Hi Guys i got a nice kit from velleman the K8089 and want to drive a big 12VDC driven LED display. Can somebody give me a hint, i used now the ULN2004 and the 7 segment display works reversed.
schematic http://www.onderdelenspecialist.be/schematic_k8089_rev1.pdf

The segment that have to light up goes out and the segments that dont have to light up lightning up.
On the builded kit with the original led display's its working like hell!!!
can somebody help me, i dont see it anymore grrrrrrrr

 

I can't see the ULN2004, but only 74HC595.
Or you want to using ULN2004 to replace the 74HC595?

 

I made a extern PCB and used the outputs from The 595 To set on The inputs For The uln

 

I made a extern PCB and used the outputs from The 595 To set on The inputs For The uln

Could you attach the circuit, maybe it just the high and low logical problem.

 

The ULN2004 will invert the signal as ScottWang thought it might. To use it between the '595's and the displays, you would need to add inverters between the '595's and the ULN2004 inputs. This assumes your larger displays are common anode like the kit displays.

EDIT: Please clarify: Was the original build with original displays working OK ?

 

Here is the simple scheme to let see
http://www.onderdelenspecialist.be/extra_k8089.JPG

just coupled the 595 tot the uln2003


i feeling


all scheme i found on the net made it like this grrrrrrrrrr

 

What kind of display unit do you have. Any links/product number

 

Here is the simple scheme to let see
http://www.onderdelenspecialist.be/extra_k8089.JPG
just coupled the 595 tot the uln2003

i feeling

all scheme i found on the net made it like this grrrrrrrrrr

That was what I thought, you have to reverse(as inverter) the logical of software from 74HC595.

It means that when you didn't add the ULN2003, you send a low to drive the 7-seg from 74HC595, but when the ULN2003 was cascaded then you have to send a high to the ULN2003, and ULN2003 output a low to drive the 7-seg.

Original:
74HC595 (Vout=0) → (0)7-seg, 7-seg(+) → +5V

ULN2003 added:
74HC595 (Vout=1) → (Vin=1) ULN2003,ULN2003 (Vout=0) → (0)7-seg, 7-seg(+) → +5V

When you using ULN2003 to drive the 7-seg, you have to adding seven resistor to limilting the current, and the pin9(com) of ULN2003 connected to GND.

 

As others have stated, the ULN2003 sinks current when it sees a high signal on its input which means you need an inverter between the 595 and the ULN2003. I made a quick drawing showing how to connect a 74HC14. Unfortunately, these only have 6 inverters, so you'll need 5x 74HC14s total for your four digits.