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By JOHN CLARKE Programmable Ignition System For Cars; Pt.2 Six Versions To Build To Suit Your Car’s Trigger Input! This month, we describe the circuit for the LCD Hand Controller module and provide all the assembly details for the Programmable Ignition. There are six versions to build. L AST MONTH, we published the circuit details for the Programmable Ignition Timing Module and its companion Ignition Coil Driver Module and described their operation in some detail. The various input trigger circuits (points, reluctor, Hall sensor, optical, etc) were also described. LCD Hand Controller That just leaves the LCD Hand Controller Module. Its circuit is shown in Fig.7. It comprises an LCD module, a 4017 decade counter (IC1), a DB25 socket and several pushbutton switches. This unit connects to the main circuit via a standard DB25 RS-232 cable. Signals from the microcontroller 66  Silicon Chip in the Programmable Ignition Timing Module drive both the LCD module and IC1. IC1 has 10 outputs and each output independently goes high in sequence as it is clocked at its pin 14 input. A high at the reset (MR, pin 15) sets the “0” output at pin 3 high. Each output connects to a switch. When a switch is closed, it pulls pin 9 of the DB25 socket high whenever its corresponding output on IC1 is high. This allows the microcontroller (in the Ignition Timing Module) to recognise which switch is closed. The LCD is driven using data lines DB7-DB4. The display readings are entered via the data lines and are controlled via the EN and RS (Enable and Register Select) inputs. Note that the data lines and the EN & RS lines are all connected to ground via 330W resistors. These resistors allow the LCD module to be driven without the signals being corrupted by interference from the car’s ignition. Finally, trimpot VR1 is used to adjust the display contrast. Construction OK, that completes the circuit description. Let’s now build all the modules for the unit. As shown in the accompanying diagrams, the Programmable Ignition system is built on three PC boards – one for the Programmable Ignition Timing Module (code 05104071, 103 x 82mm); one for the Ignition Coil Driver Module (code 05104072, 40 x 39mm); and one for the LCD Hand Controller (code 05104073, 115 x 65mm). The Programmable Ignition Timing Module board is housed in a diecast aluminium case measuring 119 x 93 x 57mm, while the Ignition Coil Driver board goes into a much smaller diecast case measuring siliconchip.com.au Fig.7: the circuit for the LCD Hand Controller is quite simple. It uses 10 switches, an LCD module, a 4017 counter (IC1), a DB25 socket, a 10mF capacitor and a few resistors. Trimpot VR1 sets the display contrast. 51 x 51 x 32mm. The LCD Hand Controller board goes into a 120 x 70 x 30mm plastic case with a clear lid. Before installing any parts, check each PC board for etching defects by comparing it against a printout of its pattern (you can download the relevant board files from the SILICON CHIP website). Check also that all the holes have been drilled and that the hole sizes for the larger parts are correct. Ignition timing module There are six different component layouts for this board, one for each different trigger input. It’s just a matter of choosing the one that’s applicable to your car. For example, if your car has a reluctor distributor, follow the reluctor version overlay diagram – see Fig.10. Similarly, if it has a Hall effect or Lumenition pickup module, use the layout of Fig.11, etc. It’s not difficult to recognise the different sensor types. Reluctor dissiliconchip.com.au tributors have a coil and a magnetic ring that has as many points (or protrusions) as the number of engine cylinders. By contrast, Hall effect distributors include a metal vane that passes through a gap in the Hall sensor itself. Lumenition triggers are similar to Hall effect sensors and so the overlay diagrams for these trigger types are the same – see Fig.9. Start construction by installing PC stakes at the external wiring points, then solder in all the wire links. That done, install the resistors, using Table 1 as a guide to select the values. In addition, it’s also a good idea to check each resistor using a digital multimeter (DMM) to make sure you have the