# How do I reliably connect power, ground and signal to a remote device?

I am building an arduino-based multi-event (light, sound, vibration) high speed photo trigger. I'd like to house the arduino and display in one box, then be able to connect a remote sensor device to the main box.

+-----------+
|  arduino  |     5v, GND, signal    +----------+
|     +     |========================|  sensor  |
|  display  |                        +----------+
+-----------+


I had considered using a 3.5" TRS cable, but it seems there would be a risk of a short when plugging and unplugging the cable. Is there a better connector/cable combination I could use to connect these together in a way that can be (dis)connected very easily?

You want to look at connectors with "ip67" protection to fully protect against dust and water immersion. If all you need is "resistance" to dust and splashes, "ip54" is about as low as you'll want to go. (Wikipedia on IP ratings) Note that the ratings assume you assemble cabling correctly with the right diameter cable, heat shrinking, possible gaskets, cable sleeve rating, etc.

These connectors will then come with some number of pins -- choose as many as you need (from 3 and up.) Also, the pins will have current ratings; choose a current rating that is suitable for your power needs. Finally, you need a mating set of male and female in both ends.

Many applications use round connectors (think "XLR" from audio) with screw rings to securely tighten the plug to the socket on each end. You can start looking on Digi-Key for ready-made cables, if you don't want to be poking connecting pins into sockets yourself before you start soldering...

• Where is the requirement for this to be waterproof? – Cybergibbons Mar 3 '13 at 21:16
• "reliable" is a very wide area. Personally, I find cables that fail because I spill coffee on them to be "unreliable." Your requirements may be different. – Jon Watte Mar 4 '13 at 23:36
• So USB, HDMI, VGA, XLR, all household mains sockets are unreliable? – Cybergibbons Mar 5 '13 at 20:10
• I've had USB, HDMI, and mains connectors fall out and need re-inserting, so I'd say yes, those are unreliable (for cost reasons.) VGA and XLR only do that if you don't use a locking version. The locking versions are also typically splash proof (often IP54 equivalent.) The normal NEMA 5-15R connector is IP52, which is rated against dust and light splashes. – Jon Watte Mar 6 '13 at 21:31
• So every computer built in the last 5 years, by design, is unreliable as they use those connectors heavily? It's a very odd call to decide high IP ratings is the primary goal of the question. – Cybergibbons Mar 7 '13 at 10:21

I feel like you are looking for a very straightforward answer. So the first thing that comes to my mind would be D-Sub connectors.

A DB9 connection would give you 9 connections, 2 of which you could dedicate to power and ground, and the rest can be used for whatever type of signal you are looking to transmit.

To keep things simple you could buy a DB9 cable assembly, and then just get 2 receptacles (one for each end of cable). This way you don't have to worry about soldering the cable, but you will still have to solder the connections that go to your Arduino/Sensor Box.

I use these in most of my projects and have never had any issues, that being said they would not be well suited for outdoor use.