ULN2803 Question...

[AtomSoft]

Hey guys i know im a huge pain. I was going to use a ULN2803 for driving my LED Matrix but noticed i cant use it for the Column Driver without using another IC to invert it. I wanted to know if i can simply use a 4017 to drive each LED Column directly im using 270 OHM resistors and plan on using 5v supply... so thats a max of:

130mA per column but remember since it will never be a solid on its actually going to be less since its basically strobbing. The column is ANODE and the ROW are CATHODE.

 

[ericgibbs]

Hey guys i know im a huge pain. I was going to use a ULN2803 for driving my LED Matrix but noticed i cant use it for the Column Driver without using another IC to invert it. I wanted to know if i can simply use a 4017 to drive each LED Column directly im using 270 OHM resistors and plan on using 5v supply... so thats a max of:

130mA per column but remember since it will never be a solid on its actually going to be less since its basically strobbing. The column is ANODE and the ROW are CATHODE.

hi atom,
Have you seen this device.?

 

[AtomSoft]

i saw info on it somewhere but cant remember... I guess ill have to order some heh No of a good place to source with cheap shipping?

EDIT:

These ICs are about $2 each wow. Thats a lot for a single IC...

 

[Mike - K8LH]

Hi Jason,

I don't think you've thought your design thru'. How many rows and columns? And you're going to be scanning columns?

 

[AtomSoft]

i havent thats the thing.. heh i never fully plan anything heh... The LED Matrixs i have are 5x7 and have ANODE Columns and CATHODE Rows...
I plan on Using RB0:6 for ROWs 1-7 and using the 4017's for selecting the current column on.

So i assume you call that scanning columns?

I havent made anything official on the board im doing yet only that all the Rows are tied together from each matrix.

 

[AtomSoft]

Here take a look at the video on how i wanted it: (May not be fully processed yet ...)
https://atomsoft.wordpress.com/2010/02/06/test-matrix-001/
[embed]http://www.youtube.com/v/Z-qvcNXnmGU[/embed]

 

[supra_2010]

i saw info on it somewhere but cant remember... I guess ill have to order some heh No of a good place to source with cheap shipping?

EDIT:

These ICs are about $2 each wow. Thats a lot for a single IC...

Nope! IC cost 53 cents from ebay including free shipping
**broken link removed**


The best bet is 74HC154, 74HC595 or 74HC164. They all driving 20 mA/pins. U don't needed resistor

If u r using cd4017, u will need resistor and transistor per columns. Ouch!

If u want to used uln2803 for negative and uln2802 for positive... u don't needed resistors

If u followed ericquibbs......u will need this UDN2981

 

[AtomSoft]

i mean the UDN2981 is $2 i have about 10 2803's here heh

Are you sure the 2802 is for positive? I doubt it cuz it would be what i need heh

 

[supra_2010]

i mean the UDN2981 is $2 i have about 10 2803's here heh

Are you sure the 2802 is for positive? I doubt it cuz it would be what i need heh

Sorry! Id didn't say udn2981. U will have to do google search. hehehehehe

 

[AtomSoft]

Heh No problem also i noticed i have the resistors on the wrong side. heh there supposed to be on the ULN2803 heh i guess i tried to rush it

 

[supra_2010]

Heh No problem also i noticed i have the resistors on the wrong side. heh there supposed to be on the ULN2803 heh i guess i tried to rush it

U don't needed resistors for uln2803. Just leave them out.

 

[AtomSoft]

im planing on only using resistors on the 7 pins for the 2803... this way i save on resistors heh.. even tho i have a ton!! but this ensures each LED has the same brightness also.

 

[supra_2010]

im planing on only using resistors on the 7 pins for the 2803... this way i save on resistors heh.. even tho i have a ton!! but this ensures each LED has the same brightness also.

Instead of resistors. Fastest way is network resistor(7 pins)...2 wires only

 

[AtomSoft]

i dont have the networks for 220 ohm or 270 ohm which is what i would use. I only have networks in 4.7k....

 

[auri_z]

i use this schematic for my projec and it working nice

 

[Wilksey]

Are they PNP transistors?
You haven't said what IC's you are using, is that shift registers into darlington IC's?

What is IC8? AND Gate chip?

Which variant is IC4? 16F?

Did you build that LED array or did you use bought matrixes?

What ratings are the resistors for the row driver?

Wilksey

 

[auri_z]

sorry..
in my work i usually view the list text file.
transistor can use pnp or npn, if PNP like picture, data to send to make led on is low and visa versa.

IC5-IC7 decode counter 4017.

IC8 is AND gate like 7408 or varian

IC4 is pic16f877

i build led array because in my town difficult buy matrixes

R for row driver depend at rating led and power apply to transistor.
if we use Vs 5 volt and current led 30 Ma R is 100 ohm.

sorry my englsih bad.

 

[Wilksey]

Please dont apologise, I can understand your English fine.

I have built a LED array in the past, took ages! I built an 8x8.

Nice circuit, I did mine similar apart from the 4017, just looking at ways to make it simpler.

Do you have any associated code for the PIC you can share?

Thank you for posting your circuit and description.

Regards

Wilksey

 

[Wilksey]

What is IC1, 2 and 3?
Also, on IC2, you have a wire connected to CD+, should this be the pin before like the other 2 IC's (O8) ?

Regards

Wilksey

 

[auri_z]

my bad. on IC2 CD+ not connected like IC1 and IC3.
IC1,IC2,IC3 = ULN2803.
IC8 AND gate. like 7408 or 74ls08, 74hc08 etc.

i posting my code in
**broken link removed**

it working and i still deploving my code for communication with PC.
you can tri this code and schematic in proteus. in proteus you can change led with matrix array but
must change ULN 2803 with hex inverter or NOT gate, i don't understan why led matrix not working with ULN2803 in proteus.

and if you use PNP transistor like my schematic you must invert data table otherwise your display will inverted.
or if you not change code you can change transistor to NPN.