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Get rid of those old-fashioned points Convert your car to breakerless ignition Fitting electronic ignition to your car is one thing but that is only doing it half right. Why not get the full benefit of electronic ignition by whipping out the points and fitting a Hall Effect pickup in your distributor? By LEO SIMPSON & JOHN CLARKE Let's be frank; the electronic ignition presented in last month's issue is good but it could be better. It is a vast improvement over the outdated Kettering system fitted to tens of thousands of cars but it does not give the full benefit. After all, no new cars fitted with electronic ignition as original equipment still have points, do they? No, the designers have gone all the way and designed the ignition system from the ground up to work without points. Even when mated to an electronic ignition as presented last month, points still hold the system back. As we noted in that article, you still need to adjust the points and re-do the timing every 20,000km or so, to compensate for wear on the rubbing block. If you don't do this, one day you'll attempt to start the car and then find that it won't, because the points are operating with virtually no gap at all. We know, we've seen it happen. Even without the wear problem on the rubbing block, points are far from perfect. Not only do they bounce on every closure but as the distributor shaft wears (due to the loading from the points rubbing By combining the Bosch rotor and vane assembly (left) with the Siemens Hall effect pickup (right), you can eliminate the points in your car. Such a breakerless system never requires adjustment or maintenance. 44 SILICON CHIP block), the distributor cam tends to wobble. Both these effects lead to less precise timing and so the engine does not run as smoothly as it otherwise would if the ignition timing was perfectly consistent. By contrast, with a Hall Effect switch in place of the distributor's points, the engine timing only has to be adjusted once and then it will stay correct, for the life of the vehicle. The engine will run noticeably smoother, particularly at idle. One thing to remember though is that even an all-electronic ignition requires some maintenance. You still have to check and replace spark plugs at regular intervals, to obtain best performance and fuel economy. Many owners ignore this fact and let their cars run for years without replacing the spark plugs, or even so much as cleaning and regapping. That says a great deal for the reliability of modern ignition systems but it is a foolish omission. With these points in mind (pun fully intended), we designed the printed board of our new electronic system so it could also be used with Hall Effect triggers. These are used in the electronic ignition systems of many new cars, chiefly those from Europe. Two types of Hall Effect trigger device are described here, one from Siemens and one from Sparkrite of the UK. With one or other of these devices, virtually all vehicles available in Australia can be fitted with breakerless ignition. A separate panel in this article gives a brief description of the Hall · Effect. We suggest you read it now. Hall Effect Devices In many ways, the Hall Effect device is the ideal replacement for I REGULATED_ SUPPLY +VSO--W>lr-_ .,....._ _ _ _ _ _ ___ OUTPUT .,. X HALL GENERATOR....._____, GND . .,. HALL EFFECT HALL EFFECT SWITCH Fig.1: although discovered in 1879 the Hall Effect did not become useful until it was produced in semiconductor form. Fig.2: this is the schematic of a typical digital Hall Effect device as used in the Siemens HKZ-101 trigger. What is the Hall Effect? Most people know that when a conductor is moved through a magentic field, a voltage is generated at its ends. This principle is used in alternators and generators to produce electricity. And when a conductor carrying a current is placed in a magnetic field, a force is applied to the conductor. This principle is used in all electric motors. But there is another possible interaction with magnetic fields and electric currents and this is known as the Hall Effect. It was discovered in 1879 by E.E. Hall at the Johns Hopkins Unviersity, in the USA. It happens in all electric conductors but is about ten million times more pronounced in semiconductors. Fig.1 demonstrates the principle of the Hall Effect. A thin plate of semiconductor material carries an electric current and is placed in a magnetic field which passes at right angles through the surface of the plate. A DC voltage then appears between the two edges of the