Electronics > Projects, Designs, and Technical Stuff
No way of bypassing this Lasertrigger circuit - and about calculating stuff
HendriXML:
--- Quote from: mycroft on January 15, 2019, 01:42:51 pm ---Beware of real life! In real life a fly or a leaf can interrupt the beam. You will have too many false positives!
--- End quote ---
Purely hypothetical, because the circuit is not really worth defending...
If a fly crosses the beam it should signal that, that is not really a false possitive in regard to this circuit. If there would be exceptions / margins at this level, then it is also more vulnerable against attack’s. At a higher level when processing the output of this circuit one could define rules that take more things in account. Maybe 2 beams out of 10 should be signaled to set an alarm. Also I hate flies so I don’t want them to intrude as well :).
HendriXML:
--- Quote from: tggzzz on January 15, 2019, 01:57:56 pm ---In every system where safety is in question, you should concentrate on how the system can fail. That's much more difficult than how the system works. Understanding that is a key difference between professional engineering and amateur tinkering.
Start by understanding that extra complexity means extra failure mechanisms.
Continue by determining what will happen if a component or connection fails.
And don't forget to consider all the things that are outside the system.
--- End quote ---
Your absolutely right. This circuit is amateurish and for study only, and I really like it in that regard. Installing laserbeams for protection is not very practical. And has very little WAF.
You should see my other circuit:
https://www.eevblog.com/forum/projects/bi-regulated-power-supply/
That one is too sensitive and prone to failure as well, it would really give you the shivers. But is also an exploration of possibilities. One should allow themselves to do projects like that as well. And maybe only thoose before having sufficient skills.
HendriXML:
--- Quote from: xani on January 15, 2019, 01:00:40 pm ---Clearly if you want max security you should instead beam AES-encoded and signed (or even go whole hog with ECDH and public/private key encryption) stream that sends ever-increasing number(to avoid replay attack) to the receiver 8)
--- End quote ---
I think random signals would suffice as well, ‘cause the end point knows what to expect!
In both cases the system could be attacked by copying the laser pulses. But that can be made very hard to implement when the sensor is in a thin tube. The copying laser in that case won’t be able to hit the sensor without blocking the sytems one.
HendriXML:
:PI added functionality to my BOM reporter (just another script in the same tool) to merge calculated values in the designator report as well. If calculated values exists, they are reported on a second line. Specifications can also include powerratings, voltage ratings, etc. This way lots of information can be packed in to a single report. Another tab, the actual BOM report shows where stuff is located and how much (PartKeepr), I'll post that as well.
By reporting the max current / voltage a resistor can take, it is easy to check which resistors might be at risk and do a calculation of its power consumption. The E-series are shown, because I prefer to use lower E-serie values over higher ones, because then its easer to maintain a stock.
HendriXML:
Designator specifications
C1 10nF E3 50V ceramic THT capacitor
D1 LED led
D2 3,3V E6 1W 303mA zener diode
D3 LDD photodiode
D4 1N4004 diode
D5 LED led
D6 1N5817 schottky diode
D7 LED led
D8 1N5817 schottky diode
D9 1N5817 schottky diode
D10 1N5817 schottky diode
D11 1N5817 schottky diode
D12 1N5817 schottky diode
Q1 2N7000 n-mosfet
Q2 2N7000 n-mosfet
Q3 2N3906 pnp transistor
Q4 2N3904 npn transistor
Q5 2N3906 pnp transistor
Q6 2N7000 n-mosfet
Q7 2N7000 n-mosfet
R1 56Ω E12 250mW 3,74V|66,8mA 2% metal film THT resistor
56Ω E12
R2 1,8kΩ E12 250mW 21,2V|11,7mA 2% metal film THT resistor
1,8kΩ E12
R3 100kΩ E3 250mW 158V|1,58mA 2% metal film THT resistor
100kΩ E3
R4 68Ω E6 250mW 4,12V|60,6mA 2% metal film THT resistor
68Ω E6
R5 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
4,7kΩ E3
R6 47kΩ E3 250mW 108V|2,3mA 2% metal film THT resistor
47kΩ E3
R7 47kΩ E3 250mW 108V|2,3mA 2% metal film THT resistor
R8 12kΩ E12 250mW 54,7V|4,56mA 2% metal film THT resistor
R9 180Ω E12 250mW 6,7V|37,2mA 2% metal film THT resistor
R10 51kΩ E24 250mW 112V|2,21mA 2% metal film THT resistor
R11 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R12 1,8kΩ E12 250mW 21,2V|11,7mA 2% metal film THT resistor
1,8kΩ E12
R13 56Ω E12 250mW 3,74V|66,8mA 2% metal film THT resistor
56Ω E12
R14 470Ω E3 250mW 10,8V|23mA 2% metal film THT resistor
470Ω E3
R15 12kΩ E12 250mW 54,7V|4,56mA 2% metal film THT resistor
12kΩ E12
R16 27kΩ E12 250mW 82,1V|3,04mA 2% metal film THT resistor
27kΩ E12
R17 82kΩ E12 250mW 143V|1,74mA 2% metal film THT resistor
82kΩ E12
R18 33kΩ E6 250mW 90,8V|2,75mA 2% metal film THT resistor
33kΩ E6
R19 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R20 39kΩ E12 250mW 98,7V|2,53mA 2% metal film THT resistor
39kΩ E12
R21 150Ω E6 250mW 6,12V|40,8mA 2% metal film THT resistor
150Ω E6
R22 12kΩ E12 250mW 54,7V|4,56mA 2% metal film THT resistor
R23 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
4,7kΩ E3
R24 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R25 100kΩ E3 250mW 158V|1,58mA 2% metal film THT resistor
R26 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R27 33kΩ E6 250mW 90,8V|2,75mA 2% metal film THT resistor
33kΩ E6
R28 27kΩ E12 250mW 82,1V|3,04mA 2% metal film THT resistor
27kΩ E12
R29 12kΩ E12 250mW 54,7V|4,56mA 2% metal film THT resistor
12kΩ E12
R30 82kΩ E12 250mW 143V|1,74mA 2% metal film THT resistor
82kΩ E12
R31 39kΩ E12 250mW 98,7V|2,53mA 2% metal film THT resistor
39kΩ E12
R32 75Ω E24 250mW 4,33V|57,7mA 2% metal film THT resistor
75Ω E24
R33 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R34 4,7kΩ E3 250mW 34,2V|7,29mA 2% metal film THT resistor
R35 100kΩ E3 250mW 158V|1,58mA 2% metal film THT resistor
RV1 1kΩ E3 variable resistor
1kΩ E3
RV2 5kΩ variable resistor
RV3 500Ω variable resistor
500Ω
SW1 Reset latch component
SW2 SW_Push component
U1 TL082 op amp
U2 LM339 comparator
U3 LM339 comparator
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