Introduction: Power Your Mindstorms NXT Brick With a 9V Wall Adapter.

About: I'm a social-worker, working with 12 - 23 year-olds. I used to be a printer. In 2018 I opened a small makerspace ( in my house, where I have lasercutters, 3d-printers, Arduino's, Mindstorms and ot…

For this holiday, I bought myself an old second hand Mindstorms NXT to play with. It just sounded like more fun than spending my money on fireworks and alcohol.

Just playing with it, I noticed that you can go through quite a lot of batteries, just experimenting and programming this smart brick. There must be a better way, so I designed a 9V wall adapter mount for my NXT smart brick.

***** WARNING! This ible is just to show you how I managed to power my Mindstorms NXT. If you try this yourself and blow up or damage your Mindstorms, than I won't be responsible for that. *****

Step 1: You Will Need


  • wire
  • 9V wall adapter
  • plug
  • 2 M3 bolts, washers and nut


  • 3D-printer
  • soldering material
  • pliers
  • hot glue gun

Step 2: Printing the Battery Lid Replacement

I really like to draw and design parts like this in 123D-design.

My first design warped to bad in the printer, so the final design has all the slits in it to prevent this.

The part really looks cool and even better, fits the Mindstorms brick like a glove.

On the final part I used the nice orange color to make it stick out and I think it looks nice next to the other orange parts in the NXT set.

Both the 123D and STL files are included.

Step 3: Salvaging the Plug

I found an old broken toy to salvage the plug from. It took some heavy desoldering to get the part out, but it was a perfect fit with my 9V adapter.

Step 4: Wiring It Up

For the connectors I used 2 3mm bolts.

One bolt has to be long enough to go all the way through the hole, with a washer and nut on the other end.

For the other bolt was not enough space, so I used a shorter bolt with the wire soldered directly to it.

  • Solder the negative, black wire to the short bolt. It is hard to solder to a bolt so it might be more like sticking it to it than really soldering. This is not a big problem.
  • Feed the wire and the bolt through the hole.
  • Solder the other end of the black wire to the outer connector on the plug. (normally the outer connector on a adapter is the negative and the inner the positive. CHECK THIS!)
  • Solder the red, positive wire to the inner connector on the plug.
  • Put the long bolt through the other hole.
  • Put a washer on the bolt.
  • Coil the other end of the red wire around the bolt.
  • Put a nut on the bolt to hold both the bolt and the red wire in place.
  • Glue the plug, directly behind the hole with the short bolt in it. (I had to snip off one lip to get it to fit)

Step 5: Turn Your Mindstorms NXT on Without Batteries

  • Remove the battery lid
  • Remove the batteries :)
  • Carefully place the replacement lid. (this is a bit hard to do right. LEGO has special instructions on how to place their accu-pack. Placing this replacement lid is the same)
  • Check the polarity and voltage on your wall adapter!!! In my design the positive must be on the inside and negative on the outside. The adapter must be 9V direct current.
  • Plug the adapter in the plug. (this is your own responsibility. If something goes wrong, than I'm sorry, but you should understand enough of what you are doing, before trying something like this. Your Minstorms smart brick is to expensive to mess with)
  • Your Mindstorms NXT smart brick should power up now :)

Now you can play with your Mindstorms without replacing batteries every day. Have fun!