The Owad Laboratory

Uses for fishpaper

Fishpaper is an insulative paper that used to be common in antique radios. It's often used to insulate transformers.

The history of the name is pretty interesting. According to Alvin G. Sydor:

In 1729 Stephen Gray made the discovery of the conducting and non-conducting power of different substances. Gray found that by using woven silk served as an excellent insulator. Some years later it was found that the paper industry could provide what was equivalent to woven silk. Later it was discovered that if the paper was saturated with fish oil its ability as an insulator was much improved particularly when used in harsh environments and high voltages.

Recently, I've been using it for fast and cheap electronics cases. This is one of my backup servers:

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Cleaning handles with a brass wire wheel brush

I bought a Remline tool chest at an auction on Saturday. I've been wanting to get something a bit larger than my current chest, and I couldn't pass up these handles:

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Sonar trumps eTape

I’ve given up on the Milone eTape entirely. I just couldn’t get it to work reliably. Instead, I decided to go with a RadioShack Ultrasonic Range Sensor as my backup method for detecting water. It’s mounted on the basement ceiling and will alarm when it detects an inch of water on the floor. The floor is sloped, so an inch isn’t nearly as bad as it sounds. It’s been working well. I’m leaning towards a pressure transducer for the main sensor.

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Calibrating Milone eTape

Milone's eTape is proving to be rather finicky. Per Milone's instructions, I have it installed in a 1" pipe, so that it can't stick to the sides. Readings fluctuate by up to 1/2", even with no change in water level. The eTape seems very sensitive to any sort of pressure. It needs to be suspended to give a proper reading. I neglected to suspend it during one test, and in an empty pipe, readings gradually reached 14", apparently just from the pressure on the bottom of the tape. Worse, according to this discussion, it appears that the eTape can be permanently damaged if it is submerged. That seems to contradict the Operating Instructions, which state:

The vent hole allows the eTape to equilibrate with atmospheric pressure and must not be submerged in the fluid to work properly. The vent hole is fitted with a hydrophobic filter membrane to prevent the eTape from being swamped if inadvertently submerged.

I've emailed Milone for clarification.

Update:

According to Chris at Milone, it's ok to submerge the vent hole, but submerging the connector tab will permanently damage the sensor - a detail I'd have thought would be worth mentioning in the Operating Instructions. The newer eTapes that come in tubes are sealed so that this isn't a problem. Chris says that bare eTape can be sealed by using RTV or Silicone II to completely cover the connector tab.

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Prototyping a Sump Pump Controller

Most mechanical relays and switches are rated for 1 million cycles or less. That sounds like a lot at first, but if you have a sump pump that runs every 30 seconds, that's less than a year. Lowes used to sell a sump pump with a lifetime warranty. Every year, the manufacturer would mail me a new switch, and about every three years, a new pump, until they finally insisted on refunding my money.

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Rebuilding a Porter Cable 18V battery

I have a large collection of 18V Porter Cable tools. The oldest are from 2010, and the batteries are starting to fail. I've heard that Harbor Freight's 18V battery uses the same cells. A new Porter Cable battery is about $40, whereas the Harbor Freight battery, with the ubiquitous 20% off coupon, is just $10.40.

Both batteries open by just removing a few screws. The Porter Cable battery is better packaged, but the layout of the cells is identical:

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Unboxing the Laser Cutter

The Chinese 40W laser cutter, sometimes called the K40, has been around several years now, and prices have finally dropped below $400. After waiting for discounts to line up, I was finally able to purchase one last week for about $360 shipped. How bad (or how good?) is a $360 laser cutter?

The unit is larger than I pictured it, given the cutting size. The box is 37"x25"x16". With its weight and bulk, it was too large for me to get my arms around, so I slid it in the front door and unboxed it.

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Raspberry Pi Zero and NTC CHIP size comparison

CHIP is on the left, Pi is on the right.

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CHIPbag - Customizable Case for NTC's C.H.I.P.

CHIPbag is a customizeable case for Next Thing Co's C.H.I.P..

Options in Customizer, or by downloading the attached OpenSCAD file, include:

Standard or Low-Profile design
Openings for headers
Opening for battery connector
Screw mounts added to sides
Bitbeam added to sides or back
Building bricks added to sides or back

I'm making a lot of tweaks yet, but wanted to share.

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C.H.I.P. is here!

My alpha version of Next Thing Co's new $9 computer, C.H.I.P. arrived today, straight from Hong Kong. The fun begins!

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