fcd fuel cut defencer

There has been a great deal of interest on the Team FC3S
list in a cheaper (and if possible, superior) alternative to the
expensive FCD`s offered commercially. This is understandable
given that no modification to the Turbo II that raises the
possible boost pressures can be attempted without an FCD. This
article presents a simple FCD circuit that can be built by
anyone with moderate electronics assembly expertise. In addition,
the article covers the reasons why an FCD is needed, why this
FCD is superior to other FCD designs, and the theory of
operation. By the time you are done reading this article, you
will hopefully understand a little more about how your TII works,
and a little electronics as well.

What is an FCD?

The FCD (acronym for Fuel Cut Defencer) is any device that
prevents the stock ECU from cutting fuel to the rear rotor when
the boost exceeds a preset boost level. This maximum safe boost
level and behavior is coded into the firm ware in the engine
management unit and can not be changed without reprogramming the
ECU. The maximum allowed boost pressure is about 8.6 psi.
The way an FCD defeats the fuel cut is by lying to the ECU about
what the boost pressure is. The FCD is placed betw1een the boost
sensor and the ECU where it modifies the boost pressure signal by
some amount so that as the boost pressure rises above the preset
“safe limit”, the ECU continues to see a signal that is below
the limit.

There are a couple of immediate consequences to this fooling
around. As the boost rises, the ECU must increase the amount of
fuel being delivered to the engine in order to maintain safe and
efficient operation. As the FCD starts lying to the ECU, the ECU
will begin to under-compensate for the rise in pressure
leading to a gradual leaning of the air-fuel mixture. The amount
of error increases as the boost rises. For relatively small
errors, the only penalty is efficiency. As the error gets larger,
however, detonation becomes likely, exacerbated by the high
boost pressures and accompanying high intake charge temperatures.
Detonation under these conditions will quickly kill an engine.
So, before we go any further, be forewarned that using an
FCD and increasing boost pressure without also compensating for
the ECU error with fuel enrichment (and preferably more efficient
intercooling) can cause serious damage to your engine!

What you would like to have is an FCD that leaves the boost
signal alone until it approaches the cutoff level, and then kicks
in, holding the signal below the critical level. This can be
accomplished with a circuit element called a clamp. The FCD
circuit described in this article utilizes an active clamp which
红包扫雷苹果下载地址 performs the necessary function very efficiently.

Following is a graph of the boost sensor signal without an
FCD, with tw1o commercially available FCDs, and with our cheap
红包扫雷苹果下载地址 little DIY FCD.

Fcd fuel cut defencer

As you can see from the graph, FCD #1 is a clamp circuit. The
output follows the input until the clamp voltage of 3.33 V (about
6 psi) is reached. At this point the output stops rising. FCD #2
works by reducing the input by a percentage. This creates an
error across the entire range, as opposed to only when the
boost is over the limit. (At a safe 5.5 psi, the computer is only
seeing 4 psi.) This is not the desired behavior. Our FCD works
similarly to FCD #1, except we have raised the clamping voltage
to 3.65V (about 7.9 psi).

a linear regression ran on the data gathered shows that the equation for the best fit line is:

Out(V) = 0.169V/psi*P(psi) + 2.318V

红包扫雷苹果下载地址solving for pressure, we get:

P(psi) = (Out(V) – 2.318V)/0.169V/psi

NOTE: If you look closely at the graph, you can see that our
FCD has an output that is 0.05 V below the input up to the
clamping voltage. I have since fixed this problem by changing R1
from 2.2k ohms to 680 ohms. The FCD output is now within 0.02V of
the input, right up to the clamping voltage. Sorry, I didn`t
have time to rerun the numbers.

The measurements above were obtained with the FCD under test
connected to the TII boost sensor and TII wiring harness in order
to simulate actual operating conditions as closely as possible.
Pressures were read on a diagnostic pressure/vacuum gauge.
If you are interested in it, I would be happy to send you the
Excel spreadsheet containing the raw data, the linear regression,
红包扫雷苹果下载地址 and the graph above.

The Circuit

红包扫雷苹果下载地址the circuit schematic is shown in the following figure:

Fcd fuel cut defencer

Theory of Operation

There are a number of requirements on an FCD that is going to
work well and survive the stresses in your Rx7. Here are the most
红包扫雷苹果下载地址 important ones:

Sharp clamping behavior. This is, of course,
the primary requirement. The FCD output must follow the input
voltage until the clamping voltage is exceeded, at which point it
should clamp the output to the setpoint.

