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Eclipse 2017

Viewing Methods

A few weeks ago I started thinking about what to do with materials I have on hand for the August 21 Solar Eclipse. This area of Illinois (just West of Chicago) will see about an 88 percent occlusion, per this calculator, starts at 11:53, peaks at 1:19PM and ends at 2:42. Weather permitting of course – what are the odds?  This post is written six days before the event. I will update if the viewing is successful.

Pinhole projection seemed like a good traditional method, but Google research indicated the image would only be about 3/4″ diameter. One of the pinhole discussions also talked about using one side of binoculars to focus the Sun’s image. I do own a medium quality 7×30 pair with zoom so decided to try them. This is one of the first images obtained.

Close up of projected sun image

Close up of projected sun image

I was very pleased with this, if you look just below center slightly to the left, there is a genuine sunspot clearly visible. The image is about 3 inches across at minimum zoom.

Now to make a two hour viewing interval practical I explored mounting the binoculars to a good camera tripod. This tripod has the pan and tilt head on a tall crank up rod and a mechanism to tilt that rod at it’s base up to 90 degrees (parallel to the ground). Long ago I owned a telescope with an equatorial mount and I thought maybe laying the central rod down at the proper angle would enable that function.

The advantage of an equatorial mount is you can track a star, or the Sun, by adjusting only one of the two axes of the telescope mount. Having to manhandle both the azimuth (pan) and elevation (tilt) to track is a real PITA. You don’t realize how fast the Sun moves across the sky until you magnify it 7 times. The sky moves 360degrees/24hours = 15 degrees every hour. The way the mount works is, you align the primary axis of the scope, in this case the tiltable rod, with the earth’s rotational axis. Then the stars rotating around the earth’s axis also rotate around the telescope’s axis and you can keep the scope pointed at the same spot in the sky by adjusting only the azimuth. Ideally with a powered clock mechanism.

Of course it’s you that’s moving, not the Sun but the result is the same. Thank you, Nicolaus Copernicus.

First, my binoculars had to be firmly attached to the tripod. The dozen or so rubber bands I used for initial testing just didn’t work out. I drilled a block of hard wood to fit the round central spine of the binoculars. All binoculars I have seen are made like this, it is part of the mechanism that allows the two eyepieces to separate or close to match your eye spacing. Then I sawed through the drilled block and installed a couple of screws to clamp the block on the spine. Then I drilled and tapped a 1/4-20 hole in the bottom of the block to mate with the tripod screw.

You need a large shade so the projected image is in shadow. This was easily made from cardboard.

Binocular clamped to tripod

Binocular clamped to tripod

This photo shows the tripod tilt mechanism with the riser set to equatorial position.

Tripod extended in equatorial position

Tripod extended in equatorial position

I made a box to further keep out stray light. It’s about ten inches square, painted flat black with a sheet of white paper at the bottom. The string you see in the photo above helps align the shadow box axis with the binoculars. I mounted the cardboard box on a 1×6 with a hinge and a sliding prop arrangement so the box can easily be tilted to align with the projected image.  The box must be moved and realigned every now and then as the Sun moves across the sky.

Sun image projected into shadow box

Sun image projected into shadow box

If I was observing stars at night, I could align the scope by looking at the north star. But during the day the procedure for equatorial alignment is:

  1. Align the riser rod exactly North by positioning the whole tripod.
  2. Raise the central rod to the exact latitude of the location. About 42 degrees here.
  3. Uncover one side of the binoculars
  4. Hold a sheet of paper below the eyepiece and move the tripod pan and tilt until you see the Sun image. Try to center the image in the binocular field by exploring the edges.
  5. Remove temporary paper, set and align the shadow box with the projected image. Stretching the string back to the box will show you the axis.
  6. Tighten the tripod tilt but leave pan axis loosen enough to move with the Sun.

Here is the assembled Helioscope. You can see the projected image in the bottom of the box.

Binoculars with shade projecting sun image

Binoculars with shade projecting sun image

So far my only expenses are a spray can of flat black paint and new batteries for the camera.

