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Pt.2: By JOHN CLARKE Voltage Interceptor For Cars With ECUs Last month, we described the circuits for both the Voltage Interceptor and its companion Pushbutton Controller. This month, we give the full construction details and describe how the device is installed and used. A LL THE PARTS for the Voltage Interceptor are mounted on a PC board coded 05112091 and measuring 105 x 87mm. This is housed in a diecast box measuring 119 x 94 x 34mm. Two cable glands at one end of the box provide access for the power supply wiring and for the input and output wiring. Before mounting any parts, check the PC board for any defects such as shorted tracks or breaks in the copper. Check also that the corners opposite the terminal end of the PC board have been shaped to clear the internal corner sections of the box. The shape required is outlined using thin tracks on the underside of the board. Fig.5 shows the PC board parts layout. Begin by installing the six wire links and the resistors, taking care to ensure they each go in their correct place. We used 0Ω resistors for the links in our prototype but you can use 0.7mm-diameter tinned copper wire 78  Silicon Chip instead. Table 2 shows the resistor colour codes but you should also use a digital multimeter to check each one before installing it, as some colours can be difficult to read. Once the resistors are in, install the 2-way pin header for LK1, then install PC stakes at test points TP1-TP5. Follow these with the diodes, zener diodes and IC sockets, taking care to ensure that these parts are all correctly oriented. Don’t install the ICs yet – that step comes later. The capacitors are next on the list. Note that seven of these are electrolytic types and must be installed with the polarity shown. The remaining polyester types can be installed either way around. Now for regulator REG1. As shown, this is mounted horizontally on a small heatsink, with its leads bent through 90°. To do this, first bend its two outer leads down through 90° about 8mm from its body and its centre lead down about 6mm from its body. That done, secure the regulator and its heatsink to the PC board using an M3 x 6mm screw, lock washer and nut, then solder its leads. Note: do not solder REG1’s leads before tightening its mounting screw. If you do, you could stress and crack its copper pads as the screw is tightened. Transistors Q1-Q4 can go in next (don’t get them mixed up), followed by LED1. The latter should be installed with the top of its body 10mm above the surface of the PC board. It goes in with its cathode lead (the shorter of the two) towards the top edge of the PC board (note: this lead is also adjacent to the “flat” side of the LED body). Completing the PC board The PC board assembly can now be completed by installing the seven trimpots (VR1-VR7), the two 2-way screw terminal blocks, the DB25 socket and the relay. siliconchip.com.au TO PUSHBUTTON CONTROLLER 10nF 10  1W 20k IC4 PIC16F88-I/P TU O E GATL OV REIFID O M 19001150 2.2k TP4 120 22k 10k IC1 10k VR6 LMC6482 ZD4 1nF 10k 20k 10nF 5.6V D2 RELAY1 NI C OUTPUT NO NC INPUT 4004 LK1 1k TP2 VR2 100k 470 10 F Q1 BC337 CON2 LOCK VR4 1k TP1 BC547 Q3 BC337 100 7.5V VR1 500 REG1 LM317 Q2 D3 ZD3 TP3 VR3 1k GND 43k 100 F 10k D4 4148 470k 100nF 1M 10nF 100nF 10nF 10nF 100nF 10k VR5 IC2 50k TP5 LMC6482 220 VR7 50k 10k 150 IC3 10k 100 F 10nF 16V 4004 BC327 100 F 4148 10k 10k 100k D1 Q4 1k 1k + ZD1 2x 100 F 15V A 10 F +12V 2.2k LED1 CON1 0V ZD2 CON3:DB25 - Orient the trimpots with their adjusting screws positioned as shown on Fig.5 (so that the voltages increase with clockwise rotation) and be sure to use the correct value at each location. They may be marked with a code rather than the actual value in ohms, ie, 501 for the 500Ω trimpot, 102 for the 1kΩ trimpots, 103 for the 10kΩ trimpots, 503 for the 50kΩ trimpot and 104 for the 100kΩ trimpot. The 2-way screw terminal blocks are straightforward – just make sure their openings face outwards. Once they’re in, the DB25 socket can be fitted. This must be mounted with a split washer under each mounting screw to increase its height. The first step is to fit these mounting screws and the washers in place and secure them by winding on nuts on the underside of the PC board. That done, the DB25 socket is then fitted into place and two extra extension screws then fitted from the top to hold it in place. The socket’s pins are then soldered to the PC board. Finally, complete the board by installing the relay. LMC6482 10k 9.1k 10k 10nF Fig.5: install the parts on the PC board as shown here to build the Voltage Interceptor unit. The assembly is straightforward but make sure that all polarised parts (semiconductors, electrolytics etc) are correctly oriented. Fitting it in a case This step is easy. First, slide the completed board assembly into the case and use it as a template to mark out its four corner mounting holes. That done, remove the board and drill these holes to 3mm. Deburr each hole using an oversize drill. You also have to drill two holes in one end of the box to accept the two cable glands. These are positioned in line