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Building the SPARK ENERGY METER Part 2 – By Dr Hugo Holden and John Clarke Last month we introduced our new Spark Energy Meter, an essential workshop tool for anyone who tinkers with automotive ignition systems – old or new! Now we get to the good bit: putting it all together . . . T he Spark Energy Meter is built on two 111 x 85mm PCBs, which stack horizontally inside a 119 x 94 x 57mm diecast box using 9mm spacers. The first board, coded 05102151, contains the majority of components, with the exception of the 30 x 100V zener diodes – these are all on the second board, coded 05102152. A power switch protrudes out from the side of the box, while the power LED and high range LEDs pass through the lid. The LCD is also attached to the case lid. Before you start assembly, place the zener diode PCB centrally in the bottom of the diecast box and mark the positions of the four 3mm holes used for mounting. You can drill these holes now or later. Construction The complete parts list (along with the circuit diagrams and descriptions) were included in Part 1 last month – refer to that article for all components. Start by fitting 100V zener diodes ZD1 to ZD30 on the second PCB (see Fig.3). These all face the same direction on the board but the tracks underneath actually connect them with 15 in one 38  Silicon Chip orientation and 15 in the other. The connection to the spark plug is made via an M205 fuse clip. The fuse tab toward the plug bends down and around the edge and under the PCB. The fuse tab toward the zener diodes is broken off by bending this backward and forward repeatedly with a pair of pliers. Just a few times will cause it to break off. Strip a few mm of insulation from each end of a 200mm long mains-rated wire and terminate one end into the HV output on the PCB. Cover the wire in heatshrink tubing, leaving sufficient wire free at the other end for termination into the HV terminal on the second PCB. Now move onto the other PCB. Fig.4 shows the component overlay. Install the small resistors first. The resistor colour code is shown opposite but it’s always wise to double check each value with a digital multimeter. Leave the 150 5W resistor for later. Diodes are next and as they’re polarised, they need to be installed with the striped end oriented as shown in the overlay diagram. Note that there are several types. D1-D4 are UF4007, D5-D14 are BAT46, D15 a 1N4148 and D16 a 1N5819. Zener diode ZD31 can also be installed now. Solder the ICs next, with pin 1 toward the top of the PCB (S1 side) in each case. Be sure that the correct IC is placed in each position. REG1 and Q1-Q3 can go in next. Now fit the capacitors, starting with ceramic and polyester which of course are not polarised. Note the positions for the 100nF capacitor, the 10nF 630V (or 3kV) and the 1nF 100V (or 3kV) ceramic types. These have a higher voltage rating than the remaining capacitors. The electrolytic types are polarised and must be inserted the right way around – the longer lead is the + side. Install the reed relay now, then trimpot VR1. Switch S1 is fitted directly to the PCB and the two 6-way pin headers for the LCD can also be soldered in, along with the two PC stakes and adjacent 1505W resistor. LED1 and LED2 are mounted so that the top of each LED is 31mm from top surface of the PCB. Take care that the anode (longer lead) is placed in the component hole labelled “A”. The 9V battery holder is secured to the PCB using a countersunk M3 screw and nut with a piece of TOP-3 siliconchip.com.au silicone washer between it and the PCB. The washer is trimmed to size with scissors and a hole cut in the centre for the screw. There will already a hole in the silicone washer (due to it being punched for the TOP-3 package) but this will be in the wrong position. Wires for the 9V battery clip are passed through the PCB holes as shown for strain relief, helping to prevent the wires from breaking due to flexing, when terminated to the 9V inputs. The red wire is terminated to the + side, black to –. A short 70mm length of 7.5A 250VAC mains wire (green or black) is terminated into the ‘CASE’ terminal and the other end crimped to a crimp eyelet. Box bits If you haven’t drilled the mounting holes in the box, do so now. If using