semiconductor plate. Note that the semiconductor does not have to move. The voltage is produced with no moving parts. The voltage produced is called the points. It has no contacts, is unaffected by dirt or light (as optoelectronic sensors are), and its output is independent of the operating frequency (ie, engine revs). As well, it has a wide operating temperature range and high electrical noise immunity. The Sparkrite Hall Effect unit is the Hall voltage and is given by the equation: Vo = RH X I X B/t where B is the magnetic field strength, I is the current th_rough the semiconductor and t is its thickness. RH is the Hall constant of the semiconductor material. Thus, the Hall voltage is directly proportional to the strength of the magnetic field and to the current through the semiconductor. It is also inversely proportional to the thickness of the semiconductor so the thinner the material, the higher the Hall voltage generated. Note that the polarity of the Hall voltage is dependent on the direction of the magnetic field. Hall Effect devices are made from semiconductors such as indium arsenide and indium arsenide phosphide. These semiconductors are selected because of their high Hall constant, relatively . low temperature coefficient · (for the Hall effect), and a number of other parameters which go towards producing a good Hall Effect device. Typical Hall Effect devices are integrated into a three lead package which is depicted in Fig.2. This includes an internal constant Cl!rrent source, (le), an used in conjunction with a ring magnet assembly which fits over the distributor cam. The ring magnet has four or six poles, depending on the motor it is to be used with. Each time a pole comes close to the device, a voltage is generated which causes the electronic ignition circuit to produce a spark. amplifier for the voltage produced by the Hall generator, a Schmitt trigger (which is an amplifier designed to overload and clip the signal voltage), and an output transistor with open collector. Such Hall Effect devicf3s as depicted in Fig.2 have a "digital" output which is high or low: They . are typically specified for operation with the south pole of a magnet (hence the above reference to magnetic field direction). Not all Hall Effect devices have digital outputs though. Some are linear. They have an internal buffer amplifier but no Schmitt trigger. They produce an output voltage which is positive or negative with respect to a reference voltage, depending on whether they are in the vicinity of a north or south magnet pole. For further reading: (1 ). Sprague Integrated Circuits data manual. Available from VSI Electronics (Australia) Pty Ltd. Phone (02) 439 8622. (2). Discrete Electronic Components, by F. F. Mazda. Published 1981 by Cambridge University Press. ISBN 0 521 23470 0. The Sparkrite system is suitable for cars with the following distributors: Motocraft and Autolite 4 and 6 cylinders, Bosch 4 cylinder, Lucas 4 and 6 cylinders, AC Delco D202 and D204 4 cylinder, Nippondenso 4 cylinder and Hitachi Datsun 4 cylinder. It does not suit the majority of JUNE 1988 45 ,--------t-------11--------+---------------+12VVIA IGNITION SWITCH 3300 •---HTTO DISTRIBUTOR 100n 5W 2.2k 100n 8200 0.5W + RED .01 OPTIONAL CUT-OUT SWITCH H~m1 l:!ISl!!l.G·-~ SENSOR GRN GNO BLK 470k 02 BC337 22k 5 t-·lt·-__,,,Wlr-......::i IN ----<1-.--1 7 IC1 OUTl'MC3334P REF 3 0--+--\AM....-tl---"f--f GND 2 1 4x1N4761 (75V 1W) 8 0.1 56k . __ _ _ _ _ _ _ _....,__ ___._ __ _ _ _ _....,__ __.._ _ _ _ _..,__ _ _....__ _ CHASSIS .,. C B CASE eOc HIGH ENERGY IGNITION SYSTEM 0 1 0 B VIEWED FROM BELOW SIEMENS HALL SENSOR INPUT SC05·1·688 Fig.3: this is the complete circuit of our high energy system with the Siemens HKZ-101 Hall Effect sensor. It is only slightly different from the circuit published last month. Note the optional cut-out switch which can be an effective deterrent against thieves. Australian-made 4, 6 and 8cylinder vehicles but most of these are taken care of by the Siemens device. The Siemens HKZ-101 Hall Effect sensor incorporates a magnet and is used with a rotating soft iron vane which triggers it on and off. This vane assembly incorporates the distributor rotor button and is made by Bosch. It is is available for most Chrysler, Holden and Ford cars plus some other makes which have distributors made by Bosch, Delco, Lucas, Disilea and Nippondenso. The vane assembly is available on order from your local Repco auto electrical store. Operating temperature of the Siemens HKZ-101 is from - 30° to + 130° Celius. Before deciding to use the Siemens Hall Effect sensor, make