Multi-purpose safety light

A motion activated and light sensitive multi-purpose safety light, having a housing for supporting: a motion sensor; a light emitting diode which serves as both a light source and a light detector; an electronic circuit which further comprises; a motion sensor amplifier to condition the motion signal received from the motion sensor, a driver for illuminating the light emitting diode in a flashing manner, a timer enabling the operation of the driver and a photo-amplifier providing amplification of the input signal received from the light emitting diode. A user-selected control components for providing parameters relating to the conditioning and the flash rate. A printed circuit board providing an area to mount the electrical components and electric circuit and a system power source.

TECHNICAL FIELD 
The present invention relates to a safety light intended to make the 
location of people, animals, or objects more apparent under low light or 
bad weather conditions. 
BACKGROUND 
Many injuries have occurred due to poor night time visibility. In an 
attempt to alleviate this problem various devices have been proposed to 
give visible notice of one's presence under low light situations. These 
devices include, for example, various forms of reflectors, and steady and 
flashing lights which are attached to people, animals or objects. For 
example, a person running on the side of a road at night may wear a device 
which incorporates a reflector or flashing light in an attempt to be more 
visible to passing motorists. Likewise, such a device may be attached to a 
collar of a dog or to a surface on a bicycle frame enhancing the 
likelihood of visual detection. Such devices can increase visibility 
during daylight hours as well as at night. In the past, however, designs 
have fallen short of their intended purpose: to dependably and effectively 
increase detection of the person, animal, or object to which the device is 
attached. 
Reflectors, for example, since they are dependent on an external light 
source, will fail in the situation where a motorist approached an 
intersection and, after stopping, makes a right turn without noticing a 
bicyclist who had come up alongside the motorist. Also, reflectors often 
lead to confusion. If there are numerous lights in close proximity at an 
intersection, a reflector as a light source may be mistaken as another 
motorist traveling at the speed of traffic or a stationary light along the 
roadside, depending on the motorist's perception. Both situations may lead 
to serious physical injury to the motorist and bicyclist. 
Other indicators rely on various moving parts which are subject to wear and 
fatigue resulting in failure. For example, one design for a bike requires 
a generator to supply power to a light source mounted on the bike. The 
generator is activated by bringing one end of the generator rotor in 
physical contact with the bike tire or wheel. As the wheel turns the 
generator produces power for the light source. Since the generator is 
physically touching the tire or wheel, wear to the tire or wheel occurs 
which may ultimately lead to wheel failure. Additionally, since the 
generator and the light source are typically mounted in separate areas, a 
conductor to carry power to the light must be used. In operation, a bike 
is subjected to environmental elements resulting in dirt and moisture, and 
vibration invading the electrical connections leading to failure due to 
corrosion or wire breakage. While battery powered devices may solve some 
of these problems, batteries are expensive, wear out, and are hazardous to 
the environment. 
SUMMARY OF THE INVENTION 
The present invention, as claimed, is intended to provide a remedy. It 
solves the problem of how to provide for a more dependable and effective 
visual indication of the presence of an individual, pet or object, under 
low light or bad weather conditions, utilizing design techniques which 
minimize failure due to environmental conditions, while maximizing 
reliability. At the same time the inventive system combines the 
dependability of a battery powered system with long battery life and 
freedom from failure of mechanical parts. 
The inventive safety light comprises a housing, a motion sensor, an 
electronic circuit, a system power source, and various discrete electrical 
components. The electronic circuit is further comprised of a motion sensor 
amplifier, a timer, a light emitting diode (LED) output driver, and a 
photo-amplifier. 
In accordance with the preferred embodiment of the present invention, when 
motion is detected by the motion sensor a signal is provided to the motion 
sensor amplifier portion of the electronic circuit, causing the device to 
be triggered and have a blinking light output. This blinking light output 
consumes a minimal amount of power. Power saving is enhanced by operation 
only while the device is moving, thus maintaining battery life. The motion 
sensor amplifier provides signal conditioning by amplifying and filtering 
the signal prior to passing the signal to the timer portion of the 
electric circuit. The timer is a monostable multivibrator, triggered by 
the output of the motion sensor amplifier, which enables the LED output 
driver. The LED driver, when enabled, functions as an astable 
multivibrator which, in turn, illuminates the LED devices. 