countersunk screws, countersink the holes on the outside of the box. Fig.5 shows the hole positions for the spark plug and earth screw hole on the end of the box and the switch hole on the side of the box. For the spark plug, (which, as mentioned last month, needs to be of the resistor variety) this needs to be drilled smaller than required and then carefully reamed out. There will be a diameter close to 13.5mm where the spark plug will screw in, cutting some thread but mainly held in place by friction. Note that the PCB is designed for a spark plug with a 12.7mm reach. If siliconchip.com.au Resistor Colour Codes p p p p p p p p p p p p p p p p p p p p p p p p p p p p Qty 2 1 1 1 2 2 1 1 1 1 1 4 1 1 1 1 4 3 1 1 1 1 1 1 1 1 2 1 Value 4-Band Code(1%) 5-Band Code (1%) 10M brown black blue brown brown black black green brown 9.1M white brown green brown white brown black yellow brown 5.1M green brown green brown green brown black yellow brown 1M brown black green brown brown black black yellow brown 510k green brown yellow brown green brown black orange brown 470k yellow violet yellow brown yellow violet black orange brown 270k red violet yellow brown red violet black orange brown 240k red yellow yellow brown red yellow black orange brown 220k* red red yellow brown red red black orange brown 180k brown grey yellow brown brown grey black orange brown 150k brown green yellow brown brown green black orange brown 100k brown black yellow brown brown black black orange brown 91k white brown orange brown white brown black red brown 68k blue grey orange brown blue grey black red brown 62k blue red orange brown blue red black red brown 33k orange orange orange brown orange orange black red brown 20k red black orange brown red black black red brown 10k brown black orange brown brown black black red brown 8.2k grey red red brown grey red black brown brown 5.1k green brown red brown green brown black brown brown 1.5k brown green red brown brown green black brown brown 1k brown black red brown brown black black brown brown 240* red yellow brown brown red yellow black black brown 200 red black brown brown red black black black brown 100* brown black brown brown brown black black black brown 1505W (value printed on resistor body) 47 yellow violet black brown yellow violet black gold brown 10* brown black black brown brown black black gold brown * For calibrator March 2015  39 Capacitor Codes a longer reach spark plug is used (as we did), use a spacer to cover the bare thread that’s exposed on the outside of the case. This spacer can be seen in the photo above. The LCD module is mounted onto the lid of the case. The label artwork, which shows the positioning for the LCD module and the LED holes, also makes a great template. It can be photocopied or downloaded from the SILICON CHIP website (see panel). The rectangular cut out is made by drilling a series of small holes (eg 2-3mm) inside the perimeter, then knocking out the piece and filing to shape. The PCBs are attached to the box using 9mm stand-offs. Four stand-offs, held by 12mm x M3 screws, are placed in the base of the case. Next comes the lower PCB, followed by the set of four spacers screwed onto the remaining thread of the screws. The earth tag on the spark plug that bends around to face the inside insulated electrode is removed. This can be done using pliers to bend the tab back and forth to shear it off. Then file the rough edges down. Screw the spark plug in to make contact between the centre electrode and the M205 fuse clip on the PCB. The second PCB stacks on top of the first. This is done after the interconnecting wire between the HV terminals on each PCB is connected. The top PCB is secured with the M3 x 5mm screws. The crimp eyelet is secured to the case with an M4 screw, star washer and nut with the spade connector attached on the outside of the box using the same screw. Wiring the display The 9-way rainbow cable is stripped into a 5-way length and a 4-way length. Separate out the wires for about 100mm on one end and strip off the insulation by about 1mm on this end of the cable. Terminate to the LCD terminals and 40  Silicon Chip 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V SPARK M205 FUSE CLIP PLUG HV 100V 100V 100V 100V 100V 100V 100V 100V ZD1–ZD30: 05101152 100V 100V 100V 