| ??? 08/22/05 13:05 Read: times |
#99814 - even considering voltage will get you in Responding to: ???'s previous message |
After I read the spec for my LEDs, the min forward voltage is 1.3 for red in 20mA, 2.5 for green and blue in 20mA. And max. voltage is 2.4V for red and 3.9 for green and blue.
A color display id much more "sensitive" than a monochrome. Even considering voltage will get you in trouble. Vf for a bunch of "identical" LEDs will vary and using voltage and a resistor will make the intensity inconsistent. Also using a resistor makes you extremely sensitive to power supply fluctuations and swithing on a bank of LEDs can make any PS "jump". USE CC DRIVERS!!! A monochrome display is not very critical since there is no multicolor issue, if one is a bit brighter than another it is hardly noticeable. With RGB displays the relative intensity becomes 10 times (my opinion) more critical. Thus DO NOT think display, think color. THROW AWAY any "reference design" you have that is not color. Erik (500.000+ LEDs installed every month) |
| Topic | Author | Date |
| Questionn - Not even brightness for LEDs | 01/01/70 00:00 | |
| Sounds like you've answered the question | 01/01/70 00:00 | |
| What minizium change I need | 01/01/70 00:00 | |
| Test some things | 01/01/70 00:00 | |
| Test | 01/01/70 00:00 | |
| Try PNP instead of NPN | 01/01/70 00:00 | |
| Both method | 01/01/70 00:00 | |
| Increase the voltage accross the load | 01/01/70 00:00 | |
| even brightness... | 01/01/70 00:00 | |
| Spec for LED | 01/01/70 00:00 | |
| something is wrong... | 01/01/70 00:00 | |
| RGB LED's Luminous | 01/01/70 00:00 | |
| even considering voltage will get you in | 01/01/70 00:00 | |
| Explain more | 01/01/70 00:00 | |
| simple, drop the multiplexing | 01/01/70 00:00 | |
| Will this work | 01/01/70 00:00 | |
| Erik says | 01/01/70 00:00 | |
| this will | 01/01/70 00:00 | |
| Can I use UDN2891a | 01/01/70 00:00 | |
| can't say | 01/01/70 00:00 | |
| probably means 2981 | 01/01/70 00:00 | |
if so, you just don't get it do you | 01/01/70 00:00 | |
| why would you do that ? | 01/01/70 00:00 |