Opinions on using D-Sub connectors for power signal distribution?

[MrBungle]

I'm thinking of using D-sub connectors to standardise on power and signal distribution in a few projects I'm working on. Let me be clear that this is NOT RF signals but power, keying and switching only. RF is going over SMA connectors. I've found some Amphenol FCI connectors that are good to 1kv or 5A. I'd probably not put more than a couple of amps through one 12v or so. RS parts 251-728 and 251-756.

Is this is a good or bad idea?

[cmjones01]

They'll be fine. I wouldn't put 5A through all pins simultaneously, but a couple of amps on a couple of pins won't be a problem. They're available in a wide range of qualities, so if the ordinary cheap-and-cheerful ones turn out not to be up to the job, it's easy enough to upgrade to a better quality. You can't say that about many types of connector!

Chris

I find them very useful for your application, one or two amps per pin. 500V isolation etc. And you can get the hardware to screw them in place. Even RF up to a few 100MHz is ok using adjacent ground pins (AC ground, a power connexion will do). Don't do what I did, putting a large smoothing cap at each end, all is fine until you re-connect, a bit of a flash/bang, mind you the connector has survived.

I have put USB2 (400MHz ish) and ethernet (125MHz) through them without problems, all in all a bloomin' good connector, cheap too.

[MrBungle]

Excellent. Thank you both. This looks like a win. Good point with the capacitors; I hadn't thought of that and haven't designed bleeder resistors in yet. Have added to list!

They do ones with coax sub-connectors by the looks as well although they are a bit pricey!

[vidjoman]

If you've got spare pins you could double up the power supply pins.

[MrBungle]

That's a good idea. I've now got pins marked down as:

1. +12V
2. +12V
3. GND
4. GND
5. TX
6. RX
7. KEY
8. PTT
9. Unused (I will forget something!)

Nothing digital in this rig

[Refugee]

Originally Posted by MrBungle

They do ones with coax sub-connectors by the looks as well although they are a bit pricey!

They sure are pricey and after all that the coax pins cost extra money.

9. Unused (I will forget something!)

Been there, done that! use a 15 way (also less likely to be plugged into an RS32 port). And also look at the pinning 1, 2, 6 & 7 GND ?

[MrBungle]

Good plan with the 15 way and the pin arrangements. Thank you

[kalee20]

They're good connectors, as per previous comments! Generally I go for turned pin versions.

May be better to have pin 1, pin 2 b+12V and pins 6, 7 GND. That way the 'go' and 'return' are right opposite each other. And put unused pins near the middle - it's much easier to solder to the outside pins, so use them and leave the awkward one (pin 3 on a 9-way) as a spare!

Leave spares easy to do (the end pins), it's always an 'emergency'.

[turretslug]

There was even a version of "standard" 9-pin "D" sold for mains use with red insulation and just 4 pins loaded (L,N,E, signal/chassis ground), I've also worked with modular '70s kit that used standard 9-pin types on PSU bricks for mains in combined with DC power out.

Both approaches would get stern frowns and short shrift now, but they were obviously deemed OK at the time. Agree with others that they represent a good, inexpensive, widely-available solution for multi-rail distribution within common-sense bounds.

[G6Tanuki]

"D"-connector variants with appropriate connector-loadings are used professionally to handle mains and RF; look in something like a RACAL RA217 receiver for an example.

The Plessey "Clansman" PRC320 also uses them for inter-module wiring, including the 24V power-supply to the PA stage (which puts out 30W of SSB so is probably drawing 5 amps peak current...)

In the past, wide-bandwidth RGB+Sync video was also fed through the coax-pins in D-connectors - late-1980s Sun monitors did this (and charged an arm and a leg for the replacement D-plug-to-BNC-fanout connecting cable if you damaged it!)

I'd hesitate to put mains or RF straight on the standard 9- 15- or 25-way ones though!

[MrBungle]

I remember the 13W3 based framebuffers in sun4 machines. Those machines were the little devils that lured me into the IT trade instead of EE. Silly mistake that was.

Lots of interesting information here. Definitely feel like I'm on the right track now. Thank you everyone.