High input impedance. The boost pressure
sensor has a very high output impedance. That is, if you think of
it as a battery that produces a voltage that is proportional to
the input pressure, that battery has a very large resistor in
series with it. This is a common characteristic of strain gauge
based pressure sensors. If the input impedance of the circuit
that it is driving is low, there will be an error caused by the
voltage drop across the internal resistor. For this reason, our
FCD must have a high input impedance.

Noise suppression. High impedance devices
make good antennas which can pick up everything from alternator
and ignition noise to your favorite Rock-`n-Roll station. This
calls for some filtering to eliminate these sources of

Input protection. Because our FCD will live
in a hostile environment where stray voltage spikes above and
below ground may appear, we need to provide some input protection
for our device.

Thermal stability. Temperatures in the
automotive environment can range from 20 degrees below zero to
200 degrees Fahrenheit. It is necessary that our circuit be
durable enough to operate correctly given these temperature

In our circuit, the clamping is performed by op-amp U1-2 and
D3. These tw1o devices form what is called an active clamp. While
the signal at the (-) input of the op-amp is below the voltage
setting at the (+) input, the output of the op-amp will be high,
D3 will be reverse biased, and the output will follow the
input. When the signal at the (-) input of the op-amp exceeds the
voltage setting at the (+) input, D3 conducts closing the
feedback loop and causing the output to follow the (+) input,
which is set at the clamping voltage. This all happens so quickly
that it might as well be instantaneous. Notice that the output
impedance of the clamp is not zero. When clamping is not
occurring, and the output is following the input, the signal is
passing through R1, which makes the output impedance 680 ohms.
Not to worry, this output impedance is substantially lower than
红包扫雷苹果下载地址 the boost sensor`s output impedance.

The clamping voltage is adjustable and is set by the trimmer
at R3 which is wired as an adjustable voltage divider betw1een
the Vref lead to the pressure sensor and ground. Vref is supplied
by a voltage regulator in the ECU and is maintained at 5V .

High input impedance is achieved by buffering the input to the
FCD. U1-1 is wired as a voltage follower, meaning that the
output just follows the input. The input impedance of the buffer
红包扫雷苹果下载地址 is nearly infinite.

Noise suppression is achieved via the use of a low pass filter
on the input, formed by R2 and C1. High frequency roll-off is at
about 100 Hz, allowing the circuit to be responsive but
红包扫雷苹果下载地址 effectively suppressing RF noise.

Input protection is provided by D1 and D2 which clamp the
inputs to +12V and ground, effectively protecting the op-amp
inputs. Stray voltage spikes above or below ground will be
shorted to the appropriate supply rail.

Thermal stability is potentially a small problem for our
circuit. The resistance of R3 can vary as a result of extreme
temperature changes. For this reason, I would recommend
installing the FCD inside the car, alongside the ECU. This
article will provide instructions for installation in both

For the active component in our FCD, we have chosen the LM358
dual op-amp. This IC puts tw1o single supply op-amps in a single
package. It`s not a high precision op-amp, but it serves the FCD
circuit very well. Having tw1o op-amps in the package makes it
possible for us to include a buffer with the active clamp,
红包扫雷苹果下载地址 which improves the input impedance as mentioned above.

fuel injector pulse width monitor

Here is a picture of the faceplate that holds the LED
bargraphs for air/fuel and pulse width as well as the pot to
control the fuel mixture above 7psi boost. The switch allows
either the primary or secondary injector pulse to be monitored.
The faceplate is made of polished aluminum. The air/fuel (O2)
monitor, pulse width monitor, and fuel controller are all on one
printed circuit board.

Fuel injector pulse width monitor

Shown below is the schematic for the pulse width monitor. The
heart of the circuit is the transistor current source which
charges cap C10 to form an integrator. The theory is that the cap
is charged and the voltage across it increases linearly for the
amount of time that the injector is energized. As the injector
is switched off the voltage in C10 is stored in cap C9 and
then C10 is reset to 0 volts to get ready for the next cycle. The
output of the circuit is the voltage across cap C9, this voltage
is fed directly into U3 the bar graph chip to be displayed as a
value betw1een 1-10 on the LEDs. Potentiometer R31 sets the
charge rate on C10 and basically sets the max injector on time
红包扫雷苹果下载地址 that can be displayed.

