Dorcy AAA circuit in Solitaire?

Hey I saw a reference to this recently but can't find any information. If any of you have done this and have specifics I'd love to read about this mod.

I recall the thread and the guy that put the dorcy guts into a solitaire had to take all the parts off the board and stick the ones needed together in a pill form and epoxy it together. It didn't look like a task for a beginner for sure, I would rather recommend a resistored LED and a lithium ion AAA instead.

Was that pbarrette? Shoot him a PM or search his posts.

It could work. So far I've only been able to get about 100mA out of that driver no matter what I use for an inductor. I changed the Shotkey diode, but that didn't help much either. Putting a cap on the input and output sides does help a little bit. You'd have to pull the components off the board and point to point solder them together into a pill. I'd try driving a MJLED or something like that. It's hard to get enough current with 1.5 volts to drive a luxeon very well.

It would be a good start, but I'd almost go with the MAX1797 or the LTC3490 IC's since they are much more efficient.

Hi Xochi, all,

As far as I know, I was the first (possibly only?) person to post about fitting the Dorcy 1xAAA circuit into the Solitaire. The post is here, though it doesn't really have detailed instructions.

I would suggest that a better circuit to use for a 5mm LED in a Solitaire would be the Zetex ZXSC300 circuit. With the right sized inductor, it makes for a much better fit in the Solitaire pill space and is a lot easier to solder together due to the pin layouts than the Dorcy circuit.

One of my posts regarding the Zetex circuit in a Solitaire is here and I do have some detailed construction notes in another post floating around here somewhere as well.

Hope this helps,
pb

so it was pb! :twothumbs

Hi GreenLED,

Damn you're fast.

Yes, it probably was my post that was referenced.

I should probably add that the Dorcy circuit was a real bear to tear apart and resolder. I ended up buying the Zetex parts because I got tired of tearing apart the Dorcys for their guts. Buying a perfectly good light just to destroy it got old fast and the Zetex components cost less per circuit than the Dorcy lights.

Also, the main difficulty I had in all of it was getting the mechanical workings right. The circuits were easy to build by comparison. The trouble is, the ground contact on the Solitaire works the same as the Mini-Mag. As the head unscrews, the pill is pushed forward by the tailcap spring until a pad on the pill makes contact with a lip on the head end of the body. The replacement LED pill must have a beveled top edge to get the centering right and there must be a ground contact somewhere on that beveled edge. Now that I have a lathe, making a clean, round, beveled, metal ring is a snap. Before the lathe, I was using hand tools which resulted in minor variations that meant some pills made good contact and some just never fit right.

Here's a tip for an epoxy mold. Find a Sanford Uni-ball Vision pen and pop off the tail-cap. Cut 2 ~1cm sections off the cap starting from the rounded end. Discard the first section. The second section should be just the right size for a solitaire pill and should now be shaped like a short length of tube. Epoxy doesn't stick to it very well, so it should now be a perfect mold for your Solitaire pills. Set it on a flat surface, place your circuit inside and fill it with epoxy. When it hardens, slit the tube down the side and peel it off the pill. If you are careful, you can peel it off without distorting the shape and reuse the mold later.

As a bonus, you get a nice, working pen out of the deal. Personally, I prefer the "Micro" over the "Fine" for writing.

pb

I have to say bravo for the work on that mod as it was incredible. I have also searched many times for that thread and could not remember who had done the mod.

I pride myself on being able to tinker my way into many lights and somehow make things work. I tried so many times to duplicate this mod and no way was I able to pull it off. I tell you that circuit stuff kills me when it comes to putting all the Dorcy parts back together in such a small space. Thanks for the links and again that was some amazing creativity pbarrett as well as a slick little mod.

Hi robocop,

Thanks.

The trick to the Dorcy was creating a circuit diagram. I traced out the connections to the components before removing them so I would be able to recreate the circuit. I stuck a circle of copper on the bottom of the inductor for the positive battery contact and built the rest of the circuit on top of the inductor. The resistor in the circuit can be removed, so that reduced the component count and the size.

The problem with the dorcy circuit is that the IC can't really lay flat on top of the inductor due to the way the rest of the circuit is wired. The Zetex circuit fits the space much better since the IC and transistor can be bridged across the terminals of the inductor while lying flat on top of it. Despite the smaller size of the components in the Zetex circuit, I found that it was easier to solder those smaller connections than it was to shrink the Dorcy circuit.

