[Metal Working] Marble Tower

Summary:

I first ran across this project while browsing google photo's for "machining projects" and it seemed like a great way to get some practice dealing with backlash on the mill. When I ran across 3 aluminum disks in one of the shop scrap bin, it was a no brainier second project.

For this project I wen't with with a simple 5x5 pyramid, but in principle one could cut a much more complicated base pattern. Spheres pack pretty well hexagonally as well. I still have 2 more disks, so at some point in the future I may make a variant of this project with a more complex hole pattern. 

Like any good second project, this one involved a fair number of "learning opportunities" along the way. Most will be obvious to a more experienced machinist, but I have included a short list below. 

Lessons Learned: 

• When making a super glue arbor it is important to cut grooves to hold the super glue. Otherwise, the glue tends to bunch up and prevent the piece from sitting flat. (If I was doing this again I would use soft-jaws instead of a glue arbor).

• Freshly cast aluminum is very "gummy" which makes it a bit tough to work with. Fine for making the arbor, but if other choices exist those'd be better.

• Double check that the end mill used is a ball nosed rather than a bull nosed.

[Metal Working] Copper Rose

In honor of Valentines day, I figured I'd take a shot at making a copper flower.  I used 28 gauge copper sheet for the petals and 1/4 inch brass round stock for the stem. 

This project is pretty well documented in a number of places online (see link in the process section) and from my experience seems to turn out a nice product even with a fairly large number of small mistakes along the way. If you are looking for a nice evening project, this seems like a great option. I chose to do this build mostly with hand tools (and the lathe) but it'd go a lot quicker if you used a water jet/laser cutter to shape and texture the petals. 

Process: 

I roughly adhered to the following instructable (click me) with a few notable modifications. 

• I cut each set of petals pretty roughly and used a belt sander to get the final shape. 
• I found it pretty hard to texture with a crow bar and used a chisel instead. 
• While texturing the sepal I introduced a few annealing steps on the stove to prevent the copper from tearing. 
• I turned down and threaded the end of my stem and used a nut to hold the petals to the stem. (I also used a file to round the end of the stem.)
• I used a small quantity of super glue to hold each set of petals in place.

Notes:

• Parts could be water jet instead of cut with tin snips for significant time savings. 
• The 40 Watt laser is probably capable of etching a lot of the texture lines. 
• The super glue worked fine and is a lot easier than welding/soldering. 
• Variations in petal size should be avoided where possible since that creates gaps between each layer of petals. 
• Cost: 12$ (Unit cost for multiples of 2)
• Time: 7h (4h petal and stem prep, 3h assembly and patterning)

[Hell Lighting] LED Installation

Summary:

The lights are up! There is still some work to do with wiring and splicing before we will be ready to add power and control, but the LEDs themselves are now fully installed. 

Details: 

We took a few design chances this time around. In particular, the purgatory side of hell is bridged as a triple arch (see picture) rather than a single arch, and the bathroom side of hell is now bridged with a straight set of lights running across the far wall. As a result, we ended up with a much larger lighting shortfall (10m) than we had  anticipated, but between Francesco, Brian, and myself we were able to make up the difference from personal supplies and the project now has a few meters of spare lights should repairs be needed in the future.

The strips are held to the ceiling with 1" strips of 3M outdoor double stick tape placed every 6 inches. What remains of the no-stick backing on the strips themselves was also removed, but it seems like strip adhesion is unlikely to be a significant factor in holding the strips to the ceiling (their adhesive is pretty bad). We ran a 2 month test with tape every 8 inches and got no hint of peeling, but if we run into issues during my time at Tech I will update this page. The process:

Installation:

One person was responsible for cutting strips of tape and placing them along the path of the lights. This took place over the course of 3 or so weeks with the last half being done today while the other groups worked. This probably does not need to be done beforehand.

One person was responsible for soldering together smaller strips into larger ones. This ended up not happening as fast as the other groups worked which meant some of the splicing had to be done on the ceiling. Not ideal, but actually pretty feasible. In future rounds, I would suggest this happen beforehand, even though it worked fine to do splicing concurrently.

Two groups of two people worked as teams to put up the lights themselves. It seems like the pattern that worked best was to have one person working ahead removing 2/3 tape backings in blocks of 16 or so. That let the second person roughly keep up while still being able to place the lights. It really helps if the people putting up the lights have long nails (or sharp knives) since the tape backing doesn't really want to come off.

