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The Ol’ Timer: an alphanumeric clock with old-fashioned time Are you tired of looking at those boring digital clocks or at those drab looking old tickers hang­ ing on the wall? Then grab onto this old-time clock using newfan­gled technology. By ANTHONY NIXON There have been all sorts of clocks designed over the years but none actually show you the time in its most basic form – the way you think it. But now you can build the Ol’ Timer. It shows you the time just the way we all used to say it and think it and no doubt still do. It’s easy to read and can be used 20  Silicon Chip as a teach­ing aid for those people who find it difficult to understand the usual types of clocks. To show how different this clock is, let’s give a few exam­ ples of its time displays. At 12.00 AM it displays “MIDNIGHT”; at 1:15, it shows “1/4 PAST 1”; at 12.00 PM, it shows “NOON”; at 3:35, it shows “25 TO 4” and so on. In other words, it displays the time in more or less the same way as you would think it or say it. Some of the photos in this article give further examples of its time displays. Note that it will also display time in stan­dard digital format if you want it to. To provide this alphanumeric display of time, the circuit uses eight LED dot matrix (5 dots across by 7 dots vertically) displays. These displays are driven in multiplex fashion by a microcontroller to keep the circuit complexity to a minimum. Apart from ol’ time telling, this R13 220  R14 10k B D2 1N914 E 1 RTCC Q2 BC557 C 28 MCLR RA0 RB7 17 2 8 SB CLK BUZZER RA3 9 R8 10k C Q3 BC548 B R5 10k A S2 20 RC2 19 RC1 18 RC0 RB2 12 RB3 13 RB4 14 RB5 15 R11 150k R12 39k R9 100k RB6 16 3 4 LDR1 2 13 5 IC6 2003 6 7 11 DISPLAYS 10 15 2 1 16 +5V 7 D1 1N4001 6 24 RC6 4 RC7 27 X1 8MHz C1 18pF 12 8 IC8 741 R10 100k 7 14 +5V 3 2 8 SB CLK 14 1 IC5 SA 74HC164 9 CLR A B C D E F G H C8 3 4 5 6 10 11 12 13 0.1 R17-56 40x130W RB0 10 RB1 11 R7 10k FROM PIN13 IC4 TO PIN2 IC2 9 1 SA CLR A B C D E F G H 3 4 5 6 10 11 12 13 IC7 PIC16C57 B S3 R6 10k 14 IC1 74HC164 7 E MODE S1 +5V 6 R15 33k ZD1 3.3V C4 0.1 C3 0.1 2 R3 2.2k 26 C2 18pF LED1 ALARM  R16 10k B 21 RC3 22 R1 RC4 470k 23 RC5 RA1 SP1 BZW04P13B 7 OSC1 OSC2 RA2 8 R2 2.2k 25 RELAY1 4 R4 2.2k LED2 PM OL' TIMER B C Q1 BC548 E Circuit description The circuit is based on the PIC 16C57 microcontroller which has 2Kb of ROM, 72 bytes of usable RAM and 20 I/O ports. It takes care of all of the clock functions which include display multi­plexing, key scans, display dimming, timing, LED indication and relay and buzzer control. The chip is clocked using an 8MHz crystal which is divided by four internally to provide an instruction E B VIEWED FROM BELOW E C A K I GO A 7.5V WO4 240VAC  N IN 7V E Fig.1: the heart of the circuit is the PIC57 microcontroller which is programmed to drive the LED dot matrix displays. Serial data is fed from pin 17 of IC7 & converted to 40-bit wide words (ie, parallel data) by shift registers IC1-IC5. Note that IC2, IC3 & IC4 are not shown since they are cascaded between IC1 & IC5. clock features date, alarm, 99 minute timer, buzzer or relay control, daylight saving, digital format, sleep timer, leap year indicator, display dimming and power failure indication. C cycle time of 500 nanoseconds. This is further divided by 64 with a programmable prescaler to give a clock of 31.25kHz. This is used to increment an internal Real Time Clock Counter (RTCC) which, when initialised to 206, will overflow to 0 in 1.6ms. This is used as a timebase to update the display. This frequency is further divided by four for key scanning and other timing functions. Every 1.6ms, serial information from the display buffer inside the micro­ controller is sent from pin 17 of IC7 to the serial input of IC1, the first of five 8-bit serial to parallel converters which are cascaded to receive 40 bits of information. These ICs are actually C9 470 25VW REG1 7805 GND OUT +5V C10 47 16VW 74HC164 serial in/parallel out shift registers. Note that only IC1 and IC5 of this 40-bit converter string are shown on the circuit diagram but you will see that pin 13 of IC1 goes to pin 2 of IC2 and hence pin 13 of IC2 goes to pin 2 of IC3 and so on. What happens is that a 40-bit serial data stream is sent out from pin 17 of IC7 and as it is being sent out, it is clocked through the registers by a clock signal from pin 6 of IC7 to the register clock inputs (pin 8). Thus, the 40-bit serial data stream is converted to a 40-bit wide word which appears on the Q outputs of the registers. These drive the column inputs of the eight dot-matrix displays via 130Ω resistors. The seven row inputs of the dot matrix displays are driven by IC6, a November 1994  21 RELAY 1 10k BROWN BLUE D1 Q1 SP1 TERMINAL BLOCK ACTIVE BROWN NEUTRAL BLUE EARTH GREENYELLOW 1 2.2k 1 MAINS CORD 2.2k 1 2.2k MAINS CABLE CLAMP 1 40x130W X1 18pF 18pF 10k DISPLAY6 470k IC7 16C57 0.1 10k IC4 74HC164 10k 1 Q2 10k 10k 0.1 S1 DISPLAY7 IC6 2003 DISPLAY1 IC1 74HC164 7.5VAC 1 DISPLAY2 0.1 0.1 IC3 74HC164 33k POWER TRANSFORMER DISPLAY3 IC2 74HC164 DISPLAY5 220  0.1 100k D2 ZD1 Fig.2: the wiring diagram shows both patterns for the PC board. The dark grey pattern is on the underside while the light grey pattern is on top of the board. Take care to ensure that all parts are correctly oriented. 