hang out with the rest of the crew. Really looking forward to this trip but I am sure not looking forward to flying again. This is the last trip for a while. A long while, I hope.
In random other news I’ve:
Bought an Everlast PM-205 TIG/Stick Welder / Plasma Cutter combo and am learning how to TIG weld.
Am building a badass, mostly automated 10 gallon, all electric brewery for the garage.
Am still hoping to finish the first OpenPNP prototype this year.
Started fixing up my bicycle. I’m hoping to start riding a little and get back in shape.
Sold one of my TC18 clocks on eBay and it fetched a princely sum!
Today was ultra-awesome productive! I got up, fixed the lawn mower, mowed the lawn, cleaned up a lot of the mess in the backyard that Flux has made, went for a long motorcycle ride (Woodinville, Duvall, Monroe), almost pooped when a train blew it’s horn like 5 God damn feet from me, charged Courtney’s car battery and got that running, tested my generator to prep for sale, cleaned up the garage, scoped out the iron pipe offerings at Lowes (for future “shop air” project), put the hinges and clasp on the box for the eBay clock (coming soon!), got nicely buzzed and stuffed at Rock Bottom and am looking forward to a very nice night of blissful sleep.
Also, Courtney took an Introduction to Electronics class at Metrix which sounds like it was very informative!
And I spent a significant amount of time trying to figure out if I can really stick a 3 ton milling machine in my garage. Survey says? Yes we can!
Been getting a lot of spam recently on this site. Lots of stuff where someone will post a comment that almost sounds like a real comment but it’s just bullshit and their URL points to a poker site, or a porn site, or a SEO site, or in the case of one of my posts titled “Tranny”, a site you don’t want to know about.
For that reason, I’ve removed the ability to include your “website” URL when you post a comment. I’ve also caused any post that contains one or more URLs to be moderated by myself. Hopefully that will stem the tide. You can of course leave a URL in the comment if you want to, it just means I’ll look at it in person before approving it.
In a rapidly assembled, last minute (although intended for quite some time) wedding, Courtney and I got married on Saturday, March 13th! We were married by retired judge Hayek at her office in Kirkland and it was very low key. Adam, JoLynn, Scott and his new woman Anissa were in town for Courtney’s birthday party (also the 13th) so we asked them to come along. It was a 5 minute ceremony and then we headed to the Irish pub around the corner 🙂
So, that ends one era of my life and begins another. I’m very much looking forward to what it brings!
The other night I finally finished buying all the supplies I needed to try to anodize some aluminum parts. Anodizing is a process that causes aluminum hydroxide to grow into and out of the surface of aluminum metal. Aluminum hydroxide is very hard, which provides scratch protection and is also porous which allows dyes to color it. Dying the metal is reason for a lot of commercial anodizing and is the main reason I am doing it.
The basic process of anodizing is to form an electrical circuit between the part to be anodized (the anode), dilute sulphuric acid and (usually) another piece of aluminum which is the cathode. Voltage is passed through the circuit which causes the anodizing to take place. The part is then dyed and finally the pores are sealed to keep the dye in.
This post describes how I did it.
First, some safety. Most of the stuff that I am doing to anodize parts can blind or kill you. Always wear gloves. Always wear goggles. Never mix chemicals unless you know what will happen. A few of these chemicals mixed will produce horrible gases that will kill you and your family and probably your dogs too.
Next, the supplies. I bought the following:
Battery acid, 5 gallons, from NAPA Auto Parts
Lots of distilled water
Several plastic buckets from Home Depot
1 pound tube of 1/16″ aluminum tig welding rod from Central Welding Supply
40 amp battery charger from Harbor Freight
Black RIT Dye from the supermarket
2 single burner hot plates from Target
2 6 quart pots for the hot plates
The first step is to get the parts nice and clean. I first washed them in warm water and hand soap and then in a dilute mixture of Simple Green and distilled water.
Next I used the welding rod as simple aluminum wire and attached pieces about 6 inches long to each part I wanted to anodize. You have to make sure the wire is attached very well, and also keep in mind that wherever the wire is attached the metal will not anodize. Lots of people use threaded holes and jam the wire in. I just made some little clips by bending the wire.