The calibration on this circuit is pretty tricky. You`ll need
an oscilloscope and a waveform generator. Setup a 62Hz 0-12v 50%
duty cycle square wave at the input to the circuit. Use the scope
to monitor the voltage across C10 Adjust pot R31 such
that the ramping voltage across C10 just reaches the peak (starts
to flatten out). Now adjust the pot R22 in the display circuit
红包扫雷苹果下载地址 such that LED 10 just comes on.

With the calibration described above LED 1 corresponds to
about 1.5ms and LED 10 corresponds to about 8ms of injector pulse
width (on time). Injector duty cycle in dependent on engine
speed according to the following relationship:

红包扫雷苹果下载地址% duty cycle = ( pulse width / period )*100

红包扫雷苹果下载地址period = 1/[engine speed (rpm) / 60]

Fuel injector pulse width monitor

parking aid senses distance to rear of v

three leds signal bumper-barrier distance

红包扫雷苹果下载地址infra-red operation, indoor use

Circuit diagram:

Parking aid senses distance to rear of v


r1_____________10k 1/4w resistor

r2,r5,r6,r9_____1k 1/4w resistors

红包扫雷苹果下载地址r3_____________33r 1/4w resistor

红包扫雷苹果下载地址r4,r11__________1m 1/4w resistors

红包扫雷苹果下载地址r7______________4k7 1/4w resistor

r8______________1k5 1/4w resistor

r10,r12-r14_____1k 1/4w resistors

c1,c4___________1΅f 63v electrolytic or polyester capacitors

c2_____________47pf 63v ceramic capacitor

红包扫雷苹果下载地址c3,c5_________100΅f 25v electrolytic capacitors

d1_____________infra-red led

d2_____________infra-red photo diode (see notes)

红包扫雷苹果下载地址d3,d4________1n4148 75v 150ma diodes

红包扫雷苹果下载地址d5-7___________leds (any color and size)

红包扫雷苹果下载地址ic1_____________555 timer ic

ic2___________lm324 low power quad op-amp

红包扫雷苹果下载地址ic3____________7812 12v 1a positive voltage regulator ic

Device purpose:

This circuit was designed as an aid in parking the car near
the garage wall when backing up. LED D7 illuminates when
bumper-wall distance is about 20 cm., D7+D6 illuminate at about
10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted
when approaching too close to the wall.

All distances mentioned before can vary, depending on
infra-red transmitting and receiving LEDs used and are mostly
affected by the color of the reflecting surface. Black surfaces
lower greatly the device`s sensitivity.

obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.

Circuit operation:

IC1 forms an oscillator driving the infra-red LED by means of
0.8mSec. pulses at 120Hz frequency and about 300mA peak current.
D1 & D2 are placed facing the car on the same line, a couple
of centimeters apart, on a short breadboard strip fastened
to the wall. D2 picks-up the infra-red beam generated by D1 and
reflected by the surface placed in front of it. The signal is
amplified by IC2A and peak detected by D4 & C4. Diode D3,
with R5 & R6, compensate for the forward diode drop of D4. A
DC voltage proportional to the distance of the reflecting object
and D1 & D2 feeds the inverting inputs of three voltage
comparators. These comparators switch on and off the LEDs,
referring to voltages at their non-inverting inputs set by the
红包扫雷苹果下载地址 voltage divider resistor chain R7-R10.


Power supply must be regulated (hence the use of IC3) for
precise reference voltages. The circuit can be fed by a
commercial wall plug-in power supply, having a DC output voltage
in the range 12-24V.

current drawing: leds off 40ma; all leds on 60ma @ 12v dc supply.

The infra-red Photo Diode D2, should be of the type
incorporating an optical sunlight filter: these components appear
in black plastic cases. Some of them resemble TO92 transistors:
in this case, please note that the sensitive surface is the
红包扫雷苹果下载地址 curved, not the flat one.

avoid sun or artificial light hitting directly d1 & d2.

If your car has black bumpers, you can line-up the infra-red
diodes with the (mostly white) license or number plate.

