I'm checking into the legalities of this particular circuit at this time. Any type of flashing light on the main brake lights is prohibited and illegal in most states of the U.S.A. I'm verifying for the same here in Canada. In the mean time, use this circuit at your own risk and be aware that the possibility exists to be stopped by law enforcement if you implement this circuit in your vehicle.
Parts
IC1,IC2 = 555 Timer, RS #276-1723 SCR1 = NTE/ECG5402, RS #276-1067, EC103A, MCR104, etc.
Q1 = NTE/ECG197, SK3083, TIP125, or equivalent
D1,D2,D3 = 1N4148, 1N914, NTE/ECG519, RS #276-1122
D4,D5 = 1N5400, NTE/ECG5850, RS #276-1141, or equivalent
R1 = 18K
R2 = 330 ohm (RS #271-1315)
R3 = 270K
R4 = 82K
R5,R6 = 1K2
R8 = 100 ohm (RS# 271-1311)
440
P1 = 50K, 10-turn
P2 = 10K, 10-turn
C1 = 100µF/16V (RS# 272-1016)
C2 = 22µF/16V (RS# 272-1014)
C3 = 220µF/16V (RS# 272-1017)
C4 = 10µF/16V (RS# 272-1013)
Q1 is a PNP Silicon Audio Power Out/Medium Power Switch Transistor, 7A, with a TO-220 case. As long as you have a transistor which is close it will work fine. The SCR is a 100vrm, 0.8A, sensitive gate with a TO92 case. Diodes D1, D2 and D3 are standard small signal diodes. Power diodes D4 and D5 are the 6A, 50prv types, cathode case. The 60vrm type will work as well. I used for IC1 & IC2 the LM555 type. P1 controls the 'on' and pulse-duration, P2 controls the pulse-timing. Applying the Brakes: When you first press the brakes, this circuit will turn on your 3rd brake light via the main brake lights. After about a second a series of short strobe pulses occur. The number of pulses range from approximately 1 to 10, depending on the setting of P1/P2 and when the brake pedal was applied last. After the pulses have been applied the third brake light assumes normal operation. The prototype was set for five flashes which seemed more than enough. Two days later I re-adjusted the trimmer potentiometers for 4 flashes-1/2 second pause--4 flashes. Looks pretty cool!
Circuit Description:
The schematic consists of two 555 timer/oscillators in a dual timer configuration both setup in astable mode. When power is applied via the brake pedal, the brake light driver Q1 is switched on via the lowoutput pin 3 of IC2, and timer IC1 begins its timing cycle. With the output on pin 3 going high, inhibiting IC2's pin 2 (trigger) via D2, charge current begins to move through R3, R4 and C2. When IC1's output goes low, the inhibiting bias on pin 2 of IC2 is removed and IC2 begins to oscillate, pulsing the third brake light via the emitter of Q1, at the rate determined by P2, R6, and C4. That oscillation continues until the gate-threshold voltage of SCR1 is reached, causing it to fire and pull IC1's trigger (pin 2) low. With its trigger low, IC1's ouput is forced high, disabling IC2's trigger. With triggering disabled, IC2's output switches to a low state, which makes Q1 conduct turning on the 3rd Brake Lightuntil the brakes are released. Obviously, removing the power from the circuit at any time will reset the Silicon Controlled Rectifier SCR1, but the RC network consisting of R4 and C2 will not discharge immediately and will trigger SCR1 earlier. So, frequent brake use means fewer flashes or no flashes at all. But I think that's okay. You already have the attention from the driver behind you when you used your brakes seconds
before that.
The collector/emitter voltage drop accross Q1 together with the loss over the series fed diodes D4/D5, will reduce the maximum available light output, but if your car's electrical system is functioning normally in the 13 - 14volt range, these losses are not noticeable.
কোন মন্তব্য নেই:
একটি মন্তব্য পোস্ট করুন