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O ver 20 years ago, my mother was becoming infirm and had a tendency to fall and couldn’t get up. I lived too far away to visit every day, but near enough that I could attend in an emergency. What was needed was a way to alert me to any potential problem. These were the days before the internet was common in the home, so I devised a plan to connect the PIR (passive infra-red) movement sensors in the burglar alarm to a cheap landline telephone handset from the local discount store. All that was needed was an interface between the alarm panel and the ‘phone. The system potentially saved my mother’s life on three occasions, when she had fallen and couldn’t get up. On a fourth occasion, she had been taken into hospital but had not bothered to tell family, friends or the local community services, causing a major panic. I got the alert just as I landed in Amsterdam for a well-earned weekend break. However, at least I was able to inform family members of a potential problem. The original solution The original circuit is shown overleaf for interest (Fig.1). The burglar alarm’s communicator outputs and three PIR sensors on separate zones were connected to a PIC16F84 microprocessor (IC1) via NPN transistors Q1-Q5. This allowed the PIC processor to detect activity in the three PIR zones, monitor for alarm conditions and also determine whether the burglar alarm was set (armed) on unset (clear). I removed the keypad, microphone and ‘off hook’ switches from the ‘phone. The keypad was replaced Image source: https://unsplash.com/photos/a-black-and-white-alarm-clock-on-a-white-background-CfuOZPNSr6E WiFi Alarm Monitor If someone lives by themselves, especially if they are elderly, they can end up in situations where they need help but can’t get it. This alarm system provides a way to alert others when there is a problem. A project to help the elderly by Kenneth Horton by two quad opto-isolators (IC3 & IC4) driven by a 74LS139 dual 1-of-4 decoder, IC6. The ‘off hook’ switch was replaced by relay RLY1; both were activated by the PIC16F84. I replaced the microphone with a 1:1 ratio isolating transformer. The first version sent an alert in Morse code, but this was later replaced by an ISD1110 voice encoder chip (IC5) to give spoken alerts. If the burglar alarm was activated, or no movement was detected for a set period, the PIC processor would dial my mobile number and the voice chip would inform me that there was a problem. Monitoring whether the panel was set (armed) or unset (clear) allowed different time intervals to be set. The top and bottom of the PCB used to prototype the WiFi Alarm Monitor. It’s very simple compared to the older landline-based circuit shown in Fig.1 siliconchip.com.au Australia's electronics magazine My mother set the panel at night upon going to bed, and in this case, there was a much longer time delay without movement before an alert was generated than during the daytime when the panel was unset. Bringing it up to date I am not yet at the stage where I am infirm, but I know that the time may come when my family are as concerned about me as I was about my mother. I decided that I should update the design, making use of the now widely available internet and WiFi, and install it while I have my faculties. The system performs two functions: first, it will alert me or my family in case of an alarm condition, such as the burglar alarm being set off. Second, it will monitor my daily activity. If none is detected, it will alert the family of a potential problem. In my case, the alarm system consists of both door switches and PIR detectors, but the solution can be tailored to individual requirements. Monitoring alarm conditions is straightforward. However, monitoring daily activity is more in-depth. There are three different modes: • Daytime, when the occupant is at home and the alarm panel is unset. • Nighttime, when the occupant is in bed and the panel is set (armed). • When the occupant has left the premises and presumably armed the alarm. May 2026  69 Fig.1: the circuit of my original alarm dialler, which interfaced with the (now largely obsolete) public telephone network by connecting to an old handset via CON2, CON3 & CON4. That allowed it to dial me after a delay if it sensed a lack of activity. The WiFi Alarm monitor uses a single Raspberry Pi Pico W (shown enlarged). Fig.2: the new Alarm Monitor is simpler and more modern, using a Raspberry Pi Pico W to send emails and/or SMSs if the activity coming from the alarm via level-shifters IC2 and IC3 looks suspiciously quiet. ▶ During the daytime, the system needs to check on activity by monitoring door switches and PIRs. At night, when the panel is set, the system needs to check that the panel is unset the following morning. If the occupant has gone out, the activity monitor needs to be disabled because the user may simply have popped to the shops, or they may have gone on a three-month world cruise! In this case, inactivity alerts would be annoying, to say the least! The use