Cabinet Basics pt 2: Face Frames

Last week, I covered how I create the carcass of a base cabinet.  At this point, we have two sides, a back and a floor: doesn’t look much like a cabinet at this point.  Here is the fun part…

I make my face frames 1/2″ wider than my carcass.  I do this for two reasons:

  1. An exposed side accepts a 1/4″ piece of plywood nicely; the plywood tucks in just behind the edge of the face frame to make a nice flush plane.
  2. Two cabinets that sit side by side can hold a half inch thick piece of plywood between them.  This helps for spacing and for clamping the cabinets together during installation.
Knowing this rule of thumb, we can now start designing the face frame.  One of my current projects around the house is redoing the bathroom.  I’m pulling up the floor and putting down new tile, etc.  I am also putting in a new sink.  The bathroom isn’t big, so a standard sink base is much too large for the space.  A sane person would put in a pedestal sink, but my wife wants his and her sinks (two basins).  There is no way I can fit a standard double sink in my bathroom, so custom work, here I come.  I decided to make a base cabinet that is 48″ wide by 19″ deep.  This is just wide enough that I can get two sink bowls into the unit without it intruding into the tub.  Given this dimension, I had to modify my normal carcass design a bit, but I followed that process the same way, just with narrower sides.  The face frame width is the overall width, so the carcass became 47.5″ wide.
I opened up Microsoft Visio, my favorite tool for designing cabinets and other woodworking projects, and began laying out the parts that would become the face frame.  I started with some basics:
  1. All pieces are 2″ wide.  I sometimes break this rule if I have side-by-side doors, in which case I will go up to 4″ depending on the spacing of the rest of the parts (basically filler).
  2. The outside-most vertical pieces stretch the entire way up (toe kick to the counter top).  This is always unbroken; no cuts, no jogs, etc.
  3. The top-most and bottom-most horizontal but into the sides of the outer-most verticals.  Again, no cuts or jogs.
  4. If you are using premade doors like I did, know the dimensions of the doors before designing the openings for the doors.  Don’t assume that you will find a door that perfectly matches your arbitrary opening dimension.
After some design work, I came up with the following:
Face Frame
Just to note, the inner verticals are also 2″ in real life.
Time for cutting!  I picked up 2 8′ 1×6 oak boards at Menards and ripped them down to 4 1″x2″x8′.  From these, I cut two 30.5 inch boards for the outer verticals.  This takes up a total of 4″ from the overall width of 48″.  This means I have a length of 44″ for the top, middle, and bottom cross pieces.  From there, I took the dimension of the doors and subtracted one inch from both the height and width.  This gave me a half-inch overlap all the way around the door.  Using these dimensions, I was able to place the inner horizontal from the bottom horizontal and also the inner verticals.   As for the heights of the drawers, this became arbitrary.  Since I’m making the drawer faces myself, they didn’t have to match anything.   I found that four drawers with a two inch gap between seemed to create a good proportion given the remaining width after the doors and verticals.  The top three gaps will be false drawer fronts.
Assembly:  If you don’t have a pocket hole jig, please invest the money.  I have a $15 set from Kreg.  I love it.  I can’t imagine building any piece of furniture without it.  It is simple, it creates excellent joints.  Seriously, pocket hole jigs are proof that God loves us and wants us to be happy, so do yourself a favor and get one.  Seriously.
Having said that, find the worse side of each piece and designate this as the back.  The butt end of each piece that matches up against a side of another will be drilled using the pocket hole jig.  In this case, the 2″ board is wide enough for two holes.  Each hole then accepts a screw which is driven in and, therefore, into the side of the adjoining piece.  Easy as pie.
Joining the face frame to the carcass:  I’ve done this several ways.  My favorite way is using my biscuit jointer and cutting biscuit slots in the edge of the carcass sides and the back of the face frame.  This takes a little time and not everyone has a biscuit jointer.  Alternatively, I have found that a 1″ wide piece of the same material used to create the face frame can be glued to the carcass flush with the edge of the side.  This creates a 1.5″ wide flange to glue the face frame onto the carcass.  It may be a bit kludgy, but it works.
Let it all dry.  Next week, we tackle the countertop.

Cabinet Basics

Enough electronics, let’s get back to woodworking…

This spring’s big project was a re-organization of the garage.  As I’ve mentioned in previous posts, I dismantled my work bench last fall in order to create more temporary storage space in the garage.  It is now  time to get the the shop back in working order.

Earlier, I displayed my plans for my new workbench, which is basically a series of 36″ wide cabinet bases with an MDF countertop.  I wanted to take a moment to go into how I do the cabinets.

I start out with a 4′ x 8′ sheet of 1/2″ sanded pine plywood.  Cut off a 4′ x 2′ 10.5″ piece.  From this piece, make two 1′ 11.25″ pieces.  Here are the sides. 