The LED devices also operate as an ambient light detector. When light hits 
the LED devices a voltage is produced which, after amplification, is 
provided as a disabling input to the timer portion of the electronic 
circuit. This prevents battery drain under well-illuminated conditions. 
Thus, only in the absence of light, when motion is detected by the motion 
sensor, LED devices are illuminated in a flashing manner by the LED driver 
for a given time period defined by the timer. The LED devices thus have a 
dual function, serving as blinking light sources and as ambient light 
detectors. The time period is defined by selecting particular discrete 
electrical components which form a simple resistive-capacitive timing 
circuit. In similar fashion, the rate and period of the LED flash are 
user-controlled. 
In accordance with the preferred embodiment, the housing is sealed from the 
external environment. The LED devices, however, may be located inside, 
outside, or on the exterior of the housing. 
To further minimize reliability problems the electronic circuit of the 
preferred embodiment is fabricated as an application specific integrated 
circuit (ASIC) device. An ASIC design minimizes reliability problems by 
reducing the number of electrical components needed and their associated 
connections. An ASIC design also provides a more suitable operating 
environment separate from that which exists external to the ASIC circuit. 
Additionally, since the motion sensor is not dependant on items external 
to the inventive design, the motion sensor can be mounted adjacent to the 
ASIC electronic circuit reducing lead length and problems such as 
electrically induced noise, corrosion, and excess vibration. 
The use of an ASIC design along with other power-saving techniques reduces 
the power requirements of the inventive design such that, like the motion 
sensor, the small power source size allows for mounting adjacent to the 
ASIC electronic circuit. 
In addition to providing a compact design reducing power requirements and 
restricting the environmental effects on the design, the preferred 
embodiment of the present invention incorporates a series of flashing LED 
devices. Utilizing a flashing LED device signal rather than a static LED 
device signal enhances the likelihood of the person, animal, or object, 
which the inventive design is attached, to be visually detected.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A multi-purpose safety light 10 constructed in accordance with the present 
invention is illustrated in FIGS. 1-3. 
Referring to the accompanying drawings, FIG. 1 illustrates a safety light 
10 comprising generally a system power source 12, a motion sensor 40, an 
ASIC electronic circuit 20, and a series of external components, including 
filter components 17, timer components 18, and light emitting diode 
components 19. System power source 12 provides a system power voltage 14 
to the ASIC electronic circuit 20 and timing components 18, and a system 
power return 16 to the ASIC electronic circuit 20, external filter 
components 17, light emitting diode components 19, and motion sensor 40. 
System power source 12 may range from 1.8 volts DC to 12 volts DC. A 
typical system power source 12 may consist of a series combination of two 
standard size `AA` batteries resulting in a system power voltage of three 
volts. 
ASIC electronic circuit 20 further comprises a motion sensor amplifier 50, 
a timer 80, a light emitting diode (LED) driver 100, and a photo-amplifier 
140. 
Next, referring to FIG. 2, motion sensor 40 comprises a standard 
piezoelectric element. As shown, a typical piezoelectric element further 
comprises a mass 42 attached to a piezoelectric crystal element 44, both 
enclosed within a supporting structure 46. Only the base 48 of 
piezoelectric crystal element 44 is attached to supporting structure 46 
allowing the remaining sides of crystal element 44 and the mass 42 to 
freely move within the supporting structure 46. In response to movement, 
the mass 42 exerts an inertial force on the piezoelectric crystal element 
44 which, in turn, produces a proportional charge on the crystal element 
44. Since the piezoelectric crystal element 44 has an amount of inherent 
capacitance, the charge produced by the crystal also provides a 
proportional output voltage (Vout) 49 provided externally to the 
supporting structure 46 by two leads 45 attached to opposite ends of 
crystal 44 and passing through opening 47 in support structure 46. As 
discussed below, this output voltage 49 is provided to an ASIC electronic 
circuit 20 as an input 52. 
Next, referring to FIG. 3, system power voltage 14 is provided to the ASIC 
electronic circuit 20 via a pin 33. System power return 16 is provided to 
the ASIC electronic circuit 20 via a pin 21. 