correct resistor for each position. Next, install the IC socket for the microcontroller, making sure that it’s oriented with its notch at the lefthand end, as shown. Don’t install the microcontroller (IC1) at this stage though – that step comes later. Diode D1 and TVS1 are next on the list. Note that D1 must be oriented as shown, while TVS1 can be installed either way around. Follow these with the transistor(s) and REG1, taking care to ensure that these parts are oriented correctly. Trimpot VR1 should now be installed if you are building the reluctor version (Fig.10). It should be oriented with its adjusting screw to the left. The link headers for LK1 and LK2 can be installed now. LK1 is a 3-way header while LK2 is a 2-way header. Place a jumper shunt over two of the three pins for LK1 and another jumper shunt onto both pins for LK2. Now for the capacitors. Several types are used on the board: ceramic, MKT and electrolytic. The ceramic capacitors are all shown on the overlays in yellow, so that you don’t get them confused with the MKT types. Be sure to orient each electrolytic capacitor with the polarity shown. Once the capacitors are all in, install the crystal (X1). Note that the crystal’s metal case is earthed using a short wire link. This link is soldered April 2007  67 Fig.8: this is the points version. Secure all wiring leads to the board using cable ties and cover the connections to the PC stakes with heatshrink tubing or silicone, to prevent them coming loose. Fig.9: the engine management trigger version requires no additional input conditioning circuitry. In this case, the ECU trigger signal goes straight to pin 6 of IC1 via a 2.2kW resistor. to the case and runs to a pad on the PC board between the two 22pF ceramic capacitors. Sensym pressure sensor If you are using the Sensym absolute pressure sensor (eg, if you car doesn’t 68  Silicon Chip already have a MAP sensor or you are not using a seconhand MAP sensor), then this can be installed now. Note the orientation notch on the sensor – this goes towards the righthand edge of the PC board. If you get the Sensym sensor’s orientation wrong, it will not be powered but no damage will result from doing this. Inductors Inductors L1 & L2 are next on the list. First, L2 is made by passing a 0.7mm tinned copper wire link siliconchip.com.au Fig.10: follow this parts layout diagram if your car’s distributor has a reluctor pickup. The Sensym pressure sensor is used only if there is no external MAP sensor (applies to all versions). Fig.11: this is the layout to follow if the distributor uses a Hall Effect device or a Lumenition module. Take care with component orientation during assembly. through three ferrite beads. A length of the 4mm heatshrink tubing is then slid over the three cores and shrunk down to hold everything in place, after which the assembly can be soldered to the board. Inductor L1 is much larger. It’s siliconchip.com.au made by winding 23 turns of 0.5mm enamelled copper wire through a 15 x 8 x 6.5mm powdered-iron toroidal core. These turns should be evenly spaced around the core, as shown on the overlays. That done, the wire ends are stripped of insulation and soldered to the PC pads. The toroid is then secured to t he board using two plastic cable ties. Finally, the DB25 socket can be installed in position. Before doing this though, two D-connector nut extenders must to be attached to the April 2007  69 Fig.12: build this version if your distributor has been fitted with a Crane optical pickup. Make sure that inductor L1 is firmly secured, to ensure reliability (all versions). Fig.13: the Piranha optical pickup version is almost identical to the Crane version but note the different locations for the 22kW and 120W resistors. PC board. These are simply passed through their two mounting holes and secured using spring washers and nuts on the underside of the board. In addition, the righthand extender is fitted with a Nylon washer to prevent the spring washer and nut from short70  Silicon Chip ing to nearby tracks. Don’t leave this washer out! By contrast, the lefthand extender makes contact with the ground track on the PC board, so that the shell of the socket is earthed when it is installed. That way, when the DB25 lead is connected, its shield will also be earthed. The