Lambda Lights

7/31/2019 Lambda Lights

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This run time chart shows the MiniProconverter in a light engine output over

time. The green line plots 2AA NiMhcells and the blue line plots one single

AA NiMh performance.

The MiniPro also has a low levelsurvival mode so when the batteries dorun down you won't be left in the dark.The low level light is sufficient tonavigate in a dark area while you getsome fresh batteries.

Test flashlight was modified MiniMag AA

Mini-Pro Converter Kit Assembly Instructions

Check the contents of your kit and make sure you have all the required parts before beginning.

You should have:

1 - + contact circuit board

1 - Converter circuit board

2 - Ceramic capacitors

1 - IC

1 - Inductor

1 - 5/8 x 1/2 o-ring


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NOTE: MiniPro Kit does not come with 3 Watt Luxeon LED

Luxeon LEDs are available separately on the LED Page

Step 1 - Circuit Board Prep

If everything is accounted for in the inventory, then begin by lightly filingthe edges of the converter circuit board as shown in the photo. Use a finetooth file or emery board. File just enough to remove any rough materialand bring it to the edge of the copper plating. Do the same for the +

contact circuit board, but just enough to remove any rough edges. Nowclean the copper on the converter circuit board with an eraser or papertowel and alcohol.

TIP: Clean copper solders much easier

Test the four regions of the circuit board with an ohmmeter to insure theyare completely isolated from each other.

General guidance - Do not apply too much heat. Electrical components can be damaged by excessive heat during soldering. It is

recommended that you use the three count rule when soldering surface mount components. The three count rule is that duringsoldering, begin counting to three when you apply heat and remove the soldering iron when the count of three is reached (approx2-3 seconds), even if the soldering operation is not complete. Let things cool back down and re-solder the joint if not accomplishedthe first time, again using the three count rule. Surface mount components will generally need to be held in position during solderingas the surface tension of the solder paste as it melts in to liquid solder can pull the components out of position.

For the following steps it is recommended that the circuit board be mounted in a vise or other similar device to hold it stationaryduring soldering. As a general good practice, test fit components on the circuit board before adding soldering paste to insure properalignment.

Note: Although references in the instructions relate to solder paste, fine gauge solder (0.015 inch or smaller recommended) can beused in it's place.


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Step 2 - Converter Assembly

Position the IC on the converter circuit board as shown in the drawings.

Pin 1 on the IC is marked by a small indented dot next to it.

The IC will need to be held in position when soldered or it will move outof position.


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Using a toothpick, apply a very small amount of solder paste to the baseof Pin 4. It may be necessary to re-align the IC after applying the solderpaste. Solder Pin 4 by placing the tip of your soldering iron on the

copper right next to the pin. Observe the solder paste and continueheating until it all has melted and flowed; remove heat immediately. Thiswill anchor the IC in place so the rest of the leads can be soldered.

Check the alignment of Pins 5 thru 8 and make any slight adjustmentsnecessary to align the pins into position.

Again using a toothpick, place a small amount of solder paste along thebase of Pins 5 thru 8.

Solder pins 5 thru 8 by placing your soldering iron on the copper andsliding the tip up to the base of the IC pins. Inspect for solder bridgesbetween pins and between copper circuit patterns. If solder bridges arefound, use solder wick to carefully remove.


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Now use a toothpick to apply a small amount of solder paste to pins 1thru 3 and solder Pins 1 thru 3.

Position the output capacitor as shown in the drawing above and solder

in place. You will need to hold the capacitor in place during soldering orit may move out of position. Apply a small amount of solder paste andapply heat using the three count rule. Do the same for the other endcontact of the capacitor.

Do not allow capacitor to stick out past the edge of the board. Keep itwithin the edges of the circuit board.

Position the input capacitor as shown in the drawing above and solder inplace. You will need to hold the capacitor in place during soldering or itmay move out of position. Apply a small amount of solder paste andapply heat using the three count rule. Do the same for the other endcontact of the capacitor.

Do not allow capacitor to stick out past the edge of the board. Keep itwithin the edges of the circuit board.


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Position the inductor as shown in the photo and solder in place. You willneed to hold the inductor in place during soldering or it may move out ofposition. Apply a small amount of solder paste and apply heat using the

three count rule. Do the same for the other contact of the inductor.

Do not allow inductor to stick out past the edge of the board. Keep itwithin the edges of the circuit board.

Cut Three 1 inch (2.54cm) lengths of 26 gauge wire. Strip the insulationfrom the wire; save the insulation for use latter.

Form the end of one piece as shown in the photo.

Solder this wire to the ground connection as shown in the photo. Alsosolder to the copper on the top side of the board if it will be used as thenegative contact, such as for drop in assemblies for AA flashlights.


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Bend the end of one piece as shown in the photo.

You may want to use an insulated wire here for the positive output lead,depending on the intended application.