5W SPARK ENERGY METER EIA code 224 104 473 103 102 C 2015 Value μF   IEC value code 220nF 0.22μF 220n 100nF 0.1μF 100n 47nF 0.047μF 47n 10nF 0.01μF 10n 1.0nF    NA 1n Fig.3 (above) is the component overlay for the zener diode PCB. All zeners are oriented the same direction, so construction is easy! Below is a matching photo of this board, again printed very close to life size. The fuse clip on this board is obscured by the spade lug insulator. solder in place after a short length of heatshrink cable is placed over each wire. The heatshrink supports the wire to prevent breakage. Note that the connection pins on the rear of the display are numbered from 1 to 13, but with pin 3 missing and left as a blank space. This separates the power at pins 1 and 2 from the remaining pins. Pin 4 is not used. The other end is terminated into the header plugs and the metal contacts. These are designed to crimp the wires and then hold the wire and insulation using another set of bendable pieces on the terminal. Use pliers to crimp these down. A small amount of solder applied to the crimped connector where the wire is crimped will prevent the wire slipping out from the connector. The crimp connectors are slid into their backing shells and pressed in using a small screwdriver till they click in place. Make sure the LCD module is wired correctly before applying power. On power-up (when the 9V battery is connected or a separate supply), siliconchip.com.au BAT46 10F 10F 10M 10k 470k D14 BAT46 470k D12 10k BAT46 5.1M 1 + Q1 – 9V 4066 IC5 2N7000 9V BATTERY 15110150 1F D11 D10 To LCD Panel Meter 100F LED2 1.5k 100k 100nF 100nF 10k 200 1nF 100nF 10M 1M 68k 150k IC1 LMC6484 4013 Q2 2N7000 IC4 PWR LED1 510k 220nF 100k 240k 62k 33F HI 5819 BAT46 VR1 1M METER 0 1k A Accounting for the 150 wirewound resistor tolerance D9 100k 100k ZD31 12V 20k 33k BAT46 510k 270k D5 BAT46 IC3 LMC6484 180k BAT46 20k 4004 BAT46 BAT46 D7 D8 D13 A 20k 1F 100nF 20k IC2 9.1M 91k 3kV 47 D15 4148 D6 Q3 2N7000 COIL 4047 47nF 5.1k 47 RELAY1 HV 8.2k SPARK ENERGY METER C 2015 100nF 630V CASE 78L05 100nF 1nF 100nF REG1 S1 + D4 UF4007 D3 10nF 3kV D2 UF4007 – UF4007 D1 UF4007 150 5W 1F D16 Fig.4: similarly, the main PCB component overlay and matching photo below. 25110150 SPARK ENERGY METER Construction C 2015 order is in the text. ZD1–ZD30: 100V 5W 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V 100V HV SPARK M205 FUSE CLIP PLUG the power LED should show “.000” or close to it. VR1 can be adjusted to set the display to zero if needed. If the display does not show these numbers, check wiring between the PCB and display. Finally, make up a lead to connect to the spade connector on the case of the Spark Energy Meter. This comprises the remainder of the 1m mains wire with an alligator clip on one end and a crimp spade connector on the other. This is used to connect to mains earth when siliconchip.com.au testing the spark from an ignition coil. If you need a suitable ignition coil driver then the High Energy Ignition from November and December 2012 includes a spark test feature where the coil is driven to check ignition operation. Calibrator construction The Spark Energy Meter Calibrator is constructed using a PCB coded 05101153 and measuring 47 x 61mm. Even though you normally set the calibrator to give exactly 5V output, the reading on the Spark Energy Meter could be ±5% out due to the tolerance of the 1505W wirewound resistor at the input (ie, it could be anywhere from 143to 157). Wirewound resistors are not known for their tight tolerance! So your reading (which depend on this resistor) could also be out. If you want it exact, the way around this is to measure the resistor and compensate. If you happen to measure exactly (or even very close to) 150, you don’t have to do anything. But if it’s out, set the voltage from the calibrator higher or lower than 5V by the ratio of your resistor to a perfect (150) resistor. For example, if your resistor measures 155, set the voltage to 155/150 x 5, or 5.17V. Conversely, if it’s lower, say 145, set the calibrator output voltage to 145/150 x 5, or 4.83V. The PCB will clip into the side pillars in a standard UB5 utility box (83 x 54 x 31mm) although we present this as a bare PCB. Note that there are two versions, the calibrator and the PWM driver, so follow