Next I took 1.5 gallons of my battery acid and mixed it with 1.5 gallons of distilled water. I kept in mind the AAA rule. Always Add Acid. If you add water to acid the water can boil and “explode”. I put 1.5 gallons of distilled water in a plastic bucket and slowly poured the 1.5 gallons of acid in. Very slowly. Probably took me about 5 minutes.
Next I used some aluminum scrap I had laying around to make a cathode and used some as a rack for the anodes to hang from. It’s pretty clear from the below picture:
I drilled a bunch of holes into the anode rack to use as hook hangers and bent the ends of the anode wires into hooks. Hang the parts.
Next step is to apply the juice! Hook up the negative from the battery charger to the cathode and the positive to the anode rack. I’ve read that it’s best to start at low current and ramp it up. My charger has settings for 2 amps, 10 amps and 40 amps so I set it to 12 volts, 2 amps and let it run for 5 minutes. Almost immediately there were bubbles forming around the cathode. The bubbles are hydrogen gas which comes to the surface. Make sure you have some ventilation so you don’t blow up your house. Remember the Hindenburg.
5 minutes later I turned it up to 10 amps and then 5 minutes later I turned it up to 40 amps.
(I should probably note that I am running this batch as I type this post. Most of the experiences for this post come from a batch I did the other night with slightly different gear. )
At this point I let the anodizing bath run for about 80 more minutes. I have read that anywhere from 45 minutes to 90 minutes is good.
There’s a few ways to tell the anodizing has finished. The current draw should drop quite a bit. An anodized surface does not conduct electricity well, so as the surface becomes more anodized the part conducts less electricity. You may also notice a slight lemon yellow tint to the part. I just let it run for 90 minutes and called it good.
Once the parts are finished, turn off your power supply and rinse the parts very well in cold, clean water. The water must be cold or the parts will start to seal.
Next up is the dye. I used RIT Dye which seemed to work pretty well. There’s lots of places to get proper anodizing dye but RIT seems to work for me. I dumped a bottle the black, liquid RIT into 1 gallon of distilled water and put it on the hot plate. The dye works best heated and most people recommend about 140 degrees so that’s what I used. Once the dye was up to temperature I put the parts in and let them soak for about 15 minutes. I have read that you might get the color you need in as few as 15 seconds depending how dark you want it. I wanted dark, dark black so I left them in for 15 minutes.
At this point you can pull the parts out and you may find that some didn’t take any dye or the dye drips right off. This happened on my first batch with one part. What this means is that you didn’t have a good electrical connection to the part. You can remove the dye and anodizing by etching it in a bath of water and lye. I used a few tablespoons of lye in about a half gallon of distilled water.
Once the parts are dyed the only thing left to do is seal them. This is done with boiling water. I read that steaming the parts before putting them in boiling water can help you lose less dye, so I put a pot of water on my other hot plate, put a rack over the pot and placed the parts on the rack. Then I boiled the water letting the steam wash over the parts for about 10 minutes. Then into the bath they go. 30 minutes in boiling water and the parts should be sealed and ready for use! Hooray!
I’m still a total newbie at this, and I’m actually going to a professional anodizing shop next week to see how they do it. That said, I did get really nice results and it seemed pretty easy. Takes some time and a few dollars but the result is amazing!
My pictures of the finished results are here and Courtney’s pictures of the process are here.
So, the other day Courtney and I drove down to Kent cause I got a hot tip on some powdered red jewelers rouge at Jerry’s Rock and Gem. We went in and it was pretty clear from the start that by gem they mean “Crazy people crystals”. This was confirmed when while standing in line I heard the lady next to me (dealing with another clerk) say “Well, you know, if the cataclysm comes I hope you have 4 or 5 big trucks to get all of this stuff to higher ground.”
She said it in hushed tones and you could tell she was just dead serious.
That being said, Jerry’s was pretty cool. They did have the rouge I needed (more about that later) and they had a great selection of tumbling supplies, petrified wood sculptures, all kinds of interesting minerals and all kinds of rock and gem related stuff. Neat place.