sure that the rotating vane assembly for your particular vehicle is available. In fact, make sure you have it in your hot little hand before you start work on the rest of the system. If you don't, there might be tears of frustration later. Both the Sparkrite and Siemens sensors are available from Jaycar stores. If you use the Siemens sensor you will have to make a suitable 46 SILICON CHIP mounting bracket to mount it on the baseplate inside the distributor. The Sparkrite sensor is supplied with all the necessary mounting hardware required for installation, including a selection of ring magnets. Circuitry Different versions of our electronic ignition circuit are required, depending on whether the Siemens or Sparkrite Hall Effect devices are used. Fig.3 shows the circuit using the Siemens HKZ-101 device. The only difference between this circuit and that produced last month for the points version is in the omission OUTPUT vs 150!) HALL SWITCH . GNDI ...r1GNO SPARKRITE SENSOR The Sparkrite Hall sensor is a two-terminal device which is used in conjunction with a ring magnet fitted over the distributor cam lobes of D5 and C2 , and the substitution of an 8200 0.5W resistor for the 470 5W wirewound resistor. There is also an additional 1000 resistor to provide the positive supply to the sensor. The 8200 resistor provides a "pull up" for the open-collector output of the Hall Effect sensor. We have made provision for a cut-out switch in series with the sensor output. This could be hidden under the dash of the vehicle and would provide good anti-theft protection. If you don't want the switch, it can be left out and a link wired in its place. The output of the HKZ-101 sensor connects via a 1OkO resistor to the base of Q2. Q2 is switched on when the Hall Effect output is high (when the iron vane enters the gap of the sensor) and off when it is low (when the iron vane is not in the gap). From there on, the circuit is identical with that published last month. Whenever Q2 turns off, Qt also turns off and the ignition coil delivers a high voltage pulse to the spark plug. Sparkrite Hall sensor Whereas the Siemens device is a 3-terminal package, the Sparkrite device has only two terminals. Fig.4 shows how it is internally connected. The supply input to the Hall sensor and output are tied together with a 1500 resistor and the output is taken from the positive supply terminal. The Hall Effect unit inside the Sparkrite device is actually a Sprague UGS-3020T. It is rated for operation over a temperature range of - 40° to + 125° Celsius. When one of the poles of the ring magnet is close to the Sparkrite device, its output is low; ie, less than 5 volts. When the pole moves away, the output is high; ie, above 6 volts. The problem with the Sparkrite sensor is that its output does not go fully high (say, to 12V) and nor does it go fully low, to OV. This is because the current though the Sparkrite sensor varies from between about 5 and 10mA with the output high. When the output goes low, the Hall Effect device sinks additional current, up to 25 milliamps. This means that the Sparkrite sensor is trickier to connect and needs additional external circuitry to make it work. Fig.5 shows the circuit modifications needed to connect the Sparkrite sensor to the electronic ignition system. The mods consist of a constant current source to feed the sensor and a zener diode to detect the change in output voltage. The modified circuit works as follows. The constant current source involves transistor Q3, diodes D6 and D7, and the 180 and 1k0 resistors. The current through diodes D6 and D7 sets the voltage at the base of Q3 at 1.2V below the incoming 12V supply. Since Q3 is effectively a PNP emitter follower, this sets the voltage across the 180 resistor to 0.6 volts. The resulting current through the 180 resistor, and thus through Q3, is approximately 33 milliamps (0.6V 7 180). This current of 33 milliamps can feed to the OV rail via two paths. First, when one of the ring magnet's poles is near the Sparkrite sensor, it will be conducting and most of the current will be passing via the internal 1500 resistor. This will mean that the output voltage at the Vs ter- +12V B 1.2V EOC VIEWED FROM BELOW 08 6.8V 1W TO BASE OF 02 1k OPTIONAL CUT-OUT SWITCH 1k _ _ _ _ _ _ _ _ _ _,___.GNO SPARKRITE HALL SENSOR INPUT Fig.5. these are the modifications to the circuit when the Sparkrite Hall sensor is used instead of the Siemens device. Q3 is a constant current source while zener D8 is a voltage detector for the sensor. minal will be about 4 to 5 volts or thereabouts. When the output