Table of Contents
NE 555
- Vcc 5-15V
- Output can sink or source at 200mA (direct relay control is possible)
Output is not full rail-to-rail. To improve output sinking it is possible to connect pin 7 with 3 in some specific applications.
Monostable mode
T = 1.1 * R * C
555 Monostable Circuit Calculator
NOTE: There is no sense to use classic circuit for long delays (i.e. over 10 mintes). There is problem with capacitor current leaking, etc. Also NE555 trigger input get some current (recommended is CMOS version). Maximum usable capacitor for 12V is about 2200uF.
Long delays
Extended Period 555 On-Pulse Timer
Results with 1N4148 silicon diode and BC557B PNP transistor (hFE measured: 260), Vcc=12.1V:
| Vcc | C | R | time |
|---|---|---|---|
| 12.1 | 100uF | 100k | 16 min |
| 12.1 | 100uF | 670k | 37 min |
| 12.1 | 220uF | 10k | 23 min |
| 12.1 | 220uF | 250k | 92 min |
| 12.1 | 470uF | 100k | 55 min |
| 8 | 220uF | 10k |