So, since my last post about my clock I’ve been working on my clock and one other thing. For the clock, I decided I would make 5 total, complete clocks and then be done with it forever. The clock has a lot of parts to make a single enclosure so I spent some time trying to speed up the process of making some of the parts.
One of the components of the clock is these tiny 1/4″ polished aluminum rings. I made the first 8 for the original clock by hand but it took forever and was very difficult. I cut the little pieces of my bandsaw and then bored them out on my drill press but the parts are so small it was difficult to get them in a vise without ruining them.
So, what I did this time is I made a “ghetto lathe”. I took a piece of 1/2″ aluminum plate, drilled a 1/4″ hole and a few 10/32 tapped holes and then a 10/32 tapped hole in the side to intersect with the 1/4″ hole. Into the 1/4″ hole went a stubby 1/4″ drill and I put a set screw in the side to hold it. In one of the tapped holes I put a lathe tool post and a lathe cut-off tool. Then I put my polished tube stock in the chuck of my mill and wrote a program. The program would push the spinning stock down on the drill to bore it out and then run it against the cut-off tool to cut off a perfectly sized ring. This worked perfectly! I made the 40 rings I needed in just a few hours. There’s a video of the process below.
The next thing to do was to make the 40 metal plates that make up the body of the clock. Each clock uses pairs of 4 different shapes for 8 pieces each. I made a little fixture out of MDF on my mill and cut these all out in the course of one long Saturday. Nothing special there.
The special part was that I did not want to hand sand all of those parts, so I went to Harbor Freight and picked up a 18 lb vibratory tumbler for the low, low price of $149 and set to learning how to use it. I got some plastic triangle media from a local friend and threw in my parts in batches of 10 for about 6 hours each. This put a nice matte finish on the parts, rounded all the corners and removes burrs, which was great! After that I used walnet shell media with the aforementioned red rouge to polish the endcap pieces as these will be anodized. I let those run for about 36 hours and they came out very nice. A few steps from a “mirror” finish.
Now I am at the anodizing stage. I’ve done a lot of reading and I feel like I will try doing it myself. I picked up a bunch of plastic buckets at one of my nearly daily Lowes trips the other day, got some lye yesterday, got 5 gallons of sulphuric acid today and need to pick up a few more supplies tonight. I’ll probably wait till the weekend to give it a try and assuming I have some success I’ll write a post about how that works.
My next project, and the one I expect to consume me for the rest of this year and maybe longer is OpenPnP. I decided that I would like to own a small pick and place machine for doing PCB assembly but I don’t like the $30,000+ price tags. I figure this is something that would be fun to build and maybe in the mean time I can revolutionize home PCB manufacturing! My hope, and goal, is to design and build a fully functional pick and place machine that that can reproduced for around $1,000. I will make all the designs and software open source and maybe, if there’s interest, produce some kits or something.
OpenPnP is still in it’s very beginning stages. So far I have bought a few basic parts and I’ve been making some parts on my mill. My goal for this month is to have a working, high precision 2 axis “cartesian” platform and to be working on adding motion control. My target is to get a basic 2 axis CNC made so that I can start working on the head design, which is where all the hard work is going to be. The CNC doesn’t need to be complex, but it needs to be precise and fast. To that end I am using THK linear guides for X and I am considering Hiwin linear guides for Y. I bought the THK guides off eBay to get started but will probably spec Hiwin for both axes in the final version.
So, that’s what’s new. I’ll be posting quite a bit about OpenPnP over the next several months. Now that I have officially announced the project I intend to document my progress as much as possible.
In the mean time, if you are interested in OpenPnP please go to it’s homepage and read what I have there. I am currently interested in talking to people who have experience with computer vision systems as I expect that to be a very difficult part of the system.
So, back in September the company I worked for, Displayware, ceased operations. That’s a fancy way of saying we went out of business. We did that because we ran out of money and didn’t have enough coming in to sustain the very meager workforce we had. Since then I’ve been unemployed, but mostly as a choice. I had money in the bank and was pretty burned out from the Displayware days so I decided to just take some time off and work on my own stuff and chill out.