of the Sparkrite device goes high, it only draws some 5 to 10mA and the rest of the current from the collector of Q3 goes via zener diode DB and the series 3300 resistor. This current then goes into the base of Q2 and causes it to conduct. From there on, the circuit operation is identical with that described last month. Assembly Instructions for the assembly of the ignition circuit were fully described last month. Fig.6 shows the component overlay diagram and wiring layout if you are using the Siemens HKZ-101 device. If you intend to use the Sparkrite unit, follow Fig.7. Sparkrite sensor installation The kit for the Sparkrite Hall Effect sensor is supplied with all the necessary fittings required for installation plus detailed instructions on fitting. Fig.8 shows the general installation in exploded form. Firstly the points, damping rubbing block, flexible earth lead, the COIL - EARTH ® 01 B{!; Fig.6: follow this wiring diagram if you are using the Siemens HKZ-101 Hall sensor. If you don't want the cut-out switch, replace it with a wire link. Note that the + 12V line comes from the ignition switch. JUNE 1988 47 precision. Simply allow a small gap so there is no scraping. Reconnect the flexible earth lead between the distributor baseplate and distributor body. Static timing Fig.7: follow this diagram if your using the Sparkrite Hall sensor. Again, the cut-out switch can be replaced with a wire link. The cut-out switch could be installed at a later date, if you wish. capacitor and connecting screw for the points lead should all be removed from the distributor. Select the correct magnetic cam adaptor and adaptor plate for the trigger head, as listed in the instructions. Install the adaptor plate and trigger head on the baseplate of the distributor. The lead passes through the side entry hole of the distributor using one of the supplied grommets. Now the cam adaptor can be installed. For clockwise rotating distributors the dot on the cam adaptor should be upwards. For counter clockwise rotating distributors, the dot should face downward. This is an important part of installation since accuracy of timing is set by the magnets in the cam adaptor. These have been optimised for one direction of rotation. Check that the trigger head is centred with respect to the cam adaptor. Some of the spacers provided may be required to achieve this. The specified gap between the cam adaptor and trigger head is 0.4mm, however due to irregularities of the adaptor this adjustment cannot be made with any A static timing adjustment is necessary before connecting the trigger head lead to the electronic ignition. To do this connect a 4700 resistor between the sensor output lead and the + 12V terminal of the battery. Measure the voltage between ground and the output of the sensor using your multimeter. Now rotate the engine by hand (it might sound silly but you know what we mean) until the ignition timing marks are correctly aligned. The distributor should now be rotated until the voltage jumps from about 4.5V to 10.5V. This is the firing point for the sensor. ~ROWRARM A ee MAGNETIC ROTOR CAM ADAPTOR TRIGGER HEAD SPACER~ ~ ~ AOAPWR PCA" ADAPTOR PLATE BASEPLA,T~_.E~~~ When you purchase the Sparkrite sensor you will be supplied with an array of metal brackets and a selection of ring magnets to suit your car's distributor. The ring magent fits over the distributor cam. 48 SILICON CHIP Fig.8: this diagram from Sparkrite literature shows how the sensor is installed in a typical distributor. The original rotor button is retained. PARTS LIST 8-11.Smm l--0.1-1.Bmm HALL OUTPUT VOLTA3E t _ •ff _.__...., I TRIGGERING POINT FOR SIEMENS HALL SENSOR Fig.9: this diagram shows the critical dimensions for setting up the Siemens HKZ-101 sensor in a distributor (see text). Recheck the timing again by rotating the engine two full turns (to get cylinder No.1 back to the firing point) and readjust the distributor if necessary. The Hall sensor lead can now be connected to the electronic ignition. The ignition timing should now be set to the manufacturer's specifications using a timing light. Version No.1 (Siemens) 1 0.01 µF metallised polyester 1 PCB, code SC-5-1-588, 102 x 59mm 1 diecast box, 11 0 x 30 x 63mm 1 Bosch rotating vane assembly (see text) 4 6mm standoffs 3 solder lugs 1 grommet 1 T0-3 mica washer and insulating bushes 1 T0-3 transistor cover Resistors (0.25W, 5%) Semiconductors 1 Siemens HKZ-101 Hall Effect sensor 1 MJ10012 NPN power Darlington (Motorola) 1 BC337 NPN transistor 4 1N4761 75V 1 W zener diodes 1 MC3334P ignition IC (Motorola) Capacitors 2 O. 1µF 1OOV