of the exit door within minutes of the panel being set (armed) differentiates between the panel being set 70 Silicon Chip Australia's electronics magazine siliconchip.com.au give a degree of separation between the alarm panel and the interface. These 12 inputs, together with an optional test button (S1) are connected to a Raspberry Pi Pico W, which provides all the intelligence and a connection to the internet. The Raspberry Pi Pico W is the version with built-in WiFi. The only other components are a simple linear power supply with an axial fuse to convert the 12V from the panel to five volts for the Raspberry Pi Pico W. This is fed to the Raspberry Pi via a schottky diode so that it can safely work in parallel with a USB supply. Software description while the user is in the premises and when he or she has gone out. The system can send emails to four different groups of people, depending on what has triggered the alert, and can also send SMSs to up to four different telephone numbers. To send SMS text messages, you will need a free Twilio account. Setting one up is easy; visit www. twilio.com for more details. Twilio works in the UK, Australia, NZ, EU, USA and many other countries too. Circuit description As with many modern circuits, the siliconchip.com.au hardware is relatively simple, and all the intelligence is within the software. The updated circuit is shown in Fig.2. Up to 12 inputs from the alarm panel, both individual zones and communicator outputs, can be monitored via CON1 & CON2. Communicator outputs are typically: panel armed, alarm condition, fire, panic and abort, together with a 12V supply. The 12 inputs are connected via 10kW resistors to two 74HC4050 high-voltage input non-inverting buffers, which allow the (typically) up to 12V signals from the alarm panel to be safely converted to 3.3V. The resistors Australia's electronics magazine The software for the Raspberry Pi Pico W is written in MicroPython. There are three files: main.py, umail. py and parameters.py. The first two files should be installed as supplied. The parameters.py file needs to be edited to tailor the system to your individual requirements. The parameters.py file contains numerous constants and arrays. The program has been designed to be as flexible as possible, to allow for many different scenarios. The file parameters.py can be edited in a text editor, or with Thonny, as described later. Note that MicroPython’s code is strictly case sensitive, so great care is needed while editing to avoid unintentional errors! The first section of parameters.py contains constants that should not be altered. The user-defined parameters are from around line number 47 through to the end of the file. Looking at each section in turn: The first section of comments on lines 47 to 77 is not essential, but I found it useful in clarifying my requirements. I suggest that you review and change these comments to define your own requirements. Don’t forget to include a hash mark (#) at the start of each comment line. Editor's note: the line numbers do not match up to the Listings shown in this article (taken from “parameters. py”, as we have removed the comments and line breaks due to space restrictions. The downloaded file match the referenced lines. The next section (lines 78-101, Listing 1) sets timings for various functions in seconds, minutes or hours as appropriate. May 2026  71 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. Watchdog = const(True) Set_timeout = const(11 * Hours) Primary_timeout = const(8 * Hours) Secondary_timeout = const(5 * Hours) Exit_timeout = const(3 * Minutes) First_delay = const(30 * Seconds) Second_delay = const(5 * Minutes) WiFi_timeout = const(15) WiFi_retry = const(10 * Minutes) Maximum_retries = const(3) Periodic_checking = const(7 * Days) Listing 1: this section of the code defines various delays and settings. We have removed comments and new lines for brevity. The line numbering isn’t an exact match to the actual file, it’s just there to make it easier to follow. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122. 123. 124. 125. WiFi_username = "Your SSID" WiFi_password = "Your password" smtp_address = "smtp.aaa.com" smtp_port = 25 smtp_username = "Your login" smtp_password = "Your password" Email_from = "from<at>aaa.com" Email_subject = "Alarm status report" Email_to_1 = "Contact1<at>aaa.com" Email_to_2 = "Contact2<at>aaa.com" Email_to_3 = "Contact3<at>aaa.com" Email_to_4 = "Contact4<at>aaa.com" Twilio_Account = "Twilio account number" Twilio_Auth = "Twilio authorisation" Twilio_phone_no = "Twilio phone no" SMS_to_1 = "00000000001" SMS_to_2 = "00000000002" SMS_to_3 = "00000000003" SMS_to_4 = "00000000004" Listing 2: the WiFi, email, and SMS settings. 136. Zone_name = { 137. 0: ["Front door", Primary_zone | Exit_zone], 138. 1: ["Lounge PIR", Secondary_zone], 139. 2: ["Dining door", Primary_zone], 140. 3: ["Back door", Primary_zone], 141. 4: ["Hall PIR", Secondary_zone], 142. 5: ["Kitchen PIR", Secondary_zone], 143. 6: ["Abort", Abort_status], 144. 7: ["Panic", Communicator], 145. 