I'm just finishing the details on a front end amplifier for a semiconductor equipment vendor. It's in a fairly ugly EMI environment, with a bunch of switching motor controllers nearby, so I'm shipping the analogue output as a shielded differential signal.
For reasons of price/performance, I'm considering using a single normal-size HDMI connector for everything.
Any wisdom on which HDMI connectors are the best? The prices vary by more than a factor of 10, but it isn't obvious that the most expensive ones are the best.
I have previously used DVI cables and connectors, at what I learned a was that it is very limited what type of connectors you could get, i.e. only one gender for pcb another for cables, solder on only. and while it is specificed as an option getting ready made cables that are both dual link and analog is pretty much impossible
It'll be going between two boxes, a few feet apart, so ISTM that a normal HDMI connector on the front end box and another one in the back end box (or on a little breakout board at the far end) is probably superior to $50 connectors and $150 cables that I doubt will work as well.
However, I'm certainly open to other suggestions of how to get 2 coaxes and about 10 slow connections (power, ground, control, etc) into a box in a poor EMI environment, cost-effectively.
HDMI it would work fine, just don't do anything that isn't done in the "normal" application for the cable because then you might not get what you expect, i.e. pins that aren't used might not be wired, multiple grounds may actually be one wire
DVI might be better than hdmi, -I and -A has four coax in addition to the differential and control signals also it is a bit more robust with screws to hold it in etc.
SCSI cables are available that have known pairing and shielding. They may be a bit large for your application.
HDMI looks good, as long as you find a good and consistant supplier for the cables. The fast signals are shielded pairs, not literally coax, but that shouldn't matter. Run diff signals, or parallel the signal wires and pretend they are coax. YIMV.
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John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
I prefer chassis mount, because I want to make a break-out box. The STB's provided by Cox output HDMI video and audio, but they don't talk the handshake needed to turn downstream equipment on and off... a real PITA. I've read all the "standards" and think I can figure out how to fake the handshake. ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
One suggestion: if the "normal" HDMI pinout, as found on a DVD player, TV set, etc, includes any ground or power wires, you might arrange for those to go somewhere benign on your instrument. If you use an HDMI connector, then some day, somebody is going to say "LOOK A VIDEO OUTPUT LOL" and plug it into a TV set. It'd be nice if either nothing happens, or the TV blows up, rather than your instrument blowing up. :)
Sun did this for VGA-ish video around 1990 with the "13W3" connector: three co-axes and ten "regular" pins in a 25 pin D shell. I think the co-axes are usually 50 ohms nominal but others may be available.
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Digi-Key still stocks a few and drop-ships some more. They are $6 to $11 apiece, before you buy the co-ax inserts, so they may be more than you want to spend. You will also probably get to make the cables (or have them made). The bigger housing will make cable assembly easier, plus you have more choice of what co-ax to use.
A plain old HD15 VGA connector might even do what you want, depending on the frequencies you are using.
There is probably a reason for wanting a single connector (EMI, size, looks), but separate connectors would be really simple. TNC for one co-ax and BNC for the other, so it's harder for them to mix up the signals, and DB-9 for the control signals. Plus, it's easier to buy good BNC, TNC, and DB-9 cables off the shelf, repeatably.
I'm not sure I follow their product data. Do you have to use the Samtec jack to get the cable to lock? That is, you can't just use this cable with existing HDMI jacks and expect the cable to lock.
That's how I've solved this kind of problem in the past - "mixed signal" D-shells or DIN-41612 connectors can accommodate a useful collection of coax and conventional pins. Don't forget that the coax- sized holes can also accommodate high-current power pins. Newark/ Farnell stocked a useful range if bits when I last looked. Not all that cheap, and you can't do IDC on the small diameter pins.
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