robwerden Posted February 20, 2005 Report Share Posted February 20, 2005 Hi, I found this forum in a search and thought maybe someone knew the answer to this question.Id like to set up a light array for a display that consists of 75 leds arranged in a spiral pattern. Id like to know how to get the leds to light up insequence from the center and spiral out to the outside. I thought about putting capacitors between each led but then thought it might make the sequence to slow. Id like the entire event to happen in less than a second. Just fast enough to see its happening but not to fast that it looks like its happening all at one time.Any ideas? Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 20, 2005 Report Share Posted February 20, 2005 Hi Rob,Welcome to our forum.74HC4017 ten-output counter/decoder ICs could be used with many gates and flip-flops.74HC4051 eight-output multiplexer ICs could be used with a 74HC4060 oscillator/counter and some 74HC4040 counters could be used with a few gates.The 74HC family can provide up to 25mA to the LEDs.You are going to need about 13 or 14 ICs. Quote Link to comment Share on other sites More sharing options...
robwerden Posted February 21, 2005 Author Report Share Posted February 21, 2005 Sorry im a just getting started in electronics so im not familiar with IC's Is there a place or diagram that shows how they are connected? Quote Link to comment Share on other sites More sharing options...
robwerden Posted February 21, 2005 Author Report Share Posted February 21, 2005 I actually was just reading about those IC's.Maybe I was describing the effect im looking for incorrectly.I used the word sequence which may have been incorrect.I want the leds to turn on one at a time but stay on. It looks to me like the IC turns one on then off, then the next on then off and so on. Im looking to simply light up all of the leds and have them stay on, but make it with a small 75th of a second delay from one to the next. That way all 75 will turn on in 1 second total.Does this still require an IC or is there a way to use a CAP to control the delay. Quote Link to comment Share on other sites More sharing options...
audioguru Posted February 21, 2005 Report Share Posted February 21, 2005 Hi Rob,A capacitor won't turn on an LED and keep it on. You need ICs to control the LEDs.Now you want the LEDs to turn on sequentially and stay on. A fairly simple way would be to use LM3914 ICs connected in the bar mode.You would have a capacitor charged linearly from a PNP transistor current source. The LM3914s monitor the linear voltage rise of the capacitor. The lower-voltage measuring LM3914's would probably need an amplifier to raise their input voltage above noise and errors.If each LED is allowed 30mA to be bright, then with them all on the power supply current will be about 2.5A, so forget using a small battery. Quote Link to comment Share on other sites More sharing options...
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