One shot pulse generator Low->High->Low even if button is still pressed?

Question

I am trying to use a 555 IC to create a low-high-low pulse that will trigger only once and still go low even if the button continues to be pressed. This is the circuit I have now but the pulse stays high if I continue pressing the button:

Edit: Wrong circuit diagram

Answer 1

Figure 1. Adding C1 prevents hold-on problems. Image source: Homemade Circuits.

How it works:

• Before PB is pressed R1 charges the left side of C1 to V+ and R2 charges the right side. Both will be at +9 V.
• When PB is pressed the left side of C1 is pulled to GND. The right side is pulled down to GND as well but immediately starts to charge up to +9 V via R2 even if PB is held.
• D1 and D2 prevent pin 2 ever seeing V > 9 V or V < 0 V.

See the linked article for more.

Answer 2

74xx123 (74LS123, 74HC123, etc.).

Note that the pulse time vs. C and R values are different between the TTL parts and the CMOS parts, so read the datasheet carefully.