Thursday, Sept. 13, 2007 9:41 PM - P.H.
(effect of frequency on AC induction motors)
An AC induction motor is a synchronous motor, so the speed is determined by the input frequency through the following equation:
rpm = 120 x (frequency in Hz) / (number of motor poles)
When an AC motor is operated at a lower frequency than the nameplate rating there should be a proportional decrease in input voltage to prevent overheating. The example you give of running a 50Hz motor on 46Hz power is a small difference and should not be a problem as long as the mechanical load on the motor is not excessive. Keep in mind that there will be a small proportional reduction in motor speed.

Sunday, June 3, 2007 3:57 PM - Bob R.
(subject - transistor specs)
The bulk packaged transistors like from Radio Shack are typically for hobbyist use. I think they come from out-of-spec manufacturing runs where they can't be sold for applications that require exact specs but are fine for general purpose or hobbyist use. If you need exact spec you can also buy from them or others in single package form where the specifications are listed on the package. I've never had any problems with the bulk ones though.

Friday, June 2, 2007 8:17 PM - David W.
(subject - buying a multimeter)
I would buy a digital instead of an analog because the digital kind is usually more durable and accurate. Don't spend less than 30 bucks unless you want junk! The RMS stands for root-mean-square. This capability is good, if not necessary, for electricians and technicians who must take readings where harmonic distortion of the sine wave might exist. Harmonic distortion of the sine wave can be caused by large electronic loads on a power circuit. If you're not dealing with this stuff and just want something inexpensive for bench use then I wouldn't worry too much about that.

Saturday, May 26, 2007 1:24 PM - Kenny
(subject - high def TV)
I've heard that OLED TVs may come out later this year but I think you would be better to wait on one of those till the bugs get ironed out and you see how well they work and are guaranteed. Plasma & LCD are already proven and getting reasonable in price. Then again I tend to avoid the bleeding edge of technology. :-)

Wednesday, May 16, 2007 9:44 PM - P.H.
(subject - lightning protection/UPS)
We have an article page here on Power Protection that you may find useful. The common plug-strips that you can buy anywhere offer some protection and are better than nothing, but cannot absorb much surge energy - such as from a nearby lightning strike to your electric utility lines. If your house has a fairly modern circuit breaker panel with 2 available pole spaces you can buy and install a surge suppressor that plugs in like a 2-pole circuit breaker. These are much better at absorbing the potentially damaging energy from lightning and also protect all circuits in the house. Consider buying a small UPS (uninterruptible power supply) such as from Tripp-Lite or APC. Anything above 500 VA (volt-amp) is adequate for an average PC system. A greater VA capacity will give longer run time during a blackout. These units are the best protection for a $150 - $250 price range, and usually have feed-through ports to protect your modem or broadband line as well (this can be just as important!).

Wednesday, April 18, 2007 11:16 PM - Rob Z.
(subject - car headlights)
I think the "HID" headlights are a combination of xenon and metal halide. They have the most punch as far a the "pro", but are much more costly for a retro kit as far as the "con". There are some pretty good halogen bulbs out there such as Sylvania Silver Star that are almost as good but a lot less $. That would be my choice unless you got a real interest in HID.

Tuesday, April 17, 2007 7:19 PM - P.H.
(subject - model train electronics)
Jeff, try looking in Model Railroader magazine for an article or some vendors who might have something. This might be a good time to tinker with some invention of your own. :-) There are industrial automation companies like National Instruments (www.ni.com) or Automation Direct (www.automationdirect.com) that have a wide variety of PC interface hardware, but those products might cost a little more that what you're looking to spend on a model railroad project.

Sunday, April 15, 2007 9:21 PM - A.G.
(subject - Lost in Space robot)
Roboman, you're not the only one who loved that guy! There seem to be a lot of fans, but oddly no kits readily available. You have to either build your own from scratch I guess or buy a cheap plastic model. You could probably start a business making & selling working kits!

Monday, January 22, 2007 6:12 PM - P.H.
(subject - wire color coding standards)
Here is an excerpt from a CISCO equipment installation manual under the heading: Power Connection Guidelines for DC-Powered Systems
"The color coding of the source DC power cable leads depends on the color coding of the site DC power source. Typically, green or green and yellow indicate that the cable is a ground cable. Because there is no color code standard for source DC wiring, you must ensure that the power cables are connected to the DC-input power supply terminal block in the proper (+) and (-) polarity. In some cases, the source DC cable leads might have a positive (+) or a negative (-) label. This label is a relatively safe indication of the polarity, but you must verify the polarity by measuring the voltage between the DC cable leads. When making the measurement, the positive (+) lead and the negative (-) lead must always match the (+) and (-) labels on the DC-input power supply terminal block." This is not a definitive answer by any means, but it seems that DC power color coding is not standardized and may be determined by the equipment manufacturer, installer, or end-user. Any additional comments or corrections are welcome.

Wednesday, January 17, 2007 5:07 PM - P.H.
(subject - HDTV & DLP technology)
Tedd, your question made me curious myself so I did a little research. DLP stands for Digital Light Processing. I like to show technologies in a generic way rather than favor a particular manufacturer, but Texas Instruments seems to be the major player with this and they have an excellent flash demonstration video. You can also get some more info at the main site: www.dlp.com

Wednesday, December 27, 2006 9:07 AM  -  Technical Support Team, AutomationDirect.com
(subject - automation hardware, sensors)
The sinking and sourcing concepts are explained here

Monday, December 18, 2006 8:28 PM  -  P.H.
(subject - tin whiskers)
RoHS (Restriction of Hazardous Substances) is a directive that went into effect on July 1, 2006, and covers products sold within the European Union. This directive limits the amount of lead, as well as some other hazardous substances, that can be contained in these products. Tin whiskers are microscopic whisker-like formations that can emerge from the tin plating of circuit boards and component leads. If the whiskers grow long enough they can short circuit to adjacent conductors. It is believed that this caused the failure of the Galaxy 4 communication satellite in 1998, and disrupted the operation of a large number of communication devices (such as pagers) in the US at that time. In the past lead was mixed with the tin to solve or reduce this problem, but now that lead is being restricted the problem is re-emerging. Some current solutions being used are annealing circuit boards in ovens to reduce points of stress in the tin, and the experimentation with some other more environmentally friendly alloy metals.

Tin whiskers growing from an electronic component lead (courtesy NASA)