I'm a total beginner when it comes to soldering, and recently I've been trying (and failing) to solder together a simple circuit I put together for a Raspberry Pi sensor.

[<img src="https://i.sstatic.net/B75uX.jpg" width="300" alt="circuit on a breadboard" />][1]

Although it works fine on the breadboard, when I solder it onto one of my [perfboards][2], the sensor no longer turns on.

[<img src="https://i.sstatic.net/KT5K2.jpg" width="300" alt="Circuit on a perfboard" />][3]

Here is a topdown view of my soldered circuit:

[<img src="https://i.sstatic.net/iCkry.jpg" width="300" alt="Connections" />][4]

Here is a view of the connections (the red block is just covering up old connections from past attempts):

[<img src="https://i.sstatic.net/UbThX.jpg" width="300" alt="Connections" />][5]

More pictures of the connections.

What might I be doing wrong?

  [1]: https://i.sstatic.net/B75uX.jpg
  [2]: https://en.wikipedia.org/wiki/Perfboard
  [3]: https://i.sstatic.net/KT5K2.jpg
  [4]: https://i.sstatic.net/iCkry.jpg
  [5]: https://i.sstatic.net/UbThX.jpg