8: ["Spare", Spare_zone], 146. 9: ["Spare", Spare_zone], 147. 10:["Panel", Panel_status], 148. 11:["Alarm", Alarm_status], 149. 12:["Test", Test_button] 150. } Listing 3: the zone definitions. Watchdog should be set to “True”. Only set it to “False” while testing. Set_timeout is the amount of time before an alert is sent when the panel is set. Normally, this will be at nighttime when the alarm panel is set and the user is in bed. As noted previously, this timeout is disabled if the exit zone has been triggered, indicating that the user has left the premises. The values Primary_timeout and Secondary_timeout similarly set the amount of time before an alert when the panel is unset; usually, this will be during the day, when the user is its home. Primary zones are where there is a definite action by the person being monitored, such as opening or closing a door that has a door switch. Secondary zones are typically PIR movement sensors, and these may be triggered accidentally by a person who has fallen trying to get up unsuccessfully, or a pet wandering through. As such, they are less reliable as an indication of activity compared with the primary zone. When relying on PIRs, you need to monitor more than one zone! Exit_timeout defines the amount of time between the panel being set (armed) and the exit door being triggered; it will usually be two or three minutes. It must be set for a longer time than that set in the alarm panel itself. Otherwise, the exit condition will not be recognised. First_delay is the amount of time between an alarm condition and the first alert being sent, and is typically set to one or two minutes so that false alarms can be cancelled. Second_delay is the amount of time between the alert being sent to the first contact and the subsequent contacts. WiFi_timeout is the length of time the system tries to connect to the router before timing out. 180. Alarm_types = { 181. "Alarm": ["Alarm", Delay1 | Email_Contact1 | Delay2 | SMS_Contact2], 182. "Communicator": ["Communicator", Email_Contact1], 183. "No_Activity_Clear": ["No activity panel NOT set", Email_Contact1 | Delay2 | Email_Contact2 | SMS_Contact3], 184. "No_Activity_Set": ["No activity panel set", Email_Contact1 | Delay2 | Email_Contact2 | SMS_Contact3], 185. "Test": ["Test message", Terminal | Email_Contact1], 186. "Check_in": ["Periodic check-in", Email_Contact1], 187. "Restart": ["Alarm monitor restart", Email_Contact1] 188. } Listing 4: the actions to be performed for each alert condition. 72 Silicon Chip Australia's electronics magazine siliconchip.com.au WiFi_retry is the amount of time between attempts to connect to the WiFi network, assuming that it has been unsuccessful. Maximum_retries sets the maximum number of attempts to connect to WiFi or send an SMS text message. This is to prevent the monitor from entering an endless loop due to a WiFi or SMS problem, and allows it to move on to subsequent actions. Periodic_checking enables the monitor to send a periodic email or text message to confirm that it is up and running. A value of 0 disables it. The next section (lines 103 to 125, Listing 2) sets your WiFi username and password, and your email login details, followed by the email addresses and SMS phone numbers of your contacts. I have found different email providers to be a little fickle about the format of parameters, so some tailoring may be required. You should be able to set more than one email address, possibly separated by a semicolon (;). Caution and careful testing are needed when setting the email login parameters. Incorrect values can cause the program to crash and thus not send the alert messages. As previously mentioned, you will need a free Twilio account to send SMS text messages. The following section (lines 127 to 150, Listing 3) defines the function of each of the 13 input channels to the system. For each input channel, there are two parameters: a text description, followed by its functions. More than one function can be defined with the ‘inclusive or’ symbol (|), so “Primary_ zone | Exit_zone” defines the input as both a primary zone and an exit zone. • Panel_status defines whether the alarm panel is set (armed) or unset (clear). • Alarm_status is set when the burglar alarm is activated (an alarm condition) by an intruder. 201. Activity_conditions = [ 202. [2,0], 203. [1,2], 204. [0,3], 205. [-1,-1] 206. ] Listing 5: this section of the code sets the number of primary/secondary zones that need to be triggered to indicate activity. siliconchip.com.au Parts List – WiFi Alarm Monitor 1 single-sided PCB coded 01304261, 57 × 57mm 1 suitable plastic enclosure (eg, 3D printed) 1 Raspberry Pi Pico W microcontroller module (MOD1) 2 20-pin headers, 2.54mm pitch (for MOD1) 2 20-pin female header sockets, 2.54mm pitch (for MOD1) 1 250mA miniature axial fuse (F1) 2 74HC4050 level-shifter ICs, SOIC-16 (IC2, IC3) 1 AMS1117-5 5V LDO linear voltage regulator, SOT-223 (REG4) 1 1N5819 40V 1A axial schottky diode (D1) 12 10kW ±5% or better axial resistors (4.7kW to 22kW resistors would likely