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Tuning The Music November/December 2018

Is there a way to vary the speed of a music CD player? I play my instruments along with the recordings and need to vary the pitch slightly to match the tuning of my instrument. We used to do this easily with vinyl by varying the speed of the turntable.

Klaus Herman
Raleigh, NC


CD players for professional/DJ market have variable pitch built in.

Erik von Seggern
Escondido, CA

I would be surprised. CD players are designed to KEEP their speed. I would convert the song to one of the usual audio file formats (mp3, wav) and run it on a computer with the free audacity tool. That lets you change the speed and even allows you keep the pitch! (Effect -> Change Tempo; Effect -> Change Speed). I use audacity constantly.

Werner G
via email

About Resistors November/December 2018

Could someone explain what pull-up and pull-down resistors are, when and how they’re used, and how to calculate their values?

Andy Dietrich
Dallas, TX

Reflow Oven Opinions Needed November/December 2018

Anybody doing SMT reflow soldering at home? Trying to make the switch from TH to SMT. I was wondering what homebrew oven setups people are using and any tips and advice for a newbie.

Joey Dampier
Reston, VA

PC Joystick Interfacing November/December 2018

Is it possible to connect a joystick to a microcontroller? PIC, PICAXE, etc. I don't want to have to take apart and hack the joystick. If so, what is required?

Nick Hulst
Cedar Rapids, IA

Wireless Data To PC September/October 2018

I have a number of wireless temperature/humidity sensors made by Oregon Scientific for use as weather station sensors. I would like to use them for a data acquisition and monitoring application. Does anyone know what frequency and mode they operate on and how I might use them to send data to a PC to record seasonal trends? Would I need a microcontroller to interpret the output or could it be read directly by the PC and then logged and displayed using software such as MakerPlot?

Jai Hooley
Edmonton, AB


Oregon Scientific registered with the Federal Communications Commission (FCC) to use 433.93 MHz as the frequency for its units YPGSL109, YPG SL109, YPG-SL109, YPG-SL1O9, YPG-SLI09, YPG-5L109. For only a few dollars you can buy small transceiver modules for the Arduino family of microcontrollers (MCUs), and others.

The arduino could capture raw transmissions and send the data to your PC’s terminal software via a USB virtual serial port. Then you could look at the raw information and decide what it means and how to use it.

Oregon Scientific has published information about its communication protocol and you can find here: wmrx00.sourceforge.net/Arduino/OregonScientific-RF-Protocols.pdf. The SourceForge project has other information and code that might help you: wmrx00.sourceforge.net.

Jon Titus
Herriman, UT

PCBs With PTHs July/August 2018

Is there a hobbyist method for making circuit boards with plated through holes at home? Also curious by what is meant by multilayer boards. I'm just getting started, so forgive if this is an obvious newbie question.

Leonelo Márquez
Maplewood, MN


I gave up making boards years ago. Hazardous chemicals, lots of fiddly fine work. Double side boards require precise alignment, and multilayer boards are impossible at home.

A multilayer board is a board that has conductive layers sandwiched inside the board, usually one for power and one for a ground plane — for a total of four layers (top, ground, power and bottom). More layers are also possible, of course.

Jay R Jaeger

Etch or mill your circuit boards with space for larger holes where you need them to be plated thru. Insert small grommets made for that purpose into the holes and peen them over. In most cases this will be unnecessary because you can just solder parts like resisters on both sides of the board.

The use of sockets will make working with IC’s, DIP switches, and resister arrays much easier.

Multilayer boards are made up of several thin circuit boards glued together. Four to eight layers are common. The plated thru holes often do not reach the surface of the finished board. You can achieve much of the same effect by adding a daughter board (a shield in Arduino terms), to your design.

Dale Freye
via internet

I don’t know of any easy way to make plated-through holes using home brew PCB etching materials. However, if you use double-sided copper-clad boards, you could make front and back etching screens. Just make sure you securely attach the front etching screen to the blank and re-drill your holes from the front side.

