This is only a preview of the January 2010 issue of Silicon Chip. You can view 18 of the 104 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "A Multi-Function GPS Car Computer, Pt.1":
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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 10m
mF 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 10m
mF 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
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