Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Can someone help me with a circuit that will light up 5 leds in parallel without usin

Status
Not open for further replies.
Ishikawa said:
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 :D
Use 4 I/O to control 9 LEDs (9 stages), possible? Since the max stages of using 4 I/O is 12.
 
ericgibbs said:
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?
 

Attachments

  • tri.gif
    tri.gif
    11.1 KB · Views: 106
  • tri2.gif
    tri2.gif
    3.5 KB · Views: 100
Last edited:
This link has a video that explains charlieplexing very well

**broken link removed**

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:
iONic said:
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.:)
 
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.

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
 
Ishikawa said:
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.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top