| ??? 08/25/05 17:37 Modified: 08/25/05 17:41 Read: times |
#100098 - quite risky Responding to: ???'s previous message |
[EDIT] since Craig does not allow editing of the title I will do this: not really "risky" most transistors can handle 50mW quite well, a better title would be "inconsistent LED intensity"[END EDIT]
I connected the portpins with a 100kR resistor to the Base, the emitter direct to the ground and the collector with a 150R resistor which is connected with the LED 100k gives less than 50uA of base drive so to drive the transistor fully it will need a beta of 500. Since that would be remarkable I assume your transistors get a bit warm and the intensity of the LEDvary depending on the beta of the various transistor. I would use 1k to make saturation, at least, likely. Erik |
| Topic | Author | Date |
| I need help with LED Driver | 01/01/70 00:00 | |
| LED | 01/01/70 00:00 | |
| LED | 01/01/70 00:00 | |
| use a LED driver | 01/01/70 00:00 | |
| 74LS drivers | 01/01/70 00:00 | |
| LED Driver - My Solution | 01/01/70 00:00 | |
| quite risky | 01/01/70 00:00 | |
| MCU-resistor-NPN | 01/01/70 00:00 | |
| 8051 is open drain ! | 01/01/70 00:00 | |
| not good idea | 01/01/70 00:00 | |
| totally wrong ! | 01/01/70 00:00 | |
| This I would take with a grain of salt. | 01/01/70 00:00 | |
| But nevertheless totally unsuited! | 01/01/70 00:00 | |
| Where in Atmel errata or other informati | 01/01/70 00:00 | |
| That's standard performance of quasi bi. | 01/01/70 00:00 | |
| Try This | 01/01/70 00:00 | |
updated | 01/01/70 00:00 |