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Tech Forum

What’s In A Board? September 2017

There are plenty of high quality, double-sided printed prototyping boards readily available on eBay. They are perfect if used as they are, unless — as it often happens — the need arises to trim, grind, or otherwise shape them.

Here is my problem: I am deeply concerned that these boards are made with asbestos. I know that for any grinding job a facial mask is a must, but if the dust created in the process could contain asbestos particles, much stronger protection measures would be warranted. Or, perhaps such operations should be entirely avoided.

I imagine that many electronics enthusiasts cut or even grind these items, completely unaware of the danger they may pose. I tried to gather information from the Web about these products, with little success.

I would like to know — preferably from an authoritative source — what materials are used in production of these (mostly Chinese in origin) prototyping boards.

Jan Raj
Philadelphia, PA

Should I Switch? October 2017

I’m torn between using 3.3 and 5.0 volt components on my microcontroller projects. Many people seem to be moving to 3.3V, but components don’t seem to be as readily available as 5.0V components.  What are the advantages and disadvantages of each?

Tony Sigler
New Brunswick, NJ

PCB Layout Software August 2017

I am a retired Field Service Engineer. Over a decade and a half after early retirement from IBM, a friend asked if an idea he had could be built. I assured him it could.

He offered me partnership if I would design and build a demonstration system. I designed, built, and programmed a system that works just like he wanted it to. An existing patent that I could find no work-around for expires this year. We'd like to have systems ready to go before we start doing demonstrations.

Now, I need to convert my proto-board to a more compact layout to be mass produced. The problem is that all the design software I've found requires that work be done online. Not even a simple schematic design without being on the Web.

I need recommendations for offline software to generate a file for use by a production service. All I'll need is a library of templates for basic TH mounting components. I do not intend to put the results out in the clouds because oftentimes when I look to the clouds, there be vultures about.

T. A. Rooks
Chelsea, AL

Electromagnetics: Transformers, Generators, Motors and Other AC Machinery. September 2017

I’m trying to make sense of everything coiled, but the only thing getting wound up is me. I thought I knew a bit about electromagnetics, but recently I’ve been trying to make sense of all of these fields and flows.

What is the difference between the magnetic field and the flux? How does flux work in a transformer or a generator? Does anyone really understand Maxwell’s Equations?

So many textbooks dealing with electromagnetism speak in equations instead of English. I want to know HOW it all works, not just how to compute these things. Am I just reading the wrong books. Can you help me figure out what the flux is going on?

Taylor Street
Felton, CA

Oil Filled Caps August 2017

I’m trying to bring an old tube transmitter back to life. The power supply uses oil filled capacitors, which don't seem to have handy replacements. Assuming that I can change the oil to reduce the leakage current, what kind of oil is used?

Will motor oil work, for example?

William Helm
Eugene, OR

Audio Leveler September 2017

My wife and I are hearing impaired. We need an AVC amplifier for TV audio to keep the level constant going into WiFi to hearing aids. Commercial or build-it-yourself (no surface mount); Analog not digital.

Fred Imm
Kirtland, OH

Laser Color Choice August 2017

I want to convert a 3D printer to a laser burning station to work with wood veneers and leather goods.

Any advice on the best type and color of laser to get? I’ve heard brown wood and leather reflect more red light and so I should use a blue laser.

Kyle Hoyos
Walkerton, IN

Salt Sensor July 2017

I have a water softener that needs pellet salt added to a brine tank. I’m trying to figure out a circuit to detect when I need to add salt as the tank is opaque and salt usage varies depending on use. The simpler the circuit, the better!

Salt Sensor
Greensboro, NC

Laser Eye Protection July 2017

With high powered laser prices dropping like crazy, I decided to pick up a 3W blue laser from eBay for $50 to experiment with.

I’m concerned about eye damage and would like some advice on eye protection. What makes a pair of laser goggles good and what should I stay away from?

Gary Byrum
Milwaukee, WI

Door Chime Protection Circuit September 2017

I need a way to protect my hardwired door chimes from being accidentally “burnt up” when the doorbell button gets stuck.

A couple of times when the button got stuck, I was home and able to fix it before damage occurred. The last time it happened, however, nobody was home. Someone came to the door, and we arrived home to the smell of burnt electronics.
I’ve replaced the button more times then I can count. I guess the way the weather hits it — eventually — it becomes stuck. I am now on my third set of replacement chimes.

I have TWO 16 volt chimes (10VA) wired to a single button (LED lamp) on a 16V 30VA transformer. The transformer is much larger than normal to accommodate the two chimes.

I would like to protect the chimes in one of two ways:

  1) Simple protection — Inline fuse that would blow if the chimes were pulling current for more than (let's say) five seconds. I figure a “slow-blow” fuse would be ideal, but not sure on the rating.
  2) More complex protection — A “time out” circuit that would cut power to the chimes if the circuit was live for more than five seconds, self-resetting either after the button was released or after 60 seconds (chime would activate again, indicating a stuck button).

Eric D. Bailey
Cecilton, MD

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