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Lightning Detector
Michael Bloem
December 5, 2002
Engr 311
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
The Circuit
•The purpose of the circuit is to set off an LED when there is a lightning strike in the area (even if too far away to be seen)
•This will indicate the proximity and intensity of a storm
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
Circuit Operation: Input Stage
•A lightning strike is approximated by a small voltage pulse
•The circled part of the circuit is resonant at 300 kHz, so that is the frequency passed through the circuit
Circuit Operation: Input Stage
Frequency
0.2MHz 0.4MHz 0.6MHz 0.8MHz 1.0MHz 1.2MHz0.1MHzV(V2:+)
0V
1.0mV
2.0mVI(Q1:b)
0A
20nA
40nA
SEL>>
•This is the Fourier transform of the pulse current input and the input to the base of the first transistor
•Note that the pulse has components at all frequencies
•Also note that the input stage of the circuit picks out the 300 kHz part and sends it to the circuit
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
Circuit Operation: Input Stage
•The first transistor provides amplification of the signal before it is sent to the flasher part of the circuit
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
Circuit Operation: Flasher
•The second transistor is biased by adjustment of the variable resistor so that it doesn’t allow current to flow until a radio burst pulls the base down
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
Circuit Operation: Flasher
•Once the second transistor’s base is pulled down, it turns full on and current flows as shown by the red arrows
•This sends a relatively strong current to the third transistor
•This current flows until the capacitor discharges to ground
•Then, the current from the diode flows to the capacitor to charge it again to be ready for the next pulse (green arrows)
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
Circuit Operation: Flasher
•The third transistor should amplify the current and send it on to the LED driver
Circuit Operation: LED Driver
C51u
C910u
D8
120NQ045
1 2
D12
D1N4148
Q1
Q2N4401
L110mH
1
2
L2
390uH
1
2
C1
.001u
C2680p
C3
.001u
R11000k
R210k
R31000k
R4 3.9k
R6
4.7k
Q3
Q2N4401
Q4
Q2N4403
V13Vdc
R7
200KSET = .00001
V2TD = 20uTF = 0PW = 2.5uPER = 100000000V1 = 0TR = 0V2 = .01
R8.000001
R91000k
Q6
Q2N4403
R10
10k
R11
33
0
0
0
•The LED driver sends a current pulse to the LED, lighting it up.
Circuit Simulation Output
Time
0s 5us 10us 15us 20us 25us 30us 35us 40us 45us 50usV(V2:+)
0V
5mV
10mVI(D8:K)
-2.0nA
0A
2.0nA
SEL>>
•To simulate a lightning strike in Cadence, I just used a small (.01 V) and short (2.5us) voltage pulse.
•Why the output is good: it does create a current pulse that starts when the lightning strike occurs and then goes away
•Why the output is bad:
•Sinusoidal response- the capacitor should discharge fast enough so that it is just a pulse
•Too small of a current to set off an LED
Physical Implementation
•I have found all the parts for this circuit and put them together on a breadboard
•Testing
•To approximate a lightning strike
•Van de Graaf machine
•Square wave from function generator
•Result of testing
•Essentially the same results as from Cadence- the current that ends up at the LED is too small
Problems
Opportunities for Improvement
•Get enough current to light up the LED
•Change the biasing of the amplifying transistors (2nd and 3rd transistors) so they actually amplify
•Add my own amplification component at the output
•Opamp or transistor
•Get the current to be a single pulse rather than a sinusoid
•Play with the capacitor value
•Not as important- still get an LED flash with the sinusoid