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Danr posted:

You could try something like this instead.

http://www.ebay.com/itm/like/2...22&ul_noapp=true

That one won't measure below 100volts. I built a panel last year. I could not find a dual, digital meter that would work. I found separate meters, but it was pretty complicated to power and wire them. There is a whole thread on it. 

Can't you find the Lionel meter made for the ZW? I know they are somewhat scarce and a little pricey.

George

Chuck, I insisted.  I asked for a return shipping label since they were not as advertised, and of course a full refund.  Knowing they probably had about 50 cents into them, they decided to issue the refund and skip the return shipping.  I can only imagine what it costs to ship something to China, but I know it's not cheap!   Shipping the other way is a whole different story...

I am NOT proposing this as a solution but simply fodder for discussion for MacGyver fans (the original series). 

Self-powered LED digital AC voltmeters mentioned above that operate between 100-300V AC (or whatever) are like DC automotive voltmeters with a narrow operating range.  In other words they are application specific.

105-2362

I don't think the market is large enough for a mainstream manufacturer to produce a digital panel meter for O-gauge AC voltage (or current).

So here's the MacGyver angle.  If you take a $1 eBay LED DC voltmeter and add 50 cents or so of parts, you can make a self-powered AC voltmeter with (in my opinion) acceptable accuracy over a practical range of O-gauge track voltage, say, 10-20 V AC.

macgyver LED voltmeter for O-gauge

Note that for another 25 cents or so you can get a panel mount version of the DC LED voltmeter.

Here it is in action measuring the Z-4000 AC output as the handle is moved up and down between 10 and 20 Volts AC.

The idea is to convert the AC to DC with a bridge rectifier and capacitor.  The DC powers the $1 LED voltmeter module.  A 10k trimmer potentiometer divides the DC voltage to scale it to the magnitude of the AC voltage.  The potentiometer is adjusted to minimize error at the center of the measurement range...in this case 15V AC.  The MacGyver AC meter will under-report voltages at the bottom of the range, and over-report at the top of the range.  But as the video shows, it's really not that bad..maybe 1V error at the end points.

Note that most, if not all, AC digital voltmeters have at their core a DC voltmeter!  I recall a recent OGR thread where the application of the digital panel meter was to monitor the AC accessory voltage (14V AC).  So in that application, this self-powered $2 digital meter would be "centered" at 14V and would be suitable for monitoring/verifying the accessory voltage.

Anyone who has made it this far in reading this should be able to imagine how a $1 current-transformer off eBay can extend this technique to an AC current panel meter with similar considerations.

This is simply a take-it or leave-it idea that only took a few minutes to dream up and prototype.

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  • 105-2362
  • macgyver LED voltmeter for O-gauge

This is simpler for an AC voltmeter:

http://www.ebay.com/itm/85L1-V...b:g:sowAAOSw5cNYTMiq

Sometimes it's better to aim for mid scale for your normal reading:

http://www.ebay.com/itm/AC-30V...2:g:VakAAOSwRgJXhvwg

Here's a simple AC ammeter:

http://www.ebay.com/itm/Class-...0:g:tuoAAOSweXhXmOCA

Look around in this ebay area for analog meters, there are many, and for our purposes accurate enough if they are repeatable. Stan2004's idea is of similar or better accuracy actually.

gunrunnerjohn posted:

Chuck, I insisted.  I asked for a return shipping label since they were not as advertised, and of course a full refund.  Knowing they probably had about 50 cents into them, they decided to issue the refund and skip the return shipping.  I can only imagine what it costs to ship something to China, but I know it's not cheap!   Shipping the other way is a whole different story...

Same exact thing happened to me. I am lucky I checked the meter label, because the box was labeled different. I had four meters. They made me pay return shipping to China, but reimbursed me for it. I was shocked that it was only about $15 shipping.

Yes if I had looked at the meter face in the original ebay ad, I would have seen the dc symbol right on the meter. Of course, sometimes the pictures are generic, but this time not. Anyway, I made use of them and would have ordered them for a future project for my sign power supplies.

I bought this 

http://www.ebay.com/itm/1pcs-A...?hash=item51ef6f5949

and this

http://www.ebay.com/itm/3-1-2-...?hash=item1e7a6ee515

and something like these 

http://www.ebay.com/itm/DC-DC-...?hash=item232c131329

I bought 4 of each to handle 4 train power feeds. The isolated converters are critical. I powered the converters with a laptop power supply. I added a power jack and switch to a Radio Shack breadboard to wire everything. This was a fair amount of soldering for me. The meters are mounted to a black chalkboard panel from Home Depot. I suggest making a cardboard template first. 