Now consider the outside width of the cabinet and subtract one inch.  This will be the width of the floor.  My outside dimension is 36″ overall, so my floor is 35″.  Obviously, yours will vary.  Assuming your cabinet is no more than 49″ wide overall, you can continue making the floor.  Cut   1′ 11.25″ from the original sheet.  Cut the 1′ 11.25″ wide  piece down from 4′ to your calculated floor length.

The last piece is the back.  The back will be the same with as the floor, but it is a little deeper.  From the original stock sheet, cut a piece 2′ 4.5″ deep.  Cut this piece down to the width of the floor.

At this point, we can turn our attention back to the sides, since they require a little work.  First, find the nicer side of each side piece.  Note the nicer side of each piece as the inside (the same will be true for the floor and back).  The inside will require two dado cuts.  (If you don’t yet have a stack dado set for your table saw, this is a great reason to go get one.  It doesn’t need to be fancy; mine was about $10 and has paid for itself many times over in terms of saving frustration.)  Set your stack dado to a width of 1/2″ and set your rip fence to 1/2″ away from the blade.  Set the height of the blade to 1/4″.  Cut a dado across what you consider the back of the inside of each piece (this groove will accept the back).  Next, set your rip fence to 5.5″ and cut a dado across the bottom of the side (this groove will accept the floor).

The front side edge of the sides now need to be notched for the toe kick.  Cut a 4.5″ deep x 2.25″ wide rectangle out of the front corners of each side.  At this point, you should have the following:

Base side

All the parts are now ready to assemble.  Fill the dado grooves with a bead of glue and press in the floor and back.  I like to have the cabinet laying on its side at this point, but do whatever works best for you.  Set the floor in first.  The back will reach from the top of the floor to the top of the sides.  4d finish nails will hold the panels in place while the glue dries.

The carcass is now complete.  Next week: face frames!

Wifi Phone?

There is a bunch of talk going around about cities hosting publicly available wifi.  While I am hessitant to ditch my ISP with plans to tap the public internet access, I’m optimistic that one day (perhaps years from now), we will live in a society where a person can get wifi access everywhere in the country.  I like to think of it like electricity; there was once a point where electricity was only available in the homes of the rich who lived in urban centers. The middle class and the rual population, however, were not included in the service area.  About sixty years ago, however, the US made a big push to get electric service to all homes.  My mom, who grew up in a small farm town in the middle of Nowhere, Minnesota, talks about getting electricity when she was 13 and how different life was before electricity versus after electricity.  I figure if the US can successfully implement the initiative of distributing electricity to all homes, distributing WiFi across the country can’t be that challenging sixty years later.

Consider cellular networks: twenty-five years ago, we didn’t have cell phones, but now the majority of the US is covered in 3G access.  I admit that a 3G signal can travel further than a WiFi signal and therefore the 3G model requries fewer towers to cover the same amount of area, but it can be considered a proof of concept that we can blanket the country with a form of wireless network access.

The question could be asked, “Why should we consider covering the country, or the globe for that matter, with WiFi access if we can already do it with 3G?”  My answer is simple; 3G is slow and expensive compared to WiFi.  Wifi has a speed of roughly 54 Mbps compared to roughly 21 Mbps over 3G.  With 3G, you need to purchase a plan from a cellular provider, versus the ad-hoc nature of Wifi.  While I expect that a publicly provided wifi would not be free, I suspect it would be cheaper than the total cost of ownership of a 3G hotspot device.

Being that publicly provided, wide spread wifi would be cheaper and faster than the current 3G model, it seems natural to want to develop this solution.  If this were to happen, however, how would it affect cellular providers?  If a faster, cheaper wireless connection exists, could the current cellular model be overthrown?

With this question in mind, I sat down and designed a model of how I would build a wifi-enabled mobile phone.  The idea is to use existing IP-based networks along with Wifi, whether it is publicly provided or by using existing wifi providers (i.e. coffee shops, hotels).  The solution would include a hand held device similar to that of a common cell phone plus a VOIP bridge (more about this later).  I came up with an interesting solution.

In this scenario, audio (voice)  coming into the handheld device is processed by an audio to digital converter.  I’ve picked the VS1053 only because I’m familiar with it, but I’m sure there are others that could do just as well.  The digital signal is transfered to a micro processor which routes it out via wifi to the internet.  The handheld device not only manages its wifi connection, but also stores the configuration to connect via the internet to the user’s home network in order to route the data of the audio signal back to the VOIP bridge (home network device as noted in the image).  The bridge is merely the inverse of the handheld.  It takes the IP data and produces serialized data that can be decoded by the VS1053 into a regular audio signal.  This audio is fed into the home computer, which utilizes a VOIP solution for telephone access.  To hear the user on the other end, the whole process works in reverse.  The audio out of the home computer routes into the home network device / VOIP bridge, out through the internet to the handheld which decodes it and plays the audio back to the user.

There are plenty of details to work out, but it is a model that can be leveraged.  Imagine the paradigm shift of mobile phones if the phone service were to be decoupled from the phone vendors.  Instead of a handheld device being paired to a provider’s network via a sim card, any phone could could be used by any user regardless of the ultimate phone provider.  Instead of matching the phone to the service semi-perminently, a phone could log into any individual’s home device, thus allowing it to be used on any VOIP provider.  Say I forget my phone at home.  I could borrow my friend’s handset and log it into my service instead of his.

