Nifty Original Ideas

Test Probes Too Big?

Back in the mid-1980's I made this little adapter so I could check voltages with my new Heathkit oscilloscope without shorting adjacent circuits.

The probe is made from the following:

A brass collar, these are used on R/C model planes to hold the wheels on. There is a allen head set screw threaded into them to hold the collar on the axle.
A sewing needle, Back when I made this, sewing needles tended to be brittle, So I did a little heat treating on it to soften everything but the tip. I clamped the last 1.5 mm of the needle in some pliers to keep it cool. I then used a flame to heat the rest of it. Ideally the rest of the needle will only get to a very dull red heat. It will probably get to a orange heat the first time you try, just let it cool and try again. After you get it where you want it, put the needle in a oven at 350 F for a few minutes.
A strand of fine copper wire.
Some insulation from a fine wire.

Drill a small hole in the collar opposite the set screw. Clean any oxide off of the needle and collar. Thread the strand of copper wire through the eye of the needle , insert the needle into the hole. Wrap the wire around the collar and needle. Solder the wire and needle to the collar. Try to get a bit of solder to stick to the inside end of the set screw, this will reduce marring of your test probes.

Wristwatch Hell

I don't like to wear wristwatches, and I find pocket watches to cumbersome. So I came up with this solution. I replaced the useless piece of plastic on my keyring with a watch pouch.

The pouch holds a plain $27 Walmart watch with the band removed. The outside is some vinyl material salvaged from an old piece of luggage. The clear side was cut from the badge holder from a convention. Add some carpet thread, a sewing needle, and a pair of needle nose pliers, and you're ready to make one yourself. One trick, put some stitches between where the two prongs at the bottom of the watch go. This will keep the watch from rotating in the pouch, otherwise the prongs tend to rotate and tear holes in your handy work.

A shoestring holds it together and attaches the keys. Use a good square knot keep the keys on.

Not only is this much lighter than a pocket watch, but the clear plastic protects the crystal and the pouch protects the watch in case you drop it.

I replaced the useless plastic tab on my other keyring with a yellow Photon II.

Phone Line Indicator

I like to know when my modem gets disconnected, and here's my solution. I found an old Simpson multimeter (AN/PSM-4D) at a flea market for $4. There was just enough juice in the ohm meter battery to make the movement twitch, so I figured, what the heck, $4.

It turns out that the movement zero tends to change when it's moved around, but otherwise it cleaned up nicely. Added half of a telephone extension cord, a couple nails, and some heat shrink tubing, and wala! The meter is 20,000 ohms/VDC, so on the 100 VDC range it has 2 megaohms resistance. I think the phone company wants 10 meg minimum, but I think it's close enough. In any case, I have a switch on my modem line to prevent those nasty voltage spikes from frying my modem when I'm not using it.

If you have experience working on this kind old meter movement, please answer the following:
Are there any tricks to opening the meter movement without damaging it?
Is there supposed to be any lubrication on the bearing point? I was using it out in sub freezing temperatures and the needle seemed to stick.

Another idea I had was to use an old LCD clock as a phone line indicator. I have an old one that has a couple of display segments missing. Power consumption is about one microamp at 1.5 volts. At first I thought that it would just take a couple of resistors and three diodes to supply the needed power to cause the display to blink when the phone was on hook. But looking at my old EE text, I noticed that it took a lot more than the 5 microamps availiable to develop the .6 volt drops I was expecting. Does anyone know of any diodes, or other parts that would provide the needed voltage regulation with that little current availble?

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