SamGordon Digital Clock

1. Main Clock

SG_clock_main.gif (25734 bytes)

With pleasure the lot of friends of digital clocks that use discernible components, will see this circuit. It's a clock, with 12hour clue, little simpler in the manufacture from the SamClock. Itís a designing that became from the friend George Kordogiannis in 1990, which was modified and corrected in enough points by my, until it reach in the current form. Most completed that uses is TTL, apart from the IC9 until IC13, that is CMOS, that they have the faculty to drive display Common Cathode. In the place of 4511 [6], can be placed the 74LS47 [7], which can drive display Common Anode. In this case it will be supposed they are changed display Common Cathode in the Fig.2, with Common Anode, changing of course and connection in DIS1 until DIS5 display. In the SL10, come in the pulses frequ. 1HZ [fig.3-4], which then are divided successively by the IC2 until IC4 and the round this gates, ensuring the clue of time, in Hours, Minutes and Seconds. The Q1 drive display the tens of hours [Fig.2], but only the B and C Led of DIS6 display [Fig.2], ensuring clue 1, when needs the clue of hours itís 10, 11, 12. The voltages that supply the circuit are divided in two lines. The voltage +5VA supplies all IC except the IC9 until IC13 and is supplied with voltage in case of break of network voltage, on the contrary the voltage of +5VB, supplies only the IC9 until IC13 and display and is interrupted in case of interruption of network voltage, ensuring thus economy in battery [Fig.5]. If the Q1 is hot, can be placed on a small heatsink

Main Clock Part List

R1=2.2Kohm 1/4W 5% IC5-7=74HC32    [3] Q1=BD139 on Heatsink
R2......R38=470ohm 1/4W 5% IC6=74HC08       [4] SL1....SL5=7 pin connector
IC1-4=74HC390 [1] IC8=74HC04       [5] SL6-7=2 pin connector
IC2-3=74HC92   [2] IC9....IC13=4511 [6] or [74LS47] [7] SL8=3 pin connector
[1] 74HC390 or 74LS390= Dual 4bit Decade and Binary COUNTER [5] 74HC04 or 74LS04=  Hex inverter
[2] 74HC92 or 74LS92=  Decade, divide by 12 and Binary COUNTER [6] 4511= BCD to 7-segment Latch/Decoder/Driver for CC Display*
[3] 74HC32 or 74LS32=  Quad 2-input OR gate [7] 74LS47=   BCD to 7-segment Decoder/Driver for CA Display*
[4] 74HC08 or 74LS08=  Quad 2-input AND gate CC=Common Cathode    CA=Common Anode

2. Display

SG_clock_display.gif (13544 bytes)

In the Fig.2, exist the clue display. As he is drawn, the drive of display becomes when in the place of IC9Ö.IC13, are used the 4511 [6]. Thus DIS1 until DIS5, are Common Cathode and DIS6 of itís in every case Common Anode. If are used the 74LS47 [7], then the DIS1ÖDIS5 it should they are changed with Common Anode, the pins 1 and 6 of DIS1 until DIS5, they go to the line of + 5VB and the R39-40, in the line of 0V. The R39-40, turn on the dot in the DIS3 and DIS5, so that exist a divide the displays that shows the Hours, Minutes and Seconds.

Display Part List

R39-40=220ohm 1/2W 5% DIS6=20 mm Led Display Common Anode SL10.....SL4=7 pin connector
DIS1-5=20 mm Led Display Common Cathode* SL9-15=2 pin connector *See Text
*DIS1-5=20 mm Led Display Common Cathode with driver 4511 [6] *DIS1-5=20 mm Led Display Common Cathode with driver 74LS47 [7]

3. Time Base [A Choise]

SG_clock_time_A.gif (14243 bytes)

For the production of pulses 1HZ that constitutes also the base of time for the clock exist two proposals. And the two are based on the same beginning of operation. A oscillator with crystal in high oscillation frequency and then division of this frequency so that we take in the end the frequency 1HZ. This process us ensure very big precision and stability in the produced pulses. The oscillator in the Fig.3 is based on a crystal in frequency 1MHZ and then in frequency division of 1MHZ in stages via 10, from the IC15 until IC17. The gates IC18A-B until IC19A-B do not participate immediately in the operation, only that indirectly when are pressed the switches S1 or S2, which us allow the regulation of time. Pressing S1 [Super Fast] and S2 [Fast], are released pulses of frequency 10KHZ and 100HZ respectively, making the clue in display run very fast facilitating in the regulation of TIME, in short time interval. The supply of circuit becomes from the line + 5VA, ensuring thus the operation of oscillator, even in interruption of network voltage, supplied from the battery.

