As part of the "Make it Real Challenge" I thought I would revisit my designs for the MkII and create a brand new design to share with the Instructables community. This new model, which I've dubbed the LightHammer Mk 2.5 (see images 1 and 2), uses the same components of the MkII but adopts many of the design concepts from the MkIII. By following these instructions you will be able to build your own LightHammer and begin creating your very own "marteaugraphs".
Then lets get started!
Step 1: Materials and Preparation
To construct the body we will be using layers of 1/4" hardwood ply bound together with aluminum binding posts. In total the body will consist of 20 individual pieces cut from a 2ft by 4ft piece of oak or birch plywood (these are the two most common forms of hardwood plywood, but any hardwood species should work). The individual sheets will then be layered together and held in place by 4" and 1.5" aluminum binding posts. A 1/4" sheet of ultra-soft (50Oo Durometer) polyurethane will be used on the face of the hammer to absorb the force of impact and protect the LEDs. When completed the hammer will be 4" wide by 10" long and 5" tall.
[ Note: Most plywood sold at your local big box lumber yard is thinner than labeled. This means that 1/4" plywood is actually closer to 7/32" or roughly .22 inches. The Mk2.5 is designed for these thinner sheets, however it can be adapted to accommodate a true 1/4" plywood by omitting sheet-3 and sheets-19-20. ]
The electric "guts" of the hammer will take the form of a 4xAA battery holder, a toggle switch, a rotary potentiometer, a tilt switch, a 150-Ohm 1/8-Watt resistor and 9 super-bright LEDs. You will also want 22 gauge copper wire (I prefer solid core but braided is fine), ideally in two different colors so that you can easily distinguish between "live" wires and "ground" wires, as well as a spool of solder.
In addition to the materials listed above, you will also need access to a lasercutter, a 1/4" round hole arch punch, a soldering iron, a good pair of wire strippers/cutters, electrical tape, contact cement or similar adhesive and a hot glue gun. While not necessary, you may also find a digital caliper and a "helping hand" magnifier to be useful as well.
[ Note: With laser cutters becoming more inexpensive and consumer friendly, the task of finding a cutter has become significantly easier. A good place to start is with your local maker or hacker space. In my experience these spaces will either have their own laser cutters or will have contact with individuals who do. I have had the pleasure of working with two such groups: AS220 of Providence and Open Lab Idaho of Boise. ]
AI files of all hammer parts along with a full parts list are attached below.
Step 2: Constructing the Body: Lasercutter 101
At the same time, lasercutters present some unique challenges as well: they are relatively small (the lasercutters I've worked with have ranged in size from 12x24" to 24x36"), they work best with flat, thin materials, they can only cut through certain types of materials and can only cut or etch (ie no channels or grooves). Finally, each laser cutter is a little different, and as such you may need to adapt these instructions accordingly.
Fortunately the first two challenges can be addressed simultaneously. By cutting your 2x4' plywood down into smaller sheets you not only allow for smaller lasercutter beds, you also reduce the potential for the shallow cuts associated with warped plywood. The files I have included are based on sheets that are either 6x11" or 6x9.5", while it is not necessary to use these dimensions, they can be obtained by a single 2x4' sheet of plywood.
Once your sheets are cut and ready, you will need to prep your files. Remember! Each lasercutter is different, review your lasercutter documentation or consult with a user/admin before cutting. As a general rule cuts are represented by red lines (RGB 255 - 0 - 0) while etching is represented by black lines (RGB 0 - 0 - 0). In order to ensure the thinnest cut possible, make sure the red line thickness is set to the lowest weight possible. The attached EPS files have already been adjusted to these settings, but it is always a good idea to double check before cutting. In addition to the color/line settings, you may also need to set the lasercutter power and speed settings. Some lasercutters will have presets for common cutting materials, but others will require a manual input. Either way it is recommended that you check the power and speed settings if you are able. While power output will vary from lastercutter to lasercutter, I have had success cutting with the following settings:
Etching: 40% power output at 100% speed with a resolution of 1000 PPI
Cutting: 98% power output at 6% speed with a resolution of 300 PPI
As a general rule, the higher the power and slower the speed the deeper the cut.