It`s wiser to place all the circuitry near the infra-red LEDs
in a small box. The 3 signaling LEDs can be placed far from the
main box at an height making them well visible by the car driver.

The best setup is obtained bringing D2 nearer to D1 (without a
reflecting object) until D5 illuminates; then moving it a bit
until D5 is clearly off. Usually D1-D2 optimum distance lies in
the range 1.5-3 cm.

红包扫雷苹果下载地址if you are needing a simpler circuit of this kind driving a led or a relay, click infra-red level detector

parking sonar


automatic switch on on rear gear

led-bargraph display

红包扫雷苹果下载地址audible bleep on last led

红包扫雷苹果下载地址“good old” design style, no microcontrollers!

Parking sonar

Based on an ultrasonic amplifier from an article seen on a
1982 magazine, it was once installed on the rear bumper of my
Volvo Station Wagon. It served very well for many years.
Connecting it to the reverse gear lights, it switches on
automatically and shows you the distance to the nearest obstacle
(according to his beam) on a led scale. When the last led lights,
a buzzer is also activated telling you to stop immediately.

It works on the sonar principle, sending an ultrasound burst
and listening for first echo. The burst generated by the
oscillator built around U4D (you must set the frequency using TR2
to have 40 kHz or the maximum sensitivity), U4E buffers the
output and U4F boost the signal doubling the voltage span across
红包扫雷苹果下载地址 the TX piezo transducer.

A new burst is generated each time the decade counter (4017 in
the circuit diagram) is in its reset state, that is output 0 is
selected. The other outputs (1 to 9) are scanned sequentially
following burst generation, until an echo strikes back the RX
receiver. It is then amplified by the transistor input stage,
triggering the monostable built around U4A – U4B. The monostable
stops temporarily the scanning, and a led corresponding to the
obstacle distance appears as continuously lit. The buzzer bleeps
when the first led (minimum distance) il lit.

When the monostable expires, scanning is resumed and
restarting the send-and-listen sequence. If no echo is received,
红包扫雷苹果下载地址 the scanning never stops and all the leds are slightly lit.

To set up:

set tr2 for maximum sensitivity (usually 40 khz for most commercially available ultrasonic transducer pairs).

Set TR1 for your preferred range. Setting it to minimum
resistance shortens the distance for each led (minimum range). I
suggest a range of 90 cm (10 cm each led).


First of all, be careful not to exchange the ultrasonic
transmitter with the receiver: they look very similar, and I
suggest you to mark them very clearly from the moment you buy
During setup, place the ultrasonic transducers over a
soft surface, near the border of a table, 10 cm apart of
each other pointing outw1ards the table. Then adjust TR1 and TR2
using a rigid surface (for example a metal sheet) placed in front
of sensors, at a variable distance.

I enjoyed the sonar for many years. It was installed below the
car`s rear bumper in a plastic case. Do not choose an enclosure
too small: always separate the transducers by 7-10 cm and plenty
of sound-absorbing material, otherwise the receiver will
reveal the direct sound instead of the reflected one. The same
applies if the sound travels through a rigid fixture, so it is a
good idea to fix them with separated supports.

红包扫雷苹果下载地址and remember not to mount the tranducers exposed to direct sunlight nor rain.

speed alert wireless portable unit

红包扫雷苹果下载地址adaptable with most internal combustion engine vehicles

Speed alert wireless portable unit


r1,r2,r19_______1k 1/4w resistors

r3-r6,r13,r17_100k 1/4w resistors

r7,r15__________1m 1/4w resistors

r8_____________50k 1/2w trimmer cermet

r9____________470r 1/4w resistor

红包扫雷苹果下载地址r10___________470k 1/4w resistor

红包扫雷苹果下载地址r11___________100k 1/2w trimmer cermet (see notes)

r12___________220k 1/4w resistor (see notes)

r14,r16________68k 1/4w resistors

r18____________22k 1/4w resistor

r20___________150r 1/4w resistor (see notes)

红包扫雷苹果下载地址c1,c7_________100΅f 25v electrolytic capacitors

红包扫雷苹果下载地址c2,c3_________330nf 63v polyester capacitors

c4-c6___________4΅7 25v electrolytic capacitors

d1,d5______red leds 3 or 5mm.