Time Base [A] Part List

R41-42=470ohm IC14=74HC04* IC19=74HC08*
R43-44=10Kohm IC15-16-17=74HC390* S1-2=Push Button normal open
CSL1=1MHZ Crystal IC18=74HC32* *See component list in Main Clock

4. Time Base [B Choise]

SG_clock_time_B.gif (12199 bytes)

In the Fig.4, exist a proposal that is based on the same beginning of operation as on the Fig.3, but exist a crystal with higher operation frequency 3.2768MHz, with successive division, in order that in the end we take frequency 1HZ, in exit SL19. With variable capacitor C3 we can regulate thus the oscillator in order that in point TEST we take pulses of frequency 204800HZ. With switches S1 [Fast] and S2 [Super Fast] we regulate the display clue in process of regulation, with frequency 10HZ and 100HZ, respectively, making the clue in display to run very fast, facilitating in the regulation of time in short time interval. The supply of circuit becomes from the line + 5VA, ensuring thus the operation of oscillator, even in interruption of network voltage, supplied from the battery. The solution of mechanic switches, was preferred for simplicity reasons.

Time Base [B] Part List

R45=10Mohm IC20=4060          [8] CSL2=3.2768 MHZ crystal
C1-2=22pF ceramic IC21-22=4017 [9] S3-4=Push switch recrudescent
C3=22pF trimmed capacitor IC23=4013         [10]  
[8] 4060=14-stage Ripple Carry Binary Counter/Divider and Oscillator [10] 4013=dual D Flip-Flop
[9] 4017=Hex "D"-type Flip-Flop  

5. Power Supply for SamGordon Clock

SG_clock_supply.gif (15085 bytes)

In the Fig.5, exist the power supply that gives essential voltages for the operation of circuit, the battery charge and the transfer in the battery when exist interruption of network supply. The regulated from the TR1, voltage regulator IC24 is regulated so that it gives in his output + 5V [P1]. With this voltage function the circuit. Second regulator IC25, is regulated by the TR2, so that it gives in point [P2] voltage + 6.9V, with which becomes the battery charge of lead acid 6V/1Ah, which is connected in the SL17. In the case of interruption of network supply then turn off very fast the RL1 and his contacts goes to the place that is drawn in the Fig.5. The voltage line + 5VA is connected via the D5-6 in battery 6V, on the contrary the line + 5VB is led to the 0V and the Display stops they show. The remainder parts of circuit working continue and they measure the time, until changes the situation therefore display will work once again showing regularly the time. In the duration of contacts transfer from a situation in other the supply of circuit becomes from the C17. The IC24-25 should be placed on a good Heatsink and the regulations the TR1-2 he becomes without are connected the circuit in the supply output and the battery it is except.

Power Supply Part List

R46=1.2Kohm 2W C16=1uF 25V B2=4 X 1N4001
R47-49=270ohm C17=1000uF 16V RL1=12VDC 2X2 [10A]
R48= D1=12V 1W zener TR1-2=4.7Kohm trimmer
C6=2200uF 25V D2-3=1N4002 SL17-18=2 pin connector
C7-9-10-13-15=100nF 100V MKT D4-5-6=1N5408 SL16=3 pin connector
C8-12-14=10uF 25V IC24-25=LM317 on Heatsink BATT=AKKU battery 6V/1.2Ah
C11=47uF 25V B1=100V 3A Bridge Rectifier  

6. Block Diagram

SG_clock_block.gif (11622 bytes)

7.  Connection for Display common Anode or Cathode

SG_clock_display_conn.gif (10601 bytes)

In the Fig.6, exist the Block diagram of basic connections between the various inputs and outputs. In the Fig.7, exist the connectin for Display Common Anode and Common Cathode. Soon, as I will find time I will draw also the printed circuit, which I will also give. In those that him will make, I wish good success.


Sam Electronic Circuits 6/02