Camera Modification:

Hand holding a camera on the image is awkward. I decided to mount a camera directly on the box so it would always see the same image field. To enable this and not block the projecting beam, I bumped out one side of the box 2 1/2 inches. Hot glue is wonderful stuff. It took some fussing with a tapered shim to get the camera pointed at the image correctly.

Camera mounted inside box

Camera mounted inside box

It’s very hard to read this Canon A530 screen in the sun so I connected a small television which has a composite video input to remote the display. This works well. You can see the 2 1/2 inch bumpout in this photo.

Camera in box and composite monitor

Camera in box and composite monitor

The best images are shot with the camera zoomed in a bit. I’ve worked out how to crop the pictures consistently with GIMP. A stretch goal is to make a video of the whole occlusion. I’ll need a photo every 30 seconds, two hours and 45 minutes should fit on a 2 gig camera card.  But I worry about having to change camera batteries in the middle of the sequence.

I worked up a BASIC script with the Canon Hack Development Kit. It is based on a Wiki post by Keoeeit, his version 3. It should solve the setting consistency problem if I have to change the batteries and fires the camera at a set interval.

It has the following parameters to set:

  • Initial Zoom amount, a number 0-8 for the A530
  • Delay before first shot Min, Sec, Allows time to reposition the camera after a disturbance
  • Number of shots to take, zero runs forever
  • Time between shots, Min, Sec.

I run the camera in Manual mode with shutter about 1/80 sec at F4.5 (the small Canon cameras don’t really have an iris). I don’t want the exposure to change any time during the run. I put a magazine page in the box so the lens has something busy to focus on then put the camera in CHDK mode and start the script, .

The following happens:

  1. The lens zooms out to the fixed setting supplied.
  2. There is a delay countdown so you can tweak the camera position
  3. The lens focuses and then locks the focus
  4. A ten second delay to allow removing a focus target.
  5. The camera begins taking pictures at the specified interval.

 

This is the BASIC script

rem Author – Keoeeit
rem Upgraded by Mika Tanninen
rem Time accuracy and shutdown for a710is by Viktoras Stanaitis
rem h-accuracy for delay, j-accuracy for interval
rem Reset zoom added to restore the same picture
rem in case batterys have to be changed during a long session

h=-1
j=-1755

@title Eclipse Intervalometer

rem number of zoom steps to execute at beginning of script
rem A530 has steps 0 – 8
@param i Initial Zoom
@default i 3

rem the delay is after zooming so camera positon can be tweaked
@param a Delay 1st Shot (Mins)
@default a 0
@param b Delay 1st Shot (Secs)
@default b 0

@param c Numb. of Shots (0 inf)
@default c 0

rem interval is the time between shots
@param d Interval (Minutes)
@default d 0
@param e Interval (Seconds)
@default e 10

print”DISABLE THE FLASH!”

rem Move the zoom to a consistent setting
set_zoom 0
for s=1 to i
print “step”,s
set_zoom_rel 1
next s

n=0
t=d*60000+e*1000
if c<1 then let c=0
if t<1000 then let t=1000
g=(a*60)+b+h
if g<=0 then goto “focus”

rem count down seconds until begin shooting
for m=1 to g
print “Intvl Begins:”, (g-m)/60; “min”, (g-m)%60; “sec”
sleep 930
next m

rem set and lock focus
:focus
set_aflock(0)
press “shoot_half”
sleep 2500
release “shoot_half”
set_aflock(1)
print “Remove Focus Target”
sleep 10000

:interval
n=n+1
if c=0 then print “Shot”, n else print “Shot”, n, “of”, c
shoot
if n=c then goto “quit”
sleep t
goto “interval”

:quit
set_aflock(0)
shut_down
end

:restore
set_aflock(0)
exit_alt
end

 

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Arduino Iambic Keyer 2016 – Part 1: Hardware

Third Generation:

Arduino Iambic Keyer - Top

Arduino Iambic Keyer – Top

 

Arduino Iambic Keyer - Left Side

Arduino Iambic Keyer – Left Side

 