1 K LDR1 K Q3 A 39k BUZZER 7VAC 470uF REG1 O G 1 WO4 LED2 A LED1 47uF 100k IC8 741 S2 0.1 DISPLAY8 IC5 74HC164 150k 22  Silicon Chip DISPLAY4 S3 This is the view inside the clock with the rear panel (case lid) removed. Make sure that the mains cord is securely clamped & note that the Earth lead (green/ yellow) must be soldered to a solder lug that’s secured by one of the transformer mounting screws. The Active & Neutral leads go to a 2-way terminal block. 7-way Darlington array which is driven in turn by seven output lines from the microcontroller. The displays are multi­plexed in such a way that each time a row is enabled via IC6, the column lines from ICs 1-5 are updated. Thus, the LEDs are driven with a duty cycle of 14%; ie, 1.6ms on and 9.6ms off. By way of further explanation, the LED dot matrix displays are common cathode types with the cathodes of each row being pulled to 0V by Darlington transistors in IC6 and the anodes driven by the registers, IC1-IC5. In other words, the registers “source” current into the displays while IC6 sinks the current. Actual clock timing is derived from the 50Hz AC mains sup­ply. This is supplied from the 7.5V winding of the transformer via a 470kΩ resistor. A transient suppressor is connected across the output from this winding to shunt any spike voltages and thus protect IC7. The AC signal is clamped to the positive and 0V rails because of the internal protection diodes fitted to all I/O pins on the chip. These are capable of withstanding several milli­ amps of current, much more than can be supplied via the 470kΩ resistor. Transistor Q2 forms a “Brown Out” protection circuit. When the supply voltage falls below about 4V, this transistor will cease to conduct and the master clear (MCLR), pin 28, will be pulled low via the 33kΩ resistor, causing the chip to reset. The chip has internal circuitry which controls all of its resetting functions. Display dimming is achieved using IC8, a 741 op amp which has a light dependent resistor connected to its pin 3. When the ambient light level drops below a certain level, IC8’s RESISTOR COLOUR CODES ❏ No. ❏   1 ❏   1 ❏   2 ❏   1 ❏   1 ❏   6 ❏   3 ❏   1 ❏ 40 Value 470kΩ 150kΩ 100kΩ 39kΩ 33kΩ 10kΩ 2.2kΩ 220Ω 130Ω 4-Band Code (1%) yellow violet yellow brown brown green yellow brown brown black yellow brown orange white orange brown orange orange orange brown brown black orange brown red red red brown red red brown brown brown orange brown brown 5-Band Code (1%) yellow violet black orange brown brown green black orange brown brown black black orange brown orange white black red brown orange orange black red brown brown black black red brown red red black brown brown red red black black brown brown orange black black brown November 1994  23 depending on the display requirements and ranges from around 30mA to 200mA. Mechanical details The displays are mounted on the underside of the PC board & are attached to it using individual pin sockets (see text). The LDR enables dimming of the display at night while the two LEDs in­dicate the alarm mode & PM. output swings high. When the micro­ controller detects this high, it cuts the duty cycle of the displays to 50% of their normal operation, thus dimming the display. The 150kΩ resistor from pin 6 to pin 3 provides some hysteresis and stops IC8’s output from oscillating when the light level is at the changeover point. The three pushbutton switches are read via inputs RC0-RC2 (pins 18, 19 & 20) and are debounced using software delays. IC7’s outputs RA1 and RA2 drive the PM and ALARM LEDs directly, while outputs RA3 and RC7 drive the buzzer and relay via Q3 and Q1 respectively. Average current consumption varies The Ol’ Timer clock is housed in a standard black plastic jiffy box measuring 196 x 112 x 65mm. The box is stood on its side and has a red Perspex window for the dot matrix displays. All the circuitry is mounted on a double-sided PC board measuring 145 x 90mm. The PC board doesn’t