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Recent Questions

2020 Issue-3


Amplifier For VHF TV

I have a rather complicated TV reception system. I have four antennas all successfully combined into one by using modules to convert the RF signal to VHF siganls. What I am lacking is a constant input for all signals into the combiner.

I would like to take signals from 54-216 MHz with 1-8 dBmV input and put out 18-25 dBmV with as little noise as possible. It would be great if I could clamp all signals to 25 dBmV.

#03201
Howard Epstein
Gilford, NH


Model Train Controller

My son has recently become a model train enthusiast and asked me how to control multiple trains on the same track. Is it possible and how would one go about building a controller?

#0322
Paul Sills
Grand Rapids, MI


Transformer

How do I calculate the number of turns for both the primary and the secondary windings of a transformer?

#0323
Opeyemi
Ibadan, Oyo


Home Circuit Boards

Does anyone still make oneoff circuit boards at home? What methods are being used by hobbyists and where do you get supplies?

#03204
Alvaro Collazo
Gulfport, MS


Electronic Candle Circuit

I’m looking for a simple circuit for a 24 hour electronic candle that uses very little power. The candle would drive a single LED. It would run for x hours (say five), then turn off; 24 hours after it  has first activated, it would automatically turn back on for the predefined time.

I've found several ideas, but most of them surrounded the 555 chip which has a very limited time frame.

#03205
Scott Lapp
Simi Valley, CA


2020 Issue-2


Adapting a GPS Time Receiver

For more accurate timekeeping, how would I connect a GPS time receiver module to the PIC16F876A of the Numitron clock that is featured in Nuts & Volts?

#
BrunoZ
Elmira, NY


Protection Of Device Against Automotive Transients, Reverse Voltage

I was wondering what would be suggested to properly provide protection of a device with a 5V low power regulator and LED driver against automotive transients, and reverse voltage that is connected to an automotive starting battery.

I presume a TVS diode could be used, but should it be bi-directional or uni-directional? A Schottky diode could be used for low voltage drop, first in line for reverse voltage protection, but it would have to withstand the clamping current of the TVS diode.

Would it be be necessary to include a resettable fuse if the transient lasted too long and exceeds the power rating of the TVS diode?

#
Wayne Carpenter
Omak, WA


Need Suggestions For A New PIC Programmer

I haven’t done much with PICs recently and I used to use a PICKit1, which is now obsolete.

Now, I want to re-program something I made about 10 years ago, my PICKit1 is no longer usable, and my old development software won’t play nice with Windows10.

I look at the array of products available and I am overwhelmed. So, what do I need to have a modern equivalent of a PICKit1 and what software do I need to program PICs using C?

Also, in addition to a Windows set-up, is there a Linux-compatible option as well? I tried contacting MicroChip but got no help there.

#
Keith Ujvary
Oliver, British Columbia


2020 Issue-1


Gummy Lubricant

I have an old Leitz Wetzlar Type 31575 slide projector that uses two solenoids for operation by a wired remote for advance and focus. Whatever lubricant was used has thickened too much after too long in storage, keeping the solenoids from operating without coaxing. They are accessible from the bottom access plate intended for lubrication of the associated mechanisms, but removal of the plunger is not possible without a total tear-down top to bottom, which is risky on old equipment with no manuals. I’ve had plastic gears shatter in similar equipment, so that will be my last resort. Wiping down the plungers was not adequate. Something stronger than alcohol is needed.

What sprays would be safe to try, preferably that come with a flexible straw, to dissolve and flush out the sludge? Contact cleaner, such as DeoxIT D5, has a lubricant. Would that interfere with the solenoid operation? Is Fluxoff a safe choice?

#01202
Dennis L Green
Farmington Hills, MI


SPDIF Input

I have some legacy recordings on DAT I’d like to re-edit as my skills have improved, but my DAT recorder has only a SPDIF digital output. My old XP box had this on the mother board, and all I needed was the back plate with the RCA jack and the cable to the pins on the board. Adobe Audition recognized it immediately.

Newer computers do not have SPDIF inputs. I would think converting the SPDIF serial stream to serial USB would be simple enough as far as circuitry goes, a lot simpler than an analog composite video (and S-video) plus audio to a USB device I can get for $30 with software. Perhaps a Windows 10 driver is is needed and is a challenge?

Every search only returns a flood of USB to SPDIF dongles, which is the wrong direction, and a few very expensive sound cards with many other unneeded functions. Is there a simple/inexpensive solution?

#01201
Dennis L Green
Farmington Hills, MI


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