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Cell Phone Detection May 2013

I work at a counseling center where it's best to limit phone calls for the mental well-being of the residents. Is there any way to detect a cell phone in the building, either by an available device or a homebrewed circuit? Is there a way to find a hidden or lost cell phone? Is there a way to log cell phone presence, signal usage, and strength? Just show whether there was a signal, the time, and the strength (how close).

#5131
Leroy Sensenig
Penn Yan, NY


Low Power IR Remote June 2013

I would like to make an IR remote control to be used in nursing homes to activate alarm equipment.


Specifications are:
Receiver: nine volt, VERY LOW power consumption
Transmitter:
handheld, battery powered, three volt (lithium?), 2-5 meter range

#6131
Claes Kamborn
Barkarby, SWEDEN



Answers

Regarding low-power remotes, check out Linx Technologies https://www.linxtechnologies.com/en/products/remotes and https://www.linxtechnologies.com/en/products/modules


They provide receivers and keyfob-type transmitters.

Peter Goodwin
Rockport, MA


micro-SD Adapter April 2013

I have two Fuji Film digital cameras (FinePix 2650 and FinePix A210). Each came equipped with a 16 MB xD-Picture card (image memory card) which is a semiconductor memory (NAND-type Flash memory) to record digital image data.


I have a micro-SD adapter (orange) with a 1 GB card which fits EXACTLY into the xD-Picture card slot. Even though I formatted the card INSIDE the cameras several times, I'm still getting "Card Error - Card Not Initialized" messages on the camera’s LCD monitors.


Why can't I use this 1 GB micro-SD adapter with these digital cameras? Under what circumstances can I use this type of adapter?

#4131
Don
via email



Answers

After reading the question I downloaded the manuals for the two cameras in question. The FinePix 2650 manual shows it capable of using 16 to 128 megabyte memory cards.  I'm afraid 8 Gigs is more than a little out of that range. The information is not easy to find in the manual.  See page 117.

The FinePix A210 is a little more capable, but not much. On page 79 of the manual for it, the usable memory capacity is listed as 16 to 256 megs.

I have a FinePix AX200 coincidentally with an 8 Gig Micro SDHC card and the adapter that you describe. It works fine. The manual lists number of exposures for cards up to 8 Gig capacity.

This doesn't help you but it does answer your question.

Ron Anderson
via email

The simple answer is that the memory card you are trying to use is too big for the camera[s]. I looked in the manuals available online — the max size allowed is 128 MB for the 2650, and 256 MB for the A210.


Neither camera can handle the 1 GB you're trying to use. You need to find smaller capacity microSD cards. You might try to only format 128 MB [or 256 MB] and see if that works [not sure if you can do that with XD or SD memory cards].

Schneids
via email

You have two problems. The first is SD and XD cards are not interchangeable.


Problem number 2 is the only compatible cards for your cameras per the user manuals are as follows:
 

FinePix2650
DPC-16 (16 MB)
DPC-64 (64 MB)
DPC-32 (32 MB)
DPC-128 (128 MB)
 

FinePixA210
DPC-16 (16 MB)
DPC-32 (32 MB)
DPC-64 (64 MB)
DPC-128 (128 MB)
DPC-256 (256 MB)
 

So, your SD card and adapter will not work, and your cameras will not accept a 1 GB card.

Joe Fulton
Youngstown, OH


Propeller Balance Meter March 2013

I’m building a propeller balance meter. This unit was designed and built for in-house use at Rockwell International (North American Aircraft Corp.) Columbus, OH.

There were approximately 200 additional units that were built for Rockwell's Aero Commander dealers around the late 1960s. It uses a velocity type pick-up which is what I need. Best as I can find out, it was a type MU 6-7 Pn. B 11032-1.

If anyone knows where I can get one of these pick-ups or what could be substituted, I would appreciate any help; a used or surplus part is preferred.

#3131
A. Schwedler
Stroudsburg, PA


Project Building June 2013

What’s the best way to cut a one inch hole in a metal or plastic project box? What about a square hole?

#6132
George F. Powelson
Ogden, UT



Answers

The cone shaped step drills work very well for round holes in control panels. If you use a drill press it is very easy to chamfer (debur) both sides of the hole using the start of the next step. You can actually drill it half way from each side if the panel is thicker than the step on the drill.


