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Part 2 of John Clarke’s Mains Power-Up Sequencer This Sequencer solves problems that can occur when switching on multiple mains-powered devices, like circuit breakers tripping or loud thumps from speakers. It can also be used as a master/slave power-saving solution. The Sequencer can handle up to four devices but multiple units can be chained to handle 8, 12 or more. T he Sequencer can switch on one to four (or more) devices in sequence, with an adjustable delay between each power-on. It can also switch them off in sequence, either in the same order as they were switched on or in the reverse order. It can be configured to start to switch on the devices in one of three ways: immediately when power is applied to it, when the appliance plugged into the first outlet starts to draw power (in which case the first outlet is always on), or when a separate, isolated mains supply comes online. That last feature can join multiple Sequencers to control more than four devices. It can even allow you to switch on devices in sequence across multiple mains phases (eg, if you have a big lab full of equipment). In last month’s first article, we described all its features and how the circuit works. Now we pick up where we left off and move on to building it, followed by testing and configuration. Construction Most of the Mains Power-Up Sequencer’s parts are assembled onto a double-sided PCB coded 10108231 that measures 203 × 134mm. The completed assembly is housed in an ABS or polycarbonate plastic IP65 sealed enclosure measuring 222 × 146 × 55mm. siliconchip.com.au Figs.5 & 6 show where all the components go on the circuit board. You will not fill the entire PCB with components when building the Mains Power-Up Sequencer. Typically, you would only install the Current Detection section or the Mains Input Detection section, but not both. Or you could decide not to use either, in which case none of those parts are needed. The parts list last month separated out the parts for the optional sections. The OUT1 channel must always be installed, but note that there are a couple of component value changes in that section depending on whether Current Detection is installed. Additionally, if Current Detection is not used, the two pads for CON7 must be connected using a short length of 10A mains-rated wire. Before construction, you will need to decide on how many outlets you will install. The PCB is initially set for four outlets with the RA0 and RA1 pins Warning: Mains Voltage All circuitry within the Mains Sequencer operates at Line (mains) voltages. It would be an electrocution hazard if built incorrectly or used with the lid open. Only build this if you are fully experienced in building mains projects. Australia's electronics magazine on IC9 tied to the 0V supply by short tracks on the underside of the PCB. To change this, the bottom layer tracks right next to the RA0 and/or RA1 pads will need to be cut (eg, using a sharp hobby knife) and then those pad(s) soldered to the small adjacent pads on the top layer that connect to +5.1V. Refer to Table 1 to see which need to be changed for one, two or three outlets. If you can’t get the solder to reach across the gap, use a short length of component lead offcut. Ensure you’ve properly isolated the pads before soldering them to those top pads, or you could short out the 5.1V supply (which will prevent the unit from working but shouldn’t blow anything up). Circuit sections The Mains Power-Up Sequencer PCB screen printing separates the four mains output circuitry sections (OUT1 to OUT4) using lines to delineate each channel. The Current Detection and Mains Input Detection sections are also marked on the screen printing and in Fig.5, so it is easy to see where the components associated with each section are located. Before construction, decide which sections you need using the information above. You can then start by installing the smaller ¼W resistors. March 2024  77 They have colour-coded bands indicating the values (shown in the parts list last month), but it’s best to use a digital multimeter (DMM) to check each resistor before soldering it in place. Zener diodes ZD1 and ZD2 (if used) and TVS1 (if used) can also be installed now, taking care to orientate the zener diodes correctly. TVS1 can go in either way around. Mount the ICs now, including the opto-couplers, taking care to get the correct IC in each place and with the