Re: VOX switch

[Micro-Flight]

How about programming a PIC. Can't get a lower parts count than that!

"Andrew" > wrote in message
...
> I am hoping that someone could help in finding voice activation switch IC.
>
> I did find one or two very old references to a Motorola MC2830P, but have
a
> feeling that it is discontinued as I was unable to find any information on
> the Motorola site.
>
> I have found a few circuits on the web, but was hoping someone here might
> have used something that they would recommend. Something with a low
> parts count, and might work with an inexpensive computer microphone or
> a headset microphone meant for hands free telephone conversations.
>
> It only needs to be momentary on. Some sort of gain adjustment or
> background filtering would be valuable.
>
> any leads?
>
> thanks
> andy
>
>

[Micro-Flight]

How about programming a PIC. Can't get a lower parts count than that!

"Andrew" > wrote in message
...
> I am hoping that someone could help in finding voice activation switch IC.
>
> I did find one or two very old references to a Motorola MC2830P, but have
a
> feeling that it is discontinued as I was unable to find any information on
> the Motorola site.
>
> I have found a few circuits on the web, but was hoping someone here might
> have used something that they would recommend. Something with a low
> parts count, and might work with an inexpensive computer microphone or
> a headset microphone meant for hands free telephone conversations.
>
> It only needs to be momentary on. Some sort of gain adjustment or
> background filtering would be valuable.
>
> any leads?
>
> thanks
> andy
>
>

[ehsjr@bellatlantic.net]

Andrew wrote:
>
> I am hoping that someone could help in finding voice activation switch IC.
>
> I did find one or two very old references to a Motorola MC2830P, but have a
> feeling that it is discontinued as I was unable to find any information on
> the Motorola site.
>
> I have found a few circuits on the web, but was hoping someone here might
> have used something that they would recommend. Something with a low
> parts count, and might work with an inexpensive computer microphone or
> a headset microphone meant for hands free telephone conversations.
>
> It only needs to be momentary on. Some sort of gain adjustment or
> background filtering would be valuable.
>
> any leads?
>
> thanks
> andy

Ramsey electronics has a voice operated switch kit:
http://www.ramseyelectronics.com/

It is not a low parts count, but it's relatively cheap and might
be an option for you.

[ehsjr@bellatlantic.net]

Andrew wrote:
>
> I am hoping that someone could help in finding voice activation switch IC.
>
> I did find one or two very old references to a Motorola MC2830P, but have a
> feeling that it is discontinued as I was unable to find any information on
> the Motorola site.
>
> I have found a few circuits on the web, but was hoping someone here might
> have used something that they would recommend. Something with a low
> parts count, and might work with an inexpensive computer microphone or
> a headset microphone meant for hands free telephone conversations.
>
> It only needs to be momentary on. Some sort of gain adjustment or
> background filtering would be valuable.
>
> any leads?
>
> thanks
> andy

Ramsey electronics has a voice operated switch kit:
http://www.ramseyelectronics.com/

It is not a low parts count, but it's relatively cheap and might
be an option for you.

[ehsjr@bellatlantic.net]

Andrew wrote:
>
> I did see the kit, but wanted to see if I could make something myself first.
>
> There was a suggestion to us a microcontroller, and I am now considering the
> use of the analogue comparator on an AVR microcontroller that will be being
> used in the project.
>
> It seems that most VOX circuits boil down to comparing a microphone voltage
> to a threshold reference. I am not really to experienced in audio filtering
> and amplification, so I would have to find some web documentation on making
> a circuit to handle the sound in portion. I suppose it would even be
> possible to have one of the PWM channels on the microcontorller set the
> reference voltage, and in this way it would be adjustable.
>
> If anyone has some tutorial sights on sound handling hardware (filter,
> amplify, etc) please suggest.
>
> cheers,
> andy
>

A VOX is a simple circuit - no need for microcontrollers
or filters for a basic VOX. I made one with a 555 which
I triggered with a voltage created by the audio. Feed
the audio out of an amplifier to a diode & capacitor.
When there is an audio signal, the diode and capacitor
develop a voltage that triggers the 555. You don't need
a 555 - that's what I had on hand - you can use a
Schmidt trigger IC like a 4093.

[ehsjr@bellatlantic.net]

Andrew wrote:
>
> I did see the kit, but wanted to see if I could make something myself first.
>
> There was a suggestion to us a microcontroller, and I am now considering the
> use of the analogue comparator on an AVR microcontroller that will be being
> used in the project.
>
> It seems that most VOX circuits boil down to comparing a microphone voltage
> to a threshold reference. I am not really to experienced in audio filtering
> and amplification, so I would have to find some web documentation on making
> a circuit to handle the sound in portion. I suppose it would even be
> possible to have one of the PWM channels on the microcontorller set the
> reference voltage, and in this way it would be adjustable.
>
> If anyone has some tutorial sights on sound handling hardware (filter,
> amplify, etc) please suggest.
>
> cheers,
> andy
>

A VOX is a simple circuit - no need for microcontrollers
or filters for a basic VOX. I made one with a 555 which
I triggered with a voltage created by the audio. Feed
the audio out of an amplifier to a diode & capacitor.
When there is an audio signal, the diode and capacitor
develop a voltage that triggers the 555. You don't need
a 555 - that's what I had on hand - you can use a
Schmidt trigger IC like a 4093.