When motion is sensed, the motion sensor 40 generates and provides a 
voltage as an input 52 to the base of the transistor 54 via a pin 22. A 
resistor 56 is connected between the base of transistor 54 and the 
collector of transistor 54. One end of a resistor 58 is connected to the 
collector of transistor 54. The other end of resistor 58 is connected to 
power supply voltage 14 via a pin 33. The emitter of transistor 54 is 
connected to a common ground 36 of ASIC electronic circuit 20. 
Additionally, the collector of transistor 54 is connected to one side of a 
capacitor 60 and one side of a capacitor 62 via a pin 23. The opposite end 
of capacitor 60 is connected to system power ground 16. The opposite end 
of capacitor 62 is connected to the base of a transistor 64 via a pin 24. 
A resistor 66 is connected between the base of transistor 64 and the 
collector of transistor 64. One end of a resistor 68 is connected to the 
collector of transistor 64. The other end of resistor 68 is connected to 
system power voltage 14 via pin 33. The emitter of transistor 64 is 
connected to common ground 36 of ASIC electric circuit 20. Additionally, 
the collector of transistor 64 is connected to one side of a capacitor 70 
and one side of a capacitor 72 via a pin 25. The opposite end of capacitor 
70 is connected to system power ground 16. The opposite end of capacitor 
72 via a pin 25. The opposite end of capacitor 70 is connected to system 
power ground 16. The opposite end of capacitor 72 is connected to the 
cathode of a diode 74 via a pin 26 and is provided to the timer 80 as an 
input 82. The anode of diode 74 is connected to common ground 36. 
In operation, transistor 54 along with resistor 56, resistor 58, capacitor 
60, and capacitor 62 amplify and condition input 52. Under steady-state 
conditions transistor 54 is biased by resistor 56 and resistor 58 using a 
collective feedback technique which allows transistor 54 to converge to a 
semi-on state without regard to the system power voltage 14, subject to a 
minimum system power voltage 14 requirement of approximately 1.8 volts DC. 
Resistor 56 and resistor 58 values are selected to minimize power 
dissipation during steady-state operation. Thus, a resistor 56 value of 3 
megaohms, a resistor 58 value of 1 megaohm and a system power voltage 14 
of 3 volts results in a steady-state current of several microamperes, 
typically 3 microamperes. 
Under dynamic operation an alternating signal is provided by the motion 
sensor 40 as input 52 to the motion sensor amplifier 50. The alternating 
input 52, in turn, causes transistor 54 to be biased on and off resulting 
in the collector voltage of transistor 54 to move from a steady-state 
semi-on value and swing from approximately the value of the system power 
voltage 14 and common ground 36. More specifically, considering a 
sinusoidal signal at input 52, in response to an increasing positive 
voltage greater than 0.6 volts at input 52, transistor 54 enters a 
conducting mode where the collector voltage of transistor 54 is 
approximately equal to common ground 36. As the sinusoidal signal at input 
52 decreases to a value less than 0.6 volts, transistor 54 becomes biased 
off and the collector voltage of transistor 54 approaches the value of the 
system power voltage 14. Resistor 58 and capacitor 60 form a low pass 
filter which restricts system response to approximately 16 kilohertz with 
the resistor 58 value of one megaohm and the capacitor 60 value of 0.1 
microfarads. Capacitor 62 couples the amplified alternating signal at the 
collector of transistor 54 to the base of transistor 64. Capacitor 62 
typically has a value of 0.1 microfarads. 
In a similar fashion with respect to transistor 54, resistor 66 and 
resistor 68 bias transistor 64 using a collective feedback technique. 
Typically, resistor 66 has a value of 3 kilo-ohms and resister 68 has a 
value of one megaohm. Capacitor 70 and resistor 68 form a low pass filter 
which restricts system response to approximately 16 kilohertz with the 
resistor 68 value of one megaohm and the capacitor 70 value of 0.1 
microfarad. Capacitor 72 couples the alternating signal at the collector 
of transistor 64 to the input 82 of the timer 80. Diode 74 rectifies the 
input 82 of the timer 80 preventing the input 82 voltage from decreasing 
below approximately -0.6 volts, the diode 74 forward conducting voltage, 
protecting the base input of a transistor 84 while allowing capacitor 72 
to hold a suitable charge to provide an input 82 to the timer 80. 
