NiCd battery charger
Design: K. Walraven
D1
R2
The design of the charger is sim-
120
ilar to that of many commer-
cially available chargers. The
R1
*
charger consists of a mains
adaptor, two resistors and a
5W
K1
light-emitting diode (LED). In
practical use, this kind of
charger is perfectly all right.
zie tekst
BT1
*
Resistor R1 serves two func-
see text
*
tions: it establishes the correct
siehe Text
charging current and it drops *
voir texte
sufficient voltage to light the
*
diode. This means that the LED
lights only when a charging cur-
984005 - 11
rent flows into the battery. The
charging current is about 1/4 of
Battery voltage (V) 1.2 2.4 3.6 4.8 6.0 7.2
the battery capacity, which across R1. Note that the adaptor
allows a slight overcharging, and must be capable of supplying a Minimum voltage (V) 4.7 6.1 7.5 8.9 10.3 11.7
yet the charging cycle is not too current of not less than half the
Adaptor voltage (V) 4.5 6.0 7.5 9.0 12 12
long (4 5 hours). battery capacity.
Value of R1 (theoretical) ( ) 12.4 12.8 13.2 13.6 20 14.4
The value of the resistors The value of R1 in ohms is
E12 value of R1 ( ) 15 15 15 15 22 15
may be calculated as follows, for equal to 3.3 divided by 1/4 of
Value of R2 ( ) 120 120 120 120 240 120
which the nominal e.m.f. and the battery capacity. The value
the capacity of the battery must of the resistors for various bat-
be known. tery voltages is given in the capacity, the theoretical value of if a 6 V battery with a nominal
Adjust the output of the Table. The battery capacity is R1 in the table must be divided capacity of 600 mAh is to be
mains adaptor to 1.17 times the taken as 1 Ah. The rating of R1 by the battery capacity. Its charged, the value of R1 must be
nominal battery voltage plus should be 5 W. If the battery to actual value is the nearest one 20/0.6 = 33 .
3.3 V, which is the potential be charged has a different in the E12 series. For instance, [984005]
6-channel running light
Design: L. v/d Heeden
9V
The circuit of the running light
20mA
comprises two integrated cir-
cuits (ICs), a resistor, a capac- D3
S1
itor and seven light-emitting
16
D4
diodes (LEDs), Decade scaler
R1
3
S2
0
IC2 ensures that the LEDs light
2
CTRDIV10/
1 D5
sequentially. The rate at which DEC
4
2
this happens is determined by 4 8
7
3 D6
IC2
R
the clock at pin 14. 7 10
4
DIS
4017
1
The clock is generated by
5 D1
IC1
2 3 14 5
IC1, which is arranged as an T R
OUT 6
&
555
+
13 6
astable multivibrator. Its fre- 7 D2
(TLC555)
6 9
THR 8
quency is determined by
CV 15 11
CT=0 9
R1-C1.
5 1
12
CTe" 5
C1
The touch switch, consisting
of two small metal disks is
8
100n
optional. When switch S1 is in
position  off , the circuit may be
actuated by the touch switch. By
984008 - 11
the way, this enables the circuit
to be used as an electronic die
(in which case the LEDs have to The running light is powered tor. It draws a current not
be numbered from 1 to 6). by a 9 V battery or mains adap- exceeding 20 mA. [984008]
Elektor Electronics 7-8/98
92
051
052
2M2