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Recurring Event Reminder REMINDER PERIOD 6, 8, 12 or 24hrs, every week or fortnight LED REMINDER By John Clarke Crook memory? Forgot to feed and water the chooks every day? This simple circuit will remind you to perform any regular task, which needs to be done every few hours, days, weeks or fortnights. It reminds you by flashing a LED, and you can even connect a piezo siren for a more insistent reminder. L et's face it, anyone can forget to do important tasks which occur at regular intervals. Some examples include taking out the garbage bins, taking medication, feeding your pets (and the chooks!) or other similar daily routines. It’s especially suitable for older people who are prone to forget to check things. For example, it could be used to remind them that their pension payments have arrived in their account. Whoopee! Yes, we know that you can set reminders on a smartphone but that's just too much of a hassle for a lot of people. And if it happens to be an event that involves a member of the family, having a centralised method of reminding everyone can streamline the process. This is a simple, low-cost unit which provides a single reminder that can be configured in a variety of ways. If you need multiple reminders, you could build more than one unit – it's certainly cheap enough. Or you could consider our slightly fancier (but specialised) Garbage & 68 Silicon Chip flashes once every 2s, typically for 18hrs or until reset AUDIBLE REMINDER One 10ms chirp per second while the LED is flashing POWER SUPPLY 3V lithium button cell QUIESCENT CURRENT 19µA at 3V, 5.4µA at 2V CURRENT WHEN LED IS FLASHING Recycling Reminder project from the January 2013 issue (siliconchip.com. au/Article/1315). For daily events, the Event Reminder has the option of either one, two, three or four regular alerts throughout the day. In other words, it can provide a reminder every 24, 12, 8 or 6 hours. In weekly or fortnightly mode, it goes off once a week or once a fortnight. When the LED flashes to indicate the event, you can reset it by pressing a switch, but make sure you have fed the chooks! (We're very chookminded in the Silicon Chip office – we like fresh eggs). Having been reset, the Event Reminder will then wait for the set time period before alerting you again. Powered by a 3V button cell, the Event Reminder is easy to set up and we are presenting it as a bare printed circuit board (PCB) to minimise cost. Of course, you can put it in a case if you want to. Circuit description As shown in Fig.1, the circuit is built around an 8-pin PIC12F617 microconAustralia’s electronics magazine 42µA or 300µA together with piezo siren EXPECTED CELL LIFE 1-2 years troller, IC1. It uses its internal 4MHz oscillator to generate the instruction clock but there is also a 32768Hz watch crystal (X1) connected between pins 2 & 3, to run a secondary oscillator for its internal Timer 1 counter. This is used to keep track of the passage of time for the reminders. The two 100pF capacitors at pins 2 & 3 are required to make the circuit resonant, so it can be driven by the oscillator amplifier within IC1. The crystal provides good accuracy, to within a few minutes per year. The 3V supply is marginal for lighting a LED, especially given that the cell voltage can drop to around 2V at the end of its life. To solve that problem, the components connected between pins 6 and 7 provide a boosted supply voltage for driving LED1. In effect, we have diode pump: with pin 7 low and pin 6 high, the 100µF capacitor charges up to around 2.3V via diode D2. Then when the micro drives pin 7 high and pin 6 low, this 2.3V is added to the 3V at pin 7 to give 5.3V for driving the LED. The drive current passes siliconchip.com.au Fig.1: complete circuit diagram for the Recurring Event Reminder. The components at pin 6 & 7 boost the 3V supply to drive the LED. through a 220W current-limiting resistor and LED1, back to pin 6. Diode D3 prevents the 100µF capacitor from being reverse charged at the end of this process. The optional piezo siren is connected between pin 6 and ground, so that when pin 6 goes high to charge the 100µF capacitor, it also powers the piezo siren, generating a brief but loud chirp. We’ve elected to use a pulsating tone piezo siren, which generates its own short bursts of sound since it makes our