proper orientation. We used sockets for IC9 and IC10, although you could solder them directly to the PCB, assuming that IC9 has already been programmed. The opto-couplers (IC1-IC8 and IC11) are not all the same, so don’t get them mixed up. Note that on the PCB, pin 5 of the IL410/4108 and the IL420/4208 have only a tiny pad for an increased separation distance between the internal Triac pins located at pins 4 and 6. Those pins are not connected to the rest of the circuit but you can solder them if you want to. The Triacs can be mounted now. There are a few different ways to do this. One is to smear a thin layer of flux paste onto the large pad, then position the device on the PCB and solder one of the small leads. Check its alignment and, if it’s OK, solder the other one. Otherwise, reheat the initial joint and nudge it into position first. Finally, turn up your iron and feed solder slowly into the large tab, as Table 1 – number of outlets RA1 (pin 18) RA0 (pin 19) # outlets 0V (bot) GND (bot) 4 (default) 0V (bot) 5.1V (top) 3 5.1V (top) GND (bot) 2 5.1V (top) 5.1V (top) 1 it will take a while to melt. Once it gets hot enough, solder all along the exposed portion of the tab. The flux paste underneath will pull solder under the tab and solder it to the circuit board. Alternatively, it is possible to tin both the pad and the tab of the device, clamp them together while heating the tab and feeding in more solder to reflow them together, then solder the two smaller pins. Bridge rectifiers BR1 (and BR2 if used) can now be mounted. These components must be correctly orientated with the + lead inserted into the position marked with a + and seated close to the PCB before soldering. The 1W resistors can be fitted now. Ensure the correct values are used and note that for the OUT1 channel, R1 is 470W 1W when the Current Detection components are installed or 330W 1W when the Current Detection circuitry is not installed. There are 1MW resistors under the relays that are inserted from the underside of the PCB, as shown in Fig.6. Solder these in place Before soldering the inductors, they should be secured to the PCB using cable ties. 78 Silicon Chip Australia's electronics magazine and cut the leads flush with the top of the PCB. Then mount the 1kW 5W resistor with a gap of about 1mm from the PCB, to allow air to circulate. Next, fit the capacitors, of which there are three types: the mains X2-rated capacitors, electrolytic capacitors, and MKT polyester types. The electrolytic capacitors need to be orientated correctly since they are polarised, while the others can be installed either way around. For the OUT1 channel, C1 is 220nF X2 when the Current Detection components are installed or 10nF X2 when they are not installed. We have provided for the different sizes and lead spacing on the PCB. Next, install potentiometer VR1 and the three toggle switches S1-S3. Then, mount the current transformer, T1, if used. Winding inductors L1-L4 It’s much easier to mount inductors L1 to L4 before the relays. These are wound using a 500mm length of 1.25mm diameter enamelled copper wire, with 10 turns evenly spread around the powdered iron toroid. Strip the insulation back by 1mm at each end of the wire using a sharp craft knife, insert the wire ends into the holes allocated and solder them in place from the top side of the PCB. Each inductor is supported using a 200mm-long cable tie that loops through the toroid and then through the slotted holes in the PCB. It’s best to tighten and trim the cable ties before soldering the leads. Make sure the solder adheres to the bare copper; it won’t make electrical contact if you haven’t fully stripped back the enamel. The relays can now be mounted, followed by the sockets for the two-way terminal blocks. They must be inserted so the plug-in screw connectors are orientated correctly, with the screw head access positioned toward the top edge of the PCB (left side, as shown in Fig.5). The easiest way to ensure this is to plug the screw terminals into the sockets before inserting them into the PCB. The LEDs are mounted above the PCB, with the leads bent by 90° 4mm siliconchip.com.au Fig.5: the PCB is divided into sections by lines. All components outside the boxed sections should be fitted, along with the OUT1 section and however many other outputs you need. Depending on how you plan to use it, you can also add either the Mains Input Detection (‘daisy-chain’) components or the Current Detection