Big 7-segment Display Clock
I’ve bought some 14cm high red 7-segment LED Displays on EBay and started to build a clock based on AVR ATTiny2313.
The circuit is build with an AVR ATTiny2313 a UDN2982 high side and a ULN2803 low side driver/switch.
The LED Module is powered with 18-20V to give a brighter display. The forward volatge of a single segment is about 13V. 13V + voltage loss at the switches (worst case 2V + 1.6V) is about 16.6V. I used 39Ohm resistors for the segments and so 16.6V + 39Ohm x 0.08A = 19.72V. Because of multiplexing 4 modules to get an avarage current of 20mA per segment the current has to be four times higher ( 20mA x 4 = 80mA ). The dots on the modules have a lower forward voltage resulting in a higher limiting resistor: (16.6V – 3.6V – 3.6V) / 80mA = 120Ohms.
Downloads:
hi, where you buy this giant 7segments ? you can sendme the info, or the modelnumber of the 7segment, THANKS!!!
I guess it was this seller on ebay: http://cgi.ebay.com/Lot-of-4-pcs-7-Segment-Red-LED-Display-5_W0QQitemZ390086818481QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5ad2fc7ab1&_trksid=p4634.c0.m14.l1262#ht_2465wt_920
[...] for each display and maybe transistor for each segment if you want a really bright display. …Tobi's Corner Blog Archive Big 7-segment Display ClockBig 7-segment Display Clock. I've bought some 14cm high red 7-segment LED Displays on EBay … Tags: [...]
hi can u sent me sorce and hex file i cant find (Big 7-segment Display Clock)program please.
email: zahravi_masoud@yahoo.com
Maybe use a constant current sink to allow equal brilliance per segment.
A TLC5926 would do the deed or a TLC5916 / TLC5917 in place of the ULN2803
Hi,
Thanks for the recommendation.
I already created a updates version with two TLC5940 driving all the 4 segments at the same time.
Tobias