djpark
Enlightened
Old pal Doug ( vcal ) sent me a few of AAA sized Li-Ion cells and I immediately made an Arc-AAA head with 8mm cyan LED from ISP with 1 FET & 1 transistor based current regulator.
The result is somewhat pretty yet disppointment (you will see why below).
A. Construction
The current regulation circuit is based on UK Owl's design in this thread and I used the same one for H&M Contest Class2 .
Since the tab on the li cell is very low, I moved the battery retaining ring to the bottom of the body and it makes the battery contact firmer. The 8mm led is in deep recess of the head, so there is virtually no side spill except what comes out of the led with 55 degree beam.
When compared with an original Arc-AAA Turquoise (5mm), the color is almost identical to the bare eyes. Also the overall corona from the 5mm original is slightly larger than that of 8mm.
B. Battery & Run time
I charged the battery with the same charger I used to charge AA li cells. Since the max constant current is set to 256mA, it is about 0.85C of 300mAh and still safe to charge. The charging stopped at the battery voltage 4.15V.
The Vf of the led is lower than 3V and with about 0.5-0.6V voltage drop at the regulator, it is expected to go under current regulation till battery voltage drops to 3.5V which is practically the bottom line of usefulness of a li cell (IMO) and it does as shown in the run time chart below.
2 hours of very flat brightness (0.11A) followed by 30 minutes of slow declining brightness (0.11A -> 0.07A), then 45 minutes of sharp declining of brightness (0.07A->0.01A). It went on very long with quite dim light (below 10mA), but it didn't bring the battery voltage below 2.7V and it confirms again that it is pretty safe to use without over-discharge protection circuit.
C. Beam shots
This is the disappointing part when compared to the original Arc-AAA Turquoise. The old 8mm cyan led (not power led) from ISP doesn't seem to produce much light or the led used by Peter is super efficient. Not only the color, but also the amount of the light produced seem to be quite comparable.
Below are the pictures of beams with 8mm left and 5mm right:
50cm from the wall (1/4sec F2.8)
1m from the wall (1/4sec F2.8)
2m from the wall (1/4sec F2.8)
D. Conclusion
<ul type="square"> [*]I apperciate Peter's Arc-AAA-Turquoise quality. [*]Cyan is beatiful, but I shall change to some other color since 5mm is as efficient and bright. [*]It is realistic to have reasonably bright yet long run time light in Arc-AAA head with li-ion cell. [/list]
-- dj
The result is somewhat pretty yet disppointment (you will see why below).
A. Construction
The current regulation circuit is based on UK Owl's design in this thread and I used the same one for H&M Contest Class2 .
Since the tab on the li cell is very low, I moved the battery retaining ring to the bottom of the body and it makes the battery contact firmer. The 8mm led is in deep recess of the head, so there is virtually no side spill except what comes out of the led with 55 degree beam.
When compared with an original Arc-AAA Turquoise (5mm), the color is almost identical to the bare eyes. Also the overall corona from the 5mm original is slightly larger than that of 8mm.
B. Battery & Run time
I charged the battery with the same charger I used to charge AA li cells. Since the max constant current is set to 256mA, it is about 0.85C of 300mAh and still safe to charge. The charging stopped at the battery voltage 4.15V.
The Vf of the led is lower than 3V and with about 0.5-0.6V voltage drop at the regulator, it is expected to go under current regulation till battery voltage drops to 3.5V which is practically the bottom line of usefulness of a li cell (IMO) and it does as shown in the run time chart below.
2 hours of very flat brightness (0.11A) followed by 30 minutes of slow declining brightness (0.11A -> 0.07A), then 45 minutes of sharp declining of brightness (0.07A->0.01A). It went on very long with quite dim light (below 10mA), but it didn't bring the battery voltage below 2.7V and it confirms again that it is pretty safe to use without over-discharge protection circuit.
C. Beam shots
This is the disappointing part when compared to the original Arc-AAA Turquoise. The old 8mm cyan led (not power led) from ISP doesn't seem to produce much light or the led used by Peter is super efficient. Not only the color, but also the amount of the light produced seem to be quite comparable.
Below are the pictures of beams with 8mm left and 5mm right:
50cm from the wall (1/4sec F2.8)
1m from the wall (1/4sec F2.8)
2m from the wall (1/4sec F2.8)
D. Conclusion
<ul type="square"> [*]I apperciate Peter's Arc-AAA-Turquoise quality. [*]Cyan is beatiful, but I shall change to some other color since 5mm is as efficient and bright. [*]It is realistic to have reasonably bright yet long run time light in Arc-AAA head with li-ion cell. [/list]
-- dj
