[Click on any picture for a full size (800x600) image]

The schematic for the project

• The 47 uF electrolytic capacitor is polarized. The negative lead (-) goes to ground and it is the shorter of the two leads and marked "-"

• The 0.1 UF cpacitor (marked "104") and the 100 uH molded inductor are not polarized and may go into their respective holes either way

• The 1N5819 diode is polarized and the white band end (cathode) connects to that part of the circuit to which the bar on the schematic symbol attaches

• The LEDs are polarized and the cathode ends are the shorter leads and that side of the LED body has a "flat". You may use anywhere from 8 to 24 LEDs in the string

• The PIV rating of the diode and the working voltage rating of the 1 uF capacitor has been boosted and should sustain the voltages that would be generated with as many as 24 LEDs. Remember, once you get to 10 or more LEDs you are up to over 30 volts and that can sting

** Original Design Problem ** - - several people had reported blowing LEDs in the array. With 9 LEDs, I measure 25.2 volts at the top of the array to ground. (just for reference, I measured 3.9 volts to ground on the battery side of the 100 uH and also at the junction of the diode, transistor and choke, but at the junction of the diode, 1 uF cap and the top of the LED array I get 25.2 volts to ground) If you have the array disconnected and the circuit powered, the inrush current is strong enough that it will take out one or more LEDs (usually only one). I sacrificed a couple LEDs and measured as high as 60 volts open circuit. So, back to my original warning: Do not power up the charge pump without the load of the LED array!. I then tried a 4.7 ohm 1/2 watt resistor in series with the LED array, and it survived being disconnected and reconnected. The 4.7 ohms doesn't seem to noticeably affect the brightness but it definitely seems to temper that inrush current. There is nothing 'magic' about 4.7 ohms, 1/2 watt. Its what I had around!

** Danger, Danger, Will Robinson ** - thanks to a heads up from Bruce Jenkins, I found a sticky point in this circuit. If you power up the circuit without the LED array and the 1 uF capacitor attached, you can blow some or all of the other minor components. The processor unit, fortunately seems to be immune from this particular pathology. I am investigating it further and am stocking upon extra components. If anyone has this happen, I will make any replacements needed available at a nominal cost.

The circuit setup on a breadboard. The Red LED was added onto the Digital Pin 3 output to the 2N7000 switching transistor. It shows that the pulses are coming from the ATmega168 chip. It is not part of the final circuit

Bruce Jenkins' circuit setup on a breadboard.

Same circuit with + wire from battery plugged in and the LEDs lit.

DorkBoard breadboarded.

Another of my customers, Bob Cochrane, has posted a web page with some useful pix and commentary on building the flashlight kit

Inexpensive lantern bought at local True Value Hardware. Cost: $7.99

==> from Don Davenport - "Aiming the LED's toward the reflector seems to give more light.  They have such a narrow beam width, I think this helps broaden it out. I couldn't see using perf board (it's ugly and I didn't have any) so I used the plastic from a yogurt container lid.  It's easy to cut: make holes with a needle, and solder quickly."

Cut a square of perf board using a hacksaw. Used a bench disk sander to round it. then inserted 8 LEDS in more or less of a circuit oriented long lead (anode) of One LED adjacent to short LED of the next LED. Also inserted the 1uF monolithic capacitor

I bent over one long lead (anode) of one LED and wrapped it two turns around the short lead (cathode) on the next LED, snugged, clipped and soldered. Did so for each pair of long and short leadsleaving the gap of the last pair open. adjust position of cap to be adjacnet to this opened pair. Wrapped cap lead on the remaining leads, soldered and clipped cap leads.

attached two wires to the open leads, Red to the long lead (anode) and black to the short lead (cathode - ground). Soldered and clipped wires and excesslong leads. Applied hot melt glue to insulate and build up a cushion

removed reflector from lens assembly

applying a small bed of hot glue, the light assembly is inserted into refletor assembly and held while glue cools and sets

twisted leads come out the back

As stated above, on 9/8/2008 all kits are being supplied with slightly pared down DorkBoard Kits. There is a separate page now with assembly instructions. Even if you have the RBFK+ baord there are some additional mounting ideas here that you may find useful.

