MightyOhm

Gary Dion (N4TXI) created a Wifi Radio to match his entertainment center.  His project is inspired by my original Wifi Radio project and shares several of the same parts (such as the Asus WL-520gU wireless router) and design philosophy.

Interesting features of Gary’s version of the radio:

• Very cool 4 line VFD display allows more information to be shown at once (and it’s blue!)
• AVR sends actual shell commands to the router, which allows the serial console to remain enabled for debugging/other purposes – brilliant!
• Nice custom PCB for the ATmega8 microcontroller
• Rotary encoder and significantly more advanced control menus
• IR remote control support!

More details, photos, and source code are available on Gary’s site.

Thanks to the Make: blog for bringing this project to my attention!

Woot is selling a Samsung Bluetooth headset for $17.99 + $5 S/H – $20 MIR = $3 after rebate.

For that price this headset could be a great candidate to use for a DIY Retro Bluetooth Handset.

The catch is that I can’t guarantee this headset is actually hackable until someone buys one and reports back here.

Who will be the first?

Do you have a question about the Wifi Radio project or want help making your own Bluetooth Handset?

Try asking over at the discussion forums!

If you haven’t seen them before, be sure to check them out!

The rain and dropping temperatures in San Francisco this weekend reminded me of a project I made in the winter of 2006.  This was long before mightyohm.com existed, so I originally documented the project at instructables.  I’m not going to repeat everything here, but I wanted to share some pictures and provide a link to the instructable in case anyone else wants to try this at home.

The project involves using a digital programmable thermostat to control an inexpensive space heater.  The original motivation for this was that I wanted to lower the temperature of the heater at night, reducing my energy bill, while still being able to wake up to a toasty room in the morning by setting the heater to turn on full blast 30 minutes before I awoke.

Here’s a schematic of the simple circuit I made to interface the thermostat to the space heater.  The resistor/diode/capacitor circuit allows the thermostat, which is designed to control an AC load, to switch power to a 24VDC coil relay.  A 36VAC

I installed the necessary components inside the case of an old power and telephone line filter, used to protect a fax machine or office copy machine from power surges.  The case came with a handy 110V outlet mounted on the front panel which I reused for this project.  The digital thermostat mounts to the top cover of the case.

I used a barrier strip as a way to simplify the wiring and mount the few loose components:

I had to adjust the value of C1 to get reasonably clean DC to the relay while not having an annoying turn-off lag when the control line from the thermostat goes low.  100uF works well for the relay I used.

Here’s the finished product installed in my former bedroom:

I haven’t used it since I moved into a house with working central heating, but it sure came in handy during the cold winter I spent in a 100 year old farmhouse in Petaluma.  This solved the problem of the sub-50 degree mornings I was having nicely!

instructables.com: Space heater controlled by digital thermostat

Comments?  Questions?  Leave a comment below!

Welcome to Part 3 of the Diamond Chop Saw build.  In this installment I’m going to focus on the construction of the mechanical aspects of the saw structure, motor attachment, vacuum chuck, and splash guard.   This is a  picture-heavy entry…

After thinking for a while about how to build the saw, I decided that it would be best to have the blade move only in the vertical axis, and the workpiece move horizontally in two axes.   This led to the overall machine design which consists of a vertical column with pivoting cutting head assembly, and a workpiece holder that has two axes of horizontal motion.

Completed Dicing Saw

I wanted to ensure the motor and blade had a rigid, heavy mounting structure to reduce effects of vibration and flex on cutting performance.  I decided to mount the motor using the original mounting flange from the hard drive enclosure since it was nicely machined to match the motor flange.  I used a hacksaw to cut out the shape roughly to size, then straightened up the edges and machined a mounting recess on my milling machine.  The L-shaped piece of aluminum is 1/2 inch thick which gives lots of weight and provides sufficient thickness for mounting the bearing while preventing motion orthogonal to the bearing axis.

Cutting Head Assembly

Another view of the cutting head assembly.  In the upper left hand corner is the pivot bearing.  The bearing is held in place with a set screw that goes through the L-shaped aluminum piece.  Along the bottom edge of the black hard drive enclosure portion I attached a strip of white LEDs to help light the work area.  RTV Siliconeis used to seal the electrical contacts from water that migt not be caught by the splash shield.  At the lower left hand corner of the aluminum plate is a rounded off screw.  The cutting depth adjustment micrometer pushes against this rounded off screw.  Pushing against the aluminum would be less accurate (aluminum would become unevenly worn).

Cutting head assembly (rear view)

At the top of the column on either side is a hole for the screws that hold the pivot bearing (also from a hard drive) in place.   Luckily the one I used has 4-40 threaded holes on either side.  A screw on each column holds the bearing in place, and then the rest of the column assembly and adjustment plate are attached resulting in a good alignment of the column to the bearing. 

Pivot bearing/column mounting detail

Controlling the depth of the cut is critical, as my cuts will be as small as 5 thousandths of an inch deep!  I mounted a micrometer head to a plate on the back of the column which controls the height of the cutting head assembly.

Rear view of the column and depth adjustment control

 Now for a little detail on the vacuum chuck… The chuck is made from two 1/4 inch plates of aluminum.  The top surface has a shallow set of trenches cut to distribute the suction across the bottom surface of the glass plate used for holding parts.  The lower plate has a deep trench cut in it to distribute the suction to the three small holes drilled on the top plate.  The whole thing is held together with screws and sealed with silicone.  I made a set of hose barbs (one is pictured below) so that I can use 1/8 inch vinyl tubing to connect to my vacuum pump.  The barbs were made by turning down 10-32 stainless steel screws on my lathe. 

Lower half of vacuum chuck with custom-made hose barb

  The last major component of the saw is the splash guard.  This actually took a fair amount of effort to make, as I broke pieces more than once and had to start over.  Essentially it is a two-piece design with a thick piece screwed to the cutting head assembly, and a thinner piece which screws onto the first.  I used a heat gun to soften the plastic and carefully mold it to the shape of the face plates.  I then glued the curved section and the outer face plate together using epoxy and while not very pretty, it holds together well.

Splash guard on the saw