If this model were to gain strength, the role of the VOIP bridge could be centralized, easing the use of the system for the less technically-minded users.  This would probably be the future for Sprint, AT&T, Verizon, and the rest of the cellular crew if WiFi does go global.

Nixie Clock

A few weeks ago, I was sitting around with a friend of mine who told me he was interested in building a nixie clock. We spent some time looking at parts, which caused me to gain interest in the project as well. Over the next few days, I began working out how I would approach this project.

The first issue was a matter of voltage. Nixie tubes require a huge voltage (roughly 180 volts). This is a big difference from the LED lights that I’ve been working on in other projects. Unlike a regular 7-segment LED which can run off of the logic board’s 5v line, the nixie tube w0uld require a separate power supply. Off hand, I have no idea how to build a power supply that can produce that kind of voltage. I suppose I could do some research, but I can imagine that amount of research just for the power supply of a project would be a deal breaker. Luckily, I found a supplier who sells power supply units specifically for nixie tubes (see resources in the price breakdown below). The power supply requires anywhere between 9 and 30 volts, so a 12 volt wall wort will power this just fine. First challenge solved.

The next issue was how to address each character in each of the nixie tubes individually. Again, nixie tubes don’t work like a 7-segment display where a combination of 8 digital lines, easily controlled by an 8-bit shift register, each turn on a part of the character. Instead, a nixie tube has 11 lines; 1 common ground and 10 inputs (one for each character). This means that it takes 10 different signals to control the value shown in the nixie tube. Being greater than 8, a regular shift register can’t be used. Going back to the supplier of the power supply, I found an interesting IC: the 74141 nixie driver. This chip has four inputs and ten outputs. A parallel combination of the four inputs creates 16 (4^2) possible logic codes. Each one of the first ten possible combinations is mapped to a single output. For example, if lines 1 and 4 are on and 2 and 3 are off, the #8 output pin goes high.

Each of the four nixie tubes will be driven by a dedicated nixie driver IC, thus 4 driver chips are used. Each driver chip has four parallel inputs. This means there are 16 digital inputs required to drive all four nixie tubes. Sure, there are micro controllers that have 16+ digital outputs, but I don’t want to go that route. Instead, the 16 digital inputs will be driven by two daisy-chained shift registers. Daisy-chaining two 595 shift registers means that I can feed a 16-bit output over three digital outputs on my micro controller: serial, clock, and latch. By doing the logic this way, three pins on my micro controller can produce 10,000 (10^4) different numerical combinations among my four nixie tubes. Obviously, this is a clock, so most of those values won’t be used.

My last concern was how to pipe the 180 volts from the power supply to the nixie tube while driving them with 5 volt logic. Since it is a regular on/off situation, usually an NPN transistor would do the trick, but the standard NPN transistor has a maximum load voltage of 60 volts. The required 180 volts is WAY to great for this solution. I considered a solid state relay, but at $4 a piece times 40 channels, that gets expensive. After digging around for a while, I found a high-voltage MOSFET that I think will work nicely. The Fairchild FQN1N50C has a maximum voltage of 500 volts. The drain pin will connect to one of the character pins on the nixie tube, the source will connect to ground, and the gate will attach to the corresponding output line on the nixie driver IC. A resistor will actually sit between the driver and the MOSFET, but I haven’t yet done the math to figure what resistance it needs to be.

Since this is a clock, my micro controller needs to know what time it is. I will use the DS1307 real time clock module which is available at sparkfun. This will connect to the micro controller via I2C, which only requires two lines: data and clock. It also requires a 5 volt and ground line, which is shared with the micro controller.

To produce the 5 volt power for the micro controller and the real time clock module, a simple pair of 100uF capacitors and a 5 volt regulator are used as a power source. The source for this combination will also be the 12 volt plug on the wall. When it is all said and done, it looks something like this:

Nixie clock diagram

So where do I get the parts? Mostly online. Below is a chart of where each part is obtained. I’m not sold on the style of nixie tube I have listed, but it is an option. I don’t have the resistors listed yet since I need to figure out what resistance I need. I’ll probably get these from the surplus store down the street for 10 cents a piece, so add $4. Similarly, the regulator and caps are cheaper there, so I’ll probably pick them up there instead of ordering through Sparkfun.

Part QTY Price Each Total
FQN1N50C MOSFET 40 0.414 16.56 See description
Resistor 40
595 Shift Register 2 1.5 3.00 See description
74141 Nixie Driver 4 3.99 15.96 See description
Nixie Tube 4 12 48.00 See description
Nixie Tube Power Supply 1 19.99 19.99 See description
MCU (Teensy) 1 16 16.00 See description
Real time clock 1 14.95 14.95 See description
100 uF cap 2 0.35 0.70 See description
5v regulator 1 1.25 1.25 See description
Total: 136.41