■ WITH RUSSELL KINCAID
In this column, I answer questions about all
aspects of electronics, including computer hardware,
software, circuits, electronic theory, troubleshooting,
and anything else of interest to the hobbyist. Feel
free to participate with your questions, comments,
or suggestions. Send all questions and comments to:
Join us as we delve into the
basics of electronics as applied
to every day problems, like:
Solar Controller ✓
● Lithium-Ion Battery Charger
High Power LED Flasher
( http://melabs.com). Check it out.
QI’d like to know what PIC compiler you used to complete the LED flasher project that was published
in the August ‘ 11 issue.
— Sassan Amjadi
AI used the PICBASIC PRO compiler from icroEngineering Labs and MicroCode Studio from
Mecanique — it’s a program editor
and Windows interface that greatly
simplifies the programming chore.
Microcode Studio is bundled with
the free version of PICbasic
QI picked up an interesting LED flashlight at the 99 Cent Store. It is housed in rubber, uses only two AA
cells, and is very bright. I took it apart
and inside are three white LEDs, one
47 ohm resistor, and what I presume
is an IC. It is in a three-lead TO-92
package. One lead goes to battery
negative; the center lead goes to
positive. The third lead goes to three
LEDs in parallel, and the 47 ohm
resistor goes from the LEDs to battery
positive. The LEDs are connected to the
negative rail. If you measure the LEDs,
there is about 2. 5 VDC across them.
On a scope, however, there is a 4.5V
p-p distorted square wave. The period
is about 2. 6 µS, so the frequency is
about 385 kHz. The IC is marked N8
10229. I am curious to know what it
is but have been unable to find it
listed in any of the online component
databases. I think the flashlights were
there because they have a strong
odor similar to kerosene, but that will
dissipate in time. They are definitely
well worth a dollar. Would you have
any idea what the device is?
— Bill Lahr
ASince you can’t get more than the supply voltage without an inductor, I suspect that the 47 ohm
resistor is actually an inductor,
possibly 47 mH or 470 mH. The IC
consists of an oscillator and switch
which I have simulated in Figure 1.
The switch charges the inductor
when it is on, then when the switch
turns off, the inductor discharges
through the LEDs. This allows the
circuit to work even when the battery
voltage falls below the turn-on
voltage of the LEDs. It would be a lot
more efficient if the inductor
resistance was not so high, but it was
no doubt a tradeoff for size and cost.
QI’d like to use a 24-IR Illuminator in conjunction with a PIR module (Passive Infra-Red) from www.■ FIGURE 1.