metallised polyester 1 x 4 70kD, 1 x 56kD , 1 x 22kD, 1 x 1 OkD, 1 x 2.2kD , 1 x 8200 0 .5W, 1 x 3300, 1 x 1 oon, 1 x 1000 5W Miscellaneous Automotive wire, screws, nuts, shakeproof washers, solder, heatsink compound, etc. Version No 2 (Sparkrite) Delete 1 1 1 1 56kD 1 OkD 8200 1 oon resistor resistor 0.5W resistor resistor Add 1 Sparkrite contactless trigger pack 2 1N4004 1 A diodes 1 6 .8V 1W zener diode 1 BC557 PNP transistor 2 1 kn 0.25W resistors 1 3300 0.25W resistor 1 180 0 .25W resistor Siemens Hall Effect sensor installation Fig.9 shows how the Siemens Hall sensor should be installed to provide reliable triggering. The vane needs to penetrate the sensor by between 8 and 11.5mm. The triggering point is between 0.1 and 1.8mm from the centre line of the unit. To install the sensor, remove the distributor from the vehicle. To do this, rotate the engine until cylinder number one is at the firing point (ie, align the rotor button with the timing mark on the distributor). With the distributor out of the vehicle, find the position where the points just open for the number one cylinder using a multimeter set to read "Ohms". Mark the position on the distributor body where the centre of the rotor is now positioned. This is the point where the Hall effect sensor's output should go high. The Sparkrite sensor is instaJled close to the ring magnet, in the same position as the points. After initial timing, no further adjustments are required. Now remove the rotor, points and capacitor plus ancillary components such as a rubbing block if fitted. The Hall sensor should be mounted near where the points were located so that there is sufficient lead to exit from the distributor. The exact location for the Hall sensor is determined as follows: Fit the vane assembly to the JUNE 1988 49 The Siemens Hall sensor is rivetted to an adapter plate inside the distributor. Note that the original rubbing block has been retained to minimise camshaft wobble. distributor and align the rotor with the firing point previously marked. The Hall Effect sensor should now be positioned so that the leading edge of one of the metal vanes is about half way through the slot (ie, you will have to determine the direction of distributor rotation). Mark out the position of the sensor, taking care to ensure that the vane will pass through the gap without fouling. A suitable mounting plate can now be made to fit the Hall sensor to the distributor advance plate. The mounting plate must also posi- This is the same distributor but with the Bosch rotor and vane assembly installed. Clean and simple isn't it? Oil, dirt and heat are no problem with this system. tion the sensor at the correct height, so that the vane penetrates the Hall sensor by between 8 and 11.5mm. Note that Fig.9 shows the arrangement for a counter-clockwise rotating distributor. Clockwiserotating distributors are timed as the vane enters the Hall sensor from the other side. The Hall Effect sensor is rivetted to the adaptor plate through 3.5mm holes which are countersunk under the plate. The adaptor plate can then be secured to the distributor advance plate using machine This is the ignition module as wired for the Siemens sensor. Sharp eyed readers will note that a short wire link is missing. We fixed it after the photo was taken. Note the loop in one lead of each diode, included as stress relief. 50 SILICON CHIP screws, nuts and washers. Try to take advantage of any existing holes. The leads from the Hall Effect sensor should be passed through the existing points lead grommet. Check that the vanes pass through the gap in the sensor without fouling and that the leads are dressed to allow full movement of the distributor vacuum advance plate. Note that some distributors use a separate rubbing block, in addition to the points. This should be left in place so that any mechanical slack in the shaft bearings will be taken up. Reinstall the distributor in the engine, taking care to ensure that the rotor points towards the distributor timing mark. Check that the timing marks on the engine are correctly aligned, then check that the leading edge of one of the vanes is near the centre line of the sensor. Rotate the distributor slightly if necessary to get the correct static timing position. Connect the leads from the Hall Effect sensor to the electronic ignition via a suitable automotive electrical connector. A 3-pin connector will be required and these are available from kit suppliers and automotive accessory shops. Finally, the engine should be started and the timing adjusted to specification using a timing light.~