DB25 socket can now be secured in place using a second set of nut extenders and its pins soldered to the PC pads. Note that you may need to cut down the extender threads so siliconchip.com.au Fig.14: these diagrams show the modifications required to invert the output from the Ignition Timing Module. the nuts sit flush with the socket’s mounting flange. Inverting the output In normal operation, the RB3 output from the Programmable Ignition Timer Module goes high in order to turn on transistor Q1 (via Q3 & Q2) in the Ignition Coil Driver. This in turn allows current to flow through the primary of the coil. Conversely, when RB3 goes low, Q1 switches off, the current through the coil is interrupted and the coil “fires” the relevant spark plug. So a low-going signal at the Ignition Timing Module’s output normally causes the Ignition Coil Driver to fire a plug via the coil. However, there may be some applications where the output from the Programmable Ignition Timing Module needs to be inverted; ie, so that a low output “charges” the coil and a high-going output causes the plug to fire. This may be the case if you connect the Programmable Ignition Timing Module to a different ignition coil driver. In this case, an inverted output can be provided using the tachometer driver transistor (Q4). The necessary changes to the circuit and to the PC board layout are shown in Fig.14. The only extra parts required are a 220W resistor and some tinned copper wire for the link. Housing Having completed the board assembly, the next step is to install it in its metal diecast case. Fig.15 shows the assembly details. The first step is to position the board inside the case and mark out its four mounting holes. That done, remove the PC board and drill the mounting holes to 3mm. Deburr each hole using an oversize drill bit, then secure a 6mm-long tapped spacer to each mounting point using an M3 x 15mm screw inserted from the outside of the case. You will also have to drill a hole in one end of the box to accept a cable gland for the various external leads (ie, +12V lead, trigger signal leads and signal output lead). An additional hole for a second cable gland will also be required if you are using an external MAP sensor (see Fig.15). Next, a 3mm hole must be drilled through the side of the box adjacent to the GND (0V) PC stake. This mounting hole is used to terminate an earth wire from the PC board via a crimped eyelet connector. A second wire terminated in an eyelet connector is also Table 2: Capacitor Codes Value 220nF 100nF 10nF 2.2nF 1nF 470pF 22pF mF code 0.22mF 0.1mF .01mF .0022mF .001mF    NA   NA IEC Code    EIA Code 220n 224 100n 104 10n 103 2n2 222 1n0 102 470p 471 22p 22 Table 1: Resistor Colour Codes o o o o o o o o o o o o o siliconchip.com.au No. 2 3 1 7 2 1 1 3 2 1 1 9 Value 100kW 47kW 22kW 10kW 2.2kW 1.8kW 1.2kW 1kW 470W 120W 100W 10W 4-Band Code (1%) brown black yellow brown yellow violet orange brown red red orange brown brown black orange brown red red red brown brown grey red brown brown red red brown brown black red brown yellow violet brown brown brown red brown brown brown black brown brown brown black black brown 5-Band Code (1%) brown black black orange brown yellow violet black red brown red red black red brown brown black black red brown red red black brown brown brown grey black brown brown brown red black brown brown brown black black brown brown yellow violet black black brown brown red black black brown brown black black black brown brown black black gold brown April 2007  71 Fig.15: this diagram shows the final assembly and external wiring details for the Ignition Timing Module. Note how the 0V (ground) rail on the PC board is connected to one side of the case, with a lead then run from this point to the vehicle’s chassis. Use cable ties to help secure the leads, both inside and outside the case. attached to the outside of the case to make the chassis connection, with the entire assembly secured using a M3 x 9mm screw, nut and star washer – see Fig.15. Another 3mm hole is drilled to allow the metal tab of regulator REG1 to be secured to the case using two M3 x 15mm tapped metal spacers. This arrangement serves a dual purpose: (1) it mechanically secures the regulator to prevent its from breaking; and (2) it provides heatsinking for the regulator tab. The two spacers are secured to REG1’s tab using an M3 x 20mm screw, while an M3 x 9mm screw secured the spacers to the side of the case. Note that star washers must be used under each screw head, to prevent the assembly from shaking loose. Hose adapter This view shows the assembled PC board for the Ignition Timing Module with the optional internal Sensym MAP sensor fitted (ie, when there is no existing external MAP sensor or you are not using a secondhand MAP sensor). Make sure that the unit is ruggedly built (ie, so that no leads can come adrift). 