have plated through holes but uses IC pin sockets soldered to the board to complete the connections. These are used to mount the eight dot matrix displays on the underside of the board. The easiest way to solder these pins neatly is to place them on a 6-pin IC strip, then place them into the board holes and solder them. When the strip is removed, the pins are left looking tidy and with the correct spacing. These pins can be knocked out from 2 x 64 machine pin IC sockets. Some pins on the IC sockets don’t pass through the circuit board but are bent at right angles and soldered to the component side of the board. The track layout has been designed for this purpose. A quick method of knocking these PARTS LIST 1 double-sided PC board, 181 x 112mm 1 plastic Jiffy case with plastic lid, 196 x 113 x 65mm 1 transformer 7V CT + 7.5V; DSE Cat. M-2824 1 5V SPDT relay; Ritronics Cat. S-14100 1 piezoelectric buzzer; Jaycar Cat. AB-3460 3 momentary contact pushbutton switches; Jaycar Cat. SP-0710 1 8MHz crystal 1 piece of red Perspex, 180 x 95mm 2 rubber feet 1 3-core mains cord & plug 1 2 way insulated terminal block 1 cable clamp to suit mains cord 1 solder lug 2 10mm PCB spacers 13 PC stakes 96 IC pins (from 2 x 64 machine pin IC sockets) 24  Silicon Chip IC sockets 5 14-pin 1 16-pin 1 8-pin 1 28-pin Semiconductors 5 74HC164 8-bit shift registers (IC1-5) 1 2003 Darlington array (IC6) 1 16C57 preprogrammed microcontroller (IC7) 1 741 op amp (IC8) 1 7805 5V regulator (REG1) 2 BC548 transistors (Q1,Q3) 1 BC557 transistor (Q2) 1 3.3V 400mW zener diode (ZD1) 1 1N4001 diode (D1) 1 1N914 diode (D2) 1 WO4 bridge rectifier 8 7 x 5 Sun MUR18A dot-matrix column anode LED displays; C & K Elec­tronics 1 light dependent resistor; Jaycar Cat. RD-3480 (LDR1) 1 BZW04P13B transient suppressor; Farnell Electronics (SP1) 2 3mm red LEDs (LED1,2) Capacitors 1 470µF 25VW PC electrolytic 1 47µF 16VW PC electrolytic 6 0.1µF 63VW MKT polyester 2 18pF ceramic Resistors (0.25W 1%) 1 470kΩ 6 10kΩ 1 150kΩ 3 2.2kΩ 2 100kΩ 1 220Ω 1 39kΩ 40 130Ω 1 33kΩ Miscellaneous Tinned copper wire, insulated hookup wire, machine screws, nuts & washers, right-angle mounting bracket for piezo buzzer, heatshrink tubing. The three pushbuttons on the rear of the case allow selection of the various operating modes, time setting, alarm setting & so on. This close-up view shows the method of mounting the LED matrix displays. Each display is plugged into 12 machined IC pins. Take care to ensure that the displays are correctly oriented (the pins are polarised) The piezo buzzer is mounted on a small L-shaped metal bracket on the side of the case. The OL’ TIMER is an old-fashioned clock in the way it shows the time, although old-fashioned clocks never did it like this. It uses LED dot matrix displays driven by a PIC57 microcon­troller. pins out of the socket carrier is as follows. First, a piece of round steel, 3mm in diameter, is cut to a length of 25mm or so. This done, drill a 1mm hole into one end, 5mm deep. This tool is then placed over the pin and tapped lightly with a small hammer. No pins are damaged in this way. It’s a neat idea to create a pseudo through-plated hole when a socket is required. Board assembly In other respects, the PC board is quite straightforward to assemble. Sockets for the ICs are listed in the parts list and are recommended. Note that six 0.1µF capacitors are shown in the parts list but only three are shown on the circuit. The other three are associated with shift registers IC2, IC3 and IC4 which are also not on the circuit, as noted above. Note that in most cases the resistors are soldered only on the underside of the board. The 40 130Ω resistors associated with the five shift register These are just three more displays from the OL’ TIMER. It can display the date & conventional digital time as well. November 1994  25 Operating Instructions Using the Ol’ Timer clock is fairly straight­forward. Just use the MODE key to select a function and then use either the A or B keys to change the settings. After changing a setting or a function, the clock will revert back to the selected time display if no keys are pressed for three seconds. It can also be cycled back using the MODE key. If button A or B is held down, that button’s function will be repeated slowly at first and then at a faster rate. Setting the time & alarm: use the MODE key to select the time setting function. Then by pressing either A or B, the hours or minutes will be incremented respectively. Setting the alarm time is accomplished in the same manner. Setting the date: use the MODE key to select the date display and press A to select either the