work too) 2 100nF 50V X7R SMD ceramic capacitors, M2012/0805 or M3216/1206 size 1 10μF 50V X7R SMD ceramic capacitor, M3216/1206 or M3226/1210 size 4 3-way miniature (0.15in/3.81mm) screw terminal blocks (CON1, CON2) OR 3 4-way miniature (0.15in/3.81mm) screw terminal blocks (CON1, CON2) 1 2-way polarised header and matching plug, 2.54mm pitch (CON3; optional; for S1) 1 2-way miniature (0.15in/3.81mm) screw terminal block (CON4) 1 momentary pushbutton switch (S1; optional) • Communicator is typically the ‘panic’ or ‘fire’ communicator outputs, if required. • Abort_status indicates that an alarm condition has been cancelled. • Spare_zone defines any unused inputs; these should also be connected to ground electrically. • Test_button monitors the 13th input (S1) and will send a test message. The next section (lines 152 to 188, Listing 4) defines which actions are to be performed for each of the alert conditions: • alarm • communicator output • no activity while the panel is not set (clear) • no activity while the panel is set (armed) • test message • periodic ‘health’ check-in • start-up/reset These are fixed conditions in the software and should not be altered. For each of the alert conditions, there is a text description followed by a list of actions. These consist of delays, emails and SMS messages to various contacts. • Delay1 is typically a short delay to allow time for a false alarm to be cancelled. • Email_contactx sends an email to that contact or group of contacts. • SMS_contactx sends an SMS message to a single contact. • Delay2 sets a delay between contacting contact 1 and the other contacts. Australia's electronics magazine • Terminal is for testing only and sends output via the USB interface. All the actions occur in a fixed sequence, defined in the subroutine Poll_alerts() in main.py. The sequence is: Delay1, Terminal, Email_contact1, SMS_contact1, Delay2, Email_contact2, SMS_contact2, Email_contact3, SMS_contact3, Email_contact4, SMS_ contact4. If no action is required for a certain condition, it can be set to 0. For example: “Restart”: [“Alarm monitor restart”, 0] If a WiFi connection cannot be made, the interface keeps trying at WiFi_retry intervals until Maximum_ retries has occurred and will not move on to the next action until a successful connection is made or the retry limit is exceeded. Maximum_retries also applies to attempts to send emails. No check is made that emails or SMS messages have been completed successfully; the interface will simply move on to the next action. If an email or SMS is unsuccessful, it is likely to be a hard fault due to a parameter error, and the interface would be tied up indefinitely! The final section (lines 190 to 206, Listing 5) sets the number of primary and or secondary zones that need to be triggered to indicate activity. As previously mentioned, primary zones give a clear indication of activity, while secondary zones may be triggered by a person in distress or a pet. May 2026  73 So, for accurate monitoring, a minimum of two secondary zones are needed unless a primary zone has been triggered. As a result, various combinations of primary and secondary zones can be set, for example [two primary zones] or [one primary zone and two secondary zones] or [three secondary zones]. Obviously, you cannot define more primary or secondary zones than those that are being monitored. Each line has the number of primary zones followed by the number of secondary zones. Each additional line provides an ‘inclusive or’ function, so 2,0 followed by 1,2 means [two primary zones and no secondary zones] or [one primary zone and two secondary zones]. Software libraries My software makes use of a thirdparty library, uMail (MicroMail) for MicroPython (https://github.com/ shawwwn/uMail). Also, for the SMS interface, I used code from Mahmood Mustafa Shilleh at siliconchip.au/ link/acat Construction The prototype was built on a single-­ sided printed circuit board with a RPi mounted on headers and sockets so it can be easily removed (and because there’s a diode mounted underneath it). The 74HC4050 ICs, linear voltage regulator and associated capacitors are all surface-mount devices. Axial resistors were used on the inputs of the 74HC4050s, as the layout of the gates on these chips is not particularly user-friendly and resistors are a convenient way of bridging to the input connectors. The prototype used Molex KK-style connectors for compatibility with previous wiring, but the PCB has been re-designed to use miniature screw terminal blocks with 0.15-inch (3.81mm) pin spacing (not the more typical 0.2-inch/5.08mm spacing). Looking at Fig.3, I recommend fitting the surface-­ mount components first, followed by the resistors and then the other components. If you only require a maximum of six inputs, the second 74HC4050 can be omitted; the weak internal pullups on the Raspberry Pi Pico module will automatically disable the remaining inputs. The finished board can be mounted in any convenient plastic project box, or if there is room, within the alarm panel