miltiplexing question
Archiver
Posts: 46,084
Hi Group,
I have already asked one question about this, and thanks to the
group I have my project ALMOST working.
I am trying to control a group of lamps using only two wires. These
wires must carry the control information and carry power and ground.
So, I am encoding a DTMF signal that coresponds to which light I
want to turn on, and sending it up the +V wire.
Here's my circuit:
BS2 .1uF .1uF DTMF RX'ER
dtmfout
||
||
audio in
| |
+V
| |
power in
Nothing new here really, two cap's todecouple the audio, whould work
fine right??
NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
to zip.
OK, so I need to find a way to pass the DC to the DTMF encoder IC
without loading down the DTMF audio signal.
Have tried a resistor, but a 20K resistor was needed and the
resultent DC voltage drop was too high.
Tried to wind an inductor on a bit of ferrite and put it in series
with the DTMF IC's power pin, nope that didn't work either.
The tone decoder is an MT8870D
Can anyone suggest a way that I can pass the DC to power the IC,
whilst blocking the DTMF audio signal????????????
Thanks in advance,
Dwain.
I have already asked one question about this, and thanks to the
group I have my project ALMOST working.
I am trying to control a group of lamps using only two wires. These
wires must carry the control information and carry power and ground.
So, I am encoding a DTMF signal that coresponds to which light I
want to turn on, and sending it up the +V wire.
Here's my circuit:
BS2 .1uF .1uF DTMF RX'ER
dtmfout
||
||
audio in
| |
+V
| |
power in
Nothing new here really, two cap's todecouple the audio, whould work
fine right??
NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
to zip.
OK, so I need to find a way to pass the DC to the DTMF encoder IC
without loading down the DTMF audio signal.
Have tried a resistor, but a 20K resistor was needed and the
resultent DC voltage drop was too high.
Tried to wind an inductor on a bit of ferrite and put it in series
with the DTMF IC's power pin, nope that didn't work either.
The tone decoder is an MT8870D
Can anyone suggest a way that I can pass the DC to power the IC,
whilst blocking the DTMF audio signal????????????
Thanks in advance,
Dwain.
Comments
BS2 .1uF .1uF
DTMF RX'ER
dtmfout
||
||
audio in
| |
+V
| |
power
in
Original Message
From: "dwainsworld2000" <dwainsworld@e...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, May 16, 2003 3:46 PM
Subject: [noparse][[/noparse]basicstamps] miltiplexing question
> Hi Group,
>
> I have already asked one question about this, and thanks to the
> group I have my project ALMOST working.
>
> I am trying to control a group of lamps using only two wires. These
> wires must carry the control information and carry power and ground.
>
> So, I am encoding a DTMF signal that coresponds to which light I
> want to turn on, and sending it up the +V wire.
>
> Here's my circuit:
>
>
>
> BS2 .1uF .1uF DTMF RX'ER
> dtmfout
||
||
audio in
> | |
> +V
| |
power in
>
>
> Nothing new here really, two cap's todecouple the audio, whould work
> fine right??
>
> NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
> to zip.
>
> OK, so I need to find a way to pass the DC to the DTMF encoder IC
> without loading down the DTMF audio signal.
>
> Have tried a resistor, but a 20K resistor was needed and the
> resultent DC voltage drop was too high.
>
> Tried to wind an inductor on a bit of ferrite and put it in series
> with the DTMF IC's power pin, nope that didn't work either.
>
> The tone decoder is an MT8870D
>
> Can anyone suggest a way that I can pass the DC to power the IC,
> whilst blocking the DTMF audio signal????????????
>
> Thanks in advance,
>
> Dwain.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
'power in' and anode to the line. At lease the audio will not drop below .6
volts or so. You may need to increase the value of the caps to about 2.2uF
also. Where is the return for the dc? I assume it is the other wire. This
scheme should work as I have used it many times before but have used coax
for shielding and used the braid as a return. Some wire pairs have
considerable capacitive coupling and this may be causing the loss of signal.
Jim
http://www.geocities.com/jimforkin2003/
Original Message
From: dwainsworld2000 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=OBUUViGXFKX8FiWMTBhJ6Q9Ih6Fu3KXLcywu0FS4jmGzXC2OwZo_SxZkXwVVp8-zRuYKJwmIPuzi3bBGTfTqBfc]dwainsworld@e...[/url
Sent: Friday, May 16, 2003 1:47 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] miltiplexing question
Hi Group,
I have already asked one question about this, and thanks to the
group I have my project ALMOST working.