the overlay diagram for the version you are building. The PWM circuit will produce an approximately 500Hz waveform. Depending on your application, this may be too high. For a small DC motor for example, a 100Hz drive may be more suitable. The 10nF capacitor can be changed. Use a 47nF for a nominal 100Hz PWM drive. Follow Fig.6 for the PCB assembly. Install the resistors first. These are colour coded with the resistance value as shown in the table overlaf. A digital multimeter should also be used to confirm the values. Note that for the calibrator, there is a wire link required between VR1 and VR2. This wire link is replaced with a 1N4148 diode if the alternative circuit is built. Diodes are next and these need to be installed with the correct polarity with the striped end oriented as shown in the overlay diagram. Install the IC now noting the correct orientation for pin 1. REG1 and Q1 can March 2015  41 92mm Fig.5: drilling detail for the end of the Spark Energy Meter diecast case (at right) and the side of the same case (below). See pic and note at right re spark plug tapping. 12mm 24mm 4mm DIAM FOR EARTH LUG 52mm Drill and ream the spark plug hole through the end of the case to a size just smaller than the plug thread, then use the plug thread itself to “tap” the softer aluminium. This will make the spark plug captive. 39mm BOX END 13.5mm DIAM FOR SPARK PLUG 11.5mm 90mm 117mm 24mm 52.5mm 52mm 6mm DIAM FOR POWER SWITCH Similarly, the minus (-) terminal on CON2 of the Calibrator connects to the minus (-) PC stake on the Spark Energy Meter. Make sure the calibrator is powered by a different supply to the Spark Energy Meter and that at least one supply is floating with respect to earth (ie use a battery for one supply). Switch on the Spark Energy Meter and calibrator and adjust the trimpot within the LCD module for a reading of 100mJ. Using it BOX SIDE 115mm then be installed. These lie horizontally on the PCB after the leads are bent over by 90 degrees to fit into the mounting holes. The metal tabs can be held against the PCB using M3 x 10 screws and M3 nuts if required. Q2 and Q3 are mounted next, taking care not to transpose them. The capacitors can be installed next; the electrolytic types with the polarity shown. Install the three PC stakes, along with the trimpots and the two 2-way screw terminals. These are oriented with the wire entry toward the outside of the PCB. screw terminals. Connect a multimeter to the 0V and 5V PC stakes and adjust VR1 for a reading of 5.0V. The second adjustment requires access to a frequency meter. Many multimeters now include frequency metering and will be suitable for the 250Hz setting. Alternatively an oscilloscope can be used. Using the test point TP1 and the 0V PC stake as the common connection, adjust VR2 for 250Hz. On an oscilloscope this will be a square wave with a 2ms high level duration and a 2ms low duration. For calibration of the Spark Energy Meter, the plus (+) terminal on CON2 of the Calibrator connects to the plus (+) PC stake on the Spark Energy Meter. Testing and setting up Apply a 7-12V supply to the input 100F 10F REG1 LM317T IC1 7555 IN OUT ADJ 0V +12V BC337 Q2 CON2 CON1 + – 10nF 10F R1 LK1 VR2 10 100 TP1 VR1 100 V ADJ. 42  Silicon Chip Q1 IRF540 100nF OUT 35110150 SPARK TESTER CALIBRATOR 4004 4004 D2 D1 240 Fig.6: the calibrator PCB component overlay and an enlarged photo (for clarity) alongside. Trimport VR1 adjusts for exactly 5V output (or calculated output to account for wire-wound resistor tolerance – see text). VR2 adjusts for the correct frequency at 250Hz. There are two ways to use the meter. Firstly, the meter’s ground connection is clipped onto a secure ground point to avoid the meter body developing a high voltage potential during the spark. The spark plug wire can be lifted from one of the engine’s spark plugs and plugged onto the meter spark plug input. Then with the engine running (which will have a miss as one spark plug is not operational), the meter reads that spark energy in milliJoules (mJ). This can be done for all the engine’s spark plug feeds for comparison, one at a time. In a 4-cylinder car, the frequency of the sparks presented to a single plug by the distributor is about 4Hz when the idle rate is 500 RPM. Some cars which have an individual ignition