Can someone help me with a circuit that will light up 5 leds in parallel without usin - Page 2 - Electronic Circuits Projects Diagrams Free

Ishikawa · 1st November 2007, 09:00 PM

Quote:

Nigel Goddwin : Don't you think mobile phones use chips?.

Yes I do.

I'll use a pic and charlieplexing

**Nigel Goodwin** · 1st November 2007, 09:13 PM

Some one who does a lot of PIC charlieplexing will probably be along shortly!

Ishikawa · 1st November 2007, 09:27 PM

I just noticed that with the charlieplexing method will probably be hard to keep each row of leds ON like it is shown in the pictures.

This method will turn them ON and turn them off by the time it turns ON the next row of leds.

**Nigel Goodwin** · 1st November 2007, 09:39 PM

Quote:

Originally Posted by Ishikawa

I just noticed that with the charlieplexing method will probably be hard to keep each row of leds ON like it is shown in the pictures.

This method will turn them ON and turn them off by the time it turns ON the next row of leds.

You do it so fast you can't tell they are flashing, it's a VERY standard technique.

Ishikawa · 1st November 2007, 10:07 PM

deleted by original poster.

bananasiong · 1st November 2007, 11:38 PM

Quote:

Originally Posted by Ishikawa

So I need 4 inputs to drive the 8 leds.

From the picture there is 5 wires:

One for the first led always on
One for Ground
The other 3 for the 8 leds (remember the 8 leds r actually considered to be 15)

However from the equation above, 3 inputs drive only 6 leds and there 8 left.

I'm I wrong???

Thanks

Hi,
Are you sure that the first LED is always on? I can see it flashing

Use 4 I/O to control 9 LEDs (9 stages), possible? Since the max stages of using 4 I/O is 12.

iONic · 2nd November 2007, 12:24 AM

Quote:

Originally Posted by ericgibbs

hi,
Looking at your 1st posting LED pattern, I would agree with Gordz, a LM3914 set for bar mode. Drive the input of the LM3914 with a ramp voltage.

If your LED's require more current than the LM can supply, use the LM to drive 4/5 transistors, which drive the LED's.

ericgibbs, you seem to be on the right track, a triangle ramp voltage with the
LM3914. Can the triangle wave be clipped on top to allow the full heart to stay on for a shot period of time?

Ishikawa · 2nd November 2007, 08:24 AM

This link has a video that explains charlieplexing very well

http://www.brightcove.tv/title.jsp?t...eup=1028763155

At 5:50 he says: "Only one LED can be ON at any given time" which means I can't turn on more than one led at any given time?...Just wanted to confirm this, I hope I'm wrong.

But then again I saw 3 videos at youtube about charlieplexing and they had more than one led on at a time.

Also at 9:32 he says: "this will give roughly 40mA of peak current going through each led"

then he says: "and therefore the average current through the led is 40mA/20=2mA", so I'm a bit confused isn't there a contradiction??

Please watch the whole video.

ericgibbs · 2nd November 2007, 09:09 AM

Quote:

Originally Posted by iONic

ericgibbs, you seem to be on the right track, a triangle ramp voltage with the
LM3914. Can the triangle wave be clipped on top to allow the full heart to stay on for a shot period of time?

hi,
I would try using 'two' LM outputs at the 'top' to drive the same LED set.
That would give the appearance of a longer on time.

Gordz · 2nd November 2007, 11:14 AM

Quote:

Originally Posted by Ishikawa

without using a counter/decoder??

A PIC would be the answer here except the game plan was to use NO counters or decoder

**3v0** · 2nd November 2007, 11:23 AM

Use a PIC with enough pins to drive each LED (or pair) and do away with the multiplexing.

This will make the code and the hardware very simple.

Like Erick says Good enough is Perfect.

**3v0** · 2nd November 2007, 11:25 AM

Quote:

Originally Posted by Gordz

A PIC would be the answer here except the game plan was to use NO counters or decoder

I think the OP has dropped that restriction.

Quote:

The whole point of my project is to do it just like it is shown in the pictures so let's forget about the counter and timers.

**Nigel Goodwin** · 2nd November 2007, 12:56 PM

Quote:

Originally Posted by Ishikawa

At 5:50 he says: "Only one LED can be ON at any given time" which means I can't turn on more than one led at any given time?...Just wanted to confirm this, I hope I'm wrong.

I already answered this above!.

Ishikawa · 2nd November 2007, 05:44 PM

Quote:

bananasiong:
Hi,
Are you sure that the first LED is always on? I can see it flashing
Use 4 I/O to control 9 LEDs (9 stages), possible? Since the max stages of using 4 I/O is 12.

Yep looks like it.

Quote:

Nigel Goodwin: You do it so fast you can't tell they are flashing, it's a VERY standard technique.

So I have to make the pic to switch between high and low at the 5 inputs fast enough so it won't look like the leds r turning on&off. Is this what u mean?

Thanks

**Nigel Goodwin** · 2nd November 2007, 08:01 PM

Quote:

Originally Posted by Ishikawa

So I have to make the pic to switch between high and low at the 5 inputs fast enough so it won't look like the leds r turning on&off. Is this what u mean?

Yes, check my PIC tutorials for an example of multiplexing LED's.

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1st November 2007, 09:13 PM	(permalink (permalink))
Nigel Goodwin	Some one who does a lot of PIC charlieplexing will probably be along shortly! __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

1st November 2007, 09:27 PM	(permalink (permalink))
Ishikawa	I just noticed that with the charlieplexing method will probably be hard to keep each row of leds ON like it is shown in the pictures. This method will turn them ON and turn them off by the time it turns ON the next row of leds.

1st November 2007, 10:07 PM	(permalink (permalink))
Ishikawa	deleted by original poster. Last edited by Ishikawa; 1st November 2007 at 10:12 PM.

2nd November 2007, 08:24 AM	(permalink (permalink))
Ishikawa	This link has a video that explains charlieplexing very well http://www.brightcove.tv/title.jsp?t...eup=1028763155 At 5:50 he says: "Only one LED can be ON at any given time" which means I can't turn on more than one led at any given time?...Just wanted to confirm this, I hope I'm wrong. But then again I saw 3 videos at youtube about charlieplexing and they had more than one led on at a time. Also at 9:32 he says: "this will give roughly 40mA of peak current going through each led" then he says: "and therefore the average current through the led is 40mA/20=2mA", so I'm a bit confused isn't there a contradiction?? Please watch the whole video. Last edited by Ishikawa; 2nd November 2007 at 08:31 AM.

2nd November 2007, 11:23 AM	(permalink (permalink))
3v0	Use a PIC with enough pins to drive each LED (or pair) and do away with the multiplexing. This will make the code and the hardware very simple. Like Erick says *Good enough is Perfect*.