# i need help

Discussion in 'The Projects Forum' started by cdp1988, Apr 19, 2009.

1. ### cdp1988 Thread Starter New Member

Apr 19, 2009
3
0
hi, i got no experience with electronics or anything, but ive recently been given a project which requires a fair bit of knowledge on it. i was wondering if i could get any help from anyone here as i need some pretty urgently.
i got a basic knowledge of how make a circuit, and a basic knowledge of what electrical components do what, but when it comes down to it im pretty useless. what i need to do is build a circuit with about 9 LEDS and these LEDS have to turn on randomly one at a time say in about 30 secound intervals. at the same time but i need to have another circuit, with another 9 LEDS attached to 9 variable resistors so dat i can have them become brighter and duller as i wish. can anyone help me out? maybe diagram or sumthin lol, cause i seriously got no idea what to do any help would be much appreciated

2. ### KMoffett AAC Fanatic!

Dec 19, 2007
2,585
234
First, have the person who assigned you this task define "random". It's a very complex numerical concept to implement electronically.

To quote my wife: "It's only complex if you understand it.".

9 numbers taken "randomly":
195734628573841269248391756195734628 can be considered random
195734628195734628195734628195734628 can be considered random
111144111375888888234579123111177111 can be considered random
444444444444499949999999999999111111 can be considered random
555555555555555555555555555555555554 can be considered random

Start there! Then help will follow.

Ken

3. ### PRS Well-Known Member

Aug 24, 2008
989
35
The circuit where you have the pots and the LEDs is the easiest. For each LED have a current-limiting resistor to keep from it from short circuiting. This would be about 470 ohms and placed in series with the LEDs. Then use a 5Kohm pot to in series with each of the nonvariable resistors. Use a 5 or 6 volt supply.

As for the first circuit how do intend to generate a 'random' number?

Apr 5, 2008
15,806
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5. ### cdp1988 Thread Starter New Member

Apr 19, 2009
3
0
for the random generator all i need is for a different LED to light up at a time. even if they are in sequance,and light up in the same seqeance over and ovr its fine. as long as they light up one at a time and for an interval of about 30 secounds its ok. sorry i should of better explained that.

6. ### PRS Well-Known Member

Aug 24, 2008
989
35
Once lit are the LEDs to stay on? Or are does each LED light up individually and then go out when the next one goes on?

7. ### cdp1988 Thread Starter New Member

Apr 19, 2009
3
0
they are meant to light up individually and then go out.

8. ### zimbarak Active Member

Feb 8, 2009
56
0
try to look on random number generator RNG !it will be very helpfull

9. ### KMoffett AAC Fanatic!

Dec 19, 2007
2,585
234
Then all he needs is an LM555 astable for a 30 second clock and a CD4017 Johnson counter, reset for 9 outputs. He can rearrange the connections to the LED's in any "random" order he likes.

Like this, except RESET (pin 15) is connected to output 09 (pin 11), and the timing components changed for 30 Seconds.
http://delabs-circuits.com/cirdir/theory/gates/doc00020.html

If you can get by with 8 or 10 LED's, there are at least a couple of electronic kits that do this, like http://store.qkits.com/moreinfo.cfm?Product_ID=912&CFID=7281242&CFTOKEN=70782724

Ken

Last edited: Apr 20, 2009
10. ### PRS Well-Known Member

Aug 24, 2008
989
35
That works, KMoffett. There are many ways to skin this cat.