Home Up Voltmeter Interface 2012


Line Voltage Monitor

Ordering is closed for this Elmer Project. 

Listen in to the K3MJW Thursday night net at 9pm 146.640 neg offset pl 131.8.

From the November 2010 QST p43  and May 2011.

This is a 2011 Skyview, Solder Smoke Elmer Night project.  

Date October 25, 2011.  

Kit Builders:  Bring your soldering irons and hand tools.  There are five kit builders. 


The Prototype is complete and fully operational!

Volts  New color scales are being printed. 




  1. Power Point Tuesday Night presentation click here and enter login/password.

  2. No password presentation with out protected materials



I need your money before I order.  The meter comes from China and the rest of the parts are for all intensive purposes non returnable. 



100uf 50v





9v Zener







includes shipping.





1k 1/2w





1k linear pot





2.2k 1/2w





47k 1/2




R5, R6

5K linear pot




120 12 vac

Wall Wart 12 vac

12.99 in qtys of 5

data sheet





100piv bridge



Desk Top meter box Enclosure Digikey 8.81    
PCB Printed Circuit  QST OCT'10 EXPANDED SCALE VOLTMETER FOR 120 OR 240 AC BY K1SG $4.50 4.50 Tested good. 4.50


Misc dial scale printing supplies, shipping (not the meter), grommets, shop supplies inflation and unanticipated parts. $1.45




Miscellaneous parts not included (hook up wire, hardware, grommets, etc).


Below is an additional circuit from Page 41, May 2011 QST.  This will add Line Monitor Frequency Display capacities to the above project. 



C1 1.0uf timing capacitor.  Electrolytic.  647-UVZ1H010MDD1TD
M1 1ma meter.  Use switch and current divider resistor on meter above.    $0
Rm  Meter Shunt to be calculated.     
Q1, Q2 NPN gen purp Audio Transistor. 2N3904 From surplus stock.
R1 10k (All resistors are 5% 1/4w unless otherwise specified)    
R2 100k    
R3, R4 10k    
R5 ~15k see text    
R6 440 meter cal see text    
R7 Calculated value see text    
R8 500 or 1000 pot wire wound or cermet.    
R9 100 ohm    
S1 DPDT center off 108-0005-EVX 3.62
U1 12 volt reg 7812 $0.50 Hamvention.
Cregout 0.1uf 50v 667-ECQ-V1H104JL5 .29
Cregin .33 uf  667-ECQ-V1H334JL3 .33
T1 12vac transformer use same from above voltage monitor meter project.    $0
PC Radio Shack solderable Proto board.   2.19



Junk Box Line Frequency Meter


I am hoping to combine this circuit with an additional circuit from a few month later article in May 2011 QST.  The Junk Box Line Frequency Meter.  It displays the line frequency on a compressed scale.  It seems to be a good add on for the above circuit.  Below I am detailing the prototype.  

This circuit is to be build on a perf proto board.  It is similar to a PC board except there are no traces to make intra component connections.  The builder has to use additional wire to make up the circuit traces.  

A DPST toggle switch chooses from Volts or Frequency on the meter.  So far the one problem has been the selection of a meter box.  It appears not to accommodate both circuit boards.  Additionally it seems on evening at Geeks Peak will not be enough time to complete both circuits.

Both of the circuits Volt meter and Freq meter have been bread board prototyped and work great.  This is where I determined the custom resistances needed as per the articles.  This is where also the 100ua meter movement shunt resistor was determined to accommodate the 10ma Freq Meter architecture.  


Some in progress pictures.... 

bottom copper layer.jpg (29289 bytes)

Bottom copper layer to be printed on transparency.  

rev 10/13/11 

component layout.jpg (35166 bytes)

Top component layer to be printed on sticky labels.  

Click here for the Express PCB file for the above two layers.

rev 10/13/11 

IMG_5258.JPG (841673 bytes)

This is an example of the transferred PC trace.  The trace pattern in printed on a printer overhead clear slide, cut to convenient size and lined up with the above silk screen image. 

IMG_5262.JPG (645541 bytes)

Beginning to stuff the board. 

IMG_5257.JPG (766102 bytes)
IMG_5261.JPG (630801 bytes)

R5a and R5b are to be parallel wired.  

IMG_5263.JPG (603428 bytes)R6 is made up of two resistor in series.  IMG_5264.JPG (752018 bytes)

A little finesse is needed to make this pot act as a rheostat. 

IMG_5265.JPG (626095 bytes)

Under side of pot placement. There is room of options. 

IMG_5269.JPG (1005264 bytes)

Stuffed proto board. 

IMG_5271.JPG (982709 bytes)

I bent the lead wires over and soldered in place to form the traces.  


There are some minor pc trace image errors.  But nothing that can not be overcome by careful placement and soldering of components.  



Box details.

IMG_5362.JPG (255239 bytes)

Move switch up.

IMG_5357.JPG (311769 bytes)

Add key hole BUT do not drill completely through.  We will do that at Skyview.

IMG_5361.JPG (346829 bytes)

Move wire hole to middle bottom.

IMG_5360.JPG (340298 bytes)

The two boards held in with 1/4 nut driver headed screws.  I have a couple hindered of them.

Click to enlarge.  Then right click enlarged image and save to computer.  Print out using Windows Paint.  It should print out 1:1.  It did for me.

Meter Holes.jpg (296395 bytes)

This is a .jpg file and may not print out 1:1.  Check the 2" hole.



Meter Scale detail.

There are some issues to be worked out.  I want to print this scale in color but I have no functioning color printer.  So I am trying to print to a PDF file but that is not going so well.  


Using the meter in PA


I looked up some documents:  

This document describes at paragraph 57.14. Service voltage the allowable "Lighting" voltage variations and durations.  

The next paragraph below the above hyper linked paragraph 57.15  System Frequency speaks to frequency deviation. 3% is the stated deviation.  That would be 61.8 to 58.2 Hz.  

And here is the TOC of the code.  



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