If you want square or rectangular hole; start with the step drill then use a “nibbler” for the desired shape. Home Depot has the Klein #70611B for about $23. There are several other brands available, including heavy duty and power operated nibblers.

Rhodes Barnette
Henderson, TN

A one-inch round hole can be neatly cut with a step-drill.  Many come in sizes that include 1".


Also a chassis punch can be used, although the punches are more expensive. An inexpensive kit of chassis-type punches can be found at Harbor Freight Tools.


Square holes can be cut by drilling inside the corners with a small drill, then cutting between the holes with an emery wheel on a hand rotary tool, such as a Dremel. A file smooths out the cuts. They can also be cut with a "nibbler" if the gauge of the material is thin enough. Nibblers are available from many electronics supply houses that stock tools. RadioShack used to handle them, although I don't know if they still do.

Tom Wilbeck N5KGN
Longview, TX

Go to Greenlee punch and you will find your answer. They have been around a long time, but their punches are rather pricey.

Bob Haskett
via email

While it's virtually impossible to declare a "best" way to do any number of things, I'll share a couple of my favorites.


For cutting round holes in thin materials, it's hard to beat a step drill bit. These are cone shaped cutters that fit in an ordinary drill or drill press and do a great job of cutting or enlarging holes up to about 1.5 inches without mangling the material.


For square holes, I often use a nibbler tool, following up with a file to clean and square up the cut. With a bit of practice you can use the nibbler to cut all sorts of shapes.

James Sweet
via email

The best way to cut a one-inch hole in plastic or metal boxes is to use a chassis punch. Greenlee makes such punches. A one-inch punch is available from Grainger (see www.grainger.com/Grainger/GREENLEE-Round-Knockout-Punch-4A738?Pid=search) as well as many electrical distributors.


Problem is that they're expensive because they're meant for cutting through fairly thick steel. The 1" device from Grainger sells for about $87.


Best bet is to look on eBay for an antique radio chassis punch. At this writing, I found a 1-inch punch offered for under $10 (plus shipping).

Peter Goodwin
Rockport, MA


Camera Into Plasma TV monitor April 2013

I have tried connecting a color security camera to a Maxent (MX-42 HPM20) plasma TV without great results. Either the color hues are bad or it goes from color to monochrome and back again, all under great lighting conditions. The camera's composite out goes directly into the TV's AV1 or AV2 input. The TV's other inputs work fine and the camera looks great on another monitor. What's going on here?

#4132
Mike Carland
Santa Clarita, CA


Pressure Sensor Sensitivity April 2013

I’m trying to use an SDX01G2 pressure sensor to log CPAP breathing patterns. The circuit uses an LM324N op-amp, an ADC0831 CCN eight-bit A/D converter, and a BASIC Stamp 2 processor. The problem is the sensitivity. The output goes from 0 up to 191, and then back to 0. I have tried several op-amp configurations with little success. I am a newbee, and could sure use some help.

#4133
Henry
Visalia, CA



Answers

I would suggest you try using an instrumentation amplifier designed for Wheatstone bridge application. I recommend the INA 125. I would also recommend the TLC2543 12-bit ADC such as used with a Stamp based logger in the following link: [url=http://emesystems.com/OL2tlc2543.htm]http://emesystems.com/OL2tlc2543.htm[/url]


Good luck with your project.

David Erskine
via email

The SDX01G2’s datasheet shows the specs to be rather narrow.


Consider the Freescale MPXV5004 or similar. It’s range (in and out) is far wider than the SensorTechnics model. The 5004 was used in my CPAP project simply because it was a pull from an old CPAP machine.

Terry Meyer
via email


Personal Audio Amp for Hearing Loss March 2013

I lost my hearing at a very young age and have always struggled with listening to the audio out of phones, computers, MP3 players, etc. When I have my hearing aids in and try to listen, it’s actually worse!


I would like to build an audio amplifier with a programmable equalizer, to be connected to the 3.5 mm audio output jack. I will connect +5V separately.


The device will be connected to a PC temporarily through the USB jack for programming, and then be removed.


Here are my questions:
Is a one stage amplifier enough?
Is it better to amplify first then equalize, or equalize then amplify?
Who makes the best audio chips?
What software is needed to program the EQ?
Any suggested readings, websites, software, forums, etc.


