Led clock by yingyingong

Thread Starter

bertus

Joined Apr 5, 2008
20,659
Hello,

I got an email from yingyingong asking the following question:

hello. i would like to use 7490 counter and 7442 decoder to light up 60 LEDs one after another for a minutes. which means every seconds an LED will light up. if is 60 seconds then all LEDs are on. could you help me on this? thanks in advance.
As I do not answer emails I posted the question over here.

If only one led is on at the time the ciruit could be quite easy.
The request to have a growing number of leds will need some kind of latching circuit.

Perhaps others have their idea's about it.

Bertus
 
i have try it. it will only work if i put a NOT gate in front of every LEDs. is this correct? if not how should i correct it? anyone can help?
 

SgtWookie

Joined Jul 17, 2007
22,210
RiJoRI,
The LM3916 is a VU meter display; it would be very difficult to use that IC.
I think you meant the LM3914, which is in the same family, but linear. That could be made to work, but it would be rather difficult to set up, as yingyingong would have to go from digital to analog in order to get the LEDs to increment.

Bill,
yingyingong wants the LEDs to light sequentially, and stay on. Using the 4017 would make it easy to light them sequentially, but they wouldn't stay on like yingyingong wants them to.

jimkeith,
The 74HC164 shift register is a good idea. You might find that the 74HC595 is easier to use. If more current is needed, the TPIC6C595/TPIC6D595 or STPIC6C595/STPIC6D595 have eight open-drain outputs that can sink (not source) up to 100mA; other than that, their functionality is similar to the 74HC595.

You would need 8 of the 595 shift registers; the last 4 bits would not be used.
 

Wendy

Joined Mar 24, 2008
22,155
Bill,
yingyingong wants the LEDs to light sequentially, and stay on. Using the 4017 would make it easy to light them sequentially, but they wouldn't stay on like yingyingong wants them to.
I had missed that, but it still would be no problem. Small MOSFET drivers and steering diodes, lighting that many LEDs at once (more if you include seconds as well as minutes) is going to be a current hog though.

It will be component intensive, around 5 parts per LED, not counting the 4017 circuitry.
 

SgtWookie

Joined Jul 17, 2007
22,210
Well, one of the '164 or '595 shift registers would require one IC and one resistor array for 8 LEDs, so that's a pretty low parts count.
 

Wendy

Joined Mar 24, 2008
22,155
Don't forget the drivers, LEDs, and resistors. I didn't.

*****

OK, I missed the resistor array. Debatable if that really reduced part count, but I'll count it.

Are there any MOSFET array's out there?
 
Last edited:

Fenris

Joined Oct 21, 2007
288
High there

This circuit may be of use for your needs? It's actually for a 'Ghostbusters' Power pack prop.

Get rid of the U4 portion of the circuit and U3 can be replaced with a more accurate timer chip.

BC547/548 for the transistors and replace the lamps with LED's and an appropriate resistor.

If the #11 pin on the last half chip was used this circuit would light 15 LED's in sequence. You would need 8 of the 4015 IC's.

Hope this is of some help.

regards

Fenris
 

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