| ??? 08/20/05 11:42 Read: times |
#99723 - Try PNP instead of NPN Responding to: ???'s previous message |
Mary,
I use NPN transistor to give input to the anode The above method will drop more voltage accross the transistor, with consequent drop in brightness of the LEDs, it is better to drive the anodes of the LEDs with a PNP transistor, I usually use the BC557 or the DTA143EK connected to a +5V source driving the anode of the LED displays. Another method to increase the brightness is to drive the LED displays with high current pulses for short duration in your software. Regards, John. |
| 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 |