with the screw terminal blocks and drilled and reamed to 12.5mm (ie, start with small pilot holes and then carefully enlarge each hole to size using a tapered reamer). The PC board can now be mounted in the case on M3 x 6mm tapped Nylon spacers and secured using eight M3 x 4mm screws. The PC board is housed inside a rugged diecast case and the external wiring leads brought in via cable glands. Initial checks For the time being, do not install ICs1-4 (these are installed later, after some intial checks). You should also leave the Pushbutton Controller disconnected. It’s now just a matter of following this step-by-step procedure to make the initial checks: Step 1: rotate VR6 clockwise by 20 turns to ensure that the sensitivity is set to maximum. siliconchip.com.au Step 2: connect a multimeter between TP1 and the GND test point and set the meter to a low DC volts range. Step 3: apply power and adjust VR1 for a reading of 5.0V on the meter. Step 4: adjust VR3 for a reading of 0V at TP3, then adjust VR4 so that TP4 is at 1.1V. This will ensure that the relay will switch on with a supply as low as 11V. Step 5: disconnect power and insert IC4 into its socket (watch the polarity). Step 6: reapply power and check that the voltage at TP1 is still 5V. Step 7: check that the voltage across ZD4 is 5.6V and that the voltage across Note: zener diodes ZD2 & ZD4 were incorrectly specified in the parts list last month. ZD2 should be a 15V 1W zener diode, while ZD4 should be rated at 5.6V 1W – see Fig.5. January 2010  79 ZD3 is -7.5V. The voltage across ZD2 should be about 0.7V less than the supply voltage. Step 8: if all is correct, disconnect the power and install ICs1-3 into their sockets. Step 9: plug the Pushbutton Controller into the DB25 socket. Note that the lead used must be one that connects all pins from one end to the other in sequence, so that pin 1 connects to pin 1, pin 2 to pin 2 and so on. Some leads do not connect all pins and some swap pin connections. These leads are not suitable. Step 10: reapply power and check that the Pushbutton Controller shows characters on the screen. Adjust trimpot VR1 on the Pushbutton Controller to set the display contrast. The initial display with the LOCK link out should show OUTPUT 0 (dV) on the top line and INPUT 0 (RUN) on the lower line. The ‘0’ after the INPUT may be a number other than 0. If the display shows just blocks on the top line, then there is probably a missing or shorted connection on one of the DB25 connections. Check pins 6, 8, 10, 11, 12 & 13 on the DB25 connector for continuity back to the Pushbutton Controller’s LCD at pins 4, 6, 14, 13, 12 & 11 respectively. Also, check that pins 6, 8, 10, 11, 12 & 13 on the DB25 connector in the Voltage Interceptor connect to pins 17, 16, 13, 12, 11 & 10 (respectively) of IC4. Step 11: check that the switches operate correctly. Pressing the RUN/VIEW switch should cause the display to show VIEW instead of RUN on the lower line. That done, check that the OUTPUT values can be adjusted using the UP and DOWN switches. The fast UP and DOWN switches will change the values in increments of four and the range is ±127. Now check that the INPUT values can be adjusted using the LEFT and RIGHT switches. The range here is from 0-255. Finally, pressing the RESET switch for 4s should reset all OUTPUT values to 0. The word RESET appears on the top line when this occurs. Adjustments Before using the Voltage Interceptor, you first need to check out the sensor it’s to be used with and make some adjustments. This involves determining the voltage range that the sensor outputs under all driving conditions. In practice, you will be able to get some idea of the maximum range available by checking the supply rail to the sensor (if it has power applied to it). For example, a MAP sensor or airflow meter that has a 5V power supply will have an output within the range of 0-5V. Often however, the output voltage range will be restricted to a somewhat narrower range, eg, 0.5-4.5V. And a narrowband oxygen sensor will only output a maximum of about 900mV. Connecting a multimeter to the sensor’s output and measuring the voltage under driving conditions is the best way to determine its output range. The driving conditions should include full power at high and low RPM and engine overrun at high and low RPM. Once you have the determined the voltage range from the sensor, you can proceed with the adjustments to the Voltage Interceptor, as follows: Step 1: connect a 10kΩ linear potentiometer to the input of the Voltage Interceptor as shown in Fig.8. If the sensor provides an output that does not go above 5V, connect the top of the potentiometer to the 5V test point (TP1). Conversely, if the sensor output goes above 5V, connect the top of the potentiometer to +12V (ie, at CON1). Step 2: apply power to the Voltage Interceptor and check that the relay switches on, as indicated by LED1. Step 3: reset all the adjustment values by pressing the Reset switch on the Pushbutton Controller for four seconds (ie, until RESET is indicated on the LCD). Step 4: adjust VR5 so that the voltage at TP5 is as close to 0V as possible. Step 5: adjust the external pot so that the input voltage to the Voltage Interceptor (ie, the voltage on the pot’s wiper) is at or just above the maximum voltage output by the sensor. Pushbutton controller assembly The Pushbutton Controller assembly is shown in Fig.6. Start by installing the three wire links, including the one under the DB25 socket. That done, solder in the dual-inline 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. Install the two 10kΩ 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.6. 