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AVT2720

Police flash light

The kit turns on and off two light emitting areas (red and blue) alternatively. The light effects arecaused by non-synchronous work of two generators. The first one switches over a set of LED diodeswhile the second one produces flash light effect. Having a small number of components, the kit iseasy to assemble.

The schematic is shown in figure 1. It consists of two independent generators and displays made oflight emitting diodes. The "flashes" are produced by high brightness LEDs. The brighter the lightemitted by the diodes the better. The red flash is due to red LED diodes while the blue flash is due to

blue LED diodes. They are connected to two groups: D1-D24 red diodes and D25-D48 blue diodes.The generator mounted on the U1F and U1E gates with the R1, R2 and C1 passives generate squarewave signal with a duty cycle of 50%. The U1D is an inverter making the groups of diodes flash onand off alternatively. The "flash", light emitting diode switch-over (red-blue flashing light effect)

The kit shows an amazing light

effect. It imitates the flash light ofemergency vehicles. It can beused for modifying the user'svehicle or at discos. It couldadd colour to the homesecurity system or be usedas part of anadvertisement.

Recommendations: the kit isrecommended to light effectlovers as well as to those wantingto make their vehicles lookdistinctive.

Electrical characteristics

Description

two LED diode (red and blue) light emitting areas

25 LED diodes in each light emitting area for negative or positive ground vehicles

12V DC power supply

AVT 2720 Police flash light 1

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AVT 2720 Police flash light2

function is engaged in this way. TheLED diodes are directly driven by the T1and T2 transistors. They are necessary sothat the circuit can function properly.The gates alone could not drive the LEDbecause of low output current. An

oscillator is mounted on the U1A, U1Band R5, R6, R7, D49, D50, C2 passives.It drives the LEDs so that they couldsimulate flashes of strobe light. It is"faster" than the generator mentionedabove and its duty cycle exceeds thevalue of 50%. Thanks to this feature thevisual effects are great and they are morelike flashes of strobe light. The D49 and

D50 diodes guarantee the over-50%duty cycle. The T3 transistor serves thesame purpose as the T1 and T2transistors. It increases the outputcurrent capacity on the LED cathodeside. The R9 resistor limits the LEDcurrent to a safe value. The diodes aredriven as follows: the circuit is switchedbetween blue and red diodes on theanode side while it is driven by pulses

imitating the work done by flash light onthe cathode side

Figure 1. Schematic diagram

Opis ukadu

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AVT 2720 Police flash light 3

Assembly and testThe kit is assembled on three PCBs. Once properly assembled and plugged in it will work instantly. Alot of care should be taken when soldering the LED diodes. Attention should be paid not to mistakethe red diode board for the blue diode board. The D1D24 diodes are red while the D25D48diodes are blue. It is better to solder the diodes by a single pin, for example the anode. Then the boardshould be turned over with its diodes right on top. By pushing them sideways or drawing inwards theyshould be evenly arranged in rows from both the shorter and longer edges of the board. Only then the

second pin of each diode can be soldered in.

The LED boards should be connected to the controller board, namely V1 to V2, X1 to X2, Y1 to Y2and Z1 to Z2.

Figure 2. Component layout on PCB-s

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In the order of soldering:

1 R1, R5: 47kW (yellow-purple-orange-gold)2 R2, R7: 1,2 MW (brown-red-green-gold)3 R3, R4, R8: 4.7 kW (yellow-purple-red-gold)4 R6: 390kW (orange-white-yellow-gold)5 D49, D50: 1N41486 C1: 470nF7 C2, C3: 47nF8 C4: 47F/25V9 T1, T2: BC55810 T3: BC54811 IC 14-pin socket12 Insert the 4069 IC in the socket13 D1D24: 5mm high brightness red LED diodes

14 D25D48: 5mm high brightness blue LED diodes

Component list

The kit was made on the basis of a project bearing the same trade name published in "Elektronika dla wszystkich 4/04".

www.elportal.pl

AVT 2720 Police flash light

The sale offer of our self-assembly kits is available on our website www.sklep.avt.pl

Technical Assistance Dept.Phone: (48 22) 257-84-58serwis@avt.pl

Producer:AVT-Corporation, Ltd.Leszczynowa 1103-197 WarsawPoland

fax: (+48 22) 257-84-55phone.: (+48 22) 257-84-50