Arduino Iambic Keyer - Right side

Arduino Iambic Keyer – Right side

 

In a Chicago winter it’s way too cold in the garage for woodworking, so I turn to coding to pass the time. In 2014 I built an ATTINY85 Morse Code keyer in an Altoids Small box and in 2015 I expanded that with an Arduino Pro Mini based keyer in a regular Altoids tin. It was a lot of fun and consumed pretty much the whole winter. I’ve written down a few ideas for enhancements and in this year’s model some of those are implemented. The hardware wish list (so far):

  1. Battery power, enabling stand alone operation > 24 hours
  2. LCD display 16×2 minimum
  3. Real Time Clock, Local and GMT
  4. More memories (7 or 8 buttons)

Batteries and LCD won’t fit in an Altoids tin. I found a metal Crayola box at Tuesday Morning. It was made by the Tin Box Company, who produce many designs that would make interesting project enclosures. It is 3″ x 5″ x 1.5″, about three times the volume of an Altoids box, the metal is slightly sturdier than Altoids but still flimsy enough to be difficult to work without distortion. I found the inside surface was coated with a thin layer of something which repelled solder unless sanded a bit first. I don’t see this particular box available any more but there is a slightly larger version. My experience indicates that the time to complete a project is inversely proportional to the size of the enclosure (maybe to the fourth power).

Unmodified Crayola Box

Unmodified Crayola Box

 

These days “Arduinos” come in many shapes and varieties. The latest official 1.6.7 IDE is almost 100 megabytes, expanded to accommodate different versions.  I wanted to try processors other than the standard ATMEGA328, so last summer bought a Teensy2.0 (32u4) and a TeensyLC (ARM Cortex M0) made by PJRC. Both promise built in USB client support. The PJ in PJRC is Paul Stoffregan, who has contributed a great deal to the Arduino community. There’s an IDE add-on “Teensyduino” that must be downloaded from the PJRC site to use Teensy boards. Teensyduino installation is dead simple and includes Teensy versions of most familiar Arduino libraries plus a few useful additions from Paul.

Last summer I worked with the Teensy2.0 a bit, wanted to see if the DDS sine wave generation function I used in the 2015 design would work. The port was successful, the 32u4 required only a few minor tweaks, and I even got Fast PWM working as described in Atmel’s documentation. PJRC has a forum where you can brag about your accomplishments so I wrote something on the 32u4 DDS sketch thinking it might be useful to others. Paul Stoffregan replied suggesting I consider a Teensy3.2 as it has an integrated Digital-Analog Converter which would produce a cleaner waveform. I fired up the similar TeensyLC and used Paul’s suggested method. DDS on the TeensyLC was also successful so I built a breadboard version of last years keyer using the LC.  Everything worked with PJRC’s libraries including DDS side tone, the PS2 keyboard, and lcd.prints added for the display.

The small module at the upper left of the breadboard is an Adafruit PAM8302 audio amplifier. Last year I struggled with a 1 transistor class A amp for the speaker, gave up on that and built an LM386 design. The PAM8302 amp at only four bucks is clearly a winning choice. The only problem I had was later on I discovered the Output side did not like being grounded and I had to insulate the external speaker jack.

First Breadboard - TeensyLC

First Breadboard – TeensyLC

 

TeensyLC has one serious limitation for my application. Because the ARM chip handles flash differently than the MEGA328, TeensyLC has only 128 bytes of emulated EEPROM. That meant limiting stored button memory to four messages only 30 characters each. At that time I was thinking about adding a Real Time Clock so looked at getting Adafruit’s FRAM breakout and their DS1307 RTC. But for less money than these two modules plus a TeensyLC I could get a Teensy3.2 module with a Cortex-M4, lots of memory, built in RTC, and 5 volt tolerant inputs. I sent off an order to Adafruit (10% off if you watch “Ask An Engineer”).

Teensys have lots of I/O pins, same spacing as the LCD modules, so I elected to mount the Teensy board directly on the LCD.  One 3 pin header and one four pin header is needed. In the next photo you can see the headers with two short gray spacers to separate the PC boards. I had to flatten one of the LCD bezel mounting tabs for clearance but the mount is very compact and rigid. Note to self: make sure you don’t need any more connections to the bottom of the board before soldering down the headers.