72  Silicon Chip If you are using the on-board Sensym pressure sensor, then a hose connection will be required from the sensor to a chassis-mount flange (or through-piece) on the side of the box. This piece serves as both an anchor siliconchip.com.au Manifold Pressure Sensor Options I N ORDER TO utilise the vacuum advance feature provided by the Pro­grammable Ignition System, some means of monitoring manifold pressure is required. There are several options available here. The simplest option is to use the MAP (manifold air pressure) sensor that’s already installed on your car (if it has one). This sensor would normally be used to detect manifold pressure for the car’s own Engine Management Unit, to control the timing. If your car does not have a MAP sensor, then you can easily obtain one to do the job. There are different sensors to suit normally aspirated engines and to suit turbocharged engines. Normally aspirated engines do not boost the air pressure for the fuel mixture and so a 1-bar (one atmosphere, 100kPa point and as a 3mm-to-5mm adapter. This is necessary because the sensor’s hose connection is 3mm in dia­ meter while a standard automotive vacuum tube requires (at least) a 5mm fitting to enable it to stay in place without air leaks. A 15mm round brass spacer is used as the adapter. The 3mm-diameter hose from the sensor is pushed inside the spacer at one end (ie, the end inside the case), while the external vacuum tube is fitted over the spacer at the other end (outside the case). Note that it will be necessary to enlarge the hole at one end of the spacer slightly to accept the 3mm (ID) hose. Silicone sealant can be used later, when fitting the hoses, to ensure that or 15psi) sensor is all that is required. These sensors measure the air pressure compared to a vacuum and output a voltage close to 4V for atmospheric pressures and close to 0V for a vacuum. Turbo engines boost the air pressure above atmospheric and consequently a 1-bar sensor is inadequate. This is because the output from a 1-bar sensor would not change for pressures above 1-bar. There is also a possibility that the sensor could be damaged if the pressure went too far beyond its rating. In this case, a 2-bar sensor should be adequate for most applications. However, if the boost is greater than 2-bar, a 3-bar sensor will be required instead. One option is to use an on-board Sensym sensor that covers from 0-1 bar or from 0-2 bar, as specified in the parts list. the connections are air-tight. Fig.16 shows how the adapter is fitted. First, a brass nut is soldered to one end of the adapter, after which the adapter is pushed through a 5mm hole in the side of the case. It is then clamped in position using a 20mm OD washer and a couple of M3 x 6mm machine screws that go into tapped holes in the washer (or you could use M2 x 10mm screws and nuts). Alternatively, you can do away with the adapter altogether and pack the inlet on the Sensym sensor out with several layers of heatshrink tubing so that the 5mm hose is a tight fit. That way, the 5mm (ID) vacuum hose that runs to the engine manifold can simply pass through a hole in the Fig.17: this is the parts layout for the Ignition Trigger Module. Note the different orientations for ZD1-ZD4. siliconchip.com.au This device is best used at temperatures ranging from 0-85°C and so the Programmable Ignition Timing Module should be mounted inside the cabin rather than in the engine bay. Alternatively, most automotive wreckers can sell you a MAP sensor quite cheaply. These are available from various models of Holden, Honda, Toyota, Subaru and others. Details of the Holden type 1-bar, 2-bar and 3-bar MAP sensors and the Motorola 2.5-bar MAP sensor are available at