红包扫雷苹果下载地址d2,d3________1n4148 75v 150ma diodes

d4________bzx79c7v5 7.5v 500mw zener diode

红包扫雷苹果下载地址ic1__________ca3140 or tl061 op-amp ic

红包扫雷苹果下载地址ic2____________4069 hex inverter ic

ic3____________4098 or 4528 dual monostable multivibrator ic

红包扫雷苹果下载地址q1,q2_________bc238 25v 100ma npn transistors

l1_____________10mh miniature inductor (see notes)

红包扫雷苹果下载地址bz1___________piezo sounder (incorporating 3khz oscillator)

sw1____________spst slider switch

b1_______________9v pp3 battery (see notes)

Device purpose:

This circuit has been designed to alert the vehicle driver
that he has reached the maximum fixed speed limit (i.e. in a
motorway). It eliminates the necessity of looking at the
tachometer and to be distracted from driving.

There is a strict relation betw1een engine`s RPM and vehicle
speed, so this device controls RPM, starting to beep and flashing
红包扫雷苹果下载地址 a LED once per second, when maximum fixed speed is reached.

its outstanding feature lies in the fact that no connection is required from circuit to engine.

Circuit operation:

IC1 forms a differential amplifier for the electromagnetic
pulses generated by the engine sparking-plugs, picked-up by
sensor coil L1. IC2A further amplifies the pulses and IC2B to
IC2F inverters provide clean pulse squaring. The monostable
multivibrator IC3A is used as a frequency discriminator, its
pin 6 going firmly high when speed limit (settled by R11) is
reached. IC3B, the transistors and associate components provide
timings for the signaling part, formed by LED D5 and piezo
sounder BZ1. D3 introduces a small amount of hysteresis.


D1 is necessary at set-up to monitor the sparking-plugs
emission, thus permitting to find easily the best placement for
the device on the dashboard or close to it. After the setting is
done, D1 & R9 can be omitted or switched-off, with battery

During the preceding operation R8 must be adjusted for better
results. The best setting of this trimmer is usually obtained
红包扫雷苹果下载地址 when its value lies betw1een 10 and 20K.

you must do this first setting when the engine is on but the vehicle is stationary.

The final simplest setting can be made with the help of a
second person. Drive the vehicle and reach the speed needed. The
helper must adjust the trimmer R11 until the device operates the
红包扫雷苹果下载地址 beeper and D5. Reducing car`s speed the beep must stop.

L1 can be a 10mH small inductor usually sold in the form of a
tiny rectangular plastic box. If you need an higher sensitivity
you can build a special coil, winding 130 to 150 turns of 0.2 mm.
enameled wire on a 5 cm. diameter former (e.g. a can). Extract
the coil from the former and tape it with insulating tape making
thus a stand-alone coil.

Circuit`s current drawing is approx. 10mA. If you intend to
use the car`s 12V battery, you can connect the device to the
lighter socket. In this case R20 must be 330R.

Depending on the engine`s cylinders number, R11 can be unable
to set the device properly. In some cases you must use R11=200K
红包扫雷苹果下载地址 and R12=100K or less.

红包扫雷苹果下载地址if you need to set-up the device on the bench, a sine or square wave variable generator is required.

红包扫雷苹果下载地址to calculate the frequency relation to rpm in a four strokes engine you can use the following formula:

hz= (number of cylinders * rpm) / 120.

for a tw1o strokes engine the formula is: hz= (number of cylinders * rpm) / 60.

thus, for a car with a four strokes engine and four cylinders the resulting frequency @ 3000 rpm is 100hz.

Temporarily disconnect C2 from IC1`s pin 6. Connect the
generator`s output to C2 and Ground. Set the generator`s
frequency to i.e. 100Hz and regulate R11 until you hear the beeps
and LED D5 flashes. Reducing the frequency to 99 or 98 Hz,
红包扫雷苹果下载地址 beeping and flashing must stop.

this circuit is not suited to diesel engines.

synchronized multi spark module smsm

Multi-spark ignition is very useful especially in the case
of startings at low temperature and at low rpm range. Basic
idea, is to apply to spark plugs instead of only one spark, a
spark-burst having big energy. In this case, combustion of
air/fuel mixture is much better and the emissions are more
reduced. In addition, through burning improvement, the
红包扫雷苹果下载地址 consumption of fuel can be reduced.

