Jonathan Thomson's web journal

How to Replace the LED in the Victorinox Midnite Minichamp March 21, 2010

Filed under: Electronics — jethomson @ 5:08 am

Warning: Removing the cover too many times can result in it no longer fitting tightly to the knife. My cover fell off one day and I lost my battery and battery compartment door. It’s probably a good idea to use a bit of glue to make sure the cover stays when you put it back on.

The Victorinox Midnite Minichamp is a damn useful Swiss Army knife. It’s cut and picker blade is very useful for stripping wires when a proper wire stripper isn’t available. It also has a retractable pen and an LED light. The newer ones use a white LED, but I bought mine many years ago, before low cost white LEDs became available, so it has a weaker red LED. A red light can be beneficial if you want to preserve your night vision while reading constellation maps when stargazing. However, that is a very specific purpose and there have been many times I could have used a brighter light. Therefore, I’ve wanted to replace the Minichamp’s red LED for a long while, but it wasn’t until I saw Swiss Army knives being assembled on an episode of Modern Marvels that I finally gave it a go; it turned out to be a piece of cake.

The Minichamp’s CR1025 battery is removable by poking a toothpick into a small hole in the knife’s plastic cover. The toothpick pushes the battery and tiny plastic door out the opposite side. With the battery removed I was able to wedge a guitar pick between the plastic cover and the body of the knife. Then I removed the plastic cover by gently prying around its perimeter. I didn’t have to break any glue bonds or plastic tabs; it was just a simple friction fit. The LED assembly consists of a battery holder, a momentary switch, and a 3 mm LED soldered to the assembly’s substrate. I desoldered the red LED with a little solder wick, cut the white LED’s leads to the same length as the red LED, checked I had the correct polarity, and then soldered the new LED to the board. The width of the white LED was larger than the red one and prevented the plastic cover from properly fitting back onto the knife. To fix this I used the Minichamp’s file to remove plastic from the LED until it was flush with its housing. The LED assembly and cover should be refitted onto the knife so that the LED and retractable pen point in the same direction, so you can see what you’re writing in the dark. Finally, I shouted “Lumos” (*cough* Dork!) and pressed the button. Presto! Nice, bright, white light.


I was thinking about how I could use an RGB LED and a switch with more than one throw to get red and white light, when I remembered there is such a thing as bi-color LEDs that only use one anode and one cathode. This type of LED has two dies in anti-parallel in one package. Therefore, if this type of bi-color red and white LED is used in the Midnite Minichamp all the user has to do is take out the battery and flip it over to switch from red light to white light; no other changes to the circuit are necessary. I found a place online that sold red/white LEDs for a reasonable price, so I bought a pack. Unfortunately, I didn’t like the brightness of the white die in the bi-color LED so I’m sticking with the regular white LED I already have in the knife. Still, I thought this was an elegant solution and I’m posting it here in case anyone else thinks having both red and white light is worth the trade off. — This was the only place I could find two lead, bi-color red/white LEDs. Only $2.95 for shipping!

This switch might be able to fit inside the knife with a little bit whittling down.


Handheld VDG on Instructables March 2, 2010

Filed under: Uncategorized — jethomson @ 11:17 am

I just posted an instructable on how to make a handheld Van de Graaff generator similar to the Fun Fly Stick. Follow this link to instructables’ site or download the pdf to read all about it.

Here’s a short video of a light bulb taped to the collector of the VDG. When a spark is drawn through the bulb the argon inside turns into a violet-blue plasma.