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 10µF 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 its 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.7 shows how the PC board is mounted in its case. If you are building Table 1: Resistor Colour Codes: Pushbutton Controller o o No.   2 80  Silicon Chip Value 10kΩ 4-Band Code (1%) brown black orange brown 5-Band Code (1%) brown black black red brown siliconchip.com.au Fig.6: the parts layout for the Pushbutton Controller PC board. 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.7. Note how the 10mF capacitor is mounted on its side, so that it clears the front panel. 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, a cutout for the LCD and a clearance slot for the DB25 socket. A full-size artwork for the front panel (in PDF format) can be downloaded from the SILICON CHIP website. Note that S10’s access hole in the lid should only be about 3mm in diameter, just sufficient for a small probe to actuate the switch. siliconchip.com.au Fig.7: this cross-sectional diagram shows how the PC board for the Pushbutton Controller is mounted in the case. Note how the top edge of the LCD module is supported on two M3 flat washers. January 2010  81 Table 2: Resistor Colour Codes: Voltage Interceptor o o o o o o o o o o o o o o o o o No. 1 1 1 1 1 2 10 1 2 3 1 1 1 1 1 1 Value 1MΩ 470kΩ 100kΩ 43kΩ 22kΩ 20kΩ 10kΩ 9.1kΩ 2.2kΩ 1kΩ 470Ω 220Ω 150Ω 120Ω 100Ω 10Ω Step 6: adjust VR2 for 5V at TP2, then adjust VR7 so that the Interceptor’s output voltage is the same as its input voltage. Step 7: adjust the external potentiometer so that the voltage at the input to the Voltage Interceptor is at or just below the minimum voltage from the sensor. Step 8: measure the voltage at TP2, then adjust VR3 so that the voltage at TP3 is the same. Relay switching threshold There’s a possibility that an error code will be generated by the car’s ECU if the relay in the Voltage Interceptor turns on before the engine has started. An error code is usually indicated by a warning light or character on the car’s instrument panel. To prevent this error code, adjust VR4 so that the TP4 is at 1.3V. This will ensure that the relay trips only after the engine has started and when the alternator has increased the battery voltage above the 13V threshold. Conversely, if the Voltage Interceptor does not cause an error code, then leave VR4 at its previous (lower) setting. Setting VR4 to give 1.1V at TP4 will cause the relay in the Interceptor to turn on as soon as the ignition is switched on. Installation Just four external connections have to be made to the Voltage Interceptor. Two of these are for power (+12V and chassis earth), while the other two connections intercept the sensor output. The sensor’s output is connected 82  Silicon Chip 4-Band Code (1%) brown black green brown yellow violet yellow brown brown black yellow brown yellow orange orange brown red red orange brown red black orange brown brown black orange brown white brown red brown red red red brown brown black red brown yellow violet brown brown red red brown brown brown green brown brown brown red brown brown brown black brown brown brown black black gold to the Voltage Interceptor’s input and the output from the Voltage Interceptor is then connected to the sensor’s ECU wire. Note that the original sensor-to-ECU connection has to be broken for the Voltage Interceptor to intercept the signal, ie, the Interceptor is installed in series with this lead. Use automotive connectors for all wiring attachments and be sure to use automotive cable for the leads. The +12V rail for the unit should be derived from the switched side of the ignition and a suitable point can usually be found in the fusebox. The connection to the switched ignition supply should be made on the battery side of the fusebox (ie, before any fuses) and should be run to the Voltage Interceptor via a 1A inline fuse. The best location to mount the unit is inside the cabin, so that it remains cool. If you do install it in the engine bay, be sure to keep it well away from the engine and the exhaust system so that it is not unduly affected by heat. It can be secured in position using suitable brackets. Programming adjustments The Pushbutton Controller must be set to RUN in order to make real Table 3: Capacitor Codes Value 100nF 10nF 1nF µF Value IEC Code 0.1µF 100n .01µF 10n .001µF 1n0 EIA Code 104 103 102 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown brown black black orange brown yellow orange black red brown red red black red brown red black black red brown brown black black red brown white brown black brown brown red red