circuit simpler. Because this type of siren does not make any sound for about half a second after power is applied, after which it emits a short burst, we keep pin 6 high for around one second, to ensure the siren sounds, even though the 100µF capacitor charges in a much shorter time. The unit is powered by a 3V lith- ium cell in a holder, labelled BAT1. Jumper JP1 is used as a power switch while diode D1 provides reverse polarity protection. If the cell is inserted incorrectly, the diode will conduct and restrict the supply voltage for IC1 to around -0.6V. The cell holder we use does not connect to the cell if it is inserted the wrong way, so this is a “belts and braces” measure. Maximising battery life Most of the time, IC1 is in sleep mode, with the program halted and the internal 4MHz oscillator stopped but the 32768Hz oscillator running. It is “woken up” once per second, to update its internal time and date and to flash the reminder LED if necessary. Sleep mode reduces the power consumption of IC1 to a very low level (around 7µA), to maximise the life of the cell. Switch S1 has a 10kW pull-up resistor that holds input pin 4 (GP3) high unless S1 is pressed. When it is pressed and pin 4 goes low, IC1 is woken from sleep to respond. S1 is used to either clear the LED flashing indication (with a short press) or reset the timer if the switch is held closed for an extended period. Note that if the optional piezo siren is used, cell life will be slightly worse. Typically, you will not leave the piezo beeping for a long time; you would reset the reminder by pressing S1. Once the piezo stops, it will no longer be an additional drain on the cell. Jumper JP2 is used to select weekly, fortnightly or daily reminders. When power is first applied to the circuit, the GP2 input (pin 5) is set as an input with a pull-up current applied. If JP2 is not shorted then this input will be pulled high and the software produces weekly or fortnightly reminders. If JP2 is bridged, the GP2 input will be held low and daily reminders are produced (see panel). The internal pull-up current is switched off shortly after initial powerup and the GP2 input is then set as a low output to reduce the supply current and extend cell life. The selection between weekly/fortnightly or the various different daily reminder periods is made by a different method, as described below. Assembling the board The Event Reminder is built on a PCB coded 19107181 and measuring 62.5 x 38.5mm. It is presented as a bare PCB that can sit flat, be hung or otherwise attached to a cupboard or refrigerator, or mounted in a case. If mounting in a case, before assembling the board, you can use the PCB as a template to mark out the loca- Fig.2: overlay diagram for the Event Reminder with the completed PCB shown. Note the orientation of the battery holder and the location of JP2 marked in red. A wire link has been used to bridge JP2 on the prototype PCB. The production board has a pair of closelyspaced pads in the same location which can be easily bridged with solder. siliconchip.com.au Australia’s electronics magazine July 2018  69 How to set the Recurring Event Timer First of all, you need to decide which event reminder you want. The choices are once fortnightly, weekly, daily, or every twelve hours, eight hours or six hours each day. Changing to a different timer is simply a matter of following the instructions for that timer – otherwise, it will stay as set until changed. Setting and resetting the timers is achieved by shorting either or both JP1 and JP2, in conjunction with reset switch S1. All setting data is stored in flash memory so unless you want to change the mode, you will not have to reset it when you go to use it. However, the unit's time counter is reset to zero at power up (JP1 shorted). When powered up (JP1 inserted) and S1 isn't pressed, LED1 will flash the current setting (eg, once for weekly; twice for fortnightly). Weekly reminder (exactly 7 days)   Fortnightly reminder (exactly 14 days)   Daily reminder (24 hours)   This is the first default mode, without JP2 shorted. When powered up (jumper on JP1) LED1 will flash once. LED1 will then flash exactly 7 days later from this time (to the minute!) and remain flashing for 18 hours, until reset with a short press of S1. Without JP2 shorted, remove the shorting block from JP1, press and hold S1 