The whole installation process took about 4.5 hours from start to finish with an average of 5 people working throughout.

[Tooling Projects] Hammer 1.0

The Hammer:

This is my first shot at a machinists hammer! It's 1.5 inches across at the cheek, with two 1.2" long detachable hammer heads and a 10 inch handle. The handle grip is 4.5" long with a fine/medium* knurled finish and accent grooves cut every 7/8ths of an inch. The hammer grip and head both have a diameter of 7/8ths, while the handle neck and step have diameters of 17/32" and 5/8" respectively. The design for this hammer was drawn from a bunch of different builds (see resources), and the actual dimensions were chosen as a middle ground between a small claw hammer and a my favorite ball-peen hammer from the student shop.

My goal with this particular build (in addition to making myself a hammer) is to explore the design process a bit, and in particular to get a feel for what specific features or qualities are desirable in a hammer. With that in mind, I've been carrying this hammer around with me for the last few weeks and plan to keep an updated reflections section below with my thoughts. This was a pretty quick and dirty build as far as machining projects go so I haven't documented it in great detail, but I have included a build log at the end of this post if you are interested.

*that is to say fine in one direction, and medium in the other.

Update and PDF:

7 years later, this hammer remains one of the highest traffic projects on the blog and “machinists hammer plans PDF” remains one of the most frequent google searches leading people to the site. With that in mind, I wanted to upload some rough drawings and provide a bit of an update. The documentation (PDFs and STEP files) can be found below, along with an FAQ .

Drawings: [click to download PDF]

CAD File: [click to download STEP]

Is the hammer still in use?

Yes! It is one of the 3-4 hammers I have in active rotation and for a while, when I was doing a lot of machine shop work, I even EDC'd it through a belt loop. Over the years I've used it for everything from adjusting machinery, to driving punches, to even (in a pinch) building up staircases and railings. These days it mostly stays home, but it still gets plenty of use in wood, leather, and home-repair projects.

Do you like the design?

On the whole, yes. Making the heads a standard stock size was a great decision, and I'm really happy with the three-head design. The handle has held up very well and remains comfortable for extended use (unlike the ribbed design I used on the deconstruction hammer). Keeping the profile thin was also a great call since it makes carrying the hammer as a general backup tool easy and comfortable.

Is there anything you would change about the design?

Functionally I could not be happier. Aesthetically, the hammer has proven very prone to picking up nicks and scratches in use. This is particularly an issue for the softer aluminum parts since they sit flush with the hammer heads and are thus not protected from any surface the hammer might be resting on.

If I ever get the chance to use this design in a shop class project I'll likely stick with the 2000 series aluminum and just provide a warning that dings are a fact of life for un-anodized aluminum tools. On the other hand, building a second version for myself, I'd be very tempted to switch over to a titanium for the handle and a 7000 series aluminum for the handle. There is also an argument for moving to a softer material for the polymer head, but that really just depends on its intended use case and the available stock.

The Process:

Before starting this project, I spent a while looking at other hammer builds, both commercial and by other students to get a feel for what kinds of things are possible or worthwhile in a hammer. The Projects I drew most heavily from are below in the "useful resources" section. That gave me a feel for generally what I wanted the hammer to look and feel like (tapered handle, knurled grip, interchangeable heads, etc). 

The dimensions were based on hammers I was able to pick up and try at various places around campus (many thanks to Caltech's many shops for putting up with me and helping out). I really wanted this hammer to be small enough for me to carry around on a daily basis for scavenging, without being useless by virtue of being tiny.  With that in mind, I ended up splitting the difference between a small claw hammer from the Blacker tool-room, and one of the ball-peen hammers in the student shop for the handle length. The grip length was based on a tracing of my hand on raw stock, scaled slightly to the nearest 1/8th. 

I had originally planned to make the head 15/32", but after a bit of thought ended up scaling it up slightly to 7/8". The extra metal doesn't impact the weight too much, but having the hammer head be a standard stock size makes it much easier and faster to make replacement heads. 

The Plan: 

When I first set about trying to design a hammer, I very quickly realized that although I use hammers all the time, I didn't actually have any idea what made one particular hammer better or worse than any other.  With that in mind I've decided to do this project a bit differently than usual. Rather than just diving in and building a hammer, I have broken the project down into three sections, respectively, design , Build, and Materials as outlined below: 

This sub-project is intended as a design prototype. My main goal isn't so much to end up with a perfect hammer (though I do like it a lot), so much as it is to get a sense for what I do and don't like in a hammer.  Now that it's more or less complete, I plan to carry this hammer around for the next few months, to get a feel for what I like about the design, and what I might change. I'll include my thoughts below under "reflections" for reference during future hammer builds. 

