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What can you do with a bunch of LEDs, a buzzer and a PIC processor? Have a lot of fun, that's what! LEDS HAVE FUN! This little project has no less than eight modes of operation including random and chaser displays, doorbell and alarm. It will only take you 10 minutes to build it. 84  Silicon Chip By LEO SIMPSON Designed and produced in Australia, LED FUN is a kit based on a PIC microcontroller and its small PC board can be assembled to provide a wide range of operating modes. Let’s just list the eight possible modes and their variations. Mode 1 is a random LED display. Press the pushbutton and the LEDs chase, slow down and stop randomly. The piezo buzzer clicks in time with the LEDs lighting to give an acoustic accompaniment. You could use this as a dice for a board game. Mode 2 is a LED chaser with three patterns which are played in sequence. The first is a straight chaser whereby the LEDs follow each other and then loop back to start. Second, the LEDs follow each other and stay on to the end and third is a strobe whereby the LEDs all flash on in unison. To use it, you press the pushbutton and the LED pattern starts, slows down and then picks up in speed. You release the button when the speed you want is happening. You can then press the button and hold again for the speed of the next pattern. Mode 3 is a binary count-down timer. You can set it to provide a count-down period of one to 64 seconds and at the end of that time the buzzer sounds for five seconds. To set it, you press the button and hold it for the required time. The counter then times out, sounds the alarm and flashes the LEDs for five seconds. It can then be reset for the same time by pressing the button again. Mode 4 is a ladder reaction game. You get to climb the 6-LED ladder if your reactions are quick. To use it, you press the button each time you hear a clock and a LED flashes. You must press it very quickly to keep the LED alight at that level. Then the next LED flashes and you must press the button again. If you’re really good, you’ll get to the top. Mode 5 is a blinking face display using all seven LEDs. It blinks randomly and changes expressions by turning off some of the LEDs. Mode 6 is a doorbell/alarm with the blinking face and buzzer. Mode 7 is a memory sequence game. You start it and it gives a sequence of a dots and dashes from the buzzer and a LED which you must repeat with the pushbutton. Get it right and the blinking face flashes and the buzzer plays a tune as your reward. The sequences then get longer and harder and it is up to you to keep persevering. Mode 8 is a dice employing all seven LEDs in the correct pattern. You press the button and the dice chases and then stops randomly. You then “toss” again by pressing the button. You can use it anywhere you would use a die. Fig.1: this shows all the LEDs and resistors on the circuit but some are omitted depending on what mode you want. All these functions are programmed into the PIC microcontroller and all you need to do is assemble the board. Fig.1 shows the circuit and as you can see, there is very little to it. To select the actual mode you want, you install the LEDs and resistors ac- cording to Table 1. All the resistors in Table 1 have the same value of 270Ω. Board assembly The board measures just 68 x 34mm. Its component layout is shown in Fig.2. We’ve shown all possible TABLE 1 Mode      Resistor       LEDs   1 none 1-6   2 R4 only 1-6   3 R3 only 1-6   4 R3,R4 1-6   5 R2 only 2,4,8-12   6 R2,R4 2,4,8-12   7 R2,R3 2,4,8-12   8   R2,R3,R4     2-4,7,9-11 Use this table to select the parts you need to install for the various modes of operation. Fig.2: again, the component overlay shows all resistors and LEDs but use Table 1 when installing the parts. February 1999  85 most probably have missed a solder connection or one (or more) of the LEDs is the wrong way around. Finally, if you’re prepared to add a rotary switch, you could arrange to make most of the modes available to play at will. Where do you get it? LED FUN is available as kit of parts from all Dick Smith Electronics stores SC at just $14.95 (K-3167). A PIC processor provides all the circuitry to drive the LEDs in this fun project. You could put it together in 10 minutes. This life-size view does not have the battery connector or piezo buzzer connected. resistors and LEDs but you don’t install all of them, just those required for the operating mode you want. The assembly procedure is as follows. First, install resistors R1, R5 & R6 and diode D1, followed by the 0.1µF capacitor. Next, insert and solder the 8-pin socket for IC1. Then install the other resistors and the LEDs for the mode you want, making sure the LEDs all go in the right way. The anode of the LED connects to the positive labelled hole on the board. Next, solder in the pushbutton switch and piezo buzzer. You will be supplied with a 4-AA Parts List cell battery holder but only three cells are required for the 4.5V supply. All the cells are wired in series in the holder so you need to solder a wire to short out one cell position. Take care when doing this job otherwise you will melt and distort the battery holder. Then wire the battery holder to the appropriate terminals on the PC board. Insert the PIC processor into its socket, making sure that you install it the right way around. Then insert the three AA cells into the battery holder and you should be up and running. If it doesn’t work as it should, you 1 PC board, 68 x 34mm 1 PIC12C508 programmed microcontroller (IC1) 12 red LEDs 1 1N4148, 1N914 diode (D1) 6 270Ω 0.25W resistors 1 0.1µF ceramic or monolithic capacitor 1 pushbutton switch (S1) 1 piezo buzzer 1 4 AA-cell holder 3 AA cells Note: see Table 1 for resistors and LEDs to be installed. Protect Your Valuable Issues Silicon Chip Binders REAL VALUE AT ★ Heavy board covers with 2-tone green vinyl covering $12.95 PLUS P & P ★ Each binder holds up to 14 issues ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A12.95 plus $A5 p&p each (Aust. only). Just fill in & mail the handy order form in this issue; or fax (02) 9979 6503; or ring (02) 9979 5644 & quote your credit card number. 86  Silicon Chip