Search found 82 matches

by jimmy101
Sun Jul 18, 2010 10:46 am
Forum: General Discussion
Topic: CELL PHONE BLOCK
Replies: 17
Views: 3736

Re: CELL PHONE BLOCK

In general what you describe is illegal in the US. You may not deploy a device that interferes with radio transmissions.
by jimmy101
Sat Jul 17, 2010 10:02 am
Forum: General Discussion
Topic: Need accurate temperature display
Replies: 17
Views: 2894

Re: Need accurate temperature display

Most inexpensive digital thermometers are accurate to about 1C (~2F), so the results you are getting for several different thermometers is about right. Generally, that is sufficiently accurate, even for laboratory work. (An expensive mercury filled lab thermometer is typcially accurate to about 0.5C...
by jimmy101
Sat Jun 12, 2010 2:12 pm
Forum: General Discussion
Topic: Help!! Making A electro Static field meter,
Replies: 3
Views: 904

Re: Help!! Making A electro Static field meter,

Ya, 60% humidity is anything but low. The page is probably referring to something more like January in the Midwest where inside humidity might be as low as 15%. I take it this is the basic jFET-9V battery-LED setup for detecting electrostatic fields? You might get better sensitivity if you remember ...
by jimmy101
Mon May 24, 2010 3:16 pm
Forum: General Discussion
Topic: 3 1/2 digit and 4 1/2 digit displays
Replies: 14
Views: 2457

Re: 3 1/2 digit and 4 1/2 digit displays

Mr. Al The issue arises when two (or more) measurements have widely different precisions (by definition accuracy is basically always unknown). Working with the given example of a precisely known bucket count but a bucket of unknown accuracy and precision. And, the bucket's precision may also be furt...
by jimmy101
Sat May 22, 2010 1:31 pm
Forum: General Discussion
Topic: 3 1/2 digit and 4 1/2 digit displays
Replies: 14
Views: 2457

Re: 3 1/2 digit and 4 1/2 digit displays

"All those significant digits (67,435 gallons total) are totally worthless." Not quite. Though you are correct that a formula can not, in general, give an answer that is more precise than the least precise value in it**, some level of extra precision, even some that is beyond what is believable, is ...
by jimmy101
Sat May 08, 2010 10:51 am
Forum: General Discussion
Topic: LOCK WASHERS?
Replies: 9
Views: 17955

Re: LOCK WASHERS?

Have you considered replacing the lock washer with say a dab of locktight (or clear fingernail polish, or superglue or ...). Or, go old school and simply bend the nut slightly, or dimple it with a punch. Or, replace the star washer with a standard split ring washer. The split ring should work just a...
by jimmy101
Sat May 08, 2010 10:47 am
Forum: General Discussion
Topic: Redesigned product - Patent infringement?
Replies: 7
Views: 1717

Re: Redesigned product - Patent infringement?

Sounds like you are talking about the ignition circuit for a gas water heater, or some such similar appliance. The circuit has to turn on the glow igniter, verify it is on, turn on the gas, verify the flame lit, recycle if the flame signal is lost, etc. and do appropriate things when something doesn...
by jimmy101
Fri Apr 23, 2010 9:28 pm
Forum: General Discussion
Topic: Where to get Transparent Paper ?
Replies: 11
Views: 2207

Re: Where to get Transparent Paper ?

Another place to check would be at your local Fedex-Kinkos (or other print shop). They mostly use laser printers and they definitely have transparency material. (Regular inkjet transparencies melt in a laser printer.) Heck, you can probably submit your artwork online and get a single copy or two on ...
by jimmy101
Sun Apr 18, 2010 10:03 am
Forum: General Discussion
Topic: Home Audio Specs
Replies: 18
Views: 2797

Re: Home Audio Specs

"650 total watts out of 5 speaker modules" How was the power actually spec'd? It should be quoted as either RMS (reasonably accurate measure of output) and not "peak" or IHF (both are basically meaningless). And, it should spec that all channels are driven simultaneously and quote a THD (total harmo...
by jimmy101
Thu Apr 08, 2010 2:40 pm
Forum: General Discussion
Topic: 74194 Shift Register
Replies: 6
Views: 3292

Re: 74194 Shift Register

Or, debounce with just a series resistor followed by a cap to ground, it's a low pass filter. A 555 will take what two resistors and a cap and the 555 and ...

Figure something like a 10MFD cap and a 10K resistor, RC~0.1S (~10Hz).
by jimmy101
Mon Mar 22, 2010 5:09 pm
Forum: General Discussion
Topic: GOLD
Replies: 13
Views: 1930

Re: GOLD

my $0.02 Acetone is worth a shot. But, DO NOT HEAT THE ACETONE! Acetone is a gigantic fire hazard, much worse than say gasoline. A hot electric burner is enough to ignite acetone vapors. Acetone has a pretty low boiling point so even mild warming will generate a large amount of combustable vapor. An...
by jimmy101
Mon Feb 15, 2010 10:17 am
Forum: General Discussion
Topic: AC/DC ohms law
Replies: 2
Views: 869

Re: AC/DC ohms law

Like Robert said. For example, a 100W 120 VAC (RMS) incandescent light bulb has a resistance of about 140 ohms at its operting temperture. At room temperature the resistance is more like 10 ohms. (The filament of an incandescent light operates at about 4500F.) Light bulbs and heaters are, in a sense...
by jimmy101
Mon Feb 15, 2010 10:04 am
Forum: General Discussion
Topic: LED as power on indicator with AC Mains Supply
Replies: 34
Views: 5157

Re: LED as power on indicator with AC Mains Supply

Peterlonz I don't think 20,000 hours is nearly enough. A single year at 100% duty, which is nothing for a bus strip, is 8760 hours. 20K hours is less than three years. Figure the lifetime of a generic bus strip (ignoring any surge protection capability) is probably 10+ years that means the LED will ...
by jimmy101
Sun Feb 14, 2010 10:04 am
Forum: General Discussion
Topic: LED as power on indicator with AC Mains Supply
Replies: 34
Views: 5157

Re: LED as power on indicator with AC Mains Supply

Looking at the circuit the MrAl posted and the rest of this thread, reminds that a few years back a friend that works for "Ginormous Gov't Military Contractor Of High End Electronics" says all the ubiquitous 120 VAC bus strips with the NE-2 type power indicator lights were being replaced in their la...
by jimmy101
Sun Feb 14, 2010 9:46 am
Forum: General Discussion
Topic: An interval timer with a trap
Replies: 7
Views: 1326

Re: An interval timer with a trap

Besides the N&V article there are a couple other pretty simple ways to do a shooting chronometer (a device to measure the time of flight between to detectors). All you really need is a pair of phototransistors (RadioShack has suitable ones for a buck or so) and a laptop with a sound card. There a so...