The next sub-project will incorporate lessons learned from this one, and will be focused mostly on the manufacturing process itself. The build prototype will be made up in CAD beforehand, and made strictly to those dimensions with the goal of hitting tight tolerances at each step. I will also document the build process for this hammer much more extensively for use as a reference and possibly as teaching material for the metalworking club. 

The final sub-project will incorporate lessons learned in the first two, and be focused mainly on materials selection. In particular, I plan to do substantial research into what alloys are appropriate for each part of the project and why. Like the second build, this project will be sketched in CAD beforehand and built to match that model. 

A hammer in it's natural habitat...

Useful Resources:

This particular build is pretty experimental in nature, and isn't specifically based on any one of the designs or builds below, but I did find all of them useful references, and drew liberally from the lot when designing my own hammer. 

• Wrench-Hammer

• Paulding Hammer

• Brass Hammer (video)

• Knurling (video)

• Another Hammer

Reflections:

Assembly:

• The hammer pommel can be used as a head storage location if the handle is roughly the same size/styling as the hammer cheek. 

• Using a tap/die worked fine for prototyping, but the results ended up being pretty knarly. For future builds it would be well worth the setup to use the lathe instead. 

• Making knurled lengths a multiple of 5/8" (or another standard measurement) makes it easy to add additional grip of needed. 

• A high-low finish (used 60 and 1200) hides scratches much better than a mirror finish.

• The screw-on cheek works well, but tempts people to unscrew it. A press fit hammer head might work better. 

• With intensive hammering, the heads can work themselves a bit loose. This can be fixed by adding o-rings or tapers to the head-cheek interface to increase friction. 

• The threaded head can turn under heavy hammering (which does happen). For intended use it's fine, but a bit of supper glue eliminates the issue. For new hammers would recomend a press fit or similar. 

Design:

• Chamfering the head-cheek interface of the hammer is a nice way to hide an imperfect fit and adds a bit of welcome definition to the profile.

• The nut-as-a-pummel design works pretty well, but still looks a bit out of place. Future builds should have a real pummel or use that space for some sort of storage.  

• Having a rounded pummel would give the user something to play with while holding the hammer. (Jim.)

• If their are parts of the hammer you don't want people looking like, you can use makers marks or flats to draw the eye. (Jim.)

• Having a head that is harder than aluminum for hitting steel and disassembly could be pretty useful.  The aluminum does fine, but it's getting pretty beat up.

• The hammer cheek should be at least as heavy as one of the heads. Otherwise, having one heavy head and one light head makes the hammer pretty unbalanced (recommend trying a steel cheek).

 

Build Log: 

Aluminum stock from the stock room. (No pictures of the brass stock sadly.)

1/31/2017 - Got 2ft of 7/8 aluminum stock from the stockroom. Cut a 12 inch length on the Johnson saw and faced both ends. Took size down to 11.5 inches and turned the 0.6 inches on each side down 0.495 inches. Threaded both sides with 1/2-13 using a die (would use lathe and cutter if student shop had one, worth making a new one before next build). Faced 0.1 inches off both ends and cut a slot at the base of each threaded section. Cleaned up both ends with a file and used a center-drill to add live-center hole (will be important later) to both ends. The threads came out a bit knarly on both sides, but using a functional (not chipped) cut-off tool should largely mitigate that. 

Handle threads. you can see the reliefe cut is not deep enough just yet. 

2/1/2017 - Turned an 11/16" length of the handle down to just under 5/8". Then turned an additional 2 and 11/16 inches to 17/32". Used the edge of the insert to cut a taper to 7/8". (Dictated by the single insert and holder in the student shop. STRONGLY recommend against doing this.) Used side-knurler to knurl a 4 and 5/8 inch length form the other side of the handle. Student shop knurler was finer than expected and in poor repair. Used a parting tool to add a 3/32" slot every 5/8" inches starting at the inner edge of the knurling. 

Cutting the aluminum test head out of scrap. 