itself. The author made a custom 3D-printed enclosure, but that is not necessary. If you do want to print that, the STL files are included in the software package at siliconchip.au/ Shop/6/3613 Software installation The software is installed on the Raspberry Pi using the free Thonny integrated development environment (IDE). The first step is to install the IDE from https://thonny.org Installation is quite straightforward and you will find a lot of useful information on the Thonny website and also at https://github.com/thonny/ thonny/wiki Once Thonny is installed, connect the Raspberry Pi to your computer using a USB lead while holding down the white button (BOOTSEL) on the Raspberry Pi, then start Thonny. You should see a window similar to that in Screen 1. Click on the bottom right corner where it says <no backend> and then select Install MicroPython (Screen 2). You should then see Screen 3. Target volume sets the location of the Raspberry Pi and should be filled in automatically. If it is blank, you need to disconnect the Raspberry Pi and connect it again while pressing the white button. Set: • MicroPython family to ‘RP2’ • Variant to ‘Raspberry Pi • Pico W / Pico WH’ • Version should be set automatically to the latest. Check that the parameters are correct and then click Install. When the installation is complete (which should only take a few seconds), click on the stop button (white square inside the red circle) and you should see Screen 4. If it does not appear, close Thonny, disconnect and reconnect the USB without pressing the white button, and then restart Thonny. The next step is to copy the source files onto the Raspberry Pi. As previously mentioned, MicroPython is strictly case sensitive, and this applies to file names as well as the source program. In the next step, the source files from your computer will be copied onto the Raspberry Pi. Editing files either on your computer or on the Raspberry Pi, does not update the other copy. You need to explicitly make a copy. Note that it may not be obvious whether files you are editing in the Thonny editing window are located on the computer or Raspberry Pi. The files main.py, parameters.py Fig.3: the board can be easily etched as it is single-sided, with all the through-hole parts on the top and a few SMDs on the underside. Take care with the polarity of the SMD ICs (their pin 1 indicators go towards the Pico) and note how D1 is mounted underneath the Pico W module. Because of that, and to make maintenance easier, it’s best to socket the Pico W. 74 Silicon Chip Australia's electronics magazine siliconchip.com.au Screen 1: the initial state of Thonny (a Python IDE) when you run it after installation. and umail.py need to be copied from your computer onto the Raspberry Pi. This is the time to edit the parameters. py file if you haven’t already done it (use your favourite text editor). Don’t forget to save a copy both to your computer and to the Raspberry Pi. In Thonny, click File → Open... and then select “This computer”. Open umail.py from your computer, then click File → Save copy... and this time select “Raspberry Pi Pico”. Type the filename “umail.py” and click OK. Repeat the above for the files main. py and parameters.py after making your edits. Now close Thonny, disconnect and reconnect the USB lead. The green light on the Raspberry Pi should flash at one-second intervals. Connecting the interface to the alarm panel Different alarm panels will vary slightly, but all should have multiple zones and a set of communicator outputs. The communicator outputs are fairly standard, as they are designed to interface with a range of devices. Each zone usually has two connections, ignoring tamper circuits. One connection will be at a fixed voltage (or ground), while the other is used to detect the input from the switch or sensor. It is necessary to connect the interface to this active signal. A quick test with a multimeter should identify the correct input to use. Failing that, try one and, if it does not work, try the other. On my Honeywell alarm panel, the active inputs are on the left. Don’t forget to ground any unused inputs. If they are left floating, they can overwhelm the Raspberry Pi with unwanted interrupts. If you want to send SMS messages, don’t forget to get a free Twilio account! The author’s monitor has been running without failure for over 18 months, so the Raspberry Pi and MicroPython software appear to be extremely stable. If possible, once the unit is installed, there should be easy access to the USB connector so that parameter updates can be easily installed. The Raspberry Pi will need to connect to a reliable WiFi network, so this needs to be taken into account. In particular, metal enclosures are unlikely SC to be suitable. siliconchip.com.au Screen 2: this menu lets you install MicroPython on the Pico W. Screen 3: set the options in this dialog as per the instructions in the text to install MicroPython. Screen 4: the Thonny IDE with MicroPython on the Pico W up and running. Australia's electronics magazine May 2026  75