Transistor 54 and transistor 64 are type 2N3904. Diode 74 is type 1N4148. 
Timer 80 receives input 82 at the base of transistor 84. The emitter of 
transistor 84 is connected to common ground 36. The collector of 
transistor 84 is connected to the base of a transistor 86. Additionally, 
the collector of transistor 84 is connected to one end of a resistor 90 
and to the positive side of a polarized capacitor 94 via a pin 32. The 
other end of resistor 90 is connected to system power voltage 14. The 
negative terminal of polarized capacitor 94 is connected to system power 
ground 16. The collector of transistor 86 is connected to one end of a 
resistor 92. The other end of resistor 92 is connected to system power 
voltage 14 via pin 33. The emitter of transistor 86 is connected to the 
base of a transistor 88. The emitter of transistor 88 is connected to 
common ground 36. The collector of transistor 88 is connected to the base 
of a transistor 104 providing an input 102 to the LED driver 100. 
In operation, under steady-state conditions, input 82 is approximately zero 
volts and transistor 84 is biased off. Capacitor 94 charges to a value 
equal to system power voltage 14. Charge timing is a function of resistor 
90 and capacitor 94 values. With the resistor 90 value of 4.7 kilo-ohms 
and the capacitor 94 value of 47 microfarads the voltage at the collector 
of transistor 84 will charge to 0.6 volts in approximately 50 seconds, 
given a system power voltage (Vb) of three volts. As the base voltage of 
transistor 86 increases from zero volts to a value greater than 0.6 volts, 
transistor 86 transitions from a biased-off state to a biased-on state. 
With transistor 86 biased on, collector current through transistor 86 is 
allowed to flow, limited by resistor 92 which has a value of one megaohm, 
resulting in transistor 88 to be biased on, disabling the LED driver 100. 
Under dynamic conditions, when an alternating signal present at input 82 
provided by the motion sensor amplifier 50 reaches approximately 0.6 
volts, transistor 84 is biased on allowing capacitor 94 to discharge. As 
capacitor 94 discharges the base voltage of transistor 86 decreases to 
approximately zero volts, biasing transistor 86 off and, in turn, biasing 
transistor 88 off, thus enabling the LED driver 100. When the input 82 
decreases below approximately 0.6 volts, the voltage at the base of 
transistor 86 increases as a function of resistor 90 and capacitor 94. 
During this charging of capacitor 94, the time 80 can be retriggered with 
an input 82 which reaches approximately 0.6 volts, biasing transistor 84 
on, discharging capacitor 94. Transistor 84, transistor 86, and transistor 
88 are type 2N3904. 
LED driver 100 receives collector voltage of transistor 88 from the timer 
80 as input 102. The collector of transistor 88 is connected to the base 
of a transistor 104, and to one end of a resistor 110 and to the negative 
side of a polarized capacitor 120 via a pin 31. The other end of resistor 
110 is connected to system power voltage 14. The emitter of transistor 104 
is connected to common ground 36. The collector of transistor 104 is 
connected to one end of a resistor 112 and to one end of a resistor 116. 
The other end of resistor 112 is connected to the base of a PNP transistor 
106 and one end of a resistor 118. The other end of resistor 118 is 
connected to system power voltage 14 via pin 33. The other end of resistor 
116 is connected to the base of a PNP transistor 108. The emitter of 
transistor 106 and the emitter of transistor 108 are connected to system 
power voltage 14 via pin 33. The collector of transistor 108 is connected 
to one end of a resistor 114 and to the anode of a light emitting diode 
128 via a pin 29. The other end of resistor 114 is connected to the 
positive side of capacitor 120 via a pin 30. The collector of transistor 
106 is connected in a parallel fashion to the anodes of a light emitting 
diode 126, a light emitting diode 124, and a light emitting diode 122 via 
a pin 28. 
In operation, under steady-state conditions where no input 52 exists such 
that the collector voltage of transistor 88 is zero volts, transistor 104 
is biased off. With transistor 104 biased off the base voltage of PNP 
transistor 106 and PNP transistor 108 is equal to supply power voltage 14 
inhibiting PNP transistor 106 and PNP transistor 108 from conducting. 