Solder this wire to the output connection as shown in the photo.

Solder the last remaining wire to the input connection (solder joint ofinductor and input capacitor) as shown in the photo.


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The completed converter should like the sample in the photo.

Step 3 - Testing the converter

No damage will result from powering the converter up without a loadattached to the output leads. If powered up with no load attached, youshould be able to measure 5VDC at the output.

However, The converter is best tested under real world conditions, that iswith a Luxeon LED attached to the output leads.

Connect a Luxeon to the output leads with test clips and then connect abattery to the input and ground wire as shown in the photo.

Note the ground is common to both input and output.


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When the battery (red test lead) is connected to the converter Vin leadthe Luxeon should light up brightly.

If the converter does not work properly, then inspect for solder bridgesbetween pins and between copper circuit patterns. If solder bridges arefound, use solder wick to carefully remove.

Once proper operation of the converter is verified, continue on to step 4.

Step 4 - Assembling the MiniPro Converter

Rout the input wire as shown in the photo.

Position the + contact circuit board as shown in the photo to check fit.Remove the contact circuit board. Mix a small amount of 5 minuteepoxy and apply a drop to the top of the inductor. Reposition thecontact board making sure it aligns both with the diameter of theheatsink and stays parallel to the converter circuit board. If necessary,

just hold in position until the epoxy hardens. When the epoxy is nearlyset up (4-5 minutes) you can still make some fine adjustments to thecontact board position. Allow the epoxy to fully set up beforeproceeding to the next step.


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Step 5 - Potting the Pill

Trim the lead and bend over in preparation of soldering.

After soldering the + contact, it is recommended to again test and verifyproper circuit operation.

Once potted, it will be nearly impossible to do any kind of rework orrepair.

Mix some epoxy for potting the pill. You can use thermal epoxy, but plain5 minute epoxy will work just as well and will set up faster and make the

job easier. Use a toothpick to apply epoxy and fill in the space betweenthe two circuit boards. This will add mechanical strength to the finishedMiniPro pill and lock the ground screw in position. You may need to add

two or more layers depending on how good you are at this pottingoperation, and what kind of epoxy you may be using.

Once potted, allow a couple hours for the epoxy to set up nice and hardbefore proceeding to the next step to avoid "sticky fingers".


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That's it, your done with building the MiniPro converter kit.

NOTE: MiniPro Kit does not come with 3 Watt Luxeon LED

Luxeon LEDs are available separately on the LED Page

MiniPro Converter Kit - Sorry, out of stock

$12.50 including shipping (USA & Canada); International Orders please add $5.00 for shipping.

The MiniPro Converter Kit contains all the following:

Converter component replacement parts:

IC - $5.00X5R Capacitor - $2.00 ea (two required)Inductor - $3.00PCB set and oring - $2.00

Replacement parts shipping is $1.00 (USA & Canada); International Orders please add $5.50 for shipping.

Send PayPal to [email protected]

Include in the PayPal remarks block the items ordered. Most orders ship in 1 to 2 business days.

Questions, or mail order request, send email to [email protected]


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MiniPro Converter Technical Details

The MiniPro converter is based on the MAX1797 IC in the 8uMAX surface

mount package. The MAX1797 uses an internal synchronous rectifierwhich eliminates the need for an external diode and improves onefficiency.

Unlike other more complex, and less performing converters, this circuitneeds only four active components; IC, Inductor, Input Capacitor andOutput Capacitor. The circuit works very well on just one AA cell driving aLuxeon LED for a very small and bright flashlight. Two cells can be usedfor super bright output.

In the MiniPro converter Pins 1 thru 5 are connected to ground. Pin 2when connected to ground limits the maximum open circuit voltage to5VDC. The other Pins, FB, SHDN, LBI and LBO are not used andconnected to ground, but could provide additional functions such assoftware shut down and low battery indicator.

The unique layout of the MiniPro circuit board maximizes heatconduction, peak switch current and circuit stability while minimizing EMIand RF emissions. The MAX1797 also has an internal damping switch to

minimize ringing at LX. The damping switch connects a resistor acrossthe inductor when the inductors energy is depleted. This unique boardlayout coupled with a fully shielded inductor and the Max1797 dampingcircuit reduces EMI/RF emissions far below the typical levels found insimilar sized and performing DC/DC circuits.

While the MiniPro is not a current regulating circuit, it is quite evident from the runtime graphs that itachieves the same or better regulation results as current regulated circuits when driving a Luxeon LED.


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The MAX1797 has a preset, pin-selectable (Pin 2) 5V or 3.3V output. The output can also be adjusted toother voltages, using just two external resistors or a single potentiometer. Future converter only versions ofthis circuit will take advantage of these features for custom applications.

Further information and performance details of the MAX1797 can be found on the Maxim web site.

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