Then, using the drilled holes as a guide, securely attach the back screen to the blank, ensuring you accurately line it up the drilled holes. Then, with both screens still attached, expose both sides of the blank (assuming photo-resist is used), remove the screens, then develop and etch the board.

When you install the components on the front side, ensure you solder both sides of the board where a lead makes a front to back connection.

As for multilayer boards, they’re exactly what the description is. They’re a sandwich of thin boards, each layer typically 1 millimeter thick, with etched circuitry (single or double-sided) or an un-etched power or ground plane, glued together in exact (i.e., 1/10000” or better) alignment so all the through-holes will match-up when components are installed.

When completed, these boards can be as thick as 5 millimeters or so, with 8 or more layers! Most multi-layer boards use through-hole plating, especially on power and ground planes, to ensure positive through-hole connections (again, depending on how well each layer is aligned when the sandwich is made).

They’re soldered using wave-soldering equipment because hand-soldering risks damaging the board via local overheating, especially when soldering to an internal power/ground plane or even bad solder joints (the solder doesn’t make the connection on internal layers), which is why they’re very expensive to design and manufacture.

Ken Simmons
Auburn, WA

Answers to “newbie” questions always help others. You can create plated through holes in your workshop, but it involves many steps with chemical solutions.

Instead of messy and toxic chemicals, why not solder a jumper through the board to connect conductors on both sides? As an alternate, use component leads to make a side-to-side connection and solder the leads on both sides of your board.

If you truly want plated-through holes, contact a PCB fabricator that will make a run of three or four boards for you with plated-through holes. I have used ExpressPCB and a friend has used OSH Park, both with good results.

A multilayer board has etched copper layers sandwiched between insulating layers and connected with tiny plated-through holes. Search Google for multilayer PCB and you’ll find many helpful cut-away diagrams.

Jon Titus
Herriman, UT

Something Strange With The Range September/October 2018

The effective range of the key FOB for my Ford F150 seems to have decreased over recent months. While it used to work from distances of 75-100 yards easy, now I need to be nearly right in front (10-20 yards) of my vehicle to operate the systems. I changed to a fresh battery, but no difference. Is it likely there is an antenna problem? If so, where is it located and is there a test procedure?

Les Waldroup
Charlotte, NC


Yes, that could be the problem, but remember you have two antennas, one is in the car someplace as well.

The FOB is easy to take apart. the antenna is most likely a trace on the circuit card unless it is very old. I doubt every manufacturer uses the same location but the most likely location is going to be at the end you point at the car.

Remember the online posts saying to increase the range of your FOB, point it at your chin? IMHO pointing at your face or chin had nothing to do with increasing the range except that you had to lift the FOB up a bit higher to point it at your chin. I found I could raise the FOB over my head and substantially increase the range. Till you find the problem you might try that as well.

Phil Karras, KE3FL
via email

I had a similar problem with the key fob for my ‘91 BMW. It got so bad that I had to hold the fob against the drivers window for it to work. After trying new batteries and testing the range of the transmitter at the local auto supply, I decided that the problem must be with the receiver which I found up inside the dash behind the instrument panel. After removing the circuit board from its case, I found that there was an antenna matching network with an adjustable inductor on the board that was not sealed. By speculating how gravity and 27 years of thermal cycling might effect the adjustment, I gave it a quarter of a turn in the opposite direction and, as luck would have it, my effective range was restored to over 100 feet. If your unit was factory installed you can probably find a shop manual at the public library to help you locate it and perhaps my fix will work for you. Good Luck with it.

Jack Noble
Shoreline, WA

Show Me The Power July/August 2018

When renovating houses as a hobby, I need to locate powerlines inside the walls and also underground. What curcuit can I build that would be useful? Also, what is the theory of how such a detector would work?