Synchronized multi spark module smsm

why synchronized multi-spark, or what means this?

Special literature abounds in multi-spark EID schematics.
These have in common the fact, as the breaker-points dont control
directly EID, but an oscillator, which will generate a
succession of impulses, and these impulses shall command EID.
This aproach has tw1o major deficiencies:

First spark doesnt match exactly with the moment of breaking
points; so, it has an aleatory delay toward this. This is
equivalent to an aleatory modification of ignition advance,
which will leads to non-uniform run of engine.

At high rpm range, the time betw1een tw1o impulses of
multi-spark device can become comparable with the time betw1een
breaker-points impulses; this shall lead to an unstable
operation of engine, with trepidations and knockings. To avoid
this trouble, is necessary to switch-off the multi-spark
红包扫雷苹果下载地址 device when rpm of engine exceeds a certain value.

with these in mind, i imagined the device described forwards.

Few calculations elements

the crankshaft velocity of an internal combustion engine is given by following formula:

Synchronized multi spark module smsm

where :

红包扫雷苹果下载地址n = revolution speed of engine crankshaft (rpm)

m = strokes number (2 or 4)

n = number of sparks per second (sparks frequency, in hz)

b = number of ignition coils

c = cylinder number

红包扫雷苹果下载地址for usual four stroke engines, with 4 cylinders and a single ignition coil, the formula becomes :

Synchronized multi spark module smsm

红包扫雷苹果下载地址from where :

Synchronized multi spark module smsm

Synchronized multi spark module smsm

In fig.1 is shown an EID equipped with synchronized multi-spark module.

Synchronized multi spark module smsm

Shaping block has the role to provide fixed length impulses (2
mS) at each breaker-points opening. In this way are eliminated
the false impulses which appear due contacts vibrations.

As shown in drawing, shaped impulse triggers directly the EID
and act as START impulse for multi-spark module. If rpm of engine
is under speed limit, the module will generate a series of
supplementary impulses that, through an OR gate, will generate
supplementary sparks by EID. When speed limit is reached (for
example, 2000 rpm), supplementary impulses stops at module
output, thus no supplementary sparks will be generated.

Functional description

The module uses for control the shaped impulses from breaker
points. The time betw1een tw1o consecutively impulses depends on
红包扫雷苹果下载地址 rpm engine and has the values shown in upper table.

Synchronized multi spark module smsm

From whole T interval, only in the first half of this will be
generated supplementary sparks, after the main spark produced by
the breaker points. This is very important, because generating
sparks outside of half of the interval, the spinning distributor
could apply these sparks to next cylinder, and this could be very
harmful for mechanical parts of engine.

in fig. 3 is shown the block-diagram of the multi-spark module.

At breaker-points opening, the shaping circuit (not shown in
drawing) produces a square impulse having 2 mS. This, named BP,
红包扫雷苹果下载地址 is applied to EID by an OR gate and generate the main spark.

Synchronized multi spark module smsm

In multi-spark module, during 2 mS interval, a sequence timer
(a counter with decoded outputs) accomplishes the initialization
of circuits (full operations will be detailed later). When
impulse BP disappears, the gate P2 is opened and the counter N1
receives impulses with 1 mS period, from clock generator. This 8
bits counter measures, in fact, the duration betw1een tw1o
breaker-points impulses. It can count maximum 255 impulses, each
having 1 mS (see the table, this correspond to 120 rpm, far
below the free running speed !). At next BP impulse, P2 close and
the counting stop. The number stored inside N1 is in fact the
time length betw1een tw1o BP impulses.

The sequence timer copy the number stored in N1 to N2, after
this resets counter N1. When BP becomes low level, N1 restarts
the counting. In the same time, the up/down counter N2, starts
counting the impulses having 0.5 mS period, which comes via gate
P1. It counts down, but with double speed. In this way the
counter N2 reach to 0 after T/2 time. The counter N4 and gate P5
makes the impulses for supplementary sparks (2 mS length).

This counter works only if INH signal is at low level. The
fip-flop FF1 marks the interval T/2 in which will be generated
supplementary sparks. It is reseted when N2 reach 0. The gates P3
and P4 unlock the flio-flop and start supplementary sparks.
Also, these gates switch-off the multi-spark function when engine
speed limit is reached (in this case, ~ 2000 rpm). How works
this ? In the upper table we can see at about 2000 rpm, the time
length betw1een tw1o BP impulses is 15 mS.

