Transcript
RL-9V 200W GND T1 BC548
2P4M
+9V
S4
RESET
R25 2K
R26 100W
VERSATILE DIGITAL TIMER EM
32
SECOND DISPLAY INPUT
10 MINS-f
10
10 MINS-g
11
10 MINS-a&d
12
29
VDD
10 MINS-b
13
28
VSS
10 MINS-e
14
27
SLEEP OUTPUT
10 MINS-c
15
26
ALARM “OFF” INPUT
MM5387
31
ALARM DISPLAY INPUT
30
SLEEP DISPLAY INPUT
MINS-f
16
25
ALARM OUTPUT
MINS-g
17
24
SNOOZE INPUT
MINS-a
18
23
OUTPUT COMMON SOURCE
MINS-b
19
22
MINS - c
MINS-e
20
21
MINS -d
Fig. 2: Pin configuration of IC MM5387
S1
R24
34
S2 33 35
23
29
36
Fig. 3: Circuit Diagram of Digital Timer
9
XTAL 4.9152 MHz
SLOW SET INPUT
HRS-e
8
FAST SET INPUT
33
15 13
34
8
8
7
HRS-c
12
HRS-d
C2 47P
50/60Hz INPUT
5
50/60Hz SELECT
35
11
36
6
1
5
14
HRS-a HRS-b
CD4060 3
MC
CD4017
12/24 HR SELECT
37
10
38
4
16
3
16
HRS-f HRS-g
C1 47P
COLON (1Hz)
C4 0.22µ
PM OUTPUT
39
C3 0.22µ
40
2
XTAL
1
3.3M
AM OUTPUT 10 HRS. b&C
28
b
DUAL-IN-LINE PACKAGE
R2
2
c
Fig. 1: Block Diagram of Digital Timer
DIS1
Regulated +9V GND
Power Supply
25
f gabedc f g
a & d
b e c
DIS3
Relay Driver & Latch
R3
Display Unit
f gabdc e
Central Control Counters and Display Controller
50Hz Clock Pulse Generator
DIS2
his digital timer can be easily constructed using readily available ICs and components. This timer can be used to automatically switch ON/OFF any electronic or electric equipment after a pre-programmed time period, variable between a few seconds to 24 hours, with high accuracy. This timer displays the timings on a digital readout display in the
dp
T
DIS4
Narendra Sharma
IC3 MM5387
R23
TESTED
3 4 5 6 7 8 9 39 10 11 1213 14 15 16171819202122 S3 31
DEV CHARAN
EMNS003
Fig. 4: Actual - size, solder-side PCB layout for the Digital Timer RL
S2
S3
D5
C3
C2 IC1
E B C
T1
S1
XTAL C1
SCR
R1
R25
IC4
C6
R24
C4
IC3 IC2
C5
EMNS003 D2
D4
D1
D3
R2
DIS1 12V AC
Fig. 5: Component layout for the PCB.
R23
DIS2
DIS3
DIS4
S4
form of numeric characters and can be set using a pair of push-toon switches. The block diagram of the timer is shown in Fig.1. The clock chip, MM5387, forms the heart of the circuit. Pin details of IC MM5387 are shown in Fig.2. IC MM5387 is a 40-pin dual-in-line package IC operated on 8V to 26V DC. It gets the positive DC supply voltage at its pin 28. Pin 29 is grounded. Only the timer section of this chip is used here. The timekeeping function of the clock chip (IC3) operates off a 50 Hz or 60 Hz input. Operation at 50 Hz is set by connecting pin 36 (50/60 Hz SELECT) of the clock IC to Vss. To get a 50 Hz clock pulse, we use the decade counter/divider CD4017 BE (IC2) and the 14-stage binary counter CD4060 (IC1) together with a 4.9152 MHz crystal (XTAL). The IC CD4060 divides the crystal frequency of 4.9152 MHz by 16,384 and produces a 300 Hz clock pulse, which is further divided by 6 using the CD4017 BE (IC2) to get the required 50 Hz pulse. These pulses are fed to the central control counter built around IC3. The timer output is fed to the gate of the SCR that is used to drive the relay. IC3
displays the timing on the 7segment displays DIS1 to DIS4. The IC3 has the option to select 24-hour format, we have designed it to display hours in 12-hour format only. By leaving pin 38 (12/24 HR SELECT) unconnected, the tens digit of the hours display can be set to provide a 12-hour display format. The 1Hz output from pin 39 of IC3 is used to blink colon. The circuit diagram is shown in Fig. 3.
Setting Up The Clock: After soldering is done, place the ICs in the respective bases. Now set the clock to display the real time using switches S2 and S3. Now depress the S1; displays will now show the
timer settings with reference to the preset actual time. S3 should be used to make fast settings. S2 should be used to make fine settings. Press S4 to reset the relay, if energized.
Construction: The circuit can be assembled on a Vero board or single sided PCB. Sockets should be used for all ICs. The displays may be soldered directly on to the PCB. The complete circuit may be housed in a suitable cabinet with S1, S2, S3 and S4 on the front panel along with displays. This timer would be found indispensable in many industrial or domestic field of application.
Components List Semiconductors: IC1 CD4060 14-Stage binary counter IC2 CD4017 Decade counter/divider IC3 MM5387 Clock chip IC4 7809, regulator T1 BC548 npn transistor SCR 2P4M D1 1N4001rectifier diode D2-D5 1N4001, rectifier Resistors: R1 3.3MW R2-R24 560 W R25 2KW R26 100 W Capacitors: C1-C2 47pF C3-C4 0.22µF ceramic disk C5 1000µF / 25V Electrolytic C6 0.1µF ceramic disk Miscellaneous: XTAL 4.9152MHz Crystal DIS1- DIS4 LT543 Common Cathode 7-segment display X1 230V AC primary 0-12V, 500 mA Transformer RL Relay 9V, 200W S1-S4 push-to-on tactile switch IC bases
