This is my first mod of LED flashlight. This was stimulated after I bought my ARC AAA. As it uses a single AAA, I expected that it runs on IC step-up DC-DC with full regulation. After measurement, it disappointed me as it is only so called semi-regulated by Gransee of ARC :
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB31&Number=398763&fpart=&PHPSESSID=
It should only be a transistor oscillation circuit, or at most with another transistor for current limiting. Those circuits can be found from :
http://edusite10.tripod.com/led3/onetran/regulated.htm
I like full regulation, so that I do not need to care whether the battery is new enough to provide full output. And also it can squeeze the last 1% energy of the battery to provide non-dimmed output.
I started my circuit testing using DC-DC step-up IC and eventually reached :
[I annot post the image here ! Will try again.]
The IC SA57255-33 from Philips Semiconductors is a step-up regulator with 3.3V output. Philips also has built-in switching transistor version, SA57250-XX, but the current output is not enough to drive the LED at >30mA. The MOSFET is also from Philips semiconductors, BSH105, a low threshold, surface mount MOSFET.
1N5817 is also from Philips Semiconductors.
Datasheets can be found from Philips Semiconductors website :
http://www.semiconductors.philips.com/pip/SA57255-50GW.html
http://www.semiconductors.philips.com/pip/BSH105.html
http://www.semiconductors.philips.com/pip/PRLL5817.html
PRLL5817 is the surface mount version of 1N5817, both can work.
Following is the assembly :
[I annot post the image here ! Will try again.]
The SA57255 is the tiny IC marked with AEXC, beside is the BSH105. They are mounted at the bottom and the rest are at the top side.
[I annot post the image here ! Will try again.]
It is no way to position the LED at the center because of the very limited space.
The black hexagonal part is the 100uH inductor and the yellow one is the 22uF capacitor.
Following is the light output, left is the Solitaire mod, right is the ARC AAA.
[I annot post the image here ! Will try again.]
The output is lower than the ARC AAA, because :
1. The ARC LED is a Nichia LED, mine is a no-brand.
2. I only have the SA57255-33, 3.3V version. I can make a higher output if I get a SA57255-36, 3.6V version. It was out of stock from my office before I started my X’mas holiday to make this mod.
3. The LED position is not at the center, the head block some of the light. The ARC AAA has a good reflector on the head.
I am a good electronic engineer but not good at mechanic. The assembly is quite urgy, the head can marginally be screwed on the body and easily drop out when unscrewed to turn on. However I am very satisfied with the electrical performance.
Measurement :
(V) (mA) (V) (mW)
Vin Iin Vled Pin
0.6 217 3.103 130
0.7 301 3.181 211
0.8 291 3.256 233
0.9 256 3.258 230
1.0 229 3.259 229
1.1 206 3.261 227
1.2 87 3.262 224
1.3 171 3.264 222
1.4 157 3.265 220
1.5 145 3.266 218
1.6 134 3.267 214
[I annot post the image here ! Will try again.]
It provides very good regulation, means constant output, from 0.8V and up. Below 0.8V, it is out of regulation and the LED dims as voltage drop. ARC refers this as moon mode. This circuit can still provide light output when voltage drops to 0.1V !!!
Very amazing. Of course, it needs to start up at >0.85V first.
From above curve, the Iin (Input current) increases to compensate the lower voltage. This is the typical performance of a true regulation circuit, which is not found from the ARC AAA. The power input is slightly higher at lower voltage because of lower efficiency at lower voltage.
I have measured the output current (thus the efficiency) by in series a 10ohm resistor with the LED. The efficiency is 76% at 0.6V and increases to 85% at 1.6V. Very good performance !!!
I did not list out the detail measurement here, because the output level is different between with and without this resistor.
Conclusions
This mod is proved to be very efficient and well performing. I just cannot make a good housing for it. Hope that ARC can make the ARC AAA/AA in this way. A 1W Lexeon on 1xAA with full regulation is what I am looking for. This will be my next project after find a good housing from the market.
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB31&Number=398763&fpart=&PHPSESSID=
It should only be a transistor oscillation circuit, or at most with another transistor for current limiting. Those circuits can be found from :
http://edusite10.tripod.com/led3/onetran/regulated.htm
I like full regulation, so that I do not need to care whether the battery is new enough to provide full output. And also it can squeeze the last 1% energy of the battery to provide non-dimmed output.
I started my circuit testing using DC-DC step-up IC and eventually reached :
[I annot post the image here ! Will try again.]
The IC SA57255-33 from Philips Semiconductors is a step-up regulator with 3.3V output. Philips also has built-in switching transistor version, SA57250-XX, but the current output is not enough to drive the LED at >30mA. The MOSFET is also from Philips semiconductors, BSH105, a low threshold, surface mount MOSFET.
1N5817 is also from Philips Semiconductors.
Datasheets can be found from Philips Semiconductors website :
http://www.semiconductors.philips.com/pip/SA57255-50GW.html
http://www.semiconductors.philips.com/pip/BSH105.html
http://www.semiconductors.philips.com/pip/PRLL5817.html
PRLL5817 is the surface mount version of 1N5817, both can work.
Following is the assembly :
[I annot post the image here ! Will try again.]
The SA57255 is the tiny IC marked with AEXC, beside is the BSH105. They are mounted at the bottom and the rest are at the top side.
[I annot post the image here ! Will try again.]
It is no way to position the LED at the center because of the very limited space.
The black hexagonal part is the 100uH inductor and the yellow one is the 22uF capacitor.
Following is the light output, left is the Solitaire mod, right is the ARC AAA.
[I annot post the image here ! Will try again.]
The output is lower than the ARC AAA, because :
1. The ARC LED is a Nichia LED, mine is a no-brand.
2. I only have the SA57255-33, 3.3V version. I can make a higher output if I get a SA57255-36, 3.6V version. It was out of stock from my office before I started my X’mas holiday to make this mod.
3. The LED position is not at the center, the head block some of the light. The ARC AAA has a good reflector on the head.
I am a good electronic engineer but not good at mechanic. The assembly is quite urgy, the head can marginally be screwed on the body and easily drop out when unscrewed to turn on. However I am very satisfied with the electrical performance.
Measurement :
(V) (mA) (V) (mW)
Vin Iin Vled Pin
0.6 217 3.103 130
0.7 301 3.181 211
0.8 291 3.256 233
0.9 256 3.258 230
1.0 229 3.259 229
1.1 206 3.261 227
1.2 87 3.262 224
1.3 171 3.264 222
1.4 157 3.265 220
1.5 145 3.266 218
1.6 134 3.267 214
[I annot post the image here ! Will try again.]
It provides very good regulation, means constant output, from 0.8V and up. Below 0.8V, it is out of regulation and the LED dims as voltage drop. ARC refers this as moon mode. This circuit can still provide light output when voltage drops to 0.1V !!!
Very amazing. Of course, it needs to start up at >0.85V first.
From above curve, the Iin (Input current) increases to compensate the lower voltage. This is the typical performance of a true regulation circuit, which is not found from the ARC AAA. The power input is slightly higher at lower voltage because of lower efficiency at lower voltage.
I have measured the output current (thus the efficiency) by in series a 10ohm resistor with the LED. The efficiency is 76% at 0.6V and increases to 85% at 1.6V. Very good performance !!!
I did not list out the detail measurement here, because the output level is different between with and without this resistor.
Conclusions
This mod is proved to be very efficient and well performing. I just cannot make a good housing for it. Hope that ARC can make the ARC AAA/AA in this way. A 1W Lexeon on 1xAA with full regulation is what I am looking for. This will be my next project after find a good housing from the market.
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