Board assembly is straight forward.

• you may shorten the board if you wish, compare your board with this picture and use a fine hack saw to cut the board. Then use a fine file to smooth the edges

• I suggest that you insert the 6 pin right angled header from the top of the board into the six holes along the end. Invert the board and solder. A good rule of thumb with all headers is to solder one pin first the check that all is aligned straight. Then solder the rest.

• From the topside of the board take the two 14 pin sockets and insert them ito the board one after another. Align the notch on end of the socket with the notch in the outline on the PCB. The kinked legs will hold the sockets in place. Now, carefully examine that all the pins come through the board and no pins are sticking up through the socket. When all is OK solder all 28 pins

• from the topside of the board insert the 10 K (brown-black-orange) resistor into the place for R2, and the 0.1 uF capacitor ("104") into the place for C4. Then solder and clip the excess leads

• from the topside of the board insert the pushbutton switch. Their are four pins as two pairs. In each "pair" the pins curve towards each other. and are connected internally. You want to insert the switch into the four holes so that one of the pairs runs right parallel to the socket edge. When it is aligned evenly, bend the tips of the pins over and solder

• From the bottom side insert the six pin straight header into the 6 holes starting from "GND" and extending to and including "D3"

• solder one pin ("TX" or "RX"), then check for vertical alignment. If not, reheat and straighten

• solder the remaining pins

• turn board over and clip the pins corresponding to "RX", "TX", and "D2". We will only be making use of "GND", "5V", and "D3".

You need a piece of Radio Shack project baord ( p/n: 276-148 ). It comes as two pieces joig along a perforation. Just flex it and break it in half, put one piece aside. tkae some very fine steel wool and clean the copper pads on the bottom. Insert the DorkBoard/RBBB/RBFK+ leaving three four rows of holes exposed on the side where you have two pins and 6-7 rows of holes on the 3 pin side.

Project Board, Bottom Side, turn board with bottom put and put a dab of solder on each pin to hold it to the project board. You now have firm anchors for connections and pleanty of holes and solder pads to do the additional circuit. Use the 3 pin side for the circuit and the two pin side to insert power. I suggest you use a fine drill to drill out a couple of holes to just big enough for the connecting wires (unstripped) from the battery and whatever switch you select, and from the LED array. pass the wires though from the bottom run them to where you want them, strip them and push them down through and solder on the bottom. Thse extar holes will act as strain relief.

==> from Bruce Jenkins - parts laid out next to Dorkboard (could just as easily be the RBFK+/RBBB board) on Radio Shack 276-148 board.

==> from Bruce Jenkins - bottom side of board with parts placed and soldered.

• take a small piece of perbaord and either hot glue or cazy glue ot the bottom of the RBFK+ board, inserying the three pins through the holes.

• insert one lead of the 100 uF choke through a hole adjacent ot the pin at "5V", on the bottom wrap the lead a couple turns tightly around the pin, solder and clip excess lead

• back on top lay choke down flat and insert other lead through a hole and let it hand down straight

• near this unconnected pin of the choke, insert the lead of anode end of the 1N5819 diode (opposite end from the band) Lay it down also and insert the lead on the banded end and let it hang down straight.

• The 2N7000 will have it's Source lead attached to "GND", its Gate lead attached to "D3" and its Drain will go to the junction of the choke and the anode of the diode

• the 1 uF monolithic cap has already been assmebled with the LED array. The two wires coming from the LED array (red from the anode end of the LEDs and black from the cathode/ground end of the LED array) will be connected as follows. The anode/red wire will go to the cathode (band) of the 1N5819 diode (which has nothing connected to it at this point), and the cathode/black wire will go to the ground connection.

• now, at this point we need to connect a power source, strat with no batteries in the tray. Solder the black wire of the battery tray to the hole marked "GND" on the opposite side of the bard from where you soldered the 6 pin straight header. This will be near C4. Solder the red wire to the hole enxt to it marked "5V"

• now most likely you will want to be able to switch this on/off. Since that arrangement is determined by your selection of lantenr to adapt or housing built from sccratch, I can say only, cut the red wire of the battery tray harness and splice two wires into it to whatever switch you have

Under Construction - More to Come!