this web site: http://web.archive.org/ web/20050906201309/www.pgmfi.org/ twiki/bin/view/Library/MapSensor Typically, the 1-bar Holden sensors are designated with a 039, 460 or 883 code. 2-bar sensors have a 886, 012, 539 or 609 code and 3-bar sensors have a 749 code. The A, B and C labels refer to the positioning of the Ground, Signal and +5V terminals. Fig.16: a simple adapter made from a brass spacer can be used to connect the 3mm outlet on the Sensym pressure sensor to a standard 5mm vacuum hose. The metal tab of the Darlington transistor (Q1) must be insulated from the case using a TO-218 insulating washer and a Nylon screw and nut. April 2007  73 case and go straight to the Sensym pressure sensor. As before, silicone sealant can be used to ensure an airtight fit but be careful not to block the sensor inlet with the sealant. Once all the holes have been drilled in the case, the PC board can be fitted and the assembly completed as shown in Fig.15. Be sure to use automotive wiring for all external connections. These leads should all be secured using cable ties and the connections to the PC stakes covered with heatshrink tubing. This is necessary to prevent the leads from vibrating and coming adrift. Wiring the pressure sensor There are three options when it comes to wiring the pressure sensor: (1) If you are using an existing MAP sensor, connect the signal lead only. DO NOT connect the +5V and 0V supply leads (the sensor will already have supply connections). (2) If you are using an external (eg, secondhand) MAP sensor that you’ve added to the vehicle, then connect all three leads (ie, signal, +5V and 0V). (3) If you are using the on-board Sensym sensor, do not make any external connections (the second cable gland can be deleted). Ignition Coil Driver Fig.18: final assembly and external wiring details for the Ignition Coil Driver. After assembly, use a multi­meter (set to a low ohms range) to confirm that the metal tab of Darlington transistor Q1 is properly isolated – ie, it must not be shorted to the case. This is the view inside the Coil Driver Module. Note the use of a separate cable gland for the trigger input lead. As with the timing module, this unit must be ruggedly built to ensure reliability. 74  S 74    S ilicon iliconCC hip hip Fig.17 shows the assembly details for this small PC board. Begin by installing the wire link, then install the 1.2kW and 470W resistors. The 100W 5W resistor can then go in – it should be mounted all the way down onto the PC board, so that it cannot vibrate and break its leads. Zener diodes ZD1-ZD4 are next on the list. Be sure to orient them as shown (two face in one direction and two in the other, so take care here). Follow these with transistors Q2 & Q3 and the 1nF ceramic capacitor. Transistor Q1 is mounted on the underside of the PC board. This device is installed with its leads bent up through 90°, so that they go through matching holes in the PC board from the track side (ie, the metal tab of the device faces away from the board – see photo). Push the leads through their holes until the metal tab is exactly 6mm below the underside of the PC board, then lightly solder one of the leads. This will allow you to make any adjustsiliconchip.com.au Fig.19: the LCD Hand Controller PC board is easy to assemble. Install the three links first and note that the switches, IC and 10mF electrolytic capacitor are polarised. The LCD is connected via a 14-way DIL pin header. The PC board mounts inside the case on four M3 x 12mm spacers and is secured using M3 screws, nuts and flat washers – see Fig.19. Note how the 10mF capacitor is mounted on its side, so that it clears the front panel. ments as necessary before completing the soldering. Finally, complete the board assembly by installing PC stakes at the four external wiring points. Once completed, the Ignition Coil Driver PC board can be installed in its diecast case – see Fig.18. As shown, the board in mounted on the lid of the case on 6mm tapped spacers and secured using M3 x 15mm screws, nuts and star washers. Transistor Q1 (on the underside of the board) is fastened to the lid for heatsinking. The first step is to mark out all the mounting holes on the lid. Drill these holes to 3mm, then carefully deburr siliconchip.com.au them using an oversize drill. In