2/1/2017 - Cut a 2.8" length of 7/8 aluminum stock for the hammer head. Faced both sides and made holes for later use in turning the piece on centers. Turned a 0.5" length to 0.495" and used the parting tool to cut a 3/32" slot 7/64" deep. Turned the piece and faced the other side for a total length of 2.125" and then repeated the process used on the other side. 

2/2/2017 - Cut 1/2-13 threads onto both ends of the hammer head with die. (Should definitely be done with cutting bit in the future.) Clamped hammer head in mill and used edge finder to locate middle of piece. Drilled one 27/64 hole 11/16 into the side, then cut a 5/8 flat (use appropriate center drills and the like).

Cutting the threads and pocket that connect the hammer's cheek to its handle. 

2/2/2017 - Chucked 7/8ths aluminum bar. Faced piece. Center drilled and then drilled a 27/64 hole into face. Cut 1/2 inch threads to a depth of .6 inches. Cleaned up exposed face with a file. Used a parting tool to part off 1.2" and then chucked with parted side facing out. Faced exposed side and used cross slide to add 45 degree chamfer. Screwed onto hammer head and sanded/polished hammer face to a brushed finish. Repeated same process with brass stock, but polished to a mirror finish. 

2/3/2017 - Attempted final assembly. The threads for both sides of the handle were significantly drunk, likely due to poor form when using the die that was largely resolved for the head threads. Used a file to clean up the handle-thread interface and added a bolt to the pummel in place of a third head which would not sit flush.

2/14/2017 - Added 4/8" (ID) o-rings to the undercut at the base of each threaded end of the cheek. 

Page Updated: 1/14/2023

[Hell Lighting] Soldering Lessons

Project Updates:

We have laid out the old hell lights, and determined that although it's a close thing, we still have enough lights to make it all the way around the hall without using our replacements strip. 

After a bit of discussion with the denizens of hell, we've decided to roll a bit of paint patchup into the project. We were originally planning to go over some of the places where the black has pealed with sharply, but that proved less than successful. Instead, our plan is to pick up some small brushes during Blackerathon and touch up the paint with new black paint before putting up the lights. 

Pulled down all of the old tape and Velcro and put up new double-stick tape along most of the hallway. We may need to re-position it a bit depending where we end up putting the strips relative to the walls, but it should be mostly in the correct spots. 

After most of the take-takedown had been completed, we held a soldering class with about 10 frosh and 2 s'mores (plus a few more frosh who already knew how to solder and wanted to help out teaching). It was not enormously comprehensive, but everyone learned how to use heat shrink and a lineman splice to make an inline connection, as well as how to splice together two LED strips (relevant to this project) with just solder and tape.

[Tooling Projects] Metal Scriber

Summary: 

Earlier today, a friend (Francesco) and I were looking for a short machining project to fill the evening and ran across this (click me) rather excellent video tutorial by Clickspring/Make detailing how one would create a metal scriber. Since neither of us had a metal scriber, and Francesco recently acquired a benchtop lathe, it seemed like a perfect fit. Machining on a bench-top lathe is a pretty different experience than machining on a larger machine and this project was not without its minor hiccups, but overall, I would say it was a lot of fun, and definitely educational.

Results:

We used size 18 sewing needles from Michael's for the scriber points, and turned the body of each scriber from 3/8th brass rod from the stockroom. In his video, Chris mentions that he thinks CA glue would work for holding in the needle, and I can confirm that the superglue we used worked just fine (though you've got to move fast with the cleanup tissue to avoid gluing it to the scriber). I went for a stocky design, and used a 5" scriber, with a 6 degree 0.4" tapper. Francesco took a slightly different approach with a 1.5" 4 degree tapper on a 6" body, which made for a nice sleek design.

Overall, both designs ended up working pretty well. We did run into a bit of trouble getting the surface finishes right, but a graduated sandpaper set would solve that problem pretty nicely (or at least make things a lot simpler). Failing that, we had a lot of luck with using worn 600 grit sand paper with WD40 as cutting fluid to get a nice brushed look. We did take a shot at using metal backed sandpaper to try to get a more consistent finish and remove our macheing marks, but the quality of our sandpaper was pretty low and we had more luck using finer grit scrap by hand. 

Pictures: 

Future Plans:

Francesco and I are hoping to use this as an intro machining project for the metalworking club. We also have plans to take a shot at a set-screw variant. With that in mind, I have included my notes on what went well and what went less well, along with some ideas for next steps in the "notes" section below. If you are planning on working through a similar project I would recommend taking a look at them before using anything on this page, though I am very happy with how my scriber turned out for a first run.

