Nuts and Volts - September 2008

TECHFORUM

This is a READER-TO-READER Column.

All questions ANDanswers are submitted by Nuts&Volts readers and are intended to promote the exchange of ideas and provide assistance for solving problems of a technical nature. Questions are subject to editing and will be published on a space available basis if deemed suitable by the publisher. Answers are submitted by readers and NO GUARANTEES WHATSOEVER are made by the publisher. The implementation of any answer printed in this column may require varying degrees of technical experience and should only be attempted by qualified individuals. Always use common sense and good judgement!

All questions and answers should be sent by email to forum@nuts volts.com All diagrams should be computer generated and sent with your submission as an attachment.

QUESTIONS

To be considered, all questions should relate to one or more of the following:

❶ Circuit Design

❷ Electronic Theory

❸ Problem Solving

❹ Other Similar Topics

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ANSWERS
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94 September 2008

>>> QUESTIONS

I live two miles south of the US border. My TracPhone only works reliably about 3/4 miles south of the border. At my residence, I can occasionally get just one bar on my phone. I would like to improve this. Is cell phone range limited by my transmit power or my receive distance?

Can I rig some kind of reflector/ antenna/booster amp to improve the range of my phone, so I don't have to pay for international service?

#9081 G. Frank Humiston via email

How do manufacturers specify parameters of passive components?

One example is a 1A diode. Is 1A the maximum current allowed, or is the diode guaranteed to pass 1A continuously? Another example is a resistor. When you use a resistor as a 20 mA current limit to an LED powered by 13.8V, isn't a 1/4W resistor pushed over the limit?

I actually limit LED current to anywhere between 15-18 mA. The LED is just as bright, but lasts much longer (lasts forever compared to our short lifetime). I had several of these "LED lightbulbs" burn out within a year due to bad design by their manufacturers.

#9082 Dusan via email

I have several Maytag Neptune washing machine motors with the driver board.

I would like to make an adjustable speed generator so that I could use these motors on wood working tools. I was thinking that a 555 series chip would be the basis, but I don't know how to get the three phase output. Also, would I drive one or two phases of the motor at the same time?

One thought was to use the 555 to cut the power to one winding at a time sequentially and leave power on the other phases. I don't know how Maytag did this. I don't want to use a microprocessor chip if I can avoid it.

#9083 Bob McKnight via email

Does anyone have a circuit or info to safely regulate high voltages from 200 volts to about 50 volts? Or how to cascade adjustable voltage regulators to add up their outputs to any desired high voltage to about 200 volts?