Today's Message Index:
----------------------
1. 08:54 AM - Re: Constructing an automatic RCA video camera feed splitte (Eric Page)
2. 10:13 AM - Re: Re: Constructing an automatic RCA video camera feed splitte (Alec Myers)
3. 10:38 AM - Re: Constructing an automatic RCA video camera feed splitte (Eric Page)
4. 03:36 PM - Inexpensive voltage data logger (GTH)
5. 04:53 PM - Re: Inexpensive voltage data logger (Alec Myers)
6. 04:59 PM - Re: Inexpensive voltage data logger (Robert Borger)
7. 05:06 PM - Re: Re: Constructing an automatic RCA video camera feed splitte (Robert L. Nuckolls, III)
8. 11:32 PM - Re: Inexpensive voltage data logger (Eric Page)
Message 1
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Subject: | Re: Constructing an automatic RCA video camera feed |
splitte
alec(at)alecmyers.com wrote:
> I think were ok. That section is either wrong, or badly written, I cant work
out what its trying to say either. But:
>
> Look at table 1 in para 8.4 - control L gives High-Z at the output.
True, and that line of Table 1 is the most recent item on the revision history.
However, the second paragraph of the intro (Sec 3, pg 1) and paragraph 8.1 (pg
14) are consistent in their description of the outputs; that is, tied to either
Vdd when Vc is high, or to Vss when Vc is low. I presume "high" means Vc
= Vdd and "low" means Vc = Vss; that's certainly what many of the diagrams suggest.
If, as Bob says, the NTSC signal we're working with is DC biased and exists entirely
above 0V, then we can use a single supply and it shouldn't be an issue.
That will simplify the schematic, shrink the BoM and ease the layout.
There are apparent errors elsewhere in the datasheet as well. Fig 5 (pg 9, Typical
ON Characteristics) includes a wiring diagram that shows -- as you would
expect -- Vc = Vdd. However, Fig 9 (pg 10) depicts the test setup for this measurement
and it shows Vc = Vss = -5V. Then Fig 10 (pg 11, OFF Switch Input or
Output Leakage) shows exactly the same setup, with Vc = Vss. Apparently the
outputs can be ON or OFF with the control high or low. This must be a quantum
device!
This datasheet is a mess.
I guess we stand by for results of Bob's test with a sample camera, and Wade's
test with multiple cameras through a switch...
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473706#473706
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Subject: | Re: Constructing an automatic RCA video camera |
feed splitte
The code is 90% done. Ill do the other 90% in due course.
On Oct 20, 2017, at 11:53, Eric Page <edpav8r@yahoo.com> wrote:
alec(at)alecmyers.com wrote:
> I think were ok. That section is either wrong, or badly written, I cant work
out what its trying to say either. But:
>
> Look at table 1 in para 8.4 - control L gives High-Z at the output.
True, and that line of Table 1 is the most recent item on the revision history.
However, the second paragraph of the intro (Sec 3, pg 1) and paragraph 8.1 (pg
14) are consistent in their description of the outputs; that is, tied to either
Vdd when Vc is high, or to Vss when Vc is low. I presume "high" means Vc
= Vdd and "low" means Vc = Vss; that's certainly what many of the diagrams suggest.
If, as Bob says, the NTSC signal we're working with is DC biased and exists entirely
above 0V, then we can use a single supply and it shouldn't be an issue.
That will simplify the schematic, shrink the BoM and ease the layout.
There are apparent errors elsewhere in the datasheet as well. Fig 5 (pg 9, Typical
ON Characteristics) includes a wiring diagram that shows -- as you would
expect -- Vc = Vdd. However, Fig 9 (pg 10) depicts the test setup for this measurement
and it shows Vc = Vss = -5V. Then Fig 10 (pg 11, OFF Switch Input or
Output Leakage) shows exactly the same setup, with Vc = Vss. Apparently the
outputs can be ON or OFF with the control high or low. This must be a quantum
device!
This datasheet is a mess.
