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Step 3The circuit
Click the little "i" symbol in the top left of the picture to see the schematic more clearly.
The terminals "In +" and "In -" are connected to the speaker wires from your stereo. D1 protects the circuit from overvoltages if you turn your stereo volume too high.
The relays I used are 5V DPDT, so each one can trigger two flashes. I used two of them to trigger 4 flashes. My circuit is powered with 5V because my relays were 5V, but if you have 12V relays this circuit can be powered by 12V also.
The 2N2222A transistor needs a small heat sink to handle the relay coil currents.
The LM324 (U1) is an op amp that can be run from a single power supply. Other op amps may not work in this circuit.
The first part of the circuit, C1 and R1, is a high-pass filter. This is because we want the circuit to respond to the initial high-pitched 'crack' sound of the lightning, not the following rumble. The next part (D2, C2, R6) is a peak detect circuit, which generates an output pulse when the voltage level exceeds a certain threshold. The 'certain threshold' is also connected to a peak detect circuit but with a very slow decay time (D3, C3, R4), so that it automatically adjusts to the level of the last thunderclap. The LED helps when adjusting the circuit, so you can tell when the peak detect circuit is triggering. Adjust R5 so that the circuit triggers at the start of each thunderclap.
The output of the peak detect circuit triggers a 555 timer (U2), which generates a 20 ms pulse for the flash relays. The circuit portion around U1B prevents the 555 from re-triggering for about 5 seconds, this allows the flashes time to recharge..
Q1 is used to drive the relays, because the 555 does not have enough output current on its own. The schematic shows 4 SPDT (single pole, double throw) relays, because the schematic program did not have DPDT (double pole, double throw) relays, but I actually only had two DPDT relays in the circuit.. The relays I used were some scrap parts from work, I don't know the part number, but something like Omron G5V-2-DC5 would work. D6 is important, to protect Q1 from overvoltages when the relays are switched off.
The terminals "In +" and "In -" are connected to the speaker wires from your stereo. D1 protects the circuit from overvoltages if you turn your stereo volume too high.
The relays I used are 5V DPDT, so each one can trigger two flashes. I used two of them to trigger 4 flashes. My circuit is powered with 5V because my relays were 5V, but if you have 12V relays this circuit can be powered by 12V also.
The 2N2222A transistor needs a small heat sink to handle the relay coil currents.
The LM324 (U1) is an op amp that can be run from a single power supply. Other op amps may not work in this circuit.
The first part of the circuit, C1 and R1, is a high-pass filter. This is because we want the circuit to respond to the initial high-pitched 'crack' sound of the lightning, not the following rumble. The next part (D2, C2, R6) is a peak detect circuit, which generates an output pulse when the voltage level exceeds a certain threshold. The 'certain threshold' is also connected to a peak detect circuit but with a very slow decay time (D3, C3, R4), so that it automatically adjusts to the level of the last thunderclap. The LED helps when adjusting the circuit, so you can tell when the peak detect circuit is triggering. Adjust R5 so that the circuit triggers at the start of each thunderclap.
The output of the peak detect circuit triggers a 555 timer (U2), which generates a 20 ms pulse for the flash relays. The circuit portion around U1B prevents the 555 from re-triggering for about 5 seconds, this allows the flashes time to recharge..
Q1 is used to drive the relays, because the 555 does not have enough output current on its own. The schematic shows 4 SPDT (single pole, double throw) relays, because the schematic program did not have DPDT (double pole, double throw) relays, but I actually only had two DPDT relays in the circuit.. The relays I used were some scrap parts from work, I don't know the part number, but something like Omron G5V-2-DC5 would work. D6 is important, to protect Q1 from overvoltages when the relays are switched off.
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