components (including T1), but not both. Fig.6: the only components you need to fit on the underside of the PCB are these four 1MW resistors underneath the relays. You can omit those from any output sections that are not being populated. This diagram is shown at 70% of actual size. from the rear of the LED, so they sit horizontally. First, cover each lead with a 20mm length of 1mm diameter heatshrink tubing. Then shrink the tubing with a hot air gun and bend the leads, ensuring that the anode (longer lead) will be orientated correctly with the LEDs bent (anodes facing to the top in Fig.5). The LEDs stand 20mm above the siliconchip.com.au PCB when measured from the top surface of the PCB to the LED centreline. Case preparation Before attaching the PCB, the IEC connector cutouts must be made in the side of the enclosure. You will also need to drill holes in the lid for the GPO sockets and in the enclosure side for the LED indicators. The Australia's electronics magazine required holes are shown in Fig.7. It can be downloaded as a PDF from our website at 100% scale and printed at actual size to use as a template. Don’t make the holes in the lid just yet as there are some options there, which we’ll get to shortly. Additionally, the two plastic standoffs (not the ones with brass tapped inserts) that would be beneath the March 2024  79 Fig.7: here are where the holes/ cutouts are made in the case. The Mains Detect Input IEC socket hole and the adjacent screw holes are only needed if you’re using that feature. If you aren’t planning to fit the GPOs to the lid, don’t make any holes in the lid; you can mount the grommets on the opposite side of the case to the LEDs. OUT4 components on the PCB need to be shortened using a large drill to allow clearance for soldered joints under the PCB. Wiring You can install the mains outlets in one of two ways. One way (as in our prototype) is to use surface-mounting GPOs on the lid of the enclosure, as shown in Fig.8. Alternatively, you can use inline mains sockets and mains leads (possibly cut from extension cords), held in place using cord grip grommets on the side of the enclosure, as shown in Fig.9. In this case, the Earth wires are attached to an M4 bolt on the side of the enclosure. We provide cutout positions for the GPO sockets in Fig.7 since they need to be positioned on the lid so they don’t foul PCB components underneath. We haven’t provided drilling details for the alternative method using the cord grip grommets as the positioning is not so critical. However, the cutout shape for cordgrip grommets is important as it needs to be made so the grommet fits snugly when the cord is captured, so the lead cannot be pulled out from the grommet. The cutout shape is essentially an elongated circular hole. Cable glands could be used instead of cordgrip grommets. In that case, it is essential to secure the gland nut so that the mains cable cannot be pulled out. This can be done by coating the gland threads with superglue before tightening the nut to secure the mains cable lead. The LEDs are inserted into 16kV-rated bezels mounted on the side of the case to prevent shock hazards; how to mount the bezels is shown in the inset photo. The switches and potentiometers are used to adjust the sequencing settings. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au COVER EXPOSED ACTIVE BUSBAR WITH NEUTRAL CURE SILICONE OUT1 OUT4 N CURRENT DETECT MASTER CON7 1MW 1W OUTPUT2 OUTPUT3 N A N A N A OUTPUT4 CON4 N A + + COIL COIL COIL RLY4 RT334730 RLY3 RT334730 RLY2 RT334730 RLY1 RT334730 (DAISY CHAIN OUT) CON3 CON2 CON1 COIL ~ OUTPUT1 B R1 W04 – ~ 1MW 1W CON6 A 1kW 5W IEC CONNECTOR OUT3 OUT2 MAINS IN 470nF X2 10kW 15kW CON8 18kW MCP6272 IC10 470W 1W** TRIAC2 330W 1W 10nF X2 330W 1W 10nF X2 Cable tie L2 300W TRIAC3 330W 1W 10nF X2 330W 1W 10nF X2 Cable tie L3 300W TRIAC4 330W 1W 10nF X2 330W 1W Cable tie L4 300W 10nF X2 330W 1W **220nF X2 IC4 IC5 IC6 IC7 IC8 IL4208 IL4108 IL4208 IL4108 IL4208 + ~ SWITCH OFF SWITCH ON – ~ 680W A OUT3 OUT2 S3 100nF A LED4 A OUT1 S1 VR1 10kW START RATE UP DELAY NO DELAY LED3 LED1 A POWER LED2 LED5 1kW 1W 100nF 10mF 10mF CURRENT/DAISY CHAIN DETECT NON-DETECT IC9 PIC16F1459 TP 5.1V 10kW IC11 4N25 1.5kW 100kW 10kW 4.7kW ZD2 12V 22nF X2 BR2 W04 RA1 RA0 TP 0V SILICON CHIP 680W 680W 230V AC 750W IC3 IL4108 750W IC2 IL4208 750W IC1 IL4108 680W 10mF 10mF ALL PARTS AT 750W CAUTION! 