So that made things solid and clear for me. But what I would like to know is about the stuff you mention right at the end - cases where you use the thresh and trig inputs separately. what kind of crazy cool stuff could one build just using 555 ics. Could I build an eight bit computer? (I am almost sure the answer is yes but it would be cool to see sketched out. Well, I have a few 555's and a scope and assorted r's and c's... guess I should find out! thanks again!
The reason that the 10k didn't work for the discharge resistor is because when the transistor is on the two resistors form a voltage divider that will only discharge to half of vcc which isn't low enough to get to the 1/3 vcc lower hysteresis point. A low value like 100 ohms would have worked similar to your original intent of quickly discharging the capacitor, but it would discharge to 1/3 of vcc rather than 0v.
Thanks, I was having a issue with Carrier Operated Relay circuit using 10-30pF and 510 Ohm in series to pin 1 of Opto-coupler with diode IN4148 A to GND to drive opto-coupler (MOC8021M). OUTPUT: across pin 4 &5 of opto-coupler is 100uF Cap with a SSB switch with 1000uF Cap. Pin 4 to GND and Pin 5 to drive 12V relay. The relay cuts out unless I speak non-stop. Any ideas? do you think the timing circuit is a better solution?
I have taken your work in this video and used it with my students. In combination with the first video, you have rendered the 555 into a real tool for teaching the interface between analog and digital. I hope that fits your intent.
Back in the 70's I used the circuit you described to interface a Western Electric TT keypad to my 2 meter rig to keep transmitter keyed between digits.
