555
I've been reading up a bit on the 555 and I'm beginning to see it's brilliance.
Pins
- Ground
- Trigger
- Output
- Reset
- Control Voltage
- Threshold
- Discharge
- Vcc
When the trigger is below 1/3 Vcc, output goes high, and stays high. When the threshold pin goes above 2/3 Vcc, output goes low.
Output can handle up to 200mA.
The control voltage can set the 2/3 level directly. Often it is not used and connected to ground with 10uF cap.
I'm not clear on discharge, it's connected to the collector of an internal transistor, something about discharging the timing cap, but in most schematics it's tied to threshold.
Besides the basic modes (monostable, bistable and astable) it can be used for digital logic. The piece that turned me on to this was using it as a temperature controller. Where the 1/3 level corresponds to "turn on the heater" and the 2/3 level corresponds to "turn off the heater". Any logic of that nature.