coil per spark plug with custom Q3 BC327 C 2015 siliconchip.com.au assemblies can also be measured if an appropriate connector system is made to access the high voltage terminal where the spark is normally generated and using a non-powered dummy coil/plug module to re-seal the combustion chamber. The second way to use the meter is to disconnect the ignition coil from the distributor and measure the its output directly while cranking the engine (naturally, the engine will not start). This will give a higher energy reading as it bypasses the losses in the distributor’s spark gap and the differences in these measurements will give an indication of the distributor’s spark losses. In systems with wasted spark or two terminal ignition coils as in Commodore and many General Motors engines, one of the ignition coil outputs is shorted to ground and the other terminal is measured by the meter. SC Use as a low voltage speed control or dimmer The calibrator circuit published on page 62 of last month’s issue included an alternative PWM Drive Circuit (shown in a yellow panel). This modification can then make this board usable as a 12V DC motor speed control or even a 12V incandescent/LED light dimmer. See the revised component overlay below. There is a link (LK1) and a pair of unused pads alongside VR2. Replace this link with a 1N4148 diode (anode towards the PCB edge) and another 1N4148 across the unused pads (same orientation). Two other changes are needed: VR2 is changed from a 50kΩ to 250kΩ (or it could be replaced with an external pot if that’s more convenient) and R1 is reduced from 220kΩ to 1kΩ . A 12V motor or lamp needs to be run from the incoming 12V supply (at CON1), not the + output terminal on CON2, which is at 5V. You take +12V DC from the CON1 + input terminal and connect the 0V to the CON2 – output terminal, as shown below. Obviously, if you have a 5V motor or lamp, you can use both “normal” output terminals, CON2. 12VDC MOTOR OR LAMP CONNECT AS SHOWN CON2 OUT IN IC1 7555 – 10nF 5V VR1 100 V ADJ. D4 10 4148 VR2 250k D3 R1 1k TP1 4148 100 0V + OUT ADJ 0V +12V 10F 240 BC337 Q2 Q1 IRF540 100nF Q3 35110150 SPARK TESTER CALIBRATOR REG1 LM317T CON1 12V DC BC327 C 2015 Fig.7: the changes (shown in RED) required to turn the calibrator circuit into a 5V or 12V motor speed controller or incandescent/LED lamp dimmer. At 12V, connected as shown above, it will deliver up to 5A if the 12V supply is capable of that current. At 5V, the limit would be 1A, the maximum current allowed through D1 and D2. (The LM317T can deliver around 1.5A). siliconchip.com.au A nice label adds professionalism and a “finish” to your project. The label we have prepared (which also doubles as a template for drilling holes and cutting the LCD readout hole) is shown below, reproduced same size. You have several options in making a label: If you have access to a colour photocopier, it can be copied onto paper (either plain paper or photo paper). Or it can be downloaded from siliconchip.com.au and printed on a colour printer. After cutting out (don’t forget the LED holes!) it can be glued to your panel with a suitable adhesive or neutral cure silicone. However, this type of label will be easily damaged. It can be laminated (with a hot melt laminator) although this will tend to separate over time. For a more rugged label, download and print onto clear overhead projector film (using film suitable for your type of printer) as a “mirror image”, so the printout will be on the back of the film when the label is affixed. Attach with silicone sealant. A light-coloured silicone will be needed if the lid is black. Another alternative, and one which is arguably the toughest and longest-lasting, is to use a synthetic ‘Dataflex’ sticky-backed label that is suitable for inkjet printers or a ‘Datapol’ sticky label for laser printers and affix using the sticky back adhesive already on the label. Cut out the holes in the label with a sharp craft knife. These labels are available from www.blanklabels.com.au and sample sheets are available on request to test these in your printer. Google “blank labels dataflex” or “blank labels datapol” for more information. 100F 10F 4004 4004 D2 D1 M Producing a great-looking label! Fig.8: full-size label which can also be used as a template. March 2015  43