Sequence 10 leds on power up

[dee.signs]

Ok, So i have found sequencers. They count up on the leds over and over again. What i want is for the leds to come on in a sequence then stay powered, Anyone have any ideas.

How to i go about turning on a series of 10 leds on in a sequence then keep them on. I have built a sequncer with a 555 and a 4017, but this just sequences through all the leds.

 

[duke37]

The LM3914 chip will drive 10 leds in a 'thermometer' style depending on a voltage input.
You will need a resistor to charge a capacitor for the input to the chip, to get the rate correct. You can also get 10 leds in a little block as a matching display.

 

[dee.signs]

lm3916...

So i am wanting to just use this ic to turn on a sequence of leds. Once all the leds are powered, i want them to stay powered. Any suggestions??

 

[duke37]

That is what the LM3914 does as long as there is power.

 

[dee.signs]

Thanks duke. i appriciate it. The 4017 isn't what i had in mind. I will try the 3914

 

[dee.signs]

Still need some help..

Ive got my lm3914 and i have it powering all my LEDs, but what cand i use so that there is a delay between the light ting og one led and the other? I was thinking about caps to ground on each led leg, with the cap get bigger and bigger...
Any one hav e ideas??

 

[duke37]

Show us a diagram of your circuit. It should have a resistor from the supply to feed the input and a capacitor from input to gound to slow the voltage rise. Then the 'thermometer' display will gradually grow. The time constant of the input circuit will be R*C so 1 Mohm and 10 microF will give a rise of about 10sec.
The voltage divider will need to be connected between ground (pin 4 to pin 2) and the top end (pin 6) can go to V+ (pin3).
You should not put capacitors on the outputs.
Have you looked up applications of the 3914?

 

[dee.signs]

Thanx!

Yes ive looked up applications... I forgot the cap.. I am going to have time tommorrow night to tinker once again.. I have been busy getting ready for my baby girl who is set to arrive soon.. I appreciate all the help.

 

[dee.signs]

Show us a diagram of your circuit. It should have a resistor from the supply to feed the input and a capacitor from input to gound to slow the voltage rise. Then the 'thermometer' display will gradually grow. The time constant of the input circuit will be R*C so 1 Mohm and 10 microF will give a rise of about 10sec.
The voltage divider will need to be connected between ground (pin 4 to pin 2) and the top end (pin 6) can go to V+ (pin3).
You should not put capacitors on the outputs.
Have you looked up applications of the 3914?

COuld you draw up a schematic, i cant get anything to work?

 

[duke37]

I have taken this information from the national.com site.
P8 To ground to get bar graph.
R2 Sets the led current.
R1 Included to ensure that the tenth led lights.
R3, C1 is the input voltage, this combination gives a time constant of about 10sec.

Show us your diagram.

 

[dee.signs]

Thanx, will try again tonight if BF isn't working....

 

[dee.signs]

waiting on my LEDs....

 

[Alchymist]

You could brute force it with 556 timers...
http://www.kpsec.freeuk.com/555timer.htm

 

[dee.signs]

So i built the circuit to your schematic, But it didn't work. I was wondering what cap i should use for c2. Right now i have a 450 uf in there. Also it may be my chip. I will work with it tonight. Also to decrease the current through the LEDS the R value should be lower, correct??

 

[duke37]

According to the National data, the led current is about ten times the current through R2, so the higher the resistance the lower the led current.
What are you getting? Any led on at all? Have you got the leds in the right way round? Try connecting a 10k resistor from ground to one of the leds to see if it lights up.
C2 should not be critical and 450uF should be plenty.

 

[dee.signs]

According to the National data, the led current is about ten times the current through R2, so the higher the resistance the lower the led current.
What are you getting? Any led on at all? Have you got the leds in the right way round? Try connecting a 10k resistor from ground to one of the leds to see if it lights up.
C2 should not be critical and 450uF should be plenty.

When i did the circuit last night, I got all the LEDS to light up, but not in a sequence. Two of them over currented and burned out. I am thinking that i might have got a bad chip, from all the **** i have been doing to it. I will try a new IC tonight, and see what that comes up with...

 

[(*steve*)]

Please check your wiring closely too. It is also possible that you have shorted something, or connected the wrong pins.

Initially connecting power via a 10 or 100 ohm resistor may help you to see if there's a problem. The resistor will limit the current to a value that probably won't damage stuff, yet still allow you to see if bad things are happening.

 

[dee.signs]

Yeah, im a dumba**, I had the whole chip wire backa=ward fron the start. It works great...

 

[duke37]

Hooray! That's great.