dip type reed relays as video switch

Guest
Hi Group,

Can I use a common dip reed relay to switch in/out video signals?

I would use two per channel, one would be in serial and the other used
as a shunt to ground. To enable the video, I would turn on the series
reed and open the shunt reed.

To turn off the channel, I would open the series reed and turn on the
shunt reed.

The input would be terminated into 75 ohms.

Being that video is 6MHz BW, I would expect a reed relay to work but I
would like the advice of the group.

Thanks,

PDRUNEN
 
On 1 Mar 2005 21:05:04 -0800, in sci.electronics.design
pdrunen@aol.com wrote:

Hi Group,

Can I use a common dip reed relay to switch in/out video signals?

I would use two per channel, one would be in serial and the other used
as a shunt to ground. To enable the video, I would turn on the series
reed and open the shunt reed.

To turn off the channel, I would open the series reed and turn on the
shunt reed.

The input would be terminated into 75 ohms.

Being that video is 6MHz BW, I would expect a reed relay to work but I
would like the advice of the group.

Thanks,

PDRUNEN
I dont think that there is any problem, just look at the capacitance
Click to expand...
of the open contacts, and you can work out the crosstalk/breakthrough.
My favorite relay company (Pickering)make VHF reed relays that are
quite adequate for video.

The only prob would be that if you try to switch during syncs, they
may not be fast enough, and the on time is generally faster than the
switch off time, a potential shorting problem, but the overlap
shouldnt cause any significant problem for a 75R system

martin

"An eye for an eye makes the whole world blind"
Gandhi
 
On 1 Mar 2005 21:05:04 -0800, pdrunen@aol.com wrote:

Hi Group,

Can I use a common dip reed relay to switch in/out video signals?

I would use two per channel, one would be in serial and the other used
as a shunt to ground. To enable the video, I would turn on the series
reed and open the shunt reed.

To turn off the channel, I would open the series reed and turn on the
shunt reed.

The input would be terminated into 75 ohms.

Being that video is 6MHz BW, I would expect a reed relay to work but I
would like the advice of the group.

Thanks,

PDRUNEN
Click to expand...
Reeds are horrible. Just use a single small relay, like an Aromat TQ
or something. There are lots of similar parts in Mouser and Digikey.

John
 
In article <4225C523.514F964B@earthlink.net>,
"Michael A. Terrell" <mike.terrell@earthlink.net> wrote:

pdrunen@aol.com wrote:

Hi Group,

Can I use a common dip reed relay to switch in/out video signals?

I would use two per channel, one would be in serial and the other used
as a shunt to ground. To enable the video, I would turn on the series
reed and open the shunt reed.

To turn off the channel, I would open the series reed and turn on the
shunt reed.

The input would be terminated into 75 ohms.

Being that video is 6MHz BW, I would expect a reed relay to work but I
would like the advice of the group.

Thanks,

PDRUNEN

Relays work ok, but there are nice ICs made to select video. Maxim
and others provide a wide range of input to output combinations,
including ones with built in buffers. Board layout is simpler, and a
failure is quickly fixed by replacing a chip or two instead of a handful
of relays.

One word of warning about using relays. Over time they will become
erratic and are a pain in the ass to troubleshoot when you get different
faults at different times. I worked on products that used dip relays
for video to 10 Mhz and they were a pain. In this case they were used
to select the input and output of 10 bandpass filters.
Click to expand...
Many years ago I designed a TV line grabber for use in a lab. I could
select one of the lines of video and display it on an oscilloscope. I
did the switching using CMOS 4051 chips. Worked great. I suppose they
are no longer available. Yes, and I did it like the suggestion above,
one in series with the line and one shunt to ground. Open series, ground
input line. Open ground, close series.

Al
 
Al wrote...
Many years ago I designed a TV line grabber for use in a lab. I could
select one of the lines of video and display it on an oscilloscope. I
did the switching using CMOS 4051 chips. Worked great. I suppose they
are no longer available. Yes, and I did it like the suggestion above,
one in series with the line and one shunt to ground. Open series,
ground input line. Open ground, close series.
Click to expand...
Not only are 4051 chips still available, they're quite popular
and are available in perhaps a dozen different technologies,
each with various aspects to recommend them, such as 18 to 20V
signal range (CD4051, MC14051), or 30-ohm Ron, 12 to 15V range
(74HC4051), or supply-operation down to 2.5V (74LVXT4051) or 2V
(74AHC4051). The lower Ron parts tend to have higher capacitance.

I'm a big fan of another member of the family, the '4053 series
of triple single-throw switches.


--
Thanks,
- Win
 
On 3 Mar 2005 06:04:28 -0800, Winfield Hill
<hill_a@t_rowland-dotties-harvard-dot.s-edu> wrote:

Al wrote...

Many years ago I designed a TV line grabber for use in a lab. I could
select one of the lines of video and display it on an oscilloscope. I
did the switching using CMOS 4051 chips. Worked great. I suppose they
are no longer available. Yes, and I did it like the suggestion above,
one in series with the line and one shunt to ground. Open series,
ground input line. Open ground, close series.

Not only are 4051 chips still available, they're quite popular
and are available in perhaps a dozen different technologies,
each with various aspects to recommend them, such as 18 to 20V
signal range (CD4051, MC14051), or 30-ohm Ron, 12 to 15V range
(74HC4051), or supply-operation down to 2.5V (74LVXT4051) or 2V
(74AHC4051). The lower Ron parts tend to have higher capacitance.

I'm a big fan of another member of the family, the '4053 series
of triple single-throw switches.
Click to expand...
Caution. The high voltage versions operated with large VDD-VSS and
relatively small signals will yield the best distortion. (Observe the
data sheet Ron versus signal voltage.)

My preference is toward tri-stated buffer amplifiers.

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.
 
Al wrote:
Many years ago I designed a TV line grabber for use in a lab. I could
select one of the lines of video and display it on an oscilloscope. I
did the switching using CMOS 4051 chips. Worked great. I suppose they
are no longer available. Yes, and I did it like the suggestion above,
one in series with the line and one shunt to ground. Open series, ground
input line. Open ground, close series.

Al
Click to expand...
the 4051 is still available, but I prefer using the matrix chips with
buffers. 8 * 8 with buffered outputs in one chip makes a clean layout
and reduces the assembly time. My preferences come from a background in
TV broadcast where 32 in, 24 out and larger switcher / routers are
common. Phase shift, noise and distortion are critical in a studio
setting as well.
--
Cyber stalking is a crime!

Michael A. Terrell
Central Florida
 
pdrunen@aol.com wrote:
Hi Group,

Can I use a common dip reed relay to switch in/out video signals?

I would use two per channel, one would be in serial and the other used
as a shunt to ground. To enable the video, I would turn on the series
reed and open the shunt reed.

To turn off the channel, I would open the series reed and turn on the
shunt reed.

The input would be terminated into 75 ohms.

Being that video is 6MHz BW, I would expect a reed relay to work but I
would like the advice of the group.

Thanks,

PDRUNEN
Click to expand...
Relays work ok, but there are nice ICs made to select video. Maxim
and others provide a wide range of input to output combinations,
including ones with built in buffers. Board layout is simpler, and a
failure is quickly fixed by replacing a chip or two instead of a handful
of relays.

One word of warning about using relays. Over time they will become
erratic and are a pain in the ass to troubleshoot when you get different
faults at different times. I worked on products that used dip relays
for video to 10 Mhz and they were a pain. In this case they were used
to select the input and output of 10 bandpass filters.

--

Michael A. Terrell
Central Florida
 
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