Sonsivri

I wanted to post this in AVR section, but I thought PIC guys will also have some ideas. I googled how to drive those 2.3" CA 7-segment displays, should I use ULN2003, are there other options to do it, still I am willing to hear from you guys, may be someone can offer the best way to do it  ::)

A Darlington is the simple straight forward method to drive them, and would probably be my first go to for a project...  Although there are some LED driver chips out there now that can handle that current on their own that might work better in some applications, can't recommend any off hand but they are out there...

Hi

I use the same type of digit CA, green and red color type, to display the humidity
and temp. 3 digits each, all six digits multiplexed.

UDN2981 (50v, 500ma source driver) is used to drive the common anodes of all digits.

UL2803 is used to drive the 7 segments plus decimal point.

Red and green displays have separate current limiting resistors in order to match the
brightness.

A cheap laptop switching power supply (18v) is used to power the display anode driver
chip 2981 and 7805 for the controller circuit.

You can use this setup to drive up to 4" digit easily.

Regards

I don't know which part troubled you for driving these chips but by looking at the datasheet of LTS-23805HRB, I can suggest a simple ULN2003(ULN2803 if you'll drive the dot point too) and 12V power supply with a resistor of (12-V_{voltage drop for segment})/I_segment or (12-V_{voltage drop dot point})/I_{dot point} for dot point between each segment and +12V. As an example datasheet says nominal voltage drop for a segment is 8V (4V for dot point) so the resistor should be (12-8)/0.02 Ohms for a driving current of 20mA.

IMO uln2003 should be able to handle the current requirement.
They are also much easier to source than other exotic components.

You can consider using power drivers with serial inputs. e.g: TPIC6C595N
It can spare you some valuable ports for other purposes.

Best regards,
Mris

there is a thread for MAX7219/21, I think this is a better solution.

I source the LTS-23805HRB with a MICREL MIC5891, which has serial input and its latched drivers can source 500mA all together.

If you want to multiplex, I would switch the cathode with logic level N-MOSFETs like a Fairchild FDN337N or a International Rectifier IRLML2060.
If you drive the segments with a duty-cycle, then you can go above 25mA per segment and have a brighter display.

The Maxim MAX7219/21 is a nice package, but not cheap.

Please, do you have sch for this combination?


Another similar solution:

http://www.electro-tech-online.com/imgcache/3539-Clock-2v2.jpg

Of course you must use hifher supply voltage.

Instead MIC5821 you can use equivalent chip UCN5821.

I am searching for the software used to draw this schematic, but unable to find.
Can anybody tell me which software is that?

Regards,
Thiru

MAX7219 (http://www.ebay.ca/itm/5PCS-IC-MAX7219CNG-MAX7219-DIP-24-DRIVER-LED-DISPLAY-8DGT-NEW-GOOD-QUALITY-/300926648821?pt=LH_DefaultDomain_0&hash=item4610a041f5) is fairly cheap on eBay, 5 for $2.50.
As for the schematic software, it beats me, never used it.
Check this (http://4cad.info/kategoria.php?id=9&page=1) link, list 100's of EDA software you might find it there.

I think i ever read somewhere some years ago that diagram is not drawn using any EDA software, but Visio (or similar) - but maybe my memory which is full of noise now :).

-ichan