Monostable.
The correct electronics term for this module is a Monostable Multivibrator. The name derives from the fact that they have a default state of 0 volts output until they are triggered by an external pulse, they then flip to the on state (usually 5 volts) for a preset length of time, once this expires they then revert to their default of 0 volts output.
The monostable module operates on the same principle. It normally outputs a “False” or 0 logic state. Once the Monostable receives a pulse signal input the leading edge of the pulse triggers the monostable, the output of which then switches to the “True” or 1 logic condition.
The gate then holds the “True” condition for a period of time determined by the voltage present on the Pulse Length (ds)- (ds stands for DeciSeconds) plug. The Time to Voltage is 1 Volt = 10 seconds. See the demo screenshots below (the small voltages are because the demo setup has quite a high pulse rate)
Note: You’ll find that once the monostable has been triggered, it won’t respond to another trigger pulse until the preset time has elapsed. Trying to trigger it a second time will not extend the length of the output pulse, also no matter how long the input pulse this will not affect the length of the output pulse.
What use is a Monostable?
What use is a monostable? Well one possible use is the following:
Say we wanted to detect when our audio level passed 2 volts, and light an LED.
We can us a comparator to detect this, but say the audio only exceeds 2 V for a few milliseconds? That’s not enough time for the LED to respond, let alone for us to see it light up. This is where a Monostable is useful. By adding this to the output, and putting 5V on the Pulse length plug, we will detect the short lived peak, and the monostable will send a half second pulse to the LED- enough to see it flash and warn us the audio will be clipping
Delaying the Trigger pulse from a keyboard.
If you needed a delayed Keyboard Trigger pulse then this is one way to approach it. By not connecting the Gate pulse from MIDI-CV 2 to the ADSR 2 module then no matter how long you hold down a key only the attack/decay portions of the envelope will be active. The decay can be set to 0 V as it’s unimportant, as are the sustain and release portions.
Note: The overall Level plug is set to 10.2 volts, otherwise the structure isn’t reliable at triggering.
Input B of the comparator is set to 10 volts, so the comparator switches to + 10 volts output when Input A of the comparator reaches 10 volts, the monostable then generates a fixed length pulse from this providing us with a delayed Trigger pulse, the delay time being set by the Attack segment timing of the ADSR 2 module (the time it takes to reach 10 V). Because the Envelope isn’t held when the Attack reaches its maximum the resulting pulse is extremely short hence using the monostable on the output, which in this usage triggers another ADSR2 module.
Note: Always connect both Trigger and Gate plugs as shown.
Using this method we can create a delayed trigger as was used in the Moog modular synthesizers.
You don’t specifically need to use the Fixed Values modules (you can specify the values needed in the module properties), but it does make it easier to work out what you have done at a later date, and here it’s done for illustration purposes.