particular, make sure that Q1’s mounting hole is perfectly smooth and free of any metal swarf that could puncture its insulating washer. Note too that Q1’s mounting hole should be chamfered (use an oversize drill bit). This is necessary to avoid sharp edges around the circumference of the hole, to prevent arcing through the insulating washer (due to the high voltages present on the transistor tab). Once the holes have been “cleaned up”, fit the four tapped spacers to the board mounting positions and secure them using the M3 x 15mm screws. That done, install transistor Q1’s Nylon mounting screw and insulating washer (see photo), then slip the board into position and secure it using M3 nuts and star washers. Don’t leave the star washers out – they are necessary to ensure that the nuts don’t shake loose due to vibration. Transistor Q1 can now be secured by installing its nut and tightening the Nylon screw (use a pair of needle-nose pliers to hold the nut in position while you “start” the screw). Finally, use your multimeter (set to a low ohms range) to confirm that Q1’s metal tab is indeed electrically isolated from April 2007  75 Programmable Ignition: Parts List Programmable Ignition Unit 1 PC board, code 05104071, 103 x 82mm 1 diecast aluminium case, 119 x 93 x 57mm 2 IP68 waterproof cable glands for 4-8mm cable 1 15 x 8 x 6.5mm powdered-iron toroid (Jaycar LO-1242 or equivalent) (L1) 3 5mm Ferrite beads (Jaycar LF1250 or equivalent) 1 20MHz crystal (X1) 1 SPDT toggle switch for map switching (optional) 1 18-pin DIL IC socket 1 DB25 female straight pin PC mount socket 4 D-connector nut extenders and two locking nuts and shake proof washers 1 2-way pin header 1 3-way pin header 2 jumper pin shorting links 2 crimp eyelets 4 6mm tapped Nylon standoffs 1 3mm Nylon washer 2 M3 tapped x 15mm brass standoffs 1 M3 x 20mm screw 4 M3 x 15mm screws 2 M3 x 9mm screws 8 M3 star washers 5 M3 nuts 10 PC stakes 1 60mm length of 4mm ID heatshrink tubing 4 100mm cable ties 1 2m length red automotive wire 1 2m length black automotive wire 1 2m length green automotive wire 1 2m length brown automotive wire 1 2m length yellow automotive wire 1 150mm length of 0.7mm tinned copper wire 1 600mm length of 0.5mm enamelled copper wire Semiconductors 1 PIC16F88-E/P microcontroller programmed with ignprgm.hex (IC1) 1 LM2940CT-5 low-dropout 5V regulator (REG1) 1 BC337 NPN transistor (Q4) 76  Silicon Chip 1 1N4004 1A diode (D1) 1 1W Transient Voltage Suppressor (TVS1) 13.6V standoff voltage (Jaycar ZR 1162 or equivalent) Capacitors 1 1000mF 16V PC electrolytic 3 100mF 16V PC electrolytics 1 10mF 16V PC electrolytic 1 220nF MKT polyester 3 100nF MKT polyester 1 10nF MKT polyester 1 10nF ceramic 1 1nF MKT polyester 2 1nF ceramic 2 22pF ceramic Resistors (0.25W 1 %) 2 100kW 1 1.8kW 2 47kW 1 1kW 3 10kW 1 470W 2 2.2kW 9 10W Points and ignition module version 1 100W 5W resistor Reluctor version 1 BC337 NPN transistor (Q5) 1 2.2nF MKT polyester capacitor 1 470pF ceramic capacitor 1 100kW top-adjust multi-turn trimpot (VR1) 1 47kW 0.25W 1 % resistor 2 10kW 0.25W 1 % resistors 1 1kW 0.25W 1 % resistor 1 PC stake Hall effect version 1 1kW 0.25W 1 % resistor 1 100W 0.25W 1 % resistor 2 PC stakes Optical pickup version 1 22kW 0.25W 1 % resistor 1 120W 0.25W 1 % resistor 2 PC stakes Manifold pressure sensor alternatives (see text) 1 ASDX015A24R Sensym (0-15PSI, 0-1bar) Absolute Pressure Transducer (RS Components Cat No. 2508593055) (Farnell Cat. No. 419-7586); or 1 ASDX030A24R Sensym (0-30PSI, 0-2bar) Abso- lute Pressure Transducer (RS Components Cat No. 2508593077); or 1 Manifold Absolute Pressure (MAP) sensor – available from an automotive wreckers. Map sensors are available from most Holden, Honda, Toyota and Subaru models and others that have an engine management computer. Try to obtain the wiring connector with the sensor. Miscellaneous Angle brackets for mounting units, automotive connectors, self-tapping screws etc. Programming Code Note: the programming code (ignprgm.hex) for the PIC16F88-E/P microprocessor featured in this project will not be released or be made available on our website. Authorised kit sellers will supply programmed microcontrollers as part of their kits. For people who do not wish to build the project from a kit, programmed micros will be available