day, month or year. Then press B to increment the selection. If the year is a leap year, the LED at the lower right-hand corner of the display will light when the complete date is being displayed. Using the 99 minute timer: select ICs are stood on end to save space. Take careful note of the orientation and polarity of the ICs, diodes, transistors and electrolytic capacitors. PC pins should be installed for all the off-board connections. Once the board is complete, you will need to make a cutout in the base of the box for the display and drill other holes that are required. The rectangular hole for the display measures 115 x 20mm and will need to be positioned precisely to line up with the dot matrix displays. The circuit board is secured using two 10mm tapper spacers fas- the timer display with the MODE switch. The number displayed indicates the time in minutes for the timer to count down from, after which the buzzer will sound or the relay will operate. This time can be increased by pressing B or decreased by pressing A. Use MODE to set the output configuration for the timer. If BUZZER is selected, then it will sound for five seconds after the timer counts down to zero. If the relay is selected, it can either operate ‘While’ (indicated by “RELAY=W”) the timer is counting down or ‘After’ (indicated by “RELAY=A”) it has finished. Press A to select either BUZZER or RELAY. If RELAY is selected, press B to chose the ‘While’ or ‘After’ option. The relay can be turned off at any time by pressing B while the display is showing normal time. Using the alarm: after the alarm time has been set and the dis­play is showing normal time, pushing button B sets the alarm. The ALARM LED now lights. When the normal time equals the alarm time the buzzer will beep for 1 hour. If the A button tened to the base of the jiffy box by two countersunk screws. These screws are concealed by the red Perspex which becomes the front panel of the clock. The Perspex was attached to the box by a pin in each corner and these are secured inside the box with 5-minute epoxy adhesive. Note the details for connection of the mains cord. This should be anchored to the side of the case as shown in the wiring diagram and the Active and Neutral wires terminated to a 2-way insulated terminal block which Where to buy the microcontroller The programmed PIC57 microcontroller is only available from the author, Anthony Nixon, who can also supply the double-sided PC board and a set of machine pins (see text). Pricing is as follows: (1). PIC57 programmed microcontroller, $30.00 including p&p; (2). PIC57 plus PC board and set of machine pins, $47.00 including p&p. Send cheque or postal money orders to Anthony Nixon, 20 Eramosa Road East, Somerville, Vic 3912. 26  Silicon Chip is pushed, the buzzer will be silenced for 10 minutes and then resound. The ALARM LED flashes while the ‘Sleep’ function is operating. This function can be continued for 1 hour. If A is pressed while the sleep function is operating, then the buzzer will stop until the two times match again. If B is pressed, the buzzer will stop, the alarm will be disabled and the ALARM LED will extinguish. Setting daylight saving time: press MODE until ‘DLS = ’ is displayed. Daylight saving is enabled if ‘DLS = Y’ is displayed, or disabled if ‘DLS = N’ is displayed. When enabled, the normal time is increased by one hour and decreased by one hour when disabled. All dates are updated in the process. Use A to en­able/disable. Display format: the last function selects the display format. Press A to alternate between OL’ TIME and DIGITAL formats. Power failure indication: when the clock is first turned on or if there has been a power failure, the display will flash “OL’ TIMER” on and off. You then must reset all time and alarm settings. also terminates the primary wind­ings of the transformer. The Earth wire of the mains cord is terminated at a solder lug which is secured to one of the transformer’s mounting lugs. A small bracket will need to be made up to mount the piezo buzzer, as shown in the photos. Ventilation holes should be drilled in the rear panel, as well as the holes for the three pushbutton switches and the cord entry. Initial tests When all assembly work is complete, carefully check your work and then apply power. The display should flash ‘OL TIMER’ on and off. Check the 5V supply rail from the regulator. If any LEDs fail to light , it is quite easy to determine which row and column they are in and then check for open circuits in the board connections. Assuming that all is well, the correct time can now be set as detail­ed in the SC operating instructions.