Elektor EPROM, Руководство пользователя

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therefore necessary for the controller to be
aware of the charge remaining in the cell.
This charge is dependant on the battery volt-
age, the discharge current, previous dis-
charge history and cell temperature. In the
torch we simply determine the charge
remaining by measuring the cell voltage
some time (1,000 s) after the light has been
switched off. The discharge characteristics of
a Li-Ion cell are shown in
Figure 2. A feature
of these cells is that when the load is
removed the cell voltage rises slowly (1,000 s
approximately) from the lower curve to the
upper curve. The arrows and numbers on the
same manufacturer can have poorly
matched efficiency values. At the
present time the most efficient white
light LEDs are made by Nichia.
These LEDs specified are only
intended for use by OEMs but it is
possible to find some outlets that
stock them.
Charge indication
An important design feature of the
torch is that the user should never be
left unexpectedly in the dark. It is
GENERAL INTEREST
61 11/2002 Elektor Electronics
012019
T1
C1
C2
C3
D1
D2 D3
D4 D5 D6
D7 D8
IC1
IC2
L1
R1
S2
+
0
S1
T2
012019
Figure 3. The two-part PCB uses
SMD components.
COMPONENTS LIST
Resistor:
R1 = 680
Ω
, SMD size 0805
Capacitors:
C1 = 220nF ceramic, SMD size
0805
C2 = 33
µ
F 20V, SMD size 2220
C3 = 1
µ
F 6.3V, SMD size 1210
Inductor:
L1 = 233
µ
H (100kHz),
ESR = 0.27
Ω
Pot core P9.0x5.0/N26 (A
l
= 250)
with 30.5 turns of 0.22mm dia.
ECW
Semiconductors:
D1= BAT48 or 1N4148
D2-D8 = LED, 5mm, white,
6400mCd (Nichia, NSPW500BS)
(
www.nichia.co.jp/lamp-e.htm ),
available from Conrad
Electronics
T1=BSP308, BSP319
(R
ON
=50m
Ω
)
T2=BS170, BSS138 (R
ON
=5
Ω
)
IC1=PIC12C672 04/SM,
programmed, order code
012019-41
IC2=LM9140-2.5 or TL431
Miscellaneous:
S1,S2 = SMD switch, 1 contact
(Mentor 1254.1007 or
1301.9314 or Omron B3FS-1052
from Farnell)
Battery = Sanyo UR18650 Li-Ion,
1350 mAh (18mm, length =
65mm, weight 40g) or Sanyo
UR18500 Li-Ion, 1100 mAh
(18mm, l = 50mm)