Once your file has been prepped and the lasercutter settings adjusted, you are ready to go!
Step 3: Constructing the Body: The Hammer Core
The body of the 2.5 can be broken down into four distinct components: the left and right halves of the hammer "core" and the left and right halves of the hammer head.
To construct the left half of the hammer core you will need sheets 1, 3, 5 and 7 (see image 1).
You may notice that sheet-1 faces opposite of sheets 3, 5 and 7, this is because sheet-1 (along with sheet-2) constitutes the inner face of the hammer and I've found it is better to have the smoother side of the plywood facing inward (less chance of splinters and a smoother joining when assembled).
[ Note: Plywood is often described as having two grades of veneer (the outermost layers of the plywood sheet) with the face being of a higher quality than the back. A piece of plywood described as AD has a high quality face and a low quality back while a BB is of equal quality on both front and back. ]
Once you have laid out the pieces and punched out any of the remaining bits you are ready to start glueing. Using the 1.5" binding posts as guides, slide sheet-1 face down onto the posts and apply a generous layer of wood glue to its back.
Immediately take sheet-3 and line it up with the binding posts inserted into sheet-1 and place it face down on the glued surface of sheet-1 (see images 2 and 3).
[ Note: When glueing together sheets 1 and 3, pay special attention to the small piece of sheet-1 that will separate the potentiometer from the switch. It has a binding post hole specifically for the purpose of aligning it with sheet-3. ]
Continue this process for sheets 5 and 7. Do not glue the lower handle portion of sheet-7, this is the battery access cover and is meant to be removable (see image 4).
To construct the right half of the hammer core simply follow the instructions above but with the parts from sheet 2, 4, 6 and 8. (see images 5, 6 and 7).
Step 4: Constructing the Body: The Hammer Head
To construct the inside of the left head you will need the parts from sheets 9, 11 and 13. These pieces are to be glued to the left core using the method outlined in Step 3 (see image 1).
[ Note: To save on materials and time, all of the head pieces come two to a sheet. As a result sheet-9 and sheet-10 are on the same piece of plywood as are 11 and 12, 13 and 14, and so on. To tell the two apart, remember that the smooth side should always face away from the core of the hammer except for sheets 15 and 16 which will face towards the core. ]
Repeat this process with sheets 10, 12 and 14 to create the inside of the right head.
For the outside of the left head use the parts from sheets 15, 17 and 19. Place sheet 19 face down on the binding posts and glue it to sheet 17. Lastly, place sheet 15 face up and glue it to sheet 17 (see images 2 and 3).
Repeat this process with sheets 16, 18 and 20 to create the outside of the right head.
Congratulations! You've completed the body of the LightHammer...
Step 5: Wiring the Hammer: Core Components
One of the major elements of the Mk2.5 design is the cavity created by bringing together the two sides hammer core. This cavity will hold the batteries, toggle switch, potentiometer, tilt switch, resistor and three of the hammer's nine LEDs.
To start, place the battery pack, toggle switch, potentiometer and tilt switch into the appropriate compartments of the left core (see image 1).
Next, solder the red (live) wire from the battery pack to the left prong of the toggle switch.
Cut a short length of red wire and solder one end to the right prong of the toggle switch and the solder the other end to the right prong of the potentiometer.
[ Note: My apologies for the lack photos. When determining where to solder use image 1 as your guide. The left prong of the toggle switch is the one closest to the body and the right prong is the one farthest from the body. Similarly, for the potentiometer the right prong is the one farthest from the body and the left is the closest. ]
Measure a length of wire from the thin wire of the tilt switch to the middle prong of the potentiometer. Strip the tips of the wire and solder. Be careful not to connect the prongs on the potentiometer when soldering.
