Stranded Wire Connection

I ordered some humidity sensors from Amazon that have the typical thru-hole pin connection (0.1mm) (

I would connect this sensor to my Arduino with some stranded wire (about 24") since I'll be running it away from MCU. I was wondering how to make a good connection between the stranded wire and the sensor (I'll be using a terminal block from the MCU to the stranded wire).

The sensor is very small, so I can't solder a terminal block on it. I was looking at wire ferrules and considering soldering those into the sensor hole with wire crimped inside of it. And the easiest route I think is to simply solder the stranded wire directly into the hole and put some heat shrink around the exposed part.

Any suggestions? I plan on putting this humidity sensor inside of a very small plastic case with a small hole drilled in it so that I can measure humidity (exposing the sensor). I was also going to hot glue the insulated part of the wire onto the plastic case to relieve stress.

You can get 0.1" terminal blocks. Sparkfun and Adafruit sell them.

You can solder stranded wire direct to PCB pads. If it is very thick, cut strands off until it fits. This is the worst option. Vibration and time will break the wire.

You can solder in a "post" and then wire-wrap to that. Wire-wrap is an almost-forgotten connection technology.

You can solder wires to the pads on the board.
You can solder the header to the board and add a Dupont connector to the wires.

Google "i2c wire" and it will show you the shielded wire size to use.


Hmm thanks for the suggestions! Would it be bad to solder a wire ferrule into the sensor pad? I can't fit a terminal block onto the sensor even with 0.1" blocks (the sensor breakout board is too small).

Also, I know it's a different question, but do you guys have a suggestion for enclosing the humidity sensor? I don't think I can just expose it directly (it'll be in pretty high humidity conditions indoors - growing oyster mushrooms with a humidifier).

Should I just cover the entire board with clear nail polish with the exception of the actual sensor and then put it into a small ABS polycase with some drilled holes?

Show us the wire ferrule. Use proper link tags so we don't have to copy-paste the link.

Or just try it. The Arduino environment is for learning by doing.

Here is the humidity sensor:

Amazon Humidity Sensor

And here's the wire ferrule kit I purchased:

Amazon Wire Ferrule Kit

Thanks so much for the help. I definitely plan on trying it out, but I just figured I'd post here first.

I am pretty sure those ferrules are ridiculously too large to fit into the sensor module holes.

The technique I use is to strip just a few mm of the stranded wire (obviously not over-size for the purpose). I then twist the exposed ends and tin them. The next step is to grab the tinned part in pliers and pull the insulation back further, again twisting the newly-exposed section which I then tin a second time. While the wire is hot and the insulation still soft, I then allow the insulation to slide back over the tinned section and "encourage" it to do so. I then solder the wire into the board.

This means that the wire at the point where the insulation stops which is butted against the board, is reinforced by the solder and more able to resist bending. This is the point where bending stress is focused and where it will be likely to break, so the reinforcement is critical.

If movement of the wires is likely, you can also cover the point of attachment with hot melt glue.

Sounds great! Thanks all!