1MW 1W COVER ANY EXPOSED TERMINALS WITH HEATSHRINK 10nF X2 TRIAC1 300W 1kW 1W 10kW IF CURRENT DETECT NOT USED 1kW 1W 30kW L4 L3 L2 1kW 1W 20kW 2.2kW L1 **10nF X2 & Cable tie L1 330W 1W CURRENT DETECTION COMPONENTS P4KE15A IEC CONNECTOR TVS1 1kW 1W NYLON SCREWS SHOULD BE USED T1 AC1010 1000mF CON5 CON9 A S2 OUT4 COVER LED LEADS IN HEATSHRINK TUBING (SHOWN HERE AT 50% FULL SIZE) Fig.8: the wiring for the GPO version, which is what we built. Use 10A mainsrated wire with the correct colours for all connections, although the optional Mains Detect Input wiring can use 10A or 7.5A mains-rated wire. Don’t skip the cable ties as they have an important safety function. OUT2 OUT1 NOTE: USE 10A MAINS WIRE EXCEPT FOR CON8 TO CON9, WHERE 7.5A WIRE CAN BE USED. OUT3 OUT4 CORD GRIP CLAMPS M4 SCREW WITH M4 NUT & STAR LOCKWASHER CRIMP EYELETS COVER EXPOSED ACTIVE BUSBAR WITH NEUTRAL CURE SILICONE MAINS IN A N CURRENT DETECT MASTER 1kW 5W CON7 OUTPUT2 OUTPUT3 N A N A OUTPUT4 CON4 N A + + COIL COIL COIL RLY4 RT334730 RLY3 RT334730 RLY2 RT334730 RLY1 RT334730 (DAISY CHAIN OUT) CON3 CON2 CON1 N COIL – ~ OUTPUT1 A BR1 W04 ~ 1MW 1W IEC CONNECTOR 1MW 1W CON6 470nF X2 ZD1 5.1V 10kW MCP6272 IC10 10nF X2 330W 1W 330W 1W TRIAC3 300W 330W 1W 10nF X2 330W 1W 10nF X2 330W 1W Cable tie L4 TRIAC4 300W 330W 1W 10nF X2 330W 1W **220nF X2 IC8 IL4108 IL4208 IL4108 IL4208 IL4108 IL4208 IL4108 IL4208 230V AC NO DELAY A OUT3 A OUT4 ~ + – ~ S3 100nF A OUT2 SWITCH OFF SWITCH ON S1 LED4 A OUT1 LED3 LED1 A POWER CURRENT/DAISY CHAIN DETECT NON-DETECT IC9 PIC16F1459 LED2 LED5 1kW 1W (SHOWN HERE AT 50% FULL SIZE) 100nF 10mF 10mF TP 5.1V 10kW 1.5kW 10kW 100kW 4.7kW ZD2 12V 22nF X2 BR2 W04 RA1 RA0 TP 0V SILICON CHIP IC11 4N25 680W IC7 750W IC6 680W IC5 750W IC4 680W IC3 750W IC2 680W 10mF 10mF ALL PARTS AT IC1 750W CAUTION! 1MW 1W COVER ANY EXPOSED TERMINALS WITH HEATSHRINK 470W 1W** TRIAC2 300W 10nF X2 Cable tie L3 1kW 1W 18kW TRIAC1 300W 10nF X2 Cable tie L2 1kW 1W 15kW CON8 IF CURRENT DETECT NOT USED L4 L3 L2 10nF X2 1kW 1W 30kW 10kW L1 **10nF X2 & Cable tie L1 330W 1W CURRENT DETECTION COMPONENTS 20kW 2.2kW P4KE15A IEC CONNECTOR TVS1 1kW 1W NYLON SCREWS SHOULD BE USED T1 AC1010 1000mF CON5 CON9 siliconchip.com.au NOTES: USE 10A MAINS WIRE EXCEPT FOR CON8 TO CON9, WHERE 7.5A WIRE CAN BE USED. ALSO EARTH LEAD SHOULD BE ONE CONTINUOUS LENGTH WITH INSULATION REMOVED AT EACH GPO EARTH CONNECTION. ZD1 5.1V The large cutouts for the mains GPO sockets and IEC connectors can be made by drilling a series of small holes around the inside perimeter, knocking out the centre piece and filing the outline to a smooth finish. Other methods include using a speed bore drill to remove most of the inner area and then filing the rest to the shape required. Once the drilling and filing are complete, install the IEC connector(s). The PCB can then be placed inside the case, and the LEDs inserted into the bezels as you drop the PCB into the enclosure. Then secure the PCB to the base of the enclosure with 6mm-long M3 machine screws into the case’s integral brass inserts. We specify Cliplite bezels specifically since they cover the LEDs and are rated to withstand 16kV, so they protect against a possible shock hazard should the LEDs fail. Using exposed LEDs at mains potential could be an electric shock hazard. Most 5mm LEDs don’t specify the insulation capability of the package between the LED dome and the LED die inside. So use the bezels specified to ensure safety. The IEC connector must be secured using countersunk 10mm Nylon M3 screws, although you can use metal nuts. The Nylon screws are essential as they avoid the possibility of the screws becoming live (at mains voltage) should a mains wire inside the enclosure come adrift and contact a screw holding the IEC connector. Before attaching the mains GPO outlets and LED indicators, you can download and print out the front panel label shown in Fig.10. Details on making a front panel label are at siliconchip.au/ Help/FrontPanels The download includes two versions of the front panel. One front panel version does not have labelling for the Mains Detect Input IEC connector if you haven’t installed it. All wiring must be run as shown in either Fig.8 or Fig.9, using mainsrated cable. Be sure to use 10A wire (7.5A is OK for the Mains Detect Input wiring). The brown wire must be used for the Active wiring, blue for Neutral and green/yellow striped for the Earth wiring. Note again that if you are not installing the Current Detection, then the two pads for CON7 need to be joined using 10A mains