Right before that happened, Ladyada of Adafruit released her design for a clock based on an old Russian vacuum fluorescent display tube called an IV-18. I thought the clock circuit was really cool and the tube was great but I didn’t care much for the acrylic case. A day or two later I somehow came across a Slashdot article about it and was reading some of the comments when I saw someone comment on the case and post a picture of his own design.
THIS was the clock I wanted. I totally fell in love with the clock design and decided I must have one. This short conversation, via Slashdot comments, followed:
I never did hear back from John. I assumed he just never saw the comment. I spent some time trying to find an email address but eventually gave up and instead decided just to build it myself.
One of the things I decided to do when Displayware croaked was spend some time learning how to use my CNC mill. I bought a 3 axis mill in November f 2008 but had never really took the time to learn to use it. So, I spent many days getting up early, going out the garage and not coming out till Courtney got home from work. Those were very enjoyable days. My hands were dirty and cut, I was chopping up bits of metal and programming the mill and learning new stuff every day.
Eventually I got to the point that I felt like I could make stuff on the mill so the next step was to learn how to use CAD and CAM. I downloaded a CAD system and set to work learning how to use it. That took some time but eventually I was able to design the three metal plates I saw in the clock picture. Since all I had to work with was a single graphic from one angle I had to guess at a lot of things but I think I eventually came up with dimensions that were pretty close to original. The only real dimensions I was sure of were those of the tube itself, so I used what I knew about that to take educated guesses at the rest.
Once I had designs ready to go I bought some sheets of stainless steel and went about trying to cut the clock parts out from it. I used stainless because from the rendering of the clock that’s what I thought it was supposed to be. It turned out that it was nearly impossible for me to cut stainless on my little mill, so I switched to aluminum sheet and had much better luck. I cut the six plates out and sanded them a bit and set them aside.
The next step was to make the metal pipes that connect the whole thing together. From the picture I thought these were polished aluminum so that’s what I started with. I bought some 6061 aluminum tube from Online Metals (where I get everything in this post) and set to trying to make it pretty. The process I eventually came up with is that I would take these 12″ sections of tube and stick one end into the chuck of my drill press. Set the speed to the lowest it would go and turn it on. Then I started with 250 grit sandpaper running up and down the spinning tube. Then 500 grit, then 1000, then 2000. After all that the tube is looking pretty smooth so I took some polishing compound to it and that really made it shine. It looked just like the picture.
I cut out 8 1/2″ sections and 4 4″ sections, drilled the small ones through to widen the inner diameter to 1/4″ and then tapped both ends of the larger ones so they would accept bolts.
The next step was to find a LOT of o-rings. If you look at the picture you’ll see there are 24 o-rings used between all the pieces of tube. It’s an awesome design element and I wanted to stick with it. Unfortunately, when I went to the plumbing store I could only find about 4-6 of the ones I needed and they were almost a buck a piece. The o-rings would cost more than the rest of the clock! Eventually I decided to check McMaster-Carr, who I had never ordered from before, and it turned out I could buy bags of 100 for something like $1.34 total. That worked!
The final step in the design was the black perforated metal sleeves around the ends of the clock. I had been worrying about these for a while. I figured I could get perforated metal just fine, and bend it into shape maybe, but I had no idea how I would connect it at the bottom and make it look nice. I started researching welding aluminum and I started looking for used TIG welders.
Since I couldn’t really afford any of the welders I was seeing I decided to just try hacking it together. What I ended up doing was using my mill to cut down a sheet of perforated aluminum to a 1″ thick strip about 14″ long. Then I made another CAD model. This one was of the shape that would fit inside this sleeve. I used this on the mill to cut out 2 3/4″ MDF forms which I glued together to make a single 1.5″ form. Using this form, a heavy pair of leather gloves and a heat gun I heated the aluminum up till it started to be easier to bend and then wrapped it around the form. I stuck a clamp on it to hold it shut and then I broke off a 1/2″ long strip of the same stuff from another piece. I put this inside the sleeve and super-glued it down to hold the sleeve together.