black brown brown brown black black brown brown yellow violet black black brown red red black black brown brown green black black brown brown red black black brown brown black black black brown NA time adjustments (see panel on using the Pusbutton Controller in Pt.1 last month). Before going further though, a word of warning: the Voltage Interceptor can cause engine damage if the programming adjustments are not done carefully and methodically. You have been warned. The best way to tune an engine using the Voltage Interceptor is with the car set up on a dynamometer and with a specialised engine tuner making the adjustments. Alternatively, you can also make initial adjustments under actual driving conditions, using suitable instruments to monitor performance. This is best done on a closed road (eg, a racetrack). However, do not use the Pushbutton Controller or closely monitor instruments while driving – leave those jobs to an assistant. Changes are made at the load sites where appropriate by using the Up and Down buttons on the Pushbutton Controller to assign values. It is not necessary to access every input load site to make changes though but you must keep a record of any sites that are actually assigned a value of 0. The VIEW display can then be selected later to manually adjust the output values between load sites that were not accessed during the tuning process. This is detailed later under the heading “Interpolating The Results”. Note that the input is likely to change during output adjustments. To minimise this, try to maintain constant engine conditions during programming. The unit locks onto the input value selected when an Up siliconchip.com.au MULTIMETER 4.750 CON1 0V 4148 - +12V DC VOLTS 4148 + 16V 15V CONNECTS TO TP1 IF SENSOR SIGNAL IS LESS THAN 5V, OR TO +12V IF SENSOR SIGNAL IS MORE THAN 5V 4004 – + 7.5V GND TP1 (5V) TP2 4004 INPUT TU O OUTPUT C NI E GATL OV REIFID O M 19001150 NO NC Fig.8: here’s how to connect an external 10kΩ potentiometer and a multi­meter to adjust the Voltage Interceptor. CON2 5.6V 10k LINEAR POTENTIOMETER TP5 or Down button is pressed so that the input load site will not alter during an adjustment, so take care to ensure that you have not drifted too far off the input load site by changing conditions. Releasing the Up or Down button will allow the latest load site to be displayed. involves the offset adjustment trimpot (VR5). This can produce a global voltage offset from zero. This could be useful for narrowband oxygen sensor modifications by allowing the output to be shifted higher (for a richer reading) or lower (for a leaner reading). Global changes As previously mentioned, the Voltage Interceptor can be used to adjust the signal from virtually any sensor that produces a varying output voltage. You will need to build a Voltage Interceptor unit for each sensor output you wish to modify. Let’s take a look at some of the changes you can make: The Voltage Interceptor can easily make global changes. Global changes affect the entire load map and can reduce the number of adjustments required using the Pushbutton Controller. A global change can be particularly useful where a sensor produces an overall lower voltage than required. For example, this could happen if a larger airflow meter is substituted for an original unit, resulting in less sensor output for a given airflow. So for example, if you want 20% more output from a sensor, then the output from the Voltage Interceptor should always be 20% higher than its input. This can be achieved simply by adjusting VR7 to give this effect. So, if a 4V signal is applied to the Interceptor’s input, then VR7 would be adjusted for a 4.8V output. Similarly, by winding VR7 back the other way, a global change can be made to reduce the input voltage by a fixed percentage to produce a lower output. A less likely global modification siliconchip.com.au Modifying sensor outputs (1) Changing The Oxygen Sensor Signal: a narrowband oxygen sensor signal can be modified but it may be difficult to make changes that have any real effect. That’s because an oxygen sensor produces such a steep response in its output as the air/fuel ratio changes. In addition, the ECU will respond to incorrect oxygen sensor signals by showing an error code. This will occur if the voltage swings from the sensor are incorrect or if the load site changes in the Interceptor are too radical. In the latter case, the injector duty cycle required to match the signal from the Interceptor may be outside the allowable range programmed into the ECU. In addition, any changes to the sensor signal may be ineffective while DMM POSITIVE LEAD GOES TO INPUT OR OUTPUT, OR TO TP2 OR TO TP5 (SEE TEXT) the engine control is in closed loop. That’s because the ECU can “learn” its way around the changes and restore mixtures to normal. (2) Changing Air/Fuel Mixtures: in order to correctly make mixture changes, you require an accurate air/fuel ratio meter to monitor the results. Note, however, that changes to an airflow meter signal may not affect mixture changes while the ECU is in closed loop mode. This mode occurs when the mixture is adjusted by the ECU by monitoring