wiring ac amp digital panel meter

bullfroggs 

From what you post, I am not exactly sure how and what you are trying to monitor with 4 meters wired in series? Hopefully not all on the same power district, if four separate districts okay. For example, on a post war ZW each Hot binding post controlled by a separate throttle, is the power source for a separate power district---same would be true for a Z4k transformer with multiple outputs or others with two outputs.

You only need one single AC ammmeter per power district[power source or throttle] wired in series on the Hot line[wire to center rail]. This applies whether monitoring railpower or accessory power.

hello dewey and thanks for your reply. what i have is one meter for accessory one, one meter for accessory 2, one for main track and one for my dcc track. all meters are separate from each other until i wire the power to the meters in series from one 5vdc power source. if i turn on the power for the accessories only, the main track powers up which i am assuming that it is getting its power from a feed back from the meters that i have wired the power in series. thanks again.

hello stan and thank you for your reply. you talk about a single transformer powering multiple isolated 5v output converter modules, can you give me a link so i can see how this works and where to buy. thanks again.

I searched ebay for “isolated DC-DC converter” and found http://www.ebay.com/itm/160693240079
which takes 9-18VDCon the input and generates isolated and regulated 5V on the output.  As you can see from the picture, there are two input pins *+ and –“ and two output pins “+ and –“ so easy to hook up. Pretty much all modules look like this.  I don’t know what kind of panel meter you have but most don’t require 3 Watts.  Say your meter requires 5V and 100 mA.  That’s 500 mW or ½ Watt so you might save money if you can find a, say, 1 Watt module - but $5 for 3 Watts is a good $/W value for these widgets in small quantity.

I have not used this particular module nor have any connection to this seller.  Assuming he’s selling what’s pictured, you can get specs and dimensions from the

http://www.tri-mag.com/Converters/TDB4W.pdf .

Pretty much any generic 12V DC transformer will have enough power to drive 4 converters but ask again if selection is an issue.  As you can see from any search, there are more variants than you can shake a stick at.  But you are looking for “isolated” and “regulated” and “5V output” with sufficient mA capability.  Then choose an input voltage or voltage range that you have available.

I suppose to save more space/clutter you could use a 10 VAC accessory fixed output from your train transformer, convert it to DC with $1-$2 in parts (rectifier and capacitor), and use that to power the converters.  Some may have philosophical issues with this but it would eliminate the meter’s transformer.

I use a 12VDC fixed voltage wall wart to power my 17 Tortoise motored switches. I have also used an old variable Voltage DC HO Power Pak in the past[still my backup]. I have a DC Voltmeter across the line to monitor it.

hello stan and dewey. thank you both for your replies. stan, here is a link to the meters i have and if i understand what you are saying, i need 2 modules to take care of my 4 meters. this should take care of my problem and if i ordered them i will let everyone know my out come. http://www.ebay.com/itm/ws/eBa...e=ADME:X:RTQ:US:1123

4 modules.

The PDF for your meter doesn't say how much 5V current is needed. If you know how to measure this do it. Otherwise email the seller and ask.  I'm assuming something less than 100mA.  The input voltage to the modules can come from a 9VDC or 12VDC wall-wart with a current rating of, say, 500mA.  I see these on ebay for under $3 shipped but I'll bet you have one in your attic or garage gathering dust...

hello stan. thank you very much for the diagram and info on this post. now, just one more question and i will be done. if i wire the modules like you show in your diagram, i shouldn't get any back feed from any of these panel meters. i hope i understand this right. thanks again. bill

Hello Bill, you are correct. Since these modules are "isolated" they break the electrical connection between the meters.  As an aside, these modules have really miniature transformers in them to perform this isolation. 

While you wait, you can perform a simple experiment to show how it will behave.  Simply run your train transformer with the shunts in place. The current from your 4 train transformer outputs will flow to your four systems through the shunts.  If you still get "backfeed" then you have a separate problem such as something powered by your accessory output is shorting to a track output.

hello stan. thank you. i have all the shunts wired and everything works fine. it is when i hook the meters up that the problems begin. i am ordering the modules today and when everything is hooked up i will post an update. thanks a lot for your help. bill

hello stan. just an update. got my panel meters today [from china, that's why this update took so long] and got everything hooked up as you said in your diagram and everything worked just fine. no feedback from the panel meters to my track. thanks again for your help and have a nice day. bill

Bill, thanks for the update – so often we never hear back what happened.  Those blue LEDs are very cool so if you get a chance to post a photo of them in action after you finish your panel, I for one would like to see it!

I got a pair of the AC voltage ones, but they sent me DC meters.  They're sending me AC meters now, I'm waiting.

hello stan and anyone else that is interested in this post. here is a picture of what the panel meters look like. enjoy. bill

Looks great, now if I could only get mine...