The super-glue worked okay but I knew I could pop it apart pretty easily if I wanted to. So, my next idea was JB Weld. This worked great! I mixed up some JB Weld, smeared it all over the inside of the sleeve and over the little brace and let it set up. After that it was rock solid. I sanded the whole thing down, spray painted it gloss black and called it good.
Once everything was dry I finally was able to put the whole thing together. After many weeks of work, here’s what I had.
I was pretty happy with it! I thought it looked quite a bit like what I was seeing in the image and for having started with nothing but a picture on the Internet I thought it was going pretty well. So, it was time to work on some electronics.
Somewhere along the way I ordered 5 of the IV-18 tubes from eBay. They were surprisingly cheap. I think I paid like $15. They actually came from Moscow, so that was pretty exciting. Unfortunately, they did not come with a datasheet and I didn’t really have a a pinout for the things. I spent an hour or two with a loupe and headache looking at all the little wires inside and figuring out a pinout. A day later the seller emailed me a datasheet. Oh well.
One of the enabling elements of this whole thing was that when Ladyada posted her clock design she also posted schematics and notes. This allowed me to learn about boost converters, which are circuits that allow you to take a very low voltage and make a very high voltage pretty easily. I knew about boost converters, but I had no idea they could be so easy to build. Ladyada’s designs really made that clear and she even posted a calculator for figuring out the proper values.
The IV-18 tube requires about 20v (volts) to light up and 50v really makes it look great. She was using a 9v wall wart to power her clock and decided that sounded good to me, so I set out to design a boost converter that could convert 9v to 20-50v. The way a boost converter works is that it takes the input voltage, runs it through an inductor and then chops it off to increase the voltage. An inductor is a electronic component that is as simple as a piece of wire wrapped around an iron core. The interesting thing about inductors is that they have electrical inertia. Once you start running power through them they like to keep it going. So, if you suddenly cut off the power the inductor tries to keep the power flowing. Ohm’s law being what it is, since the inductor can’t keep the same amount of current flowing the voltage starts to increase. By simply running a low voltage through an inductor and then turning it off the voltage inside the conductor can suddenly jump to many times what you put in, albeit at a much lower current.
So, to make a circuit that turns 9v into 50v we run 9v through an inductor and turn it off and on many times per second. We store these high voltage pulses in a capacitor until they make up enough to flow the current we need and we have a high voltage power supply. The ratio of how long the inductor is on versus off determines how high we boost.
So, with all that in mind I bought a bunch of components and more specifically, I bought a bunch of different values of inductors. I wanted to see how different values affected the output. I built the boost converter circuit on a breadboard and used an Arduino to drive the pulses and started plugging in different inductors. Using my oscilloscope I was able to learn about constant conduction and learn more about ripple and power draw on my circuit. I eventually learned that I could run my converter using a 220uH inductor and a 22uF capacitor and easily get 20-60v out of it at the current I needed without pulling the inductor out of constant mode.
So, I had a power supply. The next step was to try to drive the tube. I used the same VFD driver Ladyada was using in her clock and I got Maxim to send me a few samples for free. The driver is a MAX6921 chip. It is basically a shift register that controls 20 output at up to 76v each. It’s pretty awesome. At this point I needed a circuit board to wire everything up so there’s a solid week or two where I tried different ways of making boards. I won’t go into it all now, but the basic process I came up with is using my laser printer to print a transparency, use a UV tube to expose a positive resist board through it, etch with the sponge method using ferric-chloride and then drill all the holes using the mill. I have another long post in the works that describes that whole process.
I ended up making my first ever home made double sided board that had pinouts to hold the IV-18 tube and the MAX6921 chip. Once that was all hooked up I wrote a bunch of code and used an Arduino to drive it and I had a working tube! That first board looked like this:
Using this board and my Arduino I was able to basically write the entire program that runs the clock. I wrote all the driver routines, communication and time keeping. I considered at one point just making my circuit compatible with Ladyada’s code to save some time but after looking at her source I had some different ideas of how I wanted to do things so I just started from scratch.