Notes:

• A #54 drill bit is just a bit too big for a size 18 needle.
• 0.5" - 0.8" seems like a good range for tip extension.
• Cut brass lengths 0.3" longer than needed and face down.
• Don't dwell at the bottom of a grip groove, creates chatter.
• Using a blueing compound on the scriber before the final sanding the surface could make the grooves darker and provide a nice contrast.
• Longer grip patches (1.0" and longer) make the scriber easier to use.

Christmas Tree 2016

Summary:

This year for my Christmas lights project I decided to do something a bit different.  Rather than setting up a more elaborate temporary setup, though last year's morse code tree was very fun, I decided to plow the time into making a control box that I can hopefully use year to year. It's got an 8-relay board (hooked up to AC) for output, an Ardunio UNO for control and a phone-cord jack for user IO. Getting everything in a nice box ended up taking a fair bit of time, so for this year I just ran a bouncing ball pattern. In future years though, there should be some great possibilities for more interesting patterns and some kind of IO board (maybe with suction cups) to interact with the tree.

For the actual lights, I cut 6 strands of old colored lights in half and fit each one with a tail of wire and a deans connector in place of a power plug. This let me create bands of light moving up the tree, which could be controlled from the box. For this year, I just ran them with a bouncing ball pattern (2 balls, one moving every 2nd tick and the other every 3rd) but in future years there's some potential to do something more complex, or maybe revisit morse code in a big way.

Hopefully I don't have to spend too much time in the guts of this box in the future, but just in case the build log is below. I mostly wrote it for my own sake, so if you're considering a similar build feel free to drop me a message and I'll try to answer any questions you have and give you an update on how it has held out to date.

Stats:

The box has 8 deans outputs to mains controlled with an Arduino and 8-relay board. The system can support up to 10 amps per output, and should be limited to about 15 amps overall. In addition to the standard Arduino USB input, I added a phone jack hooked up to 2 analog and 2 digital pins on the Arduino. For now I'll use the box to run passive patterns (getting pretty close to Christmas day), but in the future that should let me make a control board, or push patterns over Software Serial.

LINKS: 

No idea why this would be relevant...

Pictures:

Build Log:

1) After a bit of scrounging, I came up with the following to run this years tree. With the exception of the screws everything is from e-waste or the remains of a prior project.  That said, most of this stuff can be gotten pretty easily on a=Amazon or Ebay if needed.

Eight-Relay breakout board.

Arduino Uno.

Deans Connectors (8 pair)

Power Entry Module.

5v power supply (for Arduino)

Screws and washers for mounting.

Christmas Lights.

Project Box.

2) Remove the PEM from a sacrificial computer power supply. It's worth hanging onto the grounding wire, if it looks well made, but re-soldering the power and return wires (with heat shrink) is well worthwhile.

3) Cut each of three LED strands in half (make sure to cut between segments so there's still a return path) and solder the deans connectors (male) onto the end.

A single layer of scotch tape should be enough to prevent the paper from tearing.

4) Cut a rectangular hole for the PEM and 8 smaller holes for each of the 8 female deans connectors. if you've got access to a mill that's definitely the way to go. Otherwise, use inkscape (or similar) to print out the cuts on a piece of paper, and secure it to the box. Then use a dremel and file to cut each hole.

5) Lay out the Arduino and relay board then use a punch (nail) to mark the hole locations and drill then. If you don't have a drill it's possible to get by with a nail and some files.

6) Next, test-mount the Arduino. If the project box is metal, use some sort of standoffs (I used washers) to keep the Arduino from shorting against the case. Then, use a pen or knife to mark around the USB port. Take the Arduino out and cut that with a dremel so the Arduino's usb port can be accessed from outside the case.

7) Test fit the the relay board, and cut lengths of black wire to run from a deans connector to each of the plug holes. Then, cut lengths of red wire to run from the deans connector to each of the relay units, and from each of the relay units to each of the plug holes. Strip 5mm off the end of both ends of each wire.

8) Solder the black and red (deans to relay) wires to a male deans connector. I am using + to mean hot, but it doesn't matter as long as you are consistent. Before soldering, plug the deans connector into its female counterpart so the tines don't shift if the plastic melts. (A problem on counterfeits.)