I guess we stand by for results of Bob's test with a sample camera, and Wade's
test with multiple cameras through a switch...
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473706#473706
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Subject: | Re: Constructing an automatic RCA video camera feed |
splitte
nuckolls.bob(at)aeroelect wrote:
>
Bob, I'm having trouble making sense of this graph. I read the National Instruments page (http://www.ni.com/white-paper/4750/en/) it comes from, but I'm not sure I've got it straight. See if this sounds right...
The Y axis ("IRE") is a somewhat arbitrary unit. That is, zero IRE is "usually
0V" but (by implication) it doesn't have to be. The zero-reference and blanking
level in the signal is set by the "back porch" following the horizontal sync
pulse, so any DC offset within reason is automatically compensated by the nature
of the format. As long as the signal is pretty close to 1V pk-pk, it doesn't
matter if it's centered on 0V -- or, as we're proposing, on 2.5V -- the
zero point is wherever the "back porch" sits.
So, if you find a signal from your test camera that's riding somewhere between
0V and 3.3 or 5V, and we power the CD4066 from a single 5V rail, we should be
in good shape.
Since the IRE scale spans -40 to +120 in the NTSC format, and an NTSC signal is
supposed to be 1V pk-pk (into 75 ohms), then you could say that 1 IRE = 12.5mV.
Is that in the ballpark?
Thanks!
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473711#473711
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Subject: | Inexpensive voltage data logger |
Hi all,
For troubleshooting purpose we would like to log the bus voltage on our
project.
I was directed to this product which seems quite suitable :
https://www.maplin.co.uk/p/maplin-usb-dc-voltage-data-logger-n70dp
Unfortunately they don't ship outside the British Isles.
Does anyone know a more easily available device ?
Thanks in advance,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 5
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Subject: | Re: Inexpensive voltage data logger |
Ill be in the UK second week in November; I can bring one back for you, if you
can wait.
Theres a more sophisticated thing with wifi called a Mooshimeter, but its expensive.
Also Adafruit might have a variety of parts you can use/program.
On Oct 20, 2017, at 6:35 PM, GTH <gilles.thesee@free.fr> wrote:
Hi all,
For troubleshooting purpose we would like to log the bus voltage on our project.
I was directed to this product which seems quite suitable :
https://www.maplin.co.uk/p/maplin-usb-dc-voltage-data-logger-n70dp
Unfortunately they don't ship outside the British Isles.
Does anyone know a more easily available device ?
Thanks in advance,
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
Message 6
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Subject: | Re: Inexpensive voltage data logger |
Giles,
Here=99s what is available on Amazon:
https://smile.amazon.com/s/ref=nb_sb_noss_2?url=search-alias%3Daps&fie
ld-keywords=voltage+data+logger
<https://smile.amazon.com/s/ref=nb_sb_noss_2?url=search-alias=aps&fi
eld-keywords=voltage+data+logger>
If would be happy to purchase one of them for you if you can not buy it
from France.
Blue skies & tailwinds,
Bob Borger
Europa XS Tri, Rotax 914, Airmaster C/S Prop (75 hrs).
Little Toot Sport Biplane, Lycoming Thunderbolt AEIO-320 EXP
3705 Lynchburg Dr.
Corinth, TX 76208-5331
Cel: 817-992-1117
rlborger@mac.com
> On Oct 20, 2017, at 5:35 PM, GTH <gilles.thesee@free.fr> wrote:
>
>
> Hi all,
>
> For troubleshooting purpose we would like to log the bus voltage on
our project.
>
> I was directed to this product which seems quite suitable :
>
> https://www.maplin.co.uk/p/maplin-usb-dc-voltage-data-logger-n70dp
>
> Unfortunately they don't ship outside the British Isles.
>
> Does anyone know a more easily available device ?
