What are two uses of the 555 timer?
Metronome, stable timer for time critical circuit
How many pins does a standard LM555 timer IC have and what are the names of each pin?
8 pins in total: (details given for astable mode, which was what was shown in the tutorial)
1) Ground - Most negative potential of the IC
2) Trigger - Connected to Threshold (pin 6) and between R2 and the capacitor
3) Output - Outputs a High (5-15v) or Low (0v) digital signal (square wave) depending on the timing set in the IC
4) Reset - Voltage (0.1-0.4V) applied to this pin resets the output to Low and restarts on-off cycle. Tied to Vcc when not in use.
5) Control Voltage - Used to vary the timing of the device independently of the RC values.
6) Threshold - When given a voltage above 2/3 of Vcc (the normal voltage of the Control Voltage pin), it resets the cycle and sets output to Low just like the Reset pin.
7) Discharge - Connects timing circuit to ground.
Vcc (+) - Input voltage
What R1/R2/C1 values could be used for a 10 milliseconds On-Time pulse from an a-stable
555 timer configuration? (use Frequency = 100 Hz)
I got a strange answer for this -- probably completely wrong.
F = 100Hz = 1/period = 1 /(Ton + Toff)
Ton = 0.01s
100Hz = 1/(0.01s + Toff) => Toff = 0s
Ton = 0.693 * (R1 + R2) * C1 = 0.01
Toff = 0.693 * R2 * C1 = 0
and Ton != 0, so the only component of Ton that can be 0 and is also in Toff's equation is R2. Therefore R2= 0.
0.01/0.693 = R1 * C1
R1 and C1 are factors which multiply to give 0.01443001