Denzel Meier
Winnsboro, SC


If you can ensure that the power is OFF (e.g., the main fuse or circuit breaker is open) you could just connect a battery at the end of the power line to be traced, and use a buzzer or test lamp to discover the power line(s) that connect to it.

But... It’s so much simpler (and a lot safer) to just buy a wiring circuit tracer. The device consists of two parts — a radio-frequency (RF) generator that is clipped to one end of the wiring to be traced, and a second instrument that will sniff out the wiring that carries the RF test signal.

Check the Internet for recommendations and merchants.

Peter A. Goodwin
Rockport, MA

The two main ways to trace wires is by inductive or capacitive pickup and by using a metal detector.

If the line is active and carries AC current, then an open inductor (coil of wire) connected to a simple audio amplifier and headphones or speaker will create an audible 50 or 60 Hz buzz near the current-carrying wires. A bulb with a blinker placed as a load on a circuit helps identify a particular line. There are also high-frequency modulated loads to help tracing, e.g. https://www.youtube.com/watch?v=GcaKaAISzjQ.

Capacitive sensors, e.g. https://www.amazon.com/Sperry-Instruments-VD6505-Non-Contact-Sensitivity/dp/B000GLAC5G/ref=sr_1_3, can detect energized lines with no current flowing, which may be useful to identify an unused line inside a wall.

Finally, metal detectors may help to trace wiring inside metallic conduit.

DrM Pippik
via internet

Phone Line Intercom July/August 2018

We use our cell phones as our main phone service, so our “land line” is no longer being used. Is there a way to use the house phone wiring along with the old phones as a whole house intercom system? I have a detached garage/workshop away from the house where this would be especially useful, not to mention almost every room is wired. Would I need to disconnect from the phone company "grid" to do this?

Jay Bousquet
Lexington, NC


Yes, you can use your landline phone as an intercom.

1st option: In our part of Canada, for example, if you dial your own phone number, then hangup when you hear a short “Beep” on the line, the phone company’s automated CO equipment will call you back, and ring all the phones on your line. When you pickup the phone, you will hear the same short “Beeps” on the line, BUT, you can also talk on the line to anyone else in the house/shop, that has also picked up the line.

Try it, it might work in your part of the world too.

2nd option: Most if not all house wiring has 4 conductors in the phone cable, but only 2 wires are used for the actual phone line (usually colour coded Red and Green), the other two (usually black and yellow) are spare. You can use the other two wires as a signalling pair to ring buzzers at other phones.

In the past, I’ve used a low voltage AC source in series with 2 diodes and two buzzers to make a signalling circuit ON THE SPARE PAIR (BLACK AND YELLOW wires).

The AC source was placed at a convenient mid point location, in series with one of the signalling wires (yellow or black). At each phone I installed a diode, in series with a DC buzzer, then placed a momentary push switch across the diode. Note, that the cathodes of each diode must be facing the AC source.

The diodes block any current flow through both buzzers, but if one diode is bypassed by the switch being pushed, the current (now DC) will flow through the both buzzers, signalling attention.

By picking up the phone and dialing any single digit (except 0), you turn off the dial tone, and have about 15 seconds of talk time before a warning tone comes on to signal you do do something, like dial another number. This is as simple as it gets, but there are many more options.

Back in the last century, phone companies didn’t like you messing with their equipment, that probably still applies today.

Using Google you can find many articles on using old style phones as intercoms (http://www.instructables.com/id/How-to-connect-two-phones-at-home-for-an-intercom-/).

A phone works just fine on 12 to 18 volts DC (my magneto phone operates on two 1.5 volt batteries), but then, you MUST, be disconnected from the phone company’s service.

Yar Nirodac
Vancouver, BC

You could use existing phones but you’d need a way to generate a ring signal. Hand-crank ring generators from old phones are for sale on eBay, but an electronic intercom costs less per station. I suggest you use your phone wires for a commercial wired intercom, or try a wireless unit instead.

Jon Titus
Herriman, UT

After disconnecting the line from the telco at the demarc (box most likely on the side of your house), you can do it with a telephone line simulator but for the same money you can just buy a cordless phone system with intercom built in.