This means as after a counting cycle, the first 4 bits of
counter N1 will be 111 and next 4, 0000. In this case, P3 gate
output will be at low level, and the same value for P4 output.
The flip-flop FF1 will be not set, and as result, no
supplementary sparks. If the speed engine decrease (time length T
increase), the last 4 bits of N1 will have at least one 1 and
the flip-flop will be set. This allow to appear supplementary
sparks until flip-flop will be reseted by borrow impulse of N2.

electronic car ignition circuit

Electronic car ignition circuit


This scheme is for 4 cylinder motor. This will make your car
spent less fuel, be a little bit faster and you wont have to
frequently open your distributor cap to change the contact
buttons thus wasting less money.

T1/T2 create one monostable multivibrator in which C2 and R5
determine the length of impulse which is 1,5 msec. Next in line
are T3 and then T4 which is Darlington transistor specially
developed for electronic ignition which is used as a switch to
turn on/off primary coil. Impulses from switch P turn on
monostable multivibrator T1/T2. You need to un-connect capacitor
that is in distributor cap because it is not needed anymore.
While switch P is closed T1 is in off state but T2 is in on
state, also T3 and T4 which enables current to flow trough
primary coil. When switch P is opened, T1 gets in on state for a
moment causing C2 to charge over R6 which makes T2 go to off
state because of voltage drop on R6. When T2 is off also T3 and
T4 are off and current that was flowing trough primary coil is
stopped. Because T2 is in off state, voltage on R8 is
increased which is passed trough R5 on T1 base which is still in
on state and C2 is still charging. After 1,5 msec. C2 value
reaches the level where T2 goes to on state again and T1 goes to
off state. Now T2, T3 and T4 are in on state, again, and current
flows trough primary coil again. R2 and D1 are used to neutralize
the effect of impulses caused from «jumping» of switch P which
could turn on monostable multivibrator when it shouldn`t.

Zener diodes Z5 and Z6 are together with R10 limit overcharged
voltage impulses that are caused by self induction of primary
coil which could damage T4. They should be connected as close as
possible to T4.

红包扫雷苹果下载地址d7 protects device from wrong polarity.

Coil should have ratio of 1:80 or 1:100 with external resistor
Rv which is used for better cooling. Total resisting value (Rp)
of primary coil and Rv resistor shouldn`t be under 1,6 ohm`s so
红包扫雷苹果下载地址 current trough T4 wouldnt be bigger than 10A.

depending on rp, r9 have different values:

红包扫雷苹果下载地址120ω/2w for rp tot > 2,2ω

100ω/2w for 1,8ω < rp tot < 2,2ω

红包扫雷苹果下载地址82ω/3w for 1,5ω < rp tot <1,8ω

红包扫雷苹果下载地址t4 has to be heatsinked!!!

红包扫雷苹果下载地址all resistors are 1/2w +/-5%


d1-d4 = 1n4148

红包扫雷苹果下载地址d5-d6 = bzx85c 180 (replicable with all equivalent types with power of 1,3w)

d7 = 1n4001

r1 = 470 – 1w

r2 = 22k

r3 = 2,2k

r4 = 1k

r5 = 4,7k

r6 = 39k

r7 r10 = 100

r8 = 680

红包扫雷苹果下载地址c1 c2 = 47nf (ceramic)

c3 = 0,22uf 400v (ceramic)

红包扫雷苹果下载地址c4 = 100uf (electrolytic)

T1 T2 = BC327 (BC327-25, BC327-40)
红包扫雷苹果下载地址 T3 = BC237B (BC547B, BC547C)

T4 = BUX37 (BU323, BU920, BU921, BU922, BUV37B (u TOP3),
红包扫雷苹果下载地址 BUW29, BUW81, MJ10012, MJ10013, MJ10014, TIP662, TIP665, 2SD683)

A Simple Transistor Based Motorcycle Alarm


Photograph Of The Prototype

红包扫雷苹果下载地址this is a simple – easy to build – transistor based motorcycle alarm. it’s designed to work at 12-volts. but – if you change the relay for one with a 6-volt coil – it’ll protect your "classic bike". the standby current is virtually zero – so it won’t drain your battery.