I had the idea to use a software driven flashing LCD back light to indicate a flat battery. ARM I/O pins are limited to 9 milliamps each, not enough for an LCD back light so a 2n2222 transistor was glued in to act as back light current switch. The trim pot on the right is for adjusting LCD contrast. It is across the back light LED pads, did not work out well, as later in development I am PWMing the 2n2222 to get adjustable back lighting. So the trim pot has been moved up on the LCD board, epoxied in place, and hard wired to ground and +3.3 volts.

Teensy3.2 Grafted on to LCD

Teensy3.2 Grafted on to LCD

 

The two wires leading off the right end of the Teensy go to a CR2032 backup battery for the Real Time Clock, and you can just see the Adafruit 32KHz crystal added on the bottom of the Teensy. With this minimal configuration I was able to test and experiment with the built in RTC using the example program furnished with the PJRC Time library, modified with LCD prints.  Initially setting the clock was a problem, you need to send a “T” followed by Unix time (seconds since 1970) into the serial port. I worked out this Linux incantation to get the proper format for Central Standard Time:
echo T$[`date +%s` – 6 * 3600]
T1453151560

Then copy “T1453151560” and paste into the Arduino serial window.  Once the clock has been set it takes care of itself though I’m not sure how. I believe it reads and sets time from code uploaded from the compiler. The Time library is more than a little obscure.

Clock Testing Processor/LCD Sandwich

Clock Testing Processor/LCD Sandwich

 

Of course many wires have to be added to interface Teensy with the rest of the keyer. It’s not so neat looking now, I’m using nearly every I/O pin plus power from the built in 3.3 volt regulator. I use mostly 24 gauge wire, solid if connecting to other points on the lid, stranded if routing to points below. I have an old Ungar fine tipped soldering iron plugged into a Variac set to about 70 percent.

Processor/LCD With Necessary Wiring

Processor/LCD With Necessary Wiring

 

There are three auxiliary perf boards in the design, One mounts seven memory switches, another holds volume control, transmit LED, and the Function button, the third has clock battery and an optoisolator for transmitter keying. These boards were carefully laid out on paper, then cut out and marked up so mounting holes could be located. Working with a hinged lid box you have to be careful to leave extra clearance for the lid to close. I did have to file a bit off the button board and the speaker.

The box needs a couple dozen holes to mount parts. Blue tape was applied to all surfaces, a layout drawn on the tape, then all holes center punched.  I start with my smallest drill bit in a drill press then enlarge 1/64 at a time to final size.  A few holes required fine tuning with a tapered reamer.  I made a rectangular cutout for the LCD bezel by using a wooden template screwed to the lid, then cutting with a 3/16 carbide router bit surrounded by a 1/4″ collar. Mounting hardware is mostly 2-56 with a few 4-40 spacers.

Crayola Lid Drilled

Crayola Lid Drilled

 

I had a pair of paralleled 18650 cells taken from a cell phone charging pack. These are fastened in the box by a strip of tin can metal soldered in, and restrained by an angle bracket soldered at one end. The small speaker was taken from a defunct IPod dock. In the next photo, most of the lid components are mounted. The small audio amp board goes on the two screws at right center of the lid, mounted mezzanine style.

Box Lid Components Mounted

Box Lid Components Mounted

 

Next is a close up of the batteries with 2 amp fuses soldered in both plus and ground leads. Also see three stereo jacks at the right side for Key/Audio Out, External Speaker, and Paddles In. You can see in the bottom three long #2 screws for mounting the third perf board and Adafruit boost/charger. Most board mounting screws have three nuts; one to secure the screw, one to support the bottom of the board at the proper height, and a third to secure the board against the second. Thank heaven I still have a Heathkit nut starter.