wire (ideally brown). S2 VR1 10kW START RATE UP DELAY COVER LED LEADS IN HEATSHRINK TUBING Fig.9: the wiring for the non-GPO version is similar to that shown in Fig.8 but the Earth wires are terminated slightly differently. The output cables can be made either by connecting mains flex to individual line sockets, or by cutting the plug ends off 10A extension cords. Australia's electronics magazine March 2024  81 For the lid-mounted GPOs, the Earth wire from the IEC socket must go straight to the first GPO Earth terminal, then to the second and so on as a single length of wire. To do that, strip the insulation off a single piece of wire at each connection point. Take great care when making the connections to the mains sockets (GPOs). In particular, be sure to run the leads to their correct terminals. The GPO sockets will have the A, N and E clearly labelled, although Active might be marked with an L (Live) instead of an A. Do the screws up tightly so the leads are held securely. Similarly, ensure that the wires to the two-way screw terminals are firmly secured. For the version without GPOs, the Earths are connected to crimp eyelets that are then all attached to the M4 Earth bolt, which is secured to the case using a star washer and nut. Be sure to insulate all the Active and Neutral connections on the IEC connectors with heatshrink tubing for safety, and cable tie the wires as shown to prevent any broken wires from coming adrift. Use 5mm diameter heatshrink for the wires to the IEC connector. Secure the Active and Neutral leads together using cable ties. Also, use neutral-cure silicone sealant (eg, roof & gutter silicone) to cover the Active bus piece that connects the Active pin to the fuse at the rear of the IEC connector. That bus is live, and there is no need to leave it exposed. Testing Always attach the lid using at least two screws at diagonally opposite locations before switching on the power. All the circuitry is operating at mains potential, so do not touch the components unless the power is off and the IEC power leads have been disconnected for at least ten seconds. Before applying power, check your wiring carefully and ensure all mains connections are covered in heatshrink tubing and the wiring is cable tied. Then install the 10A fuse inside CON5’s fuse holder and verify that IC9 is plugged into its socket and correctly orientated. If you have installed the Mains Input Detection circuitry, insert the 1A fuse into CON8. VR1 can initially be set to mid-travel for a nominal 10-second sequence interval. If set fully anti-clockwise, VR1 gives a 100ms sequence delay Fig.10: the lid label indicates which inputs and outputs have which function, while the side label shows what each LED means. There’s another version of the label that you can download from our website without the text for the Mains Detect Input if you aren’t using that feature. 82 Silicon Chip Australia's electronics magazine siliconchip.com.au period while near full-clockwise (about 10° away) gives a 22 second sequence interval. Set switch S1 to the left (open) position to disable Current Detection. Set S2 to the right for a startup delay and S3 to the left so VR1 sets the on-­ sequence period. Remember the earlier advice to unplug the unit before opening the lid and adjusting any settings. Also note that settings like the periods are only stored at power-up. Making adjustments while the power is on won’t do anything. On power-up, check that the power LED lights and that the OUT1 LED lights after about ten seconds, followed by OUT2 after another ten seconds. The remaining LEDs should light after similar periods. You can test the off-sequencing if you have installed the Current Detection or Mains Input Detection circuitry. To do this, unplug the unit, open the lid and move S1 to the right (closed) position. Reinstall the lid and power it back on. If using Mains Input Detection, plug CON8 into the mains and the startup sequence should begin. Disconnect or switch off that supply and the LEDs should switch off in sequence, starting with the last output and finishing with OUT1. The default delay for the off-sequence is two seconds. Alternatively, if using the Current Detection circuitry instead, plug an appliance into OUT1 and switch it on to trigger the on-sequence, then unplug it or switch it off to trigger the off-sequence. Again, the off-sequence should start with the last output and finish with OUT1. We have installed