while replacing the shorting block on JP1. LED1 will flash twice and you can release S1. It will start flashing exactly 14 days later and is cancelled by pressing S1 (or waiting 18 hours!). Repeating this method will reset the Event Reminder to a weekly reminder. With JP2 shorted, the unit is in default daily mode. Exactly 24 hours after turning on, LED1 will flash for 18 hours, if it is not cancelled first (by pressing S1). It then repeats this process every 24 hours. Two times/day (12 hours)   With JP2 shorted, remove JP1. Hold down S1, replace JP1 and wait for LED1 to flash twice. Exactly 12 hours later LED1 will flash for 8 hours, if it is not cancelled by pressing S1. It repeats this process every 12 hours. Three times/day reminder (8 hours) With JP2 shorted, remove JP1. Hold down S1, replace JP1 and wait for LED1 to flash thrice. Exactly 8 hours later LED1 will flash for 6 hours, if it is not cancelled by pressing S1. It repeats the process every 8 hours. Four times/day reminder (6 hours) With JP2 shorted, remove JP1. Hold down S1, replace JP1 and wait for LED1 to flash four times. Exactly 6 hours later LED1 will flash for 4 hours, if it is not cancelled by pressing S1. It repeats the process every 6 hours. Repeating this method will reset it back to a daily reminder. Set timer back to zero Press and hold S1 for 5 seconds until LED1 starts continuously flashing. This will trigger the alarm and reset the time counter to zero. Future reminders will then be related to this time. Be careful not to short any of the connections on the underside of the board with your finger. tions to drill the four corner mounting holes in the lid, along with holes for S1 and LED1. Use the PCB overlay diagram, in Fig.2, to assemble the board. Begin by installing the resistors. Use a multimeter to check the value of each before inserting into the PCB. For a reminder period of 24 hours or less, the two pads on the underside of the PCB labelled JP2 need to be bridged with solder or with a short length of tinned wire. This can be a lead off-cut from one of the resistors. Diodes D1 to D3 can be installed next, taking care to orient them correctly and noting that D1 is the 1N4004 and the remaining diodes are 1N4148s. Then fit pushbutton S1, crystal X1 and the socket for IC1. Ensure that the notched end of the socket is oriented as shown in Fig.2. Take care when soldering the crystal as the leads are very fine and it can be 70 Silicon Chip damaged by excessive heating. Then mount the 100nF and 100pF capacitors which are not polarised. Follow with the 100µF electrolytic capacitor, ensuring that its positive (longer) lead goes through the pad marked + on the PCB. The striped side of the can indicates the negative lead. Where do you get those HARD-TO-GET PARTS? Where possible, the SILICON CHIP On-Line Shop stocks hard-to-get project parts, along with PCBs, programmed micros, panels and all the other bits and pieces to enable you to complete your SILICON CHIP project. SILICON CHIP On-Line SHOP www.siliconchip.com.au/shop Australia’s electronics magazine The two-way pin header for JP1 can then be installed. Follow by fitting PC stakes at the wiring points for the piezo siren, if you plan to use one. Next, mount the cell holder, making sure its positive terminal (the release lever) is facing towards IC1. If you are planning to mount the unit in a UB3 Jiffy box, use a tactile pushbutton switch with a long shaft for S1 so that it will protrude through the lid. The board can be mounted on the underside of the lid, using four 12mm tapped spacers and eight short machine screws. LED1 should be soldered to the PCB with its lens around 10mm above the top surface, although you could mount it higher if you wanted to. The longer anode lead must be soldered to the pad marked “A”. Programming the micro Check your construction before insiliconchip.com.au Parts List – Recurring Event Reminder 1 double-sided PCB coded 19107181, 38.5 x 62.5mm 1 PCB-mount vertical tactile pushbutton switch with 6mm actuator (S1) ♦ [Jaycar SP0603, Altronics S1421] 1 20mm button cell holder (BAT1) [Jaycar PH9238, Altronics S5056] 1 CR2032 lithium cell (BAT1) [Jaycar SB2944, Altronics S4999B] 1 8-pin DIL IC socket (for IC1) 1 32768Hz watch crystal (X1) [Altronics V1902] 1 2-pin header with 2.54mm spacing (JP1) 1 jumper shunt (JP1) [Jaycar HM3240, Altronics P5450] Extra