Mounted 18650 Cells with Fuses in Both Leads

Mounted 18650 Cells with Fuses in Both Leads

 

At the right side of the box there is a power switch, PS2 jack, and a micro USB jack breakout. The power switch does not actually switch power, it grounds the Enable pin on the charger board which turns off the boost converter.  That allows charging to continue while the rest of the unit is off.  Later in debugging the hardware, I added bypass capacitors to that switch and a separate wire to the Enable pin on the audio amplifier which suppresses a weird sequence of sounds from the speaker on powering off. The PS2 jack leads wouldn’t reach the processor board so they route to the third perf board and get jumpered there to stranded wire headed for the Teensy.  It’s getting hard to find a real PS2 keyboard but the software works fine with a USB keyboard plugged into a USB/PS2 adaptor.

Power Switch, PS2, and USB Connectors

Power Switch, PS2, and USB Connectors

 

This is a good place to register a complaint. I bought the Adafruit PowerBoost 500 board to manage the battery. It charges from 5 volt USB in and boosts from the 3 volt battery, seamlessly switching sources when you pull the USB connection. It does NOT however pass through or even break out the two USB data pins from the micro USB input jack. The only way to actually use USB while charging the battery is to wire out the D+ and D- leads outside the board. Adafruit support suggested doing this by cutting up a USB cable. I was able to route the micro USB breakout data leads (Green in the next photo) to the processor and the incoming positive and negative supply leads to the PowerBoost using a plug from an Adafruit micro USB connector (red and black in the photo). An extra $2.50 in parts that wouldn’t have been needed if Adafruit had only provided pads on the PowerBoost for D+ and D- or better, added two traces to route the data signals from the input connector to the output connector.

Detail of the Hacked USB Connection

Detail of the Hacked USB Connection

 

One more issue with the PowerBoost. It has a nice pair of status LEDs (where it says CHRG) yellow when charging and green when fully charged. These operate from a single pin on the charger chip but that pin is not broken out and you can’t of course, see the LEDs when the box is closed. I added a wire (gray, leading off to the right in the photo) to the common side of the LED dropping resistors so I could have the Teensy display charging status on the LCD.  Not difficult but would have been nice to have official access to that chip pin.

The keyer has four monitoring leads between the PowerBoost and the processor. Besides the status signal mentioned above, I wired up the LowBattery pin and USB (power).  USB activates the Status signal which is only valid when USB is plugged in and receiving power from the host.  LB goes low when the battery is REALLY flat (3.25 volts I think). I also wired the BAT pin to the Teensy A10 analog input through a 10k calibration pot so software can read and display the battery voltage. You can see the calibration pot at the bottom of the board in this photo.

TX board, PowerBoost with Voltage Cal Pot

TX board, PowerBoost with Voltage Cal Pot

 

The next photo shows how I insulated the External Speaker jack by opening up the mounting hole and screwing a small piece of Lexan to the box. The plastic had to be counterbored so the jack mounting nuts would fit.

Output Jack Insulation

Output Jack Insulation

 

Here is a close up of the box lid interior. You can see the LCD contrast pot which is glued to the LCD, perfboard for the LED, volume control, and Function button. Two screws and a couple of spacers mount the PAM8302 audio amp on top of the LED board.

LCD Contrast, Audio Amp

LCD Contrast, Audio Amp On Top of LED Board

Here is the completed keyer opened up. Clockwise from top left, I/O stereo jacks, 18650 batteries, memory button board, Teensy3.2 processor on top of 16×2 LCD display, LED board, speaker, on/off switch, PS2 keyboard jack, USB input jack, PowerBoost charger/boost converter, and the transmit interface board.

Keyer Internals

Keyer Internals

 

An Eagle schematic diagram of this project can be downloaded from:
https://dl.dropboxusercontent.com/u/40929640/ArduinoMorseCode/keyer2016/KeyerDrawings.zip

Keyer 2016 Schematic Version 1

Keyer 2016 Schematic Version 1

 

Revision History

February 25, 2016       MemoryKeyerTeensy3.2_V1.0    Initial sketch
March 9, 2016             MemoryKeyerTeensy3.2_V1.1.0  Rework battery alarm logic, bug fixes.
March 16, 2016           MemoryKeyerTeensy3.2 V1.1.1   Workaround fix LCD does not have backslash in its font.