The next step was to start working on the real board. I had known all along I wanted to make a single board that would fit inside the black sleeve and I knew I wanted it to be surface mount. I really enjoy working with surface mount components and I knew I’d need to use small components to get everything I wanted in the sleeve. This took a pretty long time. It was the most complex circuit I had ever designed and I ended up adding a lot more to it than I expected to. After working on keeping time in the Arduino for a while I decided it just was not accurate enough for me and I decided to add a DS3231 real time clock. This chip basically has everything needed to keep super accurate time and it’s easy to communicate with. So, I ordered up some free samples and went back to the garage to build a breakout board for that chip.
After getting this board made and soldered up I was able to start using it with the Arduino to handle time keeping and things really started to come together. At this point I had this giant mess on my desk consisting of an Arduino, a breadboard holding the boost converter circuit, another breadboard holding the click chip and the tube + driver board. I soon added some long wires and a rotary encoder to the mess and I finally had all the major components of the clock actually on my desk and working. I wish I had a picture of the mess.
Mess or not, this allowed me to write all the code I needed to run the clock. The code handles talking to the DS3231 for getting the time, talking to the MAX6921 to drive the tube, drives and monitors the boost converter, read interrupts from the rotary encoder to drive a menu system and a dozen other little things. It’s extremely interrupt driven and I think it’s the nicest AVR code I’ve ever written.
With all the parts together and working it was time to “capture” the schematic. This is what engineers call it when they take the mess on their desk and turn it into a nice, tidy computer drawing. I used Eagle to completely design the circuit and I got to work designing the board to match it. A few weeks later I had a board design and I sent it off to Gold Phoenix for manufacturing.
This board worked really well, except for a few small errors. The main errors were that I forgot to hook up one pin of the CPU which meant I couldn’t put any code on it and the other was that I determined I needed a pull down resistor on my boost controller’s MOSFET for protection. I soldered these fixes on manually and put the board together and I finally had a clock!
This board allowed me to do all the final bug fixes and get everything ready to actually build the clock. One big problem though was that I had put components too close to the four holes around the edges and had no way to really bolt the thing down. With the electrical errors in mind and this physical issue I decided to do another version of the board and for fun decided to get the board made black. Another payment to Gold Phoenix and a week of nail biting and I had my final, final board.
While I waited for those boards to show up I ended up redrawing the CAD drawings for the three metal frames. I needed them to be a little bigger to make everything fit nicely. I also determined I needed 1/4″ long versions of the small tubes instead of 1/2″ ones so I made those. I got that work done and eventually the boards and parts showed up. Yesterday I finished final assembly, drilled a few holes in one of the sleeves for the power and rotary encoder, put the thing together and finally, after nearly four months of work I was finished*.
The eagle eyed among you (like anyone is actually still reading) will notice some flaws. I scratched up the right sleeve while drilling it, so it needs to be repainted. I think I’ll repaint both of them and put a layer of clear coat on them for protection. The holes in the back are also sloppy, so the right sleeve will probably get remade completely. The small tubes on the left are longer than the right and I’ll probably fix that today. Just need to cut four smaller ones like the right. And the middle pipes need to be about 1/4″ longer to show the entire display.
Aside from those minor things, the project is done! It was a ton of work, and a ton of learning but it’s been great fun and very rewarding.
Last night, to clear up loose ends, I finally spent some time tracking down an email address for John. I wrote him a long letter explaining all this and he wrote back and was very cool about the whole thing. He asked that I give him credit for the design, which I am very happy to do.
I’m really glad he designed it, and posted that picture of it and even more so that he was very understanding about my little obsession. I think the enclosure is gorgeous and had I not seen it I never would have started this project.
I’d also like to thank Ladyada of Adafruit at http://www.adafruit.com. Her clock design gave me the understanding I needed for the electronics side of this project. While the end result is, I think, quite different from her design it’s definitely got it’s roots in the Ice Tube clock kit that she sells. The kit looks great and you should probably go buy one now!
From here, I intend to open source the whole mess. I have some cleaning up to do but once it’s done I’m going to post the code, schematics, CAD drawings, bill of materials and everything I used to build it. Unless you have a machine shop at your disposal, or a massive obsession like myself, you probably won’t make one like it but maybe you’ll see something that gives you the idea to make something even cooler.