In the end, the Dorcy circuit is a fixed voltage boot circuit running wide open. Which means that the current ouput for a given input voltage is directly tied to the Vf of the LED and not variable. The Zetex voltage boost circuit allows the output voltage to be adjusted via a sense resistor (or thin, short wire) which means you can adjust the output current for a given input voltage. Also, the Zetex circuit is capable of supplying more current to an LED than the Dorcy AAA circuit, but with a 5mm LED that isn't really an issue.

As Flashlightguy stated, a better option for running a Luxeon would be the LTC3490 circuit. I built one of these that fits in a ~5x5mm cube. It only needs 3 parts total, so it's fairly easy to solder.

pb

Can you tell me exactly what the 3 parts needed are as I am really very ignorant when it comes to actual circuits. I really think the Solitaire was my very first project that started this whole modding thing for me....I had limited success however never really got a drop in type pill to work as I just could not get all those Dorcy parts formed in a nice circular shape once removed from that huge board they were on.

I may have to re-visit the old Solitaire mod based on the finding of this thread....pbarrett do you have any links or other info as to the LTC3490
circuit you made? I would really like to see that creation.

pbarrette said:

Hi robocop,

Thanks.

The trick to the Dorcy was creating a circuit diagram. I traced out the connections to the components before removing them so I would be able to recreate the circuit. I stuck a circle of copper on the bottom of the inductor for the positive battery contact and built the rest of the circuit on top of the inductor. The resistor in the circuit can be removed, so that reduced the component count and the size.

The problem with the dorcy circuit is that the IC can't really lay flat on top of the inductor due to the way the rest of the circuit is wired. The Zetex circuit fits the space much better since the IC and transistor can be bridged across the terminals of the inductor while lying flat on top of it. Despite the smaller size of the components in the Zetex circuit, I found that it was easier to solder those smaller connections than it was to shrink the Dorcy circuit.

In the end, the Dorcy circuit is a fixed voltage boot circuit running wide open. Which means that the current ouput for a given input voltage is directly tied to the Vf of the LED and not variable. The Zetex voltage boost circuit allows the output voltage to be adjusted via a sense resistor (or thin, short wire) which means you can adjust the output current for a given input voltage. Also, the Zetex circuit is capable of supplying more current to an LED than the Dorcy AAA circuit, but with a 5mm LED that isn't really an issue.

As Flashlightguy stated, a better option for running a Luxeon would be the LTC3490 circuit. I built one of these that fits in a ~5x5mm cube. It only needs 3 parts total, so it's fairly easy to solder.

pb

Click to expand...

What parts are you using? I made up a quickie circuit using a 3.3uH toroid and a 47uF tantalum cap. All I was getting out of it was around 180mA into the Luxeon. I tried a 10uF surface mount cap, and that was much worse at 50mA. I don't have any of the recommended 4.7uF caps.
I know this IC is running at 1.2Mhz, but is it picky about lead length to the IC? I just expected different results. I noticed a post awhile back from you looking for the part number for the Dorcy IC. It's AIC1642 in case you hadn't come across it yet. The IC is fine for running a 30-100mA LED, but that's about it on 1.5V. The thing that's a killer is the 2 Ohm Switching resistance. The inductor also has about 0.5 Ohms.
Any help would be appreciated. Thanks

Hi Robocop,

The LTC3490 circuit at it's basic minimum requires:
1x - LTC3490 IC.
1x - 3.3uH inductor.
1x - 4.7uF ceramic capacitor.

You can see the circuit that I built here and you can see a 3d model of the circuit here.

This circuit powers an LED with 350mA of constant current from a 1.5v or 3v battery with those 3 parts. If you want to have an adjustable current output from 0 - 350mA, a single potentiometer (variable resistor) would need to be added. A fixed, reduced current setup would require a resistor.

This circuit sucks a great deal of current out of the battery, and as such, requires an inductor with a very large saturation current. The DCR of the inductor (DCR = DC series resistance) should be as low as possible to maintain the efficiency of the circuit. A problem that I have noted is that it is very difficult to keep the circuit in regulation below 1.1v, which means that it is best suited for 2x Alkaline, 1x Lithium or 1-2x NiMh cells. The circuit will continue to function, but the current will drop below 350mA after the battery voltage drops below ~1 to 1.1 volts. I have been using a modded ArcAAA with an RY0J and this circuit and an Energizer Lithium AAA for over a month now. I use it roughly 1 minute (or slightly less) every day as I find my way to the car in the dark garage. I'm still on the same battery, so it seems to do fairly well.