all relevant external sensors. If the signal from one sensor is altered by the Voltage Interceptor, this may be ignored by the ECU if it does not give results that are consistent with the other sensors. This means that any changes made by the Voltage Interceptor to the airflow meter signal will only affect the Changing The Sensitivity After making adjustments, you may find that you are only using a small range of output values, eg, less than ±10. If this is the case, adjusting VR6 anticlockwise will reduce the sensitivity and allow a higher range of values to be used with improved resolution. If you do alter VR6, then the adjustments will need to be redone. Note also that changing any of the other trimpots except VR4 will affect the entire map. January 2010  83 The PC board is mounted in the case on M3 x 6mm tapped Nylon spacers and the assembly secured using eight M3 x 4mm machine screws. Don’t forget to install LK1 in the LOCK position when programming is complete. mixture when the control is open loop (such as under power conditions). Be careful when making such adjustments because engine damage can easily occur if you get it wrong. (3) Reducing Turbo Boost Cuts: turbo boost is monitored using either an airflow meter or a MAP sensor. You will need a boost gauge in order to correctly make this modification. In this role, the Voltage Interceptor can be used to alter the sensor signal to prevent the ECU from reducing the boost above certain engine loads. By using the boost gauge, the load points where the boost is cut can be observed on the Pushbutton Controller and the output from the Interceptor reduced to overcome the boost cut as required. Check that air/fuel ratios are not changed at the same time, otherwise engine damage could occur. (4) Injector Changes: when larger than standard injectors are fitted, the airflow meter output signal can be reduced by the Voltage Interceptor to give the correct air/fuel mixtures. This will allow the ECU to operate within its normal range of input values to control the injector duty cycle. (5) Adjusting For A Larger Airflow Meter: substituting a larger airflow meter will give lower airflow readings than from the original unit. The Voltage Interceptor can be used to restore the signal to the normal range required by the ECU for correct fuel injector control. Interpolating the results After making adjustments to the Table 4: Mapped Values Load Site 10 11 12 13 14 15 16 17 18 Initial Value 30 0 0 12 8 0 0 0* 0 0* = mapped at 0; 0 = unmapped Table 1: initial values for load sites 1-18. The load sites with a value of 0 (ie, 11, 12, 15, 16 & 18) have been left unchanged (ie, they are unmapped). Table 5: Final Values Load Site 10 11 12 13 14 15 16 17 18 Final Value 30 24 18 12 8 5 2 0 0 Interpolated values shown in red. Table 2: the load site values after interpolation. The interpolated values are in red. 84  Silicon Chip Voltage Interceptor, there will often be load sites that were not accessed and changed. This is because there could be up to 256 individual sites and so only a representative number of sites are adjusted. However, it’s possible to interpolate between sites. To do this, first use the View display to look for any sites that were not changed. As previously stated, you should have kept a record of any sites that were actually mapped at 0. Any other sites with a value of 0 are unchanged (or unmapped) sites, while those sites that have a number other than 0 are obviously sites that have been adjusted. The job now is to make changes to the unmapped sites that sit between the adjusted sites. This involves interpolating the values so as to smooth out the changes between adjacent adjusted sites. Interpolation involves calculating the expected values. Sometimes you can guess what the value should be but it can also be calculated. The calculation is done by first dividing the difference between two adjusted sites by one plus the number of unadjusted sites between them. This gives the difference (or step) between each site. The example shown in Table 4 will illustrate this. Here, load sites 10, 11, 12 & 13 have values of 30, 0, 0 & 12 respectively. The difference between the two adjusted sites is 18 (30-12) and there are two unadjusted sites between them. In this case, we divide 18 by 3 (ie, 1 + 2(sites)) and this gives a difference of 6 between each site. As a result, load sites 11 & 12 would be changed to 24 (30-6) and 18 (24-6) respectively – see Table 5. For load sites 14-18, the output values are interpolated from an 8 at site 14 to a 0 at site 17. As indicated, site 17 is one that was mapped as a 0 and so this is kept at 0. This means that you must keep a record of any sites which were mapped at 0 when making the original adjustments, so that they can be distinguished from unaltered load sites later on. Finally, when all the adjustments have been made, the Lock jumper link (LK1) can be installed in the Voltage Interceptor to prevent any changes to the map. You can then either leave the Pushbutton Controller connected to view the map (in either Run or View display mode) or you can disconnect it altogether. SC siliconchip.com.au