I am trying to control a group of lamps using only two wires. These
wires must carry the control information and carry power and ground.
So, I am encoding a DTMF signal that coresponds to which light I
want to turn on, and sending it up the +V wire.
Here's my circuit:
BS2 .1uF .1uF DTMF RX'ER
dtmfout
||
||
audio in
| |
+V
| |
power in
Nothing new here really, two cap's todecouple the audio, whould work
fine right??
NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
to zip.
OK, so I need to find a way to pass the DC to the DTMF encoder IC
without loading down the DTMF audio signal.
Have tried a resistor, but a 20K resistor was needed and the
resultent DC voltage drop was too high.
Tried to wind an inductor on a bit of ferrite and put it in series
with the DTMF IC's power pin, nope that didn't work either.
The tone decoder is an MT8870D
Can anyone suggest a way that I can pass the DC to power the IC,
whilst blocking the DTMF audio signal????????????
Thanks in advance,
Dwain.
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
I have used a diode at the input end as you have suggested, and it works
well. I had also planned to use coax as the conductor, but for now in runs
of inches between components, it's just plain old copper wire.
Yeah, the other wire is the ground wire.
My problem remains how to stop the load side (in particular the DTMF decoder
IC) loading down the audio, I am getting desperate. I even tried putting a
voltage regulator in front of the IC +V input and that didn't work
either...........
Original Message
From: "Jim Forkin" <jjf@p...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, May 16, 2003 10:16 PM
Subject: RE: [noparse][[/noparse]basicstamps] miltiplexing question
> you may want to try using a diode to isolate the 'power in'. Cathode to
> 'power in' and anode to the line. At lease the audio will not drop below
.6
> volts or so. You may need to increase the value of the caps to about
2.2uF
> also. Where is the return for the dc? I assume it is the other wire.
This
> scheme should work as I have used it many times before but have used coax
> for shielding and used the braid as a return. Some wire pairs have
> considerable capacitive coupling and this may be causing the loss of
signal.
>
> Jim
> http://www.geocities.com/jimforkin2003/
>
>
Original Message
> From: dwainsworld2000 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=EsZb8MfMYlEJeS1A_Y02stulJHWMrN5sMtI1HtmT00XDbEV02dxa-5orDNyhbAiidJDAuaexagF8JDi9g7tj]dwainsworld@e...[/url
> Sent: Friday, May 16, 2003 1:47 AM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] miltiplexing question
>
>
> Hi Group,
>
> I have already asked one question about this, and thanks to the
> group I have my project ALMOST working.
>
> I am trying to control a group of lamps using only two wires. These
> wires must carry the control information and carry power and ground.
>
> So, I am encoding a DTMF signal that coresponds to which light I
> want to turn on, and sending it up the +V wire.
>
> Here's my circuit:
>
>
>
> BS2 .1uF .1uF DTMF RX'ER
> dtmfout
||
||
audio in
> | |
> +V
| |
power in
>
>
> Nothing new here really, two cap's todecouple the audio, whould work
> fine right??
>
> NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
> to zip.
>
> OK, so I need to find a way to pass the DC to the DTMF encoder IC
> without loading down the DTMF audio signal.
>
> Have tried a resistor, but a 20K resistor was needed and the
> resultent DC voltage drop was too high.
>
> Tried to wind an inductor on a bit of ferrite and put it in series
> with the DTMF IC's power pin, nope that didn't work either.
>
> The tone decoder is an MT8870D
>
> Can anyone suggest a way that I can pass the DC to power the IC,
> whilst blocking the DTMF audio signal????????????
>
> Thanks in advance,
>
> Dwain.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
> Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
range, off the +5 volts from the Stamp?
>Hi Group,
>
>I have already asked one question about this, and thanks to the
>group I have my project ALMOST working.
>
>I am trying to control a group of lamps using only two wires. These
>wires must carry the control information and carry power and ground.
>
>So, I am encoding a DTMF signal that coresponds to which light I
>want to turn on, and sending it up the +V wire.
>
>Here's my circuit:
>
>
>
>BS2 .1uF .1uF DTMF RX'ER
>dtmfout
||
||
audio in
> | |
>+V
| |
power in
>
>
>Nothing new here really, two cap's todecouple the audio, whould work
>fine right??