Trim the wire on one end of the resistor and solder to the thick wire of the tilt switch. Secure the tilt switch with hot glue and insulate the exposed wires with electrical tape (see image 2).
Lastly, solder a short length of red wire to the untrimmed end of the resistor. Try to strip the end of the wire so that there is a good length of exposed wire available for future soldering (see image 3).
Step 6: Wiring the Hammer: Let There Be Light
Rather than wiring each LED into the circuit individually, the design calls for three sets of three LEDs wired together in parallel.
[ Note: When working with LEDs it is important to remember that every LED has a positive and negative side. With the super bright LEDs from Sparkfun the easiest way to tell which side is positive and which is negative is to look at the components inside the plastic bulb of the LED. The negative side will have a larger component inside the bulb and (usually) a shorter wire leading out (see image 1). ]
Bend the positive and negative LED leeds in opposite directions (creating a "T" or "Y" shape) and solder a short length of black wire to the negative end of an LED.
With the help of a pair of "helping hands" (or a very trusting assistant) solder together another short length of black wire with the first length of wire and a second LED (remember to solder to the negative wire).
Solder this second length of black wire to the third LED along with a long length of black wire (see image 2).
Wrap the soldered connections in electrical tape. Be sure to go all the way to the base of the bulb (see image 3).
Use three pieces of red wire (two short and one long) and the instructions above to wire the positive side of the LEDs (see image 4).
Repeat this process twice so that you have three sets of LEDs with long red and black "tails".
Step 7: Wiring the Hammer: Bringing it all Together
To start, solder a short length of black wire to the battery pack's ground wire. Be sure to strip a long portion of the wire's tip as this will be where you solder the negative/ground wires from the LED arrays (see image 1).
Using a piece of electrical tape, secure one of the LED arrays to the inside of the left core. Try as best you can to line up the base of the LED bulbs with the bottom edge of the notches in sheet-1 (see image 2).
Repeat the process above with the remaining two LED arrays, securing them with electrical tape to the inner left and right hammer head (see image 3).
Carefully pull the LED "tails" through head cavity so that they all terminate at the hammer core (see image 4).
Trim and strip the all three pairs of wires to the appropriate lengths and solder to the appropriate corresponding wires (ie black wires to black ground wire, red wires to red power wire). Feel free to secure loose components and wires with hot glue or electrical tape as needed (see image 5).
Step 8: The Final Touches
Remember to be gentle and not force the pieces onto the binding posts,otherwise they will get stuck. If you are having trouble lining up a particular binding post and hole, try using a different binding post. Worse case scenario, use a drill to open up the holes but be careful not to make the holes too big.
Continue to stack the components until you end with the outer left hammer head.
Once the head is secured, insert the 1.5" binding posts in the handle of the hammer along with the remaining 4" binding posts.
Use the the screws included with the binding posts to secure the various components (including the battery cover) together.
- - -
With the body fully assembled its time to mount the polyurethane "shock absorber".
To ensure that the holes punched in the polyurethane line up with the LEDs I recommend taking a piece of chalk and rubbing around the openings for the LEDs (see image 1).
Next, carefully place the square of polyurethane directly on the face of the hammer. Be sure not to shift or move the polyurethane once it is seated. Apply firm and direct pressure to the polyurethane for a few seconds and then carefully peel the rubber from the face of the hammer. If done properly you should have nine well defined marks indicating the position of the LEDs (see image 2).
If you find that your marks are too blurry to distinguish the proper location of the LEDs, simply wash the polyurethane, dry it thoroughly and try again.
Using your arch punch simply punch out the holes with a few taps from a hammer. Because the polyurethane is so thin a clean hole can be created with just a handful of strikes from the hammer...excessive force isn't necessary. However, to protect your work surface do all your hole punching on a piece of scrap wood.
Finally, attach the potentiometer knob by lining up the flat edge of the nob with the nob's set screw and tighten using a small flat-head screwdriver.
You have successfully built your very own LightHammer!!!