parts for piezo siren 1 1-13V pulsating tone piezo siren [Jaycar AB3456, Altronics S6117] 2 PC stakes (for wiring up piezo siren) 1 UB3 plastic Jiffy box, 83 x 54 x 30mm [Jaycar HB6024, Altronics H0153] Extra parts for mounting in case 1 UB3 plastic Jiffy box, 83 x 54 x 30mm 4 12mm M3 tapped Nylon spacers 8 M3 x 6mm machine screws Semiconductors 1 PIC12F617-I/P microcontroller programmed with 1910718A.hex (IC1) 1 1N4004 1A diode (D1) [Jaycar ZR1004, Altronics Z0109] 2 1N4148 diodes (D2,D3) [Jaycar ZR1100, Altronics Z0101] 1 3mm red high brightness LED (LED1) Capacitors 1 100µF 16V PC electrolytic [Jaycar RE6130, Altronics R5123] 1 100nF 50/63/100V MKT polyester or multi-layer ceramic [Jaycar RM7125, Altronics R3025B] 2 100pF C0G/NP0 ceramic [Jaycar RC5324, Altronics R2822] Resistors (0.25W, 1%) 4-digit colour code 5-digit colour code 1 10kW brown black orange brown brown black black red brown 1 220W red red brown brown red red black black brown ♦ use a longer actuator version (eg, Altronics S1119) when mounting in a UB3 case serting the programmed microcontroller (IC1) in its socket. Its pin 1 dot needs to be located near the notch in the socket. If you intend to program the PIC yourself, the HEX file (1910718A.hex) can be downloaded from the Silicon Chip website (free for subscribers). Since we are using pin 4 of IC1 as an input for sensing the state of switch S1, its MCLR function is disabled. Also, we are running the chip off its internal oscillator. Some programmers do not support programming a chip in this configuration. If you’re using a PICkit 3 and MPLAB IDE/IPE to program this chip, it will produce a warning but you can ignore that warning and continue to program the chip. With IC1 in place, fit the CR2032 cell in its holder and place a shorting block on the header marked JP1. If all is well, LED1 will momentarily flash siliconchip.com.au after about one second to acknowledge that the circuit is operating. Finishing it up The final Recurring Event Reminder PCB design includes three white boxes at the bottom that are labelled “D”, “W” and “F”. These are intended to indicate whether your unit is set up for Daily, Weekly or Fortnightly reminders respectively. You can fill in the appropriate box with a marker pen. If using the piezo siren, connect its black wire to the “Buzzer -” connection on the PCB and the yellow intermittent wire (for the Jaycar unit) or red wire (for the Altronics unit) to the “Buzzer +” terminal on the PCB. The piezo siren will not chirp on the initial power-up indications of the LED; it only sounds during reminder alerts. If mounting it in a separate box, you can solder its wires to a two-core extension cable to connect to the Event Australia’s electronics magazine The yellow (+) and black (-) wires of the Jaycar piezo siren output a pulsed tone, or you can connect the red and black wires for a continuous tone. Reminder PCB (as pictured above). For our prototype, we mounted the piezo siren in a separate UB3 Jiffy box, poking out through a 25mm hole drilled in the base. You could mount the main board on the lid of the same box, or mount them separately and run a cable between the two. Really though, there’s nothing stopping you from using the unit as a bare board. This also makes it easy to change the cell, although you shouldn’t need to do that very often. For example, you could affix the board to the side of a refrigerator using Blu-Tack or a similar putty-like substance at each corner. Or you could use double-sided, foam-cored tape. Just make sure that if there is exposed metal on the fridge (eg, if it’s made of stainless steel) that the solder joints on the underside of the board won’t be shorted out. You could also glue magnets onto the underside of the PCB and use those to hold it on the fridge. Alternatively, hang the PCB vertically on a picture frame hook, nail or screw attached to a wall. The important point is that it should be mounted somewhere that you and your family members will regularly spend time (eg, the kitchen) so that someone will notice the flashing LED and/or noise from the siren. PCB and PIC bundle To make life really easy for you, we have a special "bundle" price of just $15.00 for both the PCB and micro, plus postage. If you just want the board, or the PIC these are available separately from the SC Silicon Chip Online Store. July 2018  71