>
>NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
>to zip.
>
>OK, so I need to find a way to pass the DC to the DTMF encoder IC
>without loading down the DTMF audio signal.
>
>Have tried a resistor, but a 20K resistor was needed and the
>resultent DC voltage drop was too high.
>
>Tried to wind an inductor on a bit of ferrite and put it in series
>with the DTMF IC's power pin, nope that didn't work either.
>
>The tone decoder is an MT8870D
>
>Can anyone suggest a way that I can pass the DC to power the IC,
>whilst blocking the DTMF audio signal????????????
>
>Thanks in advance,
>
>Dwain.
If you can determine how small a resistor you can use in series with
"power in" then you can design an inductor to replace the resistor.
Note that the source of "V+" and the load "power in" both tend to short
out the audio DTMF tones.
If you need say 1 k of impedance at the "V+" source and at the "power
in" load then you need 1,000 = 2 * PI * 697 * L
or
L = 1,000 / (2 * PI * 697) = 228 mH
This is probably way more inductance than "an inductor on a bit of ferrite".
If the current is in the tens of mA range you might try using a small
audio transformer and use the 1,000 Ohm side as a choke.
Have Fun,
Brooke Clarke, N6GCE
>Date: Fri, 16 May 2003 05:46:30 -0000
> From: "dwainsworld2000" <dwainsworld@e...>
>Subject: miltiplexing question
>
>Hi Group,
>
>I have already asked one question about this, and thanks to the
>group I have my project ALMOST working.
>
>I am trying to control a group of lamps using only two wires. These
>wires must carry the control information and carry power and ground.
>
>So, I am encoding a DTMF signal that coresponds to which light I
>want to turn on, and sending it up the +V wire.
>
>Here's my circuit:
>
>
>
>BS2 .1uF .1uF DTMF RX'ER
>dtmfout
||
||
audio in
> | |
>+V
| |
power in
>
>
>Nothing new here really, two cap's todecouple the audio, whould work
>fine right??
>
>NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
>to zip.
>
>OK, so I need to find a way to pass the DC to the DTMF encoder IC
>without loading down the DTMF audio signal.
>
>Have tried a resistor, but a 20K resistor was needed and the
>resultent DC voltage drop was too high.
>
>Tried to wind an inductor on a bit of ferrite and put it in series
>with the DTMF IC's power pin, nope that didn't work either.
>
>The tone decoder is an MT8870D
>
>Can anyone suggest a way that I can pass the DC to power the IC,
>whilst blocking the DTMF audio signal????????????
>
>Thanks in advance,
>
>Dwain.
>
from a separate +5V regulator [noparse]:)[/noparse]
Original Message
From: "Tracy Allen" <tracy@e...>
To: <basicstamps@yahoogroups.com>
Sent: Saturday, May 17, 2003 1:04 AM
Subject: Re: [noparse][[/noparse]basicstamps] miltiplexing question
> Are you operating the tone decoder chip within its rated power supply
> range, off the +5 volts from the Stamp?
>
>
>
> >Hi Group,
> >
> >I have already asked one question about this, and thanks to the
> >group I have my project ALMOST working.
> >
> >I am trying to control a group of lamps using only two wires. These
> >wires must carry the control information and carry power and ground.
> >
> >So, I am encoding a DTMF signal that coresponds to which light I
> >want to turn on, and sending it up the +V wire.
> >
> >Here's my circuit:
> >
> >
> >
> >BS2 .1uF .1uF DTMF RX'ER
> >dtmfout
||
||
audio in
> > | |
> >+V
| |
power in
> >
> >
> >Nothing new here really, two cap's todecouple the audio, whould work
> >fine right??
> >
> >NOPE, the DTMF receiver IC power pin is dragging the DTMF audio down
> >to zip.
> >
> >OK, so I need to find a way to pass the DC to the DTMF encoder IC
> >without loading down the DTMF audio signal.
> >
> >Have tried a resistor, but a 20K resistor was needed and the
> >resultent DC voltage drop was too high.
> >
> >Tried to wind an inductor on a bit of ferrite and put it in series
> >with the DTMF IC's power pin, nope that didn't work either.
> >
> >The tone decoder is an MT8870D
> >
> >Can anyone suggest a way that I can pass the DC to power the IC,
> >whilst blocking the DTMF audio signal????????????
> >
> >Thanks in advance,
> >
> >Dwain.
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>