As a bonus you can buy models that have bluetooth so you can connect two cellphones and have them ring throughout the house while they sit in their chargers.

Bruce Robin

Unless you are willing to set up your own switchboard and 24 volt power supply, you cannot reuse the phone for your intercom. It is perfectly possible, however, to use the wiring to connect your own wired intercoms which I have done for years. You should have 2 pairs in your home’s phone lines. YES, you must disconnect the pair you are repurposing from the phone system. You can leave one pair connected to your existing phones as a backup.

M. Herman

Smooth LEDs? July/August 2018

What makes some LED replacement bulbs dimmable, while others are not? Some of the replacements I have purchased do not dim very smoothly. They seem to dim in steps and then just turn off before lowering to where I need them to be. The previous incandesants dimmed much more smoothly down to a soft glow. Is there a different, (maybe more expensive) type/technology that  would more closely emulate the incandesants? I'm using an X10 controller for the dimming, could this be the problem?

Everett Barham
Elvaston, IL


There is no such thing as a dimmable LED. The way we get around this is by using Pulse Width Modulation (PWM), which means the LED is turned on for shorter and shorter periods of time within a time frame. You can see that if the LED is turned on for 100% of the time, say 1/100th of a second, then it is on for 10,000 1/10,000ths of a second, the LED will be only 1/100th as "bright" if it is turned down to being on only 1/10,000th of a second for every 1/100th of a second.

I used 1/100th of a second as the time frame because the human eye can't see flickering when the flicker rate is around 1/50th of a second, this is why old analog TV's in the US used 1/60th of a second to build a picture frame, and in Europe they used 1/50th of a second for their TVs.

You can also think about this using a 1 second time frame if you want. In this case when the LED is on only 1/100th of a second for every second of time frame it would appear only 1/100th as bright. The problem here is that we would see the LED turning on and off, so we would lose the appearance of the LED dimming. We have to use a time frame that the human eye can't "see" such as a time frame of 0.01 (1/100th) seconds.

Phil Karras, KE3FL
via email

A LED is a beautiful dimmable device; lower the current, and the output brightness goes down. This can be done through simple resistors, or through PWM (Pulse Width Modulation). That is the good news.

In order to use a LED as a house incandescent lamp replacement, something needs to be done to make that possible. First of all, the voltage is WAY to high, it is AC (the LED prefers DC), and we need to feed it the correct current. So a power supply module is included to convert the 120 (or 220) Volt AC to some small DC current appropriate for the LED used.

Herein lies the problem. This PS module is designed to deliver x mA to the LED more or less regardless of the input. When you adjust the input, the PS module tries to compensate, to the point where it no longer can, often resulting in a flickering light. These are the now non-dimmable LED bulbs.

To make this “house” LED bulb dimmable, a radically different PS module must be built. It must sense that the input has changed (due to the dimmer setting), and adjust the LED current accordingly. Not easy to do! and of course, more expensive.

Several designs have been marketed, some better than others. In most cases, even with a “dimmable” LED bulb, a special dimmer is required. It is a mess, and most still don’t work perfectly.

Bill van Dijk
Carp, Ontario

I can’t answer specifically what is different about dimmable LED lamps, but will note that the type of dimmer is important. You need to use a dimmer specifically designed for LED lamps.

I have had good luck with Lutron CL line of dimmers that are made specifically for LED lamps. These are not X10, I have not seen any X10 dimmers for LED lamps. Also note that X10 light controls generally only work for incandescent lamps, they need a bit of current flowing through the filament to work correctly.

For LED lamps I have used the relay based X10 switch WS13A with good success, it also works with CFLs.

Dan Koellen AI6XG

Different bulbs behave differently so you have try some options. There are some test results on the X10 Forum that you might find useful. X10 dimmers dim in 16 levels so some bulbs may not dim smoothly.

Bruce Robin

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