Schematic Diagram



any number of normally-open switches may be used. fit the mercury switches so that they close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. use micro-switches to protect removable panels and the lids of panniers etc. while at least one switch remains closed – the siren will sound.

about one minute after all of the switches have been opened again – the alarm will reset. how long it takes to switch off depends on the characteristics of the actual parts you’ve used. you can adjust the time to suit your requirements by changing the value of c1 and/or r3.

the circuit is designed to use an electronic siren drawing 300 to 400ma. it’s not usually a good idea to use the bike’s own horn because it can be easily located and disconnected. however, if you choose to use the horn, remember that the alarm relay is too small to carry the necessary current. connect the coil of a suitably rated relay to the siren output – and use its contacts to sound the horn.

the circuit board and switches must be protected from the elements. dampness or condensation will cause malfunction. without its terminal blocks, the board is small. ideally, you should try to find a siren with enough spare space inside to accommodate it. fit a 1-amp in-line fuse as close as possible to the power source. this is very important. the fuse is there to protect the wiring – not the circuit board. instead of using a key-switch you can use a hidden switch; or you could use the normally-closed contacts of a small relay. wire the relay coil so that it’s energized while the ignition is on. then every time you turn the ignition off – the alarm will set itself.

红包扫雷苹果下载地址when it’s not sounding, the circuit uses virtually no current. this should make it useful in other circumstances. for example, powered by dry batteries and with the relay and siren voltages to suit, it could be fitted inside a computer or anything else that’s in danger of being picked up and carried away. the low standby current and automatic reset means that for this sort of application an external on/off switch may not be necessary.

when you set the alarm – if one of the switches is closed – the siren will sound. this could cause annoyance late at night. a small modification will allow you to monitor the state of the switches using leds. when the leds are all off – the switches are all open – and it’s safe to turn the alarm on.

Veroboard Layout

Veroboard Layout

A Cmos Based Motorcycle Alarm


Photograph Of The Prototype

this circuit features an intermittent siren output and automatic reset. it can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition. by adding external relays you can immobilize the bike – flash the lights etc.

Schematic Diagram



红包扫雷苹果下载地址any number of normally-open switches may be used. fit "tilt" switches that close when the steering is moved or when the bike is lifted off its side-stand or pushed forward off its centre-stand. use micro-switches to protect removable panels and the lids of panniers etc.

once activated – the rate at which the siren switches on and off is controlled by r9 & c5. for example – increasing the value of c5 will slow it down – while reducing the value of r9 will make it faster.

while at least one switch remains closed the siren will sound. about thirty seconds after all of the switches have been opened, the alarm will reset. how long it takes to switch off depends on the characteristics of the actual components used. you can adjust the time to suit your requirements by changing the value of r6 and/or c4.

the circuit is designed to use an electronic siren drawing 300 to 400ma. it’s not usually a good idea to use the bike’s own horn because it can be easily located and disconnected. however, if you choose to use the horn, remember that the alarm relay is too small to carry the necessary current. connect the coil of a suitably rated relay to the "siren" output. this can then be used to sound the horn – flash the lights etc.

红包扫雷苹果下载地址the circuit board and switches must be protected from the elements. dampness or condensation will cause malfunction. connect the 1-amp in-line fuse as close as possible to your power source. this is very important. the fuse is there to protect the wiring – not the alarm. exactly how the system is fitted will depend on the make of your particular machine – so i’m unable to provide any further help or advice in this regard.

the quiescent (standby) current of the circuit is virtually zero – so there is no drain on the battery. if you want to operate the alarm manually use a key-switch or a hidden switch connected to the "off/set" terminals. for automatic operation connect a wire from the ignition circuit to the "ignit" terminal. then every time you turn-off the ignition – the alarm will set itself. remember that this wire from the ignition switch is not protected by your 1-amp inline fuse. so unless its run is very short – fit the wire with its own 1-amp fuse as close as possible to its source.

红包扫雷苹果下载地址when you set the alarm – if one of the switches is closed – the siren will sound. this could cause annoyance late at night. a small modification will allow you to monitor the state of the switches using leds. when the leds are all off – the switches are all open – and it’s safe to turn the alarm on.

Veroboard Layout