Toastmasters Timing Light

There was a post on the Workshop88 mailing list asking for someone to construct a small manual light box for use by the timer at Toastmasters meetings. The specification was, a switched Green LED, switched Yellow LED, switched Red LED, and a fourth switch to blink all the LEDs at a 1 hz rate. The actual timing is done by a human with a stopwatch, the box just signals the speaker. The Toastmasters’ existing setup uses 110 volt incandescent lamps and is not very portable.

Much discussion ensued on the mailing list about what could be done with a Raspberry PI or Arduino, LCD screen, etc. etc. but in the end, I agreed to design and build something simple according to the original manual spec. Ultra bright LEDs could be used with a 555 timer to do the blinking. A standard MN1604 9 volt battery would easily power the LEDs for 8 – 12 hours. And I could use the standard Arduino style enclosure: and Altoids tin.

I’ve built two of these boxes. The photos on this page are from the second – but first came a prototype on a solderless breadboard.

Breadboarded Timer

Breadboarded Timer

 

On the breadboard the timer circuit was checked for reasonableness and LED illumination tested. I found with a nine volt battery I could put two LEDs in series, and with a 200 ohm limiting resistor the Red LEDs drew 15 milliamps, the Yellow 20 Ma, and a pair of Greens 12 Ma. The Red and Green were very bright, Yellow not so much. Later I checked the spec sheet on the Yellow LEDs and found they would take 50 milliamps.  I lowered the Yellow limiting resistor to 130 ohms which brought the Yellow current up to 35 Ma and then all three pairs were similarly bright.

These Ultra Bright LEDs have a clear plastic envelope with a lens formed in the end which directs most of the light straight up.  I sawed the tip of each LED off at a 45 degree angle to remove the lens. This directs more light to the front and reflects much more to the rear.

Original and Faceted LED

Original and Faceted LED

 

Here is the final schematic. This is slightly revised from the first model, the timing person wanted a separate power switch, and also wanted the blink cycle to start with LEDs on rather than LEDs off.

Toastmaster Timer Schematic

Toastmasters Timer Schematic

 

The original breadboard had all three of the grounds at the bottom of the 555 chip connected together, a switch from there to power negative activated the 555. In that configuration, the 10 microfarad capacitor started out in a discharged state which resulted in LEDs off.  Splitting that capacitor off and hard grounding it causes it to start in a charged state which turns the LEDs on. Switching the 555 pin 1 to ground starts the blinker.

I constructed the 555 module on a bit of perf board with copper pads on one side. A six hole by seven hole piece holds all the parts. This is the layout sketch I used.

Toastmaster Timer Blinker Module

Toastmasters Timer Blinker Module

 

Here is an assembled module. It measures 3/4″ by 5/8″.

Blinker Module

Blinker Module

 

With the blinker built and tested, I turned to physical construction of the box. Everything should fit in the lid.  I made an aluminum template for drilling the ten holes. In this photo, the four switches have been mounted and there are small holes drilled above the nut for the anti-rotation washer.

Altoids Lid Drilled and Template

Altoids Lid Drilled and Template

 

The LEDs don’t have any formal mounting hardware. To get maximum exposure, they are just inserted in the holes until they bottom out on the shoulder. Then a narrow strip of FR4 perf board is threaded over the leads. This photo is three strips cut from a wire wrap prototype PC board. I use a crosscut sled on a table saw for this, with a narrow carbide blade centered on the fourth row of holes.  Width of these strips is important because they help restrain the battery.

LED Retaining Strips

LED Retaining Strips

 

The fiberglass PC board strip is tacked down with bits of bent paper clip soldered to the tin lid. That paper clip in the center had to be moved later because it interfered with the battery. Soldering the LED leads in the perf board creates a very rigid assembly. I added the current limiting resistors between the LED pairs.