9) Connect one red wire from the bundle to the common pin of each relay. Then connect one of the short red jumper wires to the normally open pin of each relay. At this point, it is worth doing a continuity check with a multi-meter to make sure all the screw-terminals are connecting properly.

10) Solder one of the black wires, and one of the red jumper wires to each of 10 female deans connectors. At this point, each female deans connector should be connected to the male deans connector pictured above, via one red and one black wire, with a relay in the power path on the red side. As a side note, the relays determine the per output maximum current (10 amp in this case) while the male deans connector determines the max combined current. 

11) Fit the Arduino to its mount holes, and mark the outline of the programming port (probably a USB B) with a pen or scribe. Then cut a hole to access the port. I used a dremel and metal file from the inside, but you could also measure and cut from the outside. 

12) At this point, It's time to get the PEM set up. Solder two sets of female deans connectors to the L and N terminals. One of these provides power to the outputs, while the other will be used to run the 5v power supply. If you pulled your PEM from a computer power supply, the pre-existing ground wire is probably fine, but if it seems sketchy, it might be worth replacing that too. 

13) Next, mount the PEM. You may want to drill some mounting holes or use epoxy to hold it in place. Make sure to hook up your grounding post. Double nuts is a good idea, but as long as you are using lock nuts (or lock washers) that should be fine. 

14) With the PEM in place, decide how you want to mount your low voltage supply. In this case, I used an old 12v supply I pulled from E-waste and mounted with double-stick tape. Whatever you decide to use, test fit it and then attach a male deans connector to the AC side, and some jumper wires to the low voltage side. 

15) At this point, start assembling the box to the degree you can. There's still one more hole left to make (for the control input), but I think it makes sense to put that in once the wiring is in place. Start off by mounting the Arduino and relay board. Once both of those are in place, route the control wiring. As a side note:for this build most of the wires were already soldered from a previous project and I didn't want to risk heating up the pins again. That said, if your'e doing this with a new relay board I'd go with male-female jumpers rather than soldering. 

16) With the wiring more or less in place, take your input port of choice (I used a phone cord extender cracked in half) and sketch itss outline on the outside of the box. Make sure that its wires will play nice with the rest of the cabling. Then, dremel and sand the hole to size. 

17) Press fit the your output connectors and signal connector into place.

18) Superglue and epoxy the output and input connectors in place. Depending on your wiring, the deans connectors may not want to stay straight. This isn't the end of the world, but to make sure they are all more or less lined up I find it works well to superglue each one individually and then epoxy in batches. 

[Grizzly 704] DRO: X Axis

Summary: 

This is a super simple install for attaching a cheap digital scale (shars) to the X axis of a grizzly 704 mill. Since I wasn't able to find any good build logs that use the stock mounting hardware and don't require drilling new holes, I have included one below. 

Thoughts: 

I had originally been intending to install the X and Y scales (which I got together shortly after I bought the mill) over spring break. But decided to put the X axis on now, since I think it will be helpful for my steam engine project. 

It is worth noting that these scales are really only meaningfully accurate to a few thou. For what I'm doing that's fine (I have a dial indicator for more precise work), but if you're reading this and that sounds like a problem, maybe consider getting an official Grizzly DRO. 

Links: 

Scales I Bought. 

Alternate Install.

Materials:

I bought a 24" Digital Machine Aluminum scale from Shars (the longer of the two above). The Shars scales ship with a convenient set of mounting brackets, but really any clone of the same general nature should do. I also ended up using some washers for mounting the scale reader. The screws, I pulled from Grizzly's original center-indicator and end-stops..  Note: 24 inches ended up being a bit long, so it wouldn't hurt to get something closer to 18, though cutting down a longer scale works just fine. 

Build Log:

First, unscrew the 2 end stops and central metal indicator from the front of the mill. Save the screws, we will be using those to mount the X axis scale. (Please forgive the mess, my shop-vac is a bit under the weather. )

Next, hammer one of the L brackets flat. Take care to flip the bracket over frequently, and use a flat metal surface to hammer on. Then, screw the flattened mounting bracket to the back of the slide, with the central hole pointing upwards, towards the slide's cord.

File the oblong hole on the central mounting bracket and two end brackets such that they easily pass the screws from earlier. We will use these to attach the brackets to the front of the mill. 

