Wednesday, October 12, 2011

Turning Old Shower Curtain Hangers Into Magnets!

I recently inherited several old shower curtain hangers that looked fishy! Fortunately, they did not smell fishy. They were in reasonably good condition and I did not want to see them thrown away. At first, I thought I could make a fake-aquarium for my daughter, where she could hang them and play "pretend fish" (two year olds like to do that ya-know). Unfortunately, the other thing two year olds like to do is throw things and these hangers were not designed for high-velocity impacts. My next idea was to make some refrigerator magnets out of them!


I decided to rip off the back hangers and put some magnets on them. The back part of the hook is embedded into the fish-material, so I had to be careful to pull the hook off flush with the back of the fish. If I moved the hook slightly back and forth a few times it would break off evenly. Here is a shot of one fish with the hook and one without the hook.


Next, it was glue time! I did not use any ultra-expensive-special-purpose adhesive for this, just regular old Elmer's Glue-All (the multi-purpose glue). It claims to be a "New Stronger Formula!", I suppose we will see just how strong it is. The magnets are regular disk magnets about 3/4" in diameter. Take a look at this close-up.


Below you can see most of the fish just sitting around, waiting for their glue to dry. They are such patient creatures!


Tuesday, October 11, 2011

Testing the Sangamd 10kHz Low Pass Filter

Tonight I took a quick look at an old Sangamd 10kHz low pass filter. Here is a snapshot of the filter and all of it's majesty! It's a beautiful old piece in excellent physical condition.


Physically, the unit is 1.7" x 1.6" x .8". The leads have an outer diameter of .025". The inner diameter of the round-casing that surrounds the leads is approximately .130". The height of the lead that extends above the casing is roughly .090", this does not leave much room for pressing the unit into a breadboard. I ended up using some old wire wrap, stripping it and tying it around the leads. Here is a closeup of the wire wrap around the leads.


Three wires stripped, wrapped and pressed by hand. Piece of cake!! At least it looks that way from the image. It takes a minute or so to get the wrap just tight enough to slip over the lead. Here is a snapshot of what all of the completed wire extensions looked like.


Now, we will plug it all into a breadboard and feed 1, 2, 3, 4.... 10kc, etc, while observing the output in-and-around 10kc. In the shot below, I am feeding 10kc @ 1Vpp into it. Here you are seeing what the oscope reads at the output of the filter. Not bad!


Now 12kc.



Now 13kc.



Now 14kc.


Now 15kc. Notice the dip.



Now 16kc, notice the dip again.



And now, 17kc.


The true drop-off point for the filter is somewhere between 13 and 15kc. I will dig a bit more to determine a closer estimate for the drop off. Unfortunately, I am unable to find a specification for this unit online, so it is impossible to say whether or not it is performing within its designed tolerances. For its age, I would say the unit appears to be working well!