Switches Mounted and LED Dropping Resistors

Switches Mounted and LED Dropping Resistors

 

Spacing between the switches and the LED retaining strip is critical because the nine volt battery has to fit there, but not rattle around. A large paper clip was straightened out, then bent to capture the battery. A paper clip has just enough spring to hold the weight of the battery. This photo shows the battery clip soldered onto the lid. White arrows point to the four Z shaped wires holding the LED retaining strip in place. Ground leads are soldered to each switch and each has been cabled to it’s assigned LED pair.

Pins Holding LED Board

Pins Holding LED Board

 

Here is a photo with a battery installed in the clip. You have to be careful not to short the terminals on the lid lip.

Fitting the Battery

Fitting the Battery

 

At this point the lid is ready to receive the 555 timer blink module. It is mounted with two more bits of soldered paper clip, this time bent into an L shape. One clip is soldered into the ground hole of the perf board, the second in a vacant hole. White arrows in this photo point out the two module mounting clips also three of the LED restraining strip clips. Note the two retaining strip clips nearest the rim are bent parallel to the lid edge. This is to give clearance for the box bottom.

Blinker Module Installed

Blinker Module Installed

 

The last piece of hardware installed was the power switch. I used a small slide switch as that type will be less likely to accidentally turn on in somebody’s pocket.  Two eighth inch holes were drilled, then squared up with a small file. I soldered the ears of the switch to the inside of the box.

Power Switch Soldered In

Power Switch Soldered In

 

Finally the wires for power were added, everything tested, and all loose wires laced up with waxed dental floss. A bit of foam tape was added to the bottom to help make sure the battery clip doesn’t come loose. There’s a small paper clip loop soldered next to the power switch to take up strain on the wires there.

Internal View

Internal View

 

Here is the finished box with all three LED strings lit.  Note this is not a normal condition, only one color at a time should be on, mostly the Green which only draws 12 Ma (but is so bright it hurts your eyes). Blinking will draw about 60 Ma half the time. Duracell’s data sheet shows a useful life greater than 8 hours with a 50 milliamp draw so I expect this application to last considerably more than that.

Completed Toastmaster Timer

Completed Toastmasters Timer

 

This has been an interesting project that was well received by the users.  There is a short video on my Dropbox account.

Added: May 27, 2015

I needed a way to get consistent bevel cuts on the modified LED lenses using my bench grinder which is far quicker than the Dremel tool with cutoff wheel method.  The solution as any woodworker would know, is to make a jig. In this case though I was able to re-purpose a fixture I made years ago to hold hand plane irons while touching up the bevel. It’s just two pieces of 3/8″ x 3/4″ steel bar stock with half a dozen holes drilled. One piece is tapped, screws through the other then clamp the plane iron in the jig and it can be held tightly to the edge of the grinder’s tool rest.

Adapting this fixture to hold LEDs only required adding a washer slightly thicker than the LED wire leads to one end. I had to grind the underside of the threaded bar to get clearance for the grinding wheel. Two LEDs can be slid into the beveled end and clamped there by the screws. A single long screw through one of the threaded holes at the washer end provides a stop that can be held against the grinder tool rest.

LED Grinding Fixture

LED Grinding Fixture

 

I can tweak the grind angle by adjusting the tool rest, and a few passes across the grinding stone produces the consistent bevel I wnt. Just have to be careful not to grind away too much. I put a dab of nail polish on the ground surface to clean up the scratches.

 

 

Clothes pins in series

I have a drill battery that for some reason will not work in the factory charger. (possibly because I rebuilt it myself) So I need a way to kludge on a laptop power supply to do a trickle charge. Not having a socket for the business end of the battery, I have to attach wires somehow. I tried a standard clothes pin, will stretch to the one inch spacing if you bend the spring. It is not satisfactory. So I made a wider clothes pin by gluing two together in series. The glued blades are sawn off and the tips shaped a bit. Works great.

Clothes pins

Clothes Pins in Series 1

 

I can make a triple too.  A standard clothes pin will open less than a half inch. A double will open an inch, a triple an inch and a half.  Those are the spade tips I used to make the actual contact with the battery terminals.

 

Clothes Pins in Series 2

Clothes Pins in Series 2

 

WB8NBS

NBS
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