They are not meant for this kind of thing, but they are used for this kind of thing all the time.
Since you have 9 pins, put a bunch of pins in parallel (4 for each solenoid wire) and you should be quite OK since they will share the current.
Unless, of course, someone thinks that this connector is a serial port and tries to connect it to a PC using a serial cable. Then there will be surprises.
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The Aussie Shield: breakout all 28 pins to quick-connect terminals
Looks is my primary goal here. So the aussie shield won't do. I want my enclosure (picture attatched) to have nice panel mount jacks for my gearmotor, a solenoid, and a flowsensor.
The soenoid (watervalve) and flowsensor are right next to each other, so one cable going that direction (3' cable is about the distance I'll have) The flow sensor uses V+, Gnd, and Signal; the Solenoid uses V+, and Gnd, so a 4 conductor would work, a 5 conductor would be ideal. I could do them all in 1/8" headset jacks, which handle 1 amp I believe.
...still looking for a visually pleasing panel mount jacks.
DB9's will easily handle that current. I use them as stepper motor connectors for my CNC router running 3 amps. Just make sure you use a cable with and appropriate wire size. Most computer cables are not heavy enough.
I think I'm going to go with 2 RJ45 plugs. I need 5 wires going to my gearmotor and opti-detector, and then 5 wires going to a 575 mA solenoid and water flow sensor. The gearmotor only draws 90 mA, but could stall at 800mA.
Different specs I see show the RJ45 plugs to be rated at 1.5 A. I like Cat 5 wire, too, as it's a heavier guage than a lot of these serial cables I've cut apart to interrogate. Most of them are 28 gauge.
I can get RJ45 pcb mountable, and put them on my protoshield, so they line up with the Arduino's USB and DC jack. It'll all come out the back of the enclosure.
Does RJ45's sound like they'd work?