Analogue design question

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elway

Joined Nov 29, 2020
1
Client Requirement(Base System) The fundamental objective of this system is to provide a latching control system that provides a start and stop output, based on the presence of 1 of 2 audio frequency tones. The start and stop outputs are indicated by a start (Green LED) and a stop (Red LED) indicator. When the start tone is applied, the start indicator will come on, and remain on, until the stop tone is applied. If neither tone is applied, then the indicators retain their previous state. The base system is powered from +/- 5V, and the tone amplitude for each tone is 2Vp-p. Pick any two frequencies .
i wanna use 555 timer but dont know how to feed audio frequency as input
 

Papabravo

Joined Feb 24, 2006
16,086
Client Requirement(Base System) The fundamental objective of this system is to provide a latching control system that provides a start and stop output, based on the presence of 1 of 2 audio frequency tones. The start and stop outputs are indicated by a start (Green LED) and a stop (Red LED) indicator. When the start tone is applied, the start indicator will come on, and remain on, until the stop tone is applied. If neither tone is applied, then the indicators retain their previous state. The base system is powered from +/- 5V, and the tone amplitude for each tone is 2Vp-p. Pick any two frequencies .
i wanna use 555 timer but dont know how to feed audio frequency as input
A 555 can be configured in various ways. Was it your intention to use a pair of them to generate the two tones? If so those outputs would be square waves. Square waves have a great deal of harmonic content, their spectrum is NOT confined to a single frequency. Are you sure you want to use square waves for this project?
A good way to choose a pair of frequencies for easy detection is to make them relatively prime to each other.
 

crutschow

Joined Mar 14, 2008
27,170
i wanna use 555 timer but dont know how to feed audio frequency as input
A 555 can generate a square-wave of a given frequency. It normally doesn't have a frequency input.
Is it your intention to try to use the 555s to detect the audio frequencies?
If so, I don't think that's very feasible.

For that you could use a high-pass and a low-pass filter.
These signals could be then used to trigger a latch.
 
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