External connector options?

[TD22057]

What are people using for external sensor connectors? I'm planning on building multiple leak detector sensors and having each one support 3 leak sensors (2 wires) and 2 articulated valves (5 wires) along with a jack for an external power supply (2 wires). I'd like to have a connector on the outside of the sensor box that holds the arduino for each connection that is small, looks nice, is easy to use, and can't be confused (don't plug the power supply into the sensor input). Here are some of the options I've found so far. Generally I like the round connectors better since it's easier to mount a round jack (using just a drill bit) vs having to cut a square hole in a plastic box. Any other ideas I'm missing?

Micro USB: nice for power since micro usb cables are easy to come by. Hard to cut a square hole for mounting.

4 Pin JST plug: Maybe glue them flush to the outside of the box, don't look very nice.

2 wire JST Cheap, stick out a lot from the box, harder to mount?

12mm XLR plug: Easy to mount, various numbers of pins, locking, but somewhat large.

5mm locking power plug Easy to mount, locking, small, good for 2 wires. Or the non-locking version

I also looked at headphone style jacks butthey short across the connections when they're inserted and removed and can be noisy if rotated which I don't like at all.

[rvendrame]

@TD22057 , I'm at exactly same point right now. I do like the headphone jack ("P2"). It is very cheap and easy to get. I don't see too much problem with the short circuit , usually will do nothing else than re-booting the arduino (maybe it is a problem to you).

And If we follow the pinout like ring=gnd, middle=signal, tip=VCC, maybe the short will be only between VCC and signal?

Being not lockable is certainly a disadvantage of it, I have to agree.

I definitely would not go with DC power plugs or similar, nor micro-USB. I vote for round and simple plug.

[TD22057]

The two problems I've read about with headphone jacks are the short circuiting issue and that if you rotate them, they inject noise in the signal. So for digital pins - that's bad. Especially for my use case where a triggered signal will cause a water valve to shut off.

I agree the DC power plugs are the best, but it means building power cables (I'm using 2A regulated usb->5V power supplies) and I don't want to confuse sensor connectors with the power connector. At this point I'm probably going to try to make the USB connector work for the power, use the DC power jacks for my signal wires, and 5 pin XLR connectors for my pumps.

[rvendrame]

No, I would not go with DC plugs. Too risk of confusion. Regarding the 'rotating' and 'short-circuit' of P2 plug. Do you intend to touch them while the system is 'live'? Usually these sensors are a kind of 'install and forget'.

[TD22057]

I don't plan on it but the sensor or cable could get bumped which would cause them to rotate and I don't want that to shut off the water in that case.

[rvendrame]

Maybe you could program arduino to ignore short sparks in the readings.

[TD22057]

Perhaps. If I could figure out a way to make nice looking square holes in a plastic case, something like these wiring harness connectors would work well. They're cheap and are easy to use.

[rvendrame]

I don't have good experience with square holes. If you don't expect to plug/unplug the sensors so often --- maybe something like this? But you have to open a large hole and expose part of pcb to outside...

http://www.aliexpress.com/item/5pcs-10-Poles-10-Pin-2-54mm-0-1-PCB-Universal-Screw-Terminal-Block-Connector/32377294289.html

[b0rmann]

i use rj11 jack for sensors

[TD22057]

@b0rmann said:

i use rj11 jack for sensors

Also a good choice. But the question I'm really asking is how did you mount them in a plastic project box so they look nice? My experience with them is that they require a fairly precise square hole and can be glued in from the back so there is no covering for the edges of the hole.

[gregl]

I like these style...

http://www.aliexpress.com/item/Free-shipping-5-pin-interface-plug-12mm-GX12-5-core-cable-plug-connector-socket-5-sets/32247251729.html

You can get them in 2,3,4,5,6,7,8 pin configurations, they are keyed meaning you cant plug them in wrong.
I use 2pin for power , 3pin for temp sensors, and 8pin for interface - but its up to you what you choose.
Easy to use - solder the wires to the pins, and drill a round hole to mount.
Relatively robust and plug screws onto socket making them difficult to dislodge.

Cheap for what you get too!

[TD22057]

Thanks @gregl - those look just like the XLR connectors except they're cheaper. I ordered a selection of 2, 4, and 5 pin (GX12-2, GX12-4, and GX12-5) from this seller for ~$1/connector along with the locking 5.5 mm power plugs in my original posts.

[gregl]

No worries. They are a lot smaller than XLR connectors but im sure you realise that.

[TD22057]

I've been planning on using JST PH (2.0 mm pitch) connectors on my custom PCB's to connect the external connectors (GX12, 3.5 mm headphone jacks, 5.5 mm power sockets) from the sensor case to the board. They're nice in that they're fairly small, polarized, and cheap. But - you need to buy a good crimper - the pins are incredibly tiny. I almost decided to by the plugs with wires attached because they're so hard to crimp. None the crimpers I own was small enough so I ordered the (Engineer PA 09)]http://www.ebay.com/itm/Engineer-PA-09-Mini-Molex-Amp-JST-Crimp-Tool-Wire-Terminal-Crimping-Pliers-/252030460510?hash=item3aae2fa25e] which seems to be the cheapest "good" option.

Another option on the board (I wouldn't use these on the sensor case) are Dupont 2-pin connector. These "Dupont" connectors require a female pin (which is also really cheap) and push on to standard 0.1" pitch pins on a PCB (like the 4x2 NRF radios). They have the advantage that they use less space than the JST connectors but are not polarized. Search for "Dupont connector" on ebay to find tons of options. I can't decide if the easier crimping and less board space are worth the risk of mounting connectors backwards and potentially wrecking components.