>
> Thanks in advance,
>
> --
> Best regards,
> Gilles
> http://contrails.free.fr
> http://lapierre.skunkworks.free.fr
Message 7
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Subject: | Re: Constructing an automatic RCA video camera |
feed splitte
At 12:37 PM 10/20/2017, you wrote:
>
>
>nuckolls.bob(at)aeroelect wrote:
> >
>
>
>Bob, I'm having trouble making sense of this graph. I read the
>National Instruments page (http://www.ni.com/white-paper/4750/en/)
>it comes from, but I'm not sure I've got it straight. See if this
>sounds right...
>
>The Y axis ("IRE") is a somewhat arbitrary unit.
Yeah, it's dimensionless . . . like dB in
audio, it describes
a ratio of voltages for video painting a
max white, black, blacker-than black, burst
amplitude and sync amplitude.
>That is, zero IRE is "usually 0V" but (by implication) it doesn't
>have to be. The zero-reference and blanking level in the signal is
>set by the "back porch" following the horizontal sync pulse, so any
>DC offset within reason is automatically compensated by the nature
>of the format.
I think I understand your assertion . . . I've seen
various ways for video to be transported on a DC
stable reference. The time base correctors I used
to build had three points of dc restoration as
the signal progressed through the system. One is
advised to do this so that variations in gross
video energy don't manifest as momentary
blooms or potholes in observed luminance.
You can find video being managed at various
voltage levels, 1 v pk-pk in 75 ohms was adopted
for shipping video around studios and stations
on coax. This is equivalent to the legacy "0
VU" in audio systems being pegged at about 1.25
vrms across 600 ohms.
On further reflection (it's been 30 years or
so) I decided to refresh my recollection about
the 1 v pk-pk number. Found this little diddy
on RS-170, the industry convention for television
signals.
http://tinyurl.com/382a25m
According to this paper, the 1v value was originally
crafted in the black-n-white days where 1v = 100
IRE
RS-170 was the original "black-and-white" television signal
definition, per EIA. The original standard defined a 75 ohm system
and a 1.4 volt (peak-to-peak, including sync) signal. Signal level
specifications form RS-170 were: White = +1.000V; Black = +0.075V:
Blank = (0V reference): Sync - -0.400 Volts.
In this world, the conversion would be 10Mv/IRE
Read more at:
<http://www.epanorama.net/documents/video/rs170.html>http://www.epanorama.net/documents/video/rs170.html
So after you took a 'clean' white level of 100
IRE and added 40 IRE of sync, you had a 1.4 volt
pk-pk signal in 75 ohms
When color came along, the various levels of luminance
from black to white COULD be enhanced with some hue and
saturation of COLOR carrier that might add another 40
IRE to the white level. So add sync to that and you're
up to 180 IRE or perhaps 1.8v pk-pk.
It will be interesting to see how the cameras are supplied.
Most monitors are able to accept and accurately display
signals from 0.5 v pk-pk to perhaps 4 volts . . . after
all, it's just a 'volume control'.
The the ratio of elements in the audio stream
remains the same irrespective of actual power
or transmission impedance. IRE is video analog
to audio VU or DB.
>As long as the signal is pretty close to 1V pk-pk, it doesn't matter
>if it's centered on 0V -- or, as we're proposing, on 2.5V -- the
>zero point is wherever the "back porch" sits.
>
>So, if you find a signal from your test camera that's riding
>somewhere between 0V and 3.3 or 5V, and we power the CD4066 from a
>single 5V rail, we should be in good shape.
>
>Since the IRE scale spans -40 to +120 in the NTSC format, and an
>NTSC signal is supposed to be 1V pk-pk (into 75 ohms), then you
>could say that 1 IRE = 12.5mV.
>
>Is that in the ballpark?
Yup, the cameras we're looking at are fitted
with coaxial termination that is, no doubt,
intended to work smoothly with the constellation
of video products in a 75 ohm world.
It will be interesting to see what the cameras give us.
Bob . . .
Message 8
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Subject: | Re: Inexpensive voltage data logger |
I've played around with one of these a bit and it seemed to work quite well.
http://preview.tinyurl.com/ya7pg9sg
I do believe it has to be plugged into a computer at all times while operating;
I don't think you can just set it up and power it from a dumb USB power supply.
Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=473727#473727
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