surfacemounting GPO sockets on the interior of the lid. An alternative method is shown in Fig.9. Exposed terminals should be covered with heatshrink tubing, while the active busbar on the IEC connected must be covered with neutral cure silicone for safety. Settings Two lots of settings can be made. First, there are the on-sequence and off-sequence periods, set using VR1. The on-sequence period is set with switch S3 in the left position and is only stored at the instant that power is switched on. To set the off-sequence rate, you also use VR1, but place S3 in the right-hand position before powering it up. Each value is stored in flash memory, so it is recalled at power up, allowing you to set these two periods independently. For these settings, VR1 can be adjusted from fully anti-clockwise to siliconchip.com.au Australia's electronics magazine March 2024  83 Ideal Bridge Rectifiers Choose from six Ideal Diode Bridge Rectifier kits to build: siliconchip. com.au/Shop/?article=16043 28mm spade (SC6850, $30) Compatible with KBPC3504 10A continuous (20A peak), 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: MSOP-12 (SMD) Mosfets: TK6R9P08QM,RQ (DPAK) 21mm square pin (SC6851, $30) Compatible with PB1004 10A continuous (20A peak), 72V Connectors: solder pins on a 14mm grid (can be bent to a 13mm grid) IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ 5mm pitch SIL (SC6852, $30) Compatible with KBL604 10A continuous (20A peak), 72V Connectors: solder pins at 5mm pitch IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ mini SOT-23 (SC6853, $25) Width of W02/W04 2A continuous, 40V Connectors: solder pins 5mm apart at either end IC1 package: MSOP-12 Mosfets: SI2318DS-GE3 (SOT-23) D2PAK standalone (SC6854, $35) 20A continuous, 72V Connectors: 5mm screw terminals at each end IC1 package: MSOP-12 Mosfets: IPB057N06NATMA1 (D2PAK) TO-220 standalone (SC6855, $45) 40A continuous, 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: DIP-8 Mosfets: TK5R3E08QM,S1X (TO-220) See our article in the December 2023 issue for more details: siliconchip.au/Article/16043 84 Silicon Chip The finished Mains Power-Up Sequencer built to include the Mains Input Detection and with the panel label that includes the Mains Detect Input label. An alternative label can be used that does not have the mains detection labelling if this feature isn’t used. about 10° short of fully clockwise. That gives a range of 100ms (anticlockwise) to about 22s (near clockwise). The other settings are made with VR1 set fully clockwise, which causes the Sequencer to enter another mode. It does two things in this position. One is to measure the voltage from the precision rectifier when no appliance is connected to OUT1. This is the offset voltage from the op amp circuit, which is usually a few millivolts. This value is stored and subtracted from any future Current Detection measurements. If you are not using the Current Detection, it still happens but won’t affect anything. The other function of this mode is setting the off-sequence direction. With the power off and the unit unplugged from the wall, rotate VR1 fully clockwise. No appliance should be plugged into the sequencer GPO (OUT1) outlet or any mains power applied to the Mains Detect Input (if used). If switch S3 is set to the right, you will set the off-sequence to forward, meaning that OUT1 switches off first. If S3 is placed to the left, it sets the reverse off-sequence direction, so the last outlet switches off first. The initial setting of the programmed microcontroller is this reverse off-sequence. After a few seconds in this mode, the Sequencer can be unplugged. After that, remove the lid and rotate VR1 back from fully clockwise to the desired period for the sequence rate, depending on the position of S3. This is important as, if VR1 is left set at the fully clockwise position, the Sequencer will not run to switch on any outlets. Table 2 summarises the functions of switches S1, S2, S3 and potentiometer VR1. Settings are only changed at SC power-up. Table 2 – power-up settings Switch Left (open) Right (closed) S1 No Mains/Current Mains/Current Detection Detection enabled S2 No initial delay Delay before on and off sequences S3 VR1 sets on-rate VR1 sets off-rate 100ms to 22s (from full anti-clockwise to 10° less than clockwise) S3 Reverse off-sequence Forward off-sequence Fully clockwise (also stores full wave rectifier offset) Australia's electronics magazine VR1 siliconchip.com.au