I did a runtime plot with an Energizer 850mAh NiMh AAA battery and got ~45 mins to 50% output. Very flat output curve until the 42 minute mark, then a nose dive down to ~30% output followed by a steady decline to 10% over the next 10 minutes. I don't have the image on my website at the moment, but I'll probably add it at some point.

pb

Hi Flashlightguy,

For the LTC3490 circuit, I am currently using the following:
1x LTC3490 in SOIC format (the DFN is just too damned small for me).
1x Toko A920CY 3.3uH shielded inductor.
2x Kemet X5R 4.7uF 0603 capacitors.

The photos in my above links show the second circuit I ever built with this IC. It used the Coilcraft MSS5131 3.3uH inductor and a 2.2uF capacitor of unknown brand.

This circuit is extremely sensitive to lead lengths. Especially the lead lengths from the power source to the IC and the IC to the LED. It is also extremely sensitive to the DCR and peak current capability of the inductor. The datasheet recommends an inductor with a DCR lower than 25mohm and a saturation current in the range of 2A.

The Coilcraft MSS5131 has a DCR of 32mohm and a saturation current of 1.53A, while the Toko part has a DCR of 24mohm and a sat current of 1.89A. The coilcraft circuit lasts 30mins to 50% in my testing, while the toko based circuit lasts 45mins. All other factors were the same. Same battery charged in the same way, using the same RY0J Lux1 for testing. The reduced DCR and higher saturation current of the toko gave me results that were 50% better than the coilcraft.

Note also that I am using 2 capacitors. Even though the datasheet states that an input capacitor isn't required, I added one to reduce the pulse strain on the battery. A tantalum capacitor with its increased ESR would likely hurt efficiency as well.

This circuit has been performing very well for me, but giving me trouble in another area. I have been finding it very difficult to get good efficiency readings from this circuit due to the fact that it is very sensitive to resistance inline with the power source and the LED. Basically, you measure current by measuring the voltage across a resistor in series with the circuit and using ohms law to find the current. The problem is that the introduced resistance decreases the efficiency of the circuit and throws off the measurement.

For example.. Using the same circuit that gave me the 45 minute run time. I placed one 0.1ohm resistor in series with the battery and another in series with the LED. I used djpark's "CPF Logger Lite" to collect efficiency data while also monitoring the light output. My measurements showed ~80% efficiency from the start and fell to ~60% efficiency at the end of the usable battery life. The problem was, with the added inline resistance, the circuit only lasted 30 minutes to 50% brightness. This same circuit, with the current measurement resistors removed, lasted 45 minutes to 50% output.

So the efficency of the circuit is greatly affected by inline resistance, but I am at a loss as to how to determine the circuit efficiency without substantially decreasing the performance of the circuit.

Keep in mind though, that I am able to accurately measure 350mA output to the LED. I am just unable to accurately determine how much power the circuit burns away as heat while powering the LED.

Hope this helps,
pb

The only bad thing on this circuit (using the LTC3490) is the efficiency at voltages below 1.5V. That chart Linear posts looks ugly in terms of efficiency (the switch speed kills it, but has too be the keep parts so small). I do like how small you built the circuit though.

So the efficency of the circuit is greatly affected by inline resistance, but I am at a loss as to how to determine the circuit efficiency without substantially decreasing the performance of the circuit.

Keep in mind though, that I am able to accurately measure 350mA output to the LED. I am just unable to accurately determine how much power the circuit burns away as heat while powering the LED.

Hope this helps,
pb[/QUOTE]

Wow, Thank you very much for your help. I think it was probably the long leads to the battery, and the inuctor was a couple inches away from the IC. I'll try tightening it up a little bit better tonight.

As far as the current measurement goes, that's a tough one. There's a couple things you could try. You could use a 0.01 Ohm resistor and connect it to a op-amp to boost the voltage levels. I like the TL082. The other thing you could do is get a 50uA or 100uA panel meter and connect it with a resistor in parallel to the 0.01 resistor to measure the current. 350mA*0.01=0.0035 Volts. So, we're not dealing with much for voltage here. Most DVM's won't be very accurate with voltages that low. If you need a hand running the numbers for the meter or help with an op amp circuit. just let me know.

I have a couple projects int he works. First I'd like to convert a 2-D flashlight to a Luxeon, but I haven't put together a decent drive circuit yet. I'd also like to make something for the Dorcy, but that's more of a secondary project.

Thanks for your help.