Using RJ10 connectors for other data than intended

Question

I'm in the process of building a device for measuring various things, for instance humidity, temperature, soil moisture, etc.

Until now I've been using GX16 connectors to connect the sensors to the PCB. The GX16 connectors are a bit overkill for the purpose (3.3v , max 1A), they require a bit more soldering than I like and are a bit expensive.

I was wondering if there are any other 3pin / 4pin connectors that would be suitable for this purpose. I was thinking about using RJ10 connectors, since they are widely available, can be soldered directly onto the pcb and are relatively cheap. Now I know that these connectors are originally intended for telecommunication / phones, so it feels a bit "wrong" to use them for a different purpose.

Are there any other 4pin/3pin connectors available on the market that would be suitable for this purpose?

Currently I will just be using the device as a hobby project in my own house, but if I ever would want to bring the product to the market, would the misuse of the RJ10 connector be a issue?

Answer 1

This is acceptable. RJ10/RJ45/etc... are versatile and already used for multiple applications (phone, ethernet, RS-232, RS-485, CAN, whatever, ...), some of these applications being not really standardized, but commonly accepted. So you could add one more use of it without shocking people.

However, there are a few things to consider:

• The current capacity is usually small. And the wire gauge of premade cables is also small. If you need more than 200/300 mA on a wire, this is a problem.
• Cable that fits RJ10, unlike cat5 cable that goes with RJ45, is not usually organized in pairs. However, it is easy to mix RJ-anything cables with some existing cat5 infrastructure. So you must account for it. You don't explain what are the specific signals on your 4-wire connection, but if they are single-ended signals, there may be more crosstalk between them if you send two of your signals to the two wires of the same pair, rather than to two wires of two different pairs (in case the cabling is partially made with cat5). And if your 4-wire connection contains a differential pair, you should assign the pins appropriately so it ends up on physical pairs on cat5 cables. In short: take in consideration the fact that, in some infrastructures, a pair is formed with the two inner wires (pin 2 and 3), and another pair is formed with the two outer wires (pin 1 and 4).
• Once again, because your cabling could en up being mixed with some existing RJ infrastructure, you should take in consideration the voltage levels we can usually find in these infrastructures, in case a cabling error occurs. The most challenging one being the telephone voltage levels, than can hit ~90V when the phone rings. So if you really want to be safe, you should protect the circuit against these high voltage levels.