Specifications:
Easy to build and program using a chip like Monolithic Linear integrated circuit LA3600; www.electronics-lab.com/blog/?tag=equalizer.
Input voltage: 5V
Gain: ?
Equalizer: Seven band or better
Output: 3.5 mm


And for the hard way, using a DSP or FPGA to build an advanced equalizer/gain headset that could be used in any computer, phone, or MP3 player!

#3132
Monito
San Diego, CA



Answers

An audio amplifier with a graphic equalizer doesn't require a DSP or FPGA. Quickfilter Technologies (www.quickfiltertech.com) sells a variety of chips aimed specifically at audio applications. The company also has development kits and a neat GUI. No programming needed. A USB cable provides a link between a development board and a PC used to set parameters.


The Quickfilter QF3DFX chip includes a 10-band parametric equalizer and an eight-band graphic equalizer. Cypress Semiconductor's Programmable System on a Chip (PSoC) families (www.cypress.com) include filter blocks, and a graphical drag-and-drop GUI makes it easy to configure a system. These chips include ADCs and DACs, so I bet Monito could create what he wants with only a PSoC chip and a couple of audio amplifier ICs. Find a useful app note at www.cypress.com/?docID=21352, and info about a 10-band graphic equalizer at www.cypress.com/?rID=43672.

Jon Titus
Herriman, UT

If you're generally new to audio processing, I would stick with analog for a while. It's not as cool or widely configurable as a DSP, but it usually does a pretty good job when done right. For your project, you'll probably want:


1. Input gain
2. Three-band or more *parametric* EQ
3. Output gain
4. Power amp

Block Diagram
I included two gain stages so that the EQ's working level can be adjusted independently of both the input and output levels. This allows you to overpower the analog noise in that stage without fear of clipping and still get the output level that you want. (Professional analog mixing consoles are basically that on steroids.) The gain stages are the easiest parts of the circuit: Use a dual-gang linear potentiometer (for stereo, single-gang for mono) with an extra resistor between the center-tap and ground. This loading resistor should be roughly 10% to 15% of the pot's resistance, and makes a better audio taper than most audio pots.

Schematic
The power amp can be a single IC for small speakers or headphones. They're sometimes called power op-amps. The EQ is a little different than I think you had in mind. I think you're imagining a many-band *graphic* EQ, which is easier to understand at first glance, but I think a more useful tool for you would be a *parametric* EQ. Parametric means that you can adjust the frequency of each band, as well as the gain. For example, if you have a problem at, say, 3 kHz, and you have a graphic EQ with adjacent bands at 2.5 kHz and 3.5 kHz, it's going to be hard to adjust that satisfactorily. (This is why professional graphic EQ's have up to 31 bands. Even so, they still don't work well for everything.) With a parametric EQ, you could adjust a frequency knob to put one band exactly where you need it for each problem area. A semi-parametric EQ is easier to build than a full-parametric, and just has the two knobs per band — frequency and gain. A full-parametric EQ has a third knob that adjusts the width of each band. Despite missing a knob though, the semi-parametric version is usually sufficient because it automatically adjusts the bandwidth as a function of gain. Large gain adjustments typically make a narrow spike or notch, while smaller adjustments make a wide hill or valley.


This website (www.sound.au.com) is a great resource for analog audio projects. It has circuits for almost anything you might want to do to your sound, with schematics, detailed descriptions, and usually a PCB for purchase. One minor sticking point for you might be that these circuits are designed for ±15V supplies (30V total, with signals referenced to a center-tap). If all you have is 5V, you might be able to make a switching power supply that provides that, or you might be able to adapt the circuits to run on 5V with a higher noise floor. (Actually, the noise level stays the same, but you're using a smaller signal.)

Aaron Duerksen
via email


Low Audio On Dish Receiver February 2013

I'm looking for a schematic for a Dish Network satellite receiver model DISH311. The audio is too low and I'm wondering if there was any adjustment that could be made to increase it.

#2133
Wayne Carpenter
Omak, WA


I Want My MP3 January 2013

I want to play my MP3 player through my car stereo, but it does not have an auxilliary input to plug in at. It does, however, have a separate CD changer. Can I simply wire the CD changer and an audio jack for the MP3 player to a selector switch, and use them both on the CD input? Seems too easy. What am I missing or is there a better way?

#1133
Sam Friers
Eugene, OR

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