Under dynamic conditions, transistor 104 and PNP transistor 108 form an 
astable multivibrator whose period of operation is determined by resistor 
110 and polarized capacitor 120 while the pulse width is determined by 
resistor 114 and polarized capacitor 120. When timer 80 is activated by a 
dynamic input 52, transistor 88 will be biased off and allow the voltage 
at the base of transistor 104 to increase as a function of resistor 110 
and polarized capacitor 120. When the input 102 reaches the appropriate 
voltage, transistor 104 is biased on reducing the base voltage of PNP 
transistor 106 and PNP transistor 108. With a base voltage of 
approximately zero volts, the PNP transistor 106 is biased on allowing 
current to flow through and illuminating LED 122, LED 124, and LED 126. 
With a base voltage of approximately zero volts, the PNP transistor 108 is 
biased on allowing current to flow through and illuminate LED 128. With 
PNP transistor 108 biased on, the collector voltage of PNP transistor 108 
becomes approximately system power voltage 14, charging polarized 
capacitor 120 through resistor 114. In response to the increasing voltage 
at the positive end of polarized capacitor 120, the base voltage of 
transistor 104 decreased returning transistor 104 to a biased-off state 
and disabling the illumination of LED 122, LED 124, and LED 126. As the 
base voltage of transistor 104 increases as a function of resistor 110 and 
polarized capacitor 120, transistor 104 becomes once again biased on and 
the oscillatory LED flashing cycle begins once again. Transistor 104 is 
type 2N3904. PNP transistor 106 and PNP transistor 108 are type 2N3906. 
When LED driver 102 is disabled by the timer 80, light emitting diodes 122, 
124, and 126 form a voltage source for the photo-amplifier 140. The anodes 
of light emitting diodes 122, 124, and 128 are connected in parallel 
fashion to one end of a resistor 146 via a pin 27. The other end of 
resistor 146 is connected to the base of a transistor 144. The emitter of 
transistor 144 is connected to common ground 36. The collector of 
transistor 144 is connected to the base of transistor 84 forming an 
additional input 82 source to the timer 80. 
In operation, the light emitting diodes 122, 124, and 126 are selected to 
produce approximately one volt DC when illuminated by light. The parallel 
combination provides the requisite current to bias transistor 144 on. 
Resistor 146 limits the base current of transistor 144. Typically, 
resistor 146 has a value of one kilo-ohms. When transistor 144 is biased 
on, capacitor 72 is discharged through transistor 144 resulting in input 
82 being held at approximately zero volts which, in turn, disables the 
timer 80 and ultimately the LED driver 100. 
Thus, under low light conditions, when the safety light is attached to a 
moving object, physical motion is sensed and converted into an electrical 
signal by the motion sensor. This signal is then conditioned by the motion 
sensor amplifier and used to trigger the timer. The timer triggers and 
enables the LED driver which, in turn, responds by flashing the LED 
devices. The flash rate and duty cycle are defined by the LED driver. The 
LED devices continue to flash for a period defined by the timer. During 
this time period the timer may be re-triggered where the LED devices may 
flash indefinitely. If, however, the LED devices detect sufficient light, 
the timer will be inhibited after the previous time period is completed. 
Now referring to FIGS. 4, 5, and 6, a housing 150 of the inventive design 
is shown. LED 122, LED 124, LED 126, and LED 128 are shown mounted 
longitudinally on the surface of the housing, however, various other 
arrangements may be considered. Referring more specifically to FIGS. 5 and 
6, a strap support member 152, as part of the housing, is shown. A strap 
is passed through the openings of the strap support member 152, and then 
secured to an individual, pet, or object. 
Now referring to FIG. 7, a housing 250 of an alternative embodiment is 
shown. An LED 222, an LED 224, an LED 226, and an LED 228 are mounted 
within the housing 250. Visible light produced from and received by the 
LED devices passes through a transparent window 254. 
While an illustrative embodiment of the invention has been described above, 
it is, of course, understood that various modifications will be apparent 
to those of ordinary skill in the art. Such modifications are within the 
spirit and scope of the invention, which is limited and defined only by 
the appended claims.