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Recent Questions

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


Voltaic Cell Help

I need help to improve my neat SALT WATER Voltaic cell. I started with copper as my positive elactrode and aluminum as the negative electrode. The result is 337.5 millivolts. Then, I temporarily used a steel plate and I got 830.0 millivolts. That was better, but its an alloy and not pure iron. So, is there a better metal that can beat both of them? I need to get to 1 volt or better. So what metal will do that in salt water?

#01203
Victor Davis
Horton, AL


2019 Issue-6


Ripple Voltage Monitor

I need a circuit to monitor the AC ripple voltage on a 12 volt linear power supply? A digital display would be ideal.

#06191
Brian Lambdin
Plano, TX



Answers

Mr. Lambdin inquired about a circuit to monitor the AC ripple on the output of a linear power supply.  The inference is that the frequency response of the circuit need not be excessive. He also wanted a digital display.

I found what ought to be a suitable device, in kit form, from Amazon, for $29.95. See https://www.amazon.com/Oscilloscope-Handheld-Pocket-size-Electronic-Learning/dp/B01LWK49W3/ref=asc_df_B01LWK49W3/?tag=hyprod-20&linkCode=df0&hvadid=309778489815&hvpos=&hvnetw=g&hvrand=18068906155916055584&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1018200&hvtargid=pla-465542683176&psc=1

Peter A. Goodwin
Rockport, MA

In a linear supply the vast majority of the ripple will be at the input frequency which will normally be the power line frequency (50 or 60 hz) or two times that frequency (100 or 120 hz.) A digital multimeter on the AC volt ranges is intended primarily for that frequency range. By blocking out the DC from reaching the meter any DMM set to the AC volt ranges should measure it fairly well. A "True RMS" type meter is best since the ripple probably will not be a sine wave.

To block out the DC part simply put a capacitor in series between the positive side of the supply and the positive input of the DMM. A value of 1 microFarad or more should work. If you use any type of polarized capacitor such as an electrolytic make sure to connect the positive end to the positive output of the supply. Of course, make sure the voltage rating of the cap is higher (16 or 25 Volts should be fine) than the supply. You may need to put a fairly high value resistor (say 10 K Ohms) across the meter leads (from the negative end of the capacitor to the negative side of the power supply.

William Cooke
Adams, TN


LED Fader

I need a simple method to slowly fade an LED from bright to dim, then to bright again in about two seconds, then keep repeating. Does anyone have a circuit that does not require an IC?

#06192
Cindi Carrillo
Lexington, KY


Transistor Confusion

What determines which type of transistor to use in a given circuit? Are they interchangeable with those of a different type that I may already have on hand?

#06193
Donald Bodine
Middleham, UK


Relay Diodes

I sometimes see a diode placed across relay contacts backwards. Can someone explain the purpose of this and when it’s necessary and when it’s not and why?

#06194
Jürgen Abend
Pleasanton, CA


More Questions