Is there any way to use a single 555 chip which could be switched with a two-state switch between monostable mode (one-shot pulse of a certain width) and astable (continuous pulses of a certain width)?
Here's how I'd like it to work:
I have a two-state switch that i could set into one of the two modes of operation: astable and monostable.
- If it is in the astable mode, it generates clock pulses of a certain width automatically until I switch it to a different mode.
- If it is in the monostable mode, it waits for me to push an additional push-button called "pulse", which will generate just one clock pulse of a certain width and then return to the "wait for another push" state. In this state, I would have to release the "pulse" push-button first, and then push it once more to generate another clock pulse (to avoid generating multiple pulses at once when I push the "pulse" button for too long or if it bounces).
Is this possible to implement with just a single 555 chip?
The usual implementation schematics I found are only one or the other (either astable or bistable), but I couldn't found any schematic which could allow me to switch between those two modes of a single chip with a switch.
Best Answer
Here is a circuit that does what you want. The only real requirement here is that when you are in the manual switch monostable mode you cannot press the switch faster than the pulse rate when in the astable mode.
Note that this ignores the fact that the switches can bounce. This may be a concern for S2, the manual mode trigger switch, so it may be necessary to add some R/C filtering to this switch.
In this circuit you will have to add a diode as shown. I modeled it with a voltage controlled switch to show operation but just replace your these with your simple momentary switch and simple on/off mode switch.