Finally, take the flattened metal plate (see previous steps) and file the lower hole until it easily passes one of the mounting screws. Then, screw the plate to the back of the scale reader and screw the plate and two mounting brackets to the mill. Take care to ensure that the output wire for the scale won't interfere with your vice (or other workholding setup.)

[Hell Lighting] Color Aberration tests:

TLDR:

I wanted to determine how much the voltage across an LED strip can change before color aberration becomes noticeable to the human eye. This seems to be a drop of around 1.7v from a 5v rail.

Introduction:

Based on our current draw tests we are probably going to be using 14-16 gauge wire for our 5v rail and ground. We know from our previous Hell Lighting setup, that the voltage drop across 20 meters of 16 gauge wire can be pretty significant, on the order of 0.5-1.5v depending on the pattern being displayed. Since we want the color recreation of our LEDs to be pretty consistent along the length of the hallway, I decided to get some data on what kind of voltage drop leads to a noticeable difference.

Methods:

To get an idea of how quickly color drops off with voltage, I spliced a few of our sample strands together and wrapped them around a piece of metal that, I assume, began life as a table leg (though at present it smells suspiciously like mortars). In any case, its circumference is pretty close to an even multiple of the LED spacing so it makes for a nice clean pattern (see photo). Our experience when we put up Hell Lighting 1.0, was that color aeration was most noticeable with the system running at full brightness on each LED (pure white).

Once the system was set up, passing moles were flagged down and asked where on the pole they first started to notice color change. Pretty subjective as tests go, but since we only really care about subjective user experience that's fine.

Discussion / Results:

With the strip running at full brightness, people pretty consistently pointed to an LED somewhere between the 3.4v and 3.5v as the first place that color change became noticeable. When I lowered the strip output to 40% color change along the strip became much less noticeable, though the voltage never dropped below 4v so it is hard to say if the effects would have been noticable at lower voltages.

The strips themselves seem to get to this point after about 80 LEDs (2.6m). So if we connect the strips to our 5v and GND rails every 2m we need to hold the variability of the 5v rail itself to under .4v if we want to keep the colors consistent.

Links:

Fast LED - Arduino Library for controlling LED strips.

Bonus Image, there are probably some interesting patterns you could run on a cylindrical display.

[Hell Lighting]: Current and Brightness Testing

Overview:

Before committing to a power supply/wiring setup we wanted to get an idea of how much current each LED strand draws.  When we first setup the Hell Lighting frosh year I ran similar testing, but didn't compensate for voltage drop, and the data was lost in any case.

Note: LED technology is changing pretty quickly, and these results are pretty much only relevant to the 2014 APA104 variant we used for Hell lighting.

Procedure:

To test current, one 5m LED strip was unrolled and connected to 5.00v every 2.5m by hooking micro-grabbers directly onto the exposed contacts. Note that due to resistive losses in the strip's ground rail, connections should be made to both 5v and ground.  A UNIT UT580 was placed in the ground return path and used to measure overall current draw. The strand was controlled from a separately powered Arduino Mega ADK (any 5v Arduino can be used, though notably the DUE and 3.3v micro cannot be).

Once the setup was complete, we had the Arduino serially increase the power on our colors of interest by 5% with a 5 second delay between steps to allow us to write down the current draw. Since we want a little bit of pattern overhead even at max brightness I used a scale from 0% to 102% where a PWM value of 250 was 100%.

Results:

View fullsize

             White             Red              Blue            Green

100%    4.68a              2.71a            2.54a           2.58a

50%      3.27a              1.42a            1.37a           1.37a

25%      1.75a               0.64a           0.69a           0.68a

Each 5m strip of LEDs seems to draw about 4.7 amps when running white at full brightness. Throw in a little margin, and that becomes an amp per meter, which is going to be our working value going forward. It is interesting to note that the current drawn by the strip when running white isn't just the sum of the strip when running each of the component LEDs. Current use for each individual LED seems to increase linearly with set output, while white follows a more or less logarithmic growth pattern. It is possible that this is reflected in the brightness, though more testing would be required to determine that. At the simplest approximation it seems like the current used by a strip can be approximated as follows:

White                                  Current = 1.7ln(%) - 3.31                              R^2 = .961

Blue                                    Current = 0.025(%) + 0.99                          R^2 = .998

Green                                  Current = 0.025(%) + 0.08                          R^2 = .998

Red                                     Current = 0.027(%) + 0.05                          R^2 = .998

Links:

For the full current data in 5% increments click here.

For the Fast LED home page click here.