from SILICON CHIP for $25.00 including postage anywhere within Australia, or $30.00 by airmail elsewhere. Ignition Coil Driver 1 Ignition Coil Driver PC board, coded 05104072, 40 x 39mm 1 diecast aluminium box 50.8 x 50.8 x 31.8mm (Jaycar HB6050) 1 TO-218 insulating washer rated at 3kV 2 IP68 waterproof cable glands for 4-8mm cable 4 M3 tapped x 6mm Nylon standoffs 4 M3 x 15 screws 1 M3 x 10mm screw 1 M3 x 6mm Nylon screw 5 M3 nuts 6 3mm star washers 4 PC stakes 1 2m length red automotive wire 1 2m length black automotive wire 1 2m length green automotive wire 1 2m length brown automotive wire 1 60mm length of 0.7mm tinned copper wire siliconchip.com.au 1 40mm length of 4mm heatshrink tubing Semiconductors 1 MJH10012, BU941P TO-218 high-voltage Darlington transistor (Q1) 2 BC337 transistors (Q2,Q3) 4 75V 3W zener diodes (ZD1ZD4) Capacitors 1 1nF ceramic capacitor Resistors (0.25W 1%) 1 1.2kW 1 470W 1 100W 5W wirewound LCD Hand Controller 1 PC board, code 05104073, 115 x 65mm 1 front panel label (or screen printed lid) for case 1 plastic case, 120 x 70 x 30mm with clear lid (Jaycar HB 6082 or equivalent) 1 LCD module (Jaycar QP 5515 or backlit QP 5516) 5 white click action switches (S1,S2,S5,S7,S9) 4 black click action switches (S3,S4,S6,S8) 1 SPST micro tactile switch (S10) 1 4017 decade counter (IC1) 1 DIL 14-way pin header 1 DB25 PC mount right angle socket 1 DB25-pin male to DB25-pin male 1.8m RS-232 connecting lead (all pins connected) (Jaycar WC 7502) 4 12mm long M3 tapped plastic spacers 4 M3 x 6mm CSK screws 2 M3 x 6mm screws 2 M3 x 12mm plastic screws 2 2.5mm thick plastic washers 1 100mm length of 0.7mm tinned copper wire 1 10mF 16V PC electrolytic capacitor 2 10kW 0.25W 1% resistors 1 7-way, 8-way or 9-way 330W terminating resistor array (8-10 leads). Note: 6-resistors are used in the circuit and one end of each resistor connects to the pin 1 common 1 10kW horizontal trimpot (code 103) (VR1) siliconchip.com.au Fig.20: this cross-sectional diagram shows how the PC board for the LCD Hand Controller is mounted in the case. Note how the top edge of the LCD module is supported on two M3 flat washers. the case lid (you should get an opencircuit reading). The earth supply lead goes to a crimp eyelet and this is secured to the inside of the case using an M3 x 10mm screw, star washers and nut. This screw secures a similar eyelet and earth wire arrangement on the outside of the case (this wire goes to the vehicle chassis). As shown in Fig.18, the remaining wires exit via the cable glands. Cover these leads with heatshrink tubing at the exit points and note that the signal lead must pass through its own separate gland, while the ignition coil (-) lead and the +12V lead pass through a second gland. Note that, in addition to the heatshrink, these leads may require packing out with tubing so that they are tightly clamped by the glands. The signal lead must at all times be kept clear of the ignition coil (-) wire to prevent retriggering as the coil fires. Be sure to take it out through its own cable gland and route it well away from the ignition coil wire – see Fig.18. Hand Controller The Hand Controller assembly is shown in Fig.19. Start by installing the three wire links, including the one under the DB25 socket. That done, solder in the dual-in-line 14-pin header for the LCD module, taking care to avoid solder bridges between adjacent pins. The SIL resistor array is next. This will have a pin 1 indication at one end (usually a dot) and this end must go towards trimpot VR1. Note that all the top seven holes must be used, leaving some free adjacent to VR1 if the array does not have 10-pins. IC1 can now be installed, taking care to ensure it is correctly oriented. That done, install the two 10kW resistors, trimpot VR1 and switches S1-S9. Note that each of these switches must go in with its flat side to the left – see Fig.19. We used white and black switches as indicated on the overlay. S10 is a smaller pushbutton switch that will only fit with the correct orientation. The 10mF capacitor is next on the list. This must be mounted on its side to provide clearance when the lid is on (see photo). Take care with the polarity of this capacitor. The DB25 right-angle socket can now go in. Make sure it is seated flat against the board and take