All in, it cost a little over $90 for the project and took time ordering, waiting for and wiring the parts; probably about 3 months start to finish. 

Sorry, I forgot to take pictures today. I would have bought the Lionel unit and mounted it to my panel if it was available.

George

Recovered posted:

Thanks every one for all the input, Now I'm thinking maybe just buy a couple cheap multi meters and wire them in to my 2  ZW outputs and use my regular clamp amp probe to check amp draw.

Careful, I looked at Harbor Freight, and the cheaper model didn't read AC volts. Also, you will need to set the meter to measure current or volts, one at a time, and the LCD display is hard to read in low light.

Last edited by George S
cjack posted:

I wonder if this meter

http://www.ebay.com/itm/Blue-D...%26sd%3D400888428064

which has the separate power supply (4 wire hookup), actually reads down to 0 Volts AC

 

I bought ones like those first. They work but do not display tenths of a volt.

For the Postwar ZW, the 20 VAC meters I linked above should work, but I heard the Postwar ZW can put out up to 21 volts. I use mine with PH 180 power supplies that  put out 18 volts.

stan2004 posted:

... SNIP ...

Anyone who has made it this far in reading this should be able to imagine how a $1 current-transformer off eBay can extend this technique to an AC current panel meter with similar considerations.

This is simply a take-it or leave-it idea that only took a few minutes to dream up and prototype.

Stan, I tried this exact technique when I first did my track voltage measuring car.  I wasn't able to get a calibration close enough to make it workable, I had at least 2 volts error in spite of adjusting the range.

I wonder if it would be possible to tinker with a component value in the A/C meters to get the voltage range down into the useful range for O-gauge work?

gunrunnerjohn posted:
stan2004 posted:

... SNIP ...

Anyone who has made it this far in reading this should be able to imagine how a $1 current-transformer off eBay can extend this technique to an AC current panel meter with similar considerations.

This is simply a take-it or leave-it idea that only took a few minutes to dream up and prototype.

Stan, I tried this exact technique when I first did my track voltage measuring car.  I wasn't able to get a calibration close enough to make it workable, I had at least 2 volts error in spite of adjusting the range.

...

Well, you must first watch a few re-runs of MacGyver to focus the mind!  

With AC track voltage of 15V, the 10k trimpot sets the LED digital output between 0 and 19V...which is what I would expect.  That is, 1.4x multiplier going from AC-to-DC into a capacitor...less 1.4V DC thru the bridge rectifier.

In any event, this was inspired by comments on other OGR threads about how guys actually use an LED panel voltmeter in modern layouts.  That is, you have a KW, ZW, whatever with variable output...and you want to set it to fixed 14V AC for Accessory Voltage.  Or set it to fixed 18V AC for command track voltage.  In other words, the required operating window is somewhat narrow.  So as long as the meter does not indicate something stupid outside of that range...

As you know, when troubleshooting vexing voltage issues on a layout, it's rarely an issue solved by looking at the transformer's digital readout.  That's where your Voltmeter car saves the day because the problem is undoubtedly something in the wiring, connectors, etc. after the transformer.  In my opinion of course!

I used the analog meters like cjack linked above. I have 0-30 vac and 0-15 amp. Then I copied GRJ's voltage car (with his help) when I saw the digital combo meters, been looking ever since with no luck so far. The analog meters work fine and require no external power, just connect to the power wires to the track. I like Stan's idea too, actually I like all of his ideas like this! 

Last edited by rtr12

Good finds! Thanks for the links, from looking at them I also found this one: 

Yeeco AC 0-199.9V LCD Display Digital Voltmeter Voltage Meter Volt Testing Gauge Voltage Measuing Volt Panel Meter also from Amazon. Looks like it has a little better resolution (in tenths) and smaller/tighter range which might provide a bit more accuracy.

Unfortunately they are priced much higher than the ones that were available a few years ago, but those seem to be extinct these days. However, since I am a sucker for these things, I might just try a couple to see how they work out. 

I missed the 'Accuracy: 0.5% ± 2 words' part...  I have no idea what that means either?  A Typo, and they really meant what you said about the digits?

I am guessing they might be close enough though, I think my copy of your voltage car has the 0-199.9V meters in it and it has always been fairly accurate. Sure wish they would bring back the less expensive models and make a combo volt/amp meter that we could use for trains. 

I may have gotten the last two of those 0-20V meters? Those were the ones that burnt up rather quickly when I powered them up...no DC-DC converter that you later told me about, oops!  When I went back to order replacements, all they had was the 0-199.9V ones and I don't recall ever seeing the 0-20v again after that.  At least they still had AC meters back then and they were only about $4 or so as I recall.

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