Beloved daring ones:
Well, I'm not going to get (very) verbose on this. Around a couple of months ago I noticed my multitool wasn't working properly. The machine was losing lots of power once heated up and… damn! Its housing was getting really hot! The issue was happening with light load work and, since I could feel the heat on the housing was coming from around the switch/speed controller, I knew what was to blame.
My “Top Craft TMW-160F” (AC230V, 160W) is a Dremel (395?) clone, I was aware of. After a more or less quick Google search, I quickly realized certain Dremel tools were engineered with under-specced speed controllers. I figured out I had one of those machines. From what I was reading on the net, it was clear that replacing the internal triac wasn't going to be an effective solution since the piece of silicon was too close to the motor (heat source); moreover, the limited switch lever travel path sucked with regards to finely adjusting the engine's output. “Go big or go @#$%…” I thought.
The speed controller I ordered online was pretty cheap and had “specs to spare”, being just a small PCB with a few components and a heatsink. It goes in series with the tool's universal motor. I really wanted the tool to fit back into its snug briefcase once modded, and I achieved it. (-:
- Speed controller.
- ON/OFF switch (used a small 2A/8A SPST I had lying around).
- Some material to work with to make a housing for the speed controller. I used an old small plastic slide box.
- Soldering iron, pliers, hot glue, cellophane… and other gimmicks.
A note about the video.
I originally filmed it just to enjoy a joke with friends, and it worked! Of course I speak spanish and the first sentence I utter is "Bueno, vamos a ver si la tocapelotada estaa..." which could be translated as "Well, let's see if this ball-breaking stuff (goes)..."
Step 1: How I Made It.
Cut, mold and shape the plastic box/material you are working with in order to make the housing for the speed controller (“SCR” from now on) to fit in. My slide box was about as wide as the SCR, so I had to cut/polish the plastic box to adjust its height and lenght.
The SCR's board was inserted in a drilled hole on what once was the slide box's cover through its potentiometer's shaft (with a milling stone, I did a minor adjustment over an annoying protruding metal tab on the SCR's pot frame). Other stuff I did with the multitool: holes for the switch, cable input and cable output.
The multitool's cord was equipped with a long sheathing “on its arse”. I didn't wanted to lose the ability to hang up the tool from its clip, and that meant I couldn't stick the SCR's box too close to the tool's housing. The solution: I removed the sheathing so I could bend the cord in a springy way, minimizing its stress and making it fit inside nicely near the SCR's housing (and I later used it as cable cover for it's input/output).
After more or less I had all the work done on the SCR's box, I opened up my TMW-160F in order to bridge its internal SCR. Know what? When directly plugged to mains (bypassing the SCR) these tools run REALLY smoothly.
After that last step, I properly measured where I was going to cut the cable, made the cut, soldering, box assembly, hot glue, etc. I discovered that, since cellophane tape is quite slippery (not on the glued side of course), I could extend a line of hot glue above that slice “where one piece meets the other” on my box, cover it with a strip of cellophane upside down while pressing for it to be spread evenly and… well, it comes out really sheer and smooth!
Well, see the pics and the video. Enjoy!
Step 2: Bypassing the Internal SCR
Well, after some aluminium machining I've been working on, it was time to do some cleanup on the machine so I decided to take a couple photographs of the bypass I made on its internal SCR/brush mount assembly, for the sake of completeness.
There you have it.