care to avoid solder bridges between the pins. Finally, the LCD module can be installed by pushing it down onto its 14-pin DIL header. Push it all the way down until it is correctly seated against the header, then solder the header pins to the top of the module’s PC board. Fig.20 shows how the PC board is mounted in its case. If you are building a kit, the case will be supplied pre-drilled and with a screen-printed front panel. If not, then holes will need to be drilled in the base of the case for the four board mounting holes and a cut-out made to accommodate the DB25 socket in the side of the case. In addition, the lid will require holes for the switches and a clearance slot for the DB25 socket. Note that S10’s hole should only be about 3mm in diameter – ie, just sufficient for a small probe to actuate the switch. If you already have an LCD Hand Controller as described in “Performance Electronics for Cars”, then this can also be used with some minor April 2007  77 Inverting The Firing Sense Of The Ignition Coil Driver modifications. That earlier circuit is identical to the one described here except that it didn’t include the six 330W terminating resistors. This means that all you have to do is add these six resistors between the relevant pins on the LCD module (pins 4, 6, 11, 12, 13 & 14) and ground. These will have to be mounted on the track side of the PC board. The ground connections are best made at pins 7-10 of the LCD module. Testing Fig.21: this modified Ignition Coil Driver circuit can be used to “fire” a plug when the input signal goes high. Fig.22: this is the modified parts layout. Use a 470W resistor for R1 for a 5V input signal and a 1.2kW resistor for a 12V input signal. T HE IGNITION COIL DRIVER can be used on its own for other applications; eg, as a replacement coil driver in an existing system. However, in some cases, it may be necessary to change the “trigger sense” of the circuit. The standard set-up has the coil “charging” when the input signal is high and then “firing” a plug on a negative edge input signal. To invert this level sense, transistor Q3 and the 1.2kW resistor are deleted and a link installed between the pads normally used for Q3’s base and collector leads. This effectively bypasses Q3 and the input now drives Q2 via a base resistor (R1) – see Fig.21. Fig.22 shows the revised parts layout for the PC board. Use a 470W resistor for R1 when it is driven by a 5V input signal and a 1.2kW resistor when driven from a 12V signal. With this arrangement, the coil “charges” when the input signal is low and “fires” a plug when the signal goes high. 78  Silicon Chip OK, now for the smoke test, starting with the Programmable Ignition Timing Module. First, apply +12V to the supply input and connect the case to the 0V rail. That done, use your multimeter to check that there is 5V (±0.1V) between pins 14 & 5 of IC1’s socket. If this is correct, switch off and install IC1, making sure it is correctly oriented. Next, connect the RS-232 DB25 lead between the Programmable Ignition Timing Module and the LCD Hand Controller and apply power. You should be greeted with some characters on the LCD. If there are none, or if the display is faint or the contrast is poor, adjust VR1 on the LCD Hand Controller board for best results. If there is still no display, recheck the parts placement on both PC board assemblies. Check also that the DB25 cable is correct – each pin should be connected through to the same socket pin on the opposite end of the lead. Assuming all is well, the display shown on the LCD will depend on the position of jumper shunt LK1. Remember that the Settings position will show the settings mode (used when changing parameters), while the Timing position will show the RPM and Load site values against the timing values. The initial timing values are all set to 0° advance. Check that you can change the values using the switches on the LCD Hand Controller. Converting your distributor Finally, note that if you have a distributor with points, you can convert it to a Hall effect pick-up instead, to make it maintenance-free. The details on how to do this were published in our January 2006 issue. That all for this instalment. Next month, we will describe how the unit SC is set up and installed in a car. siliconchip.com.au