Newb needs help wiring vintage panel amp meter for Steampunk project

Thread Starter

owensct

Joined Mar 21, 2019
7
Hi All,

First off let me say I’m not an electronics guy, but I have a project I’m working on and I was hoping someone on this forum might be able to provide some information to assist me in what I’m trying to accomplish. Also, you’ll really have to dumb it down for me.

I’ve built an industrial/steampunk shelving unit in my home office for a new PC I’ve built, (Gas pipe, steam gauges, copper piping, valves etc) and I have an Amazon Echo that I want to add to the steampunk motif. What I would like to do is build an enclosure for the Echo and add copper piping, etc to it and (here is where I need the help) a vintage Westinghouse DC panel AMP meter (.1 to 1.5 amps) that I would like to fluctuate up and down depending on the amp draw of the Echo. The research I’ve done indicates that the Echo amp draw varies depending on what the Echo is doing. Further my research seems to indicate that I need to put the amp meter inline between the wall wart and the Echo like so:

Postive wire from wallwart>>>Positive terminal on amp meter >>>Positive terminal amp meter>>>Positive lead on Echo
Negative wire from wallwart>>>Negative terminal on amp meter>>>Negative terminal amp meter>>>Negative lead on Echo

I’ve seen other information that indicates not to do it this way, (but not real clear on what way to do it) and which also says I need a shunt (???) and possibly a resistor.

The Echo power supply rating is as follows Input: 100-240V~0.5A 50-60Hz Output: 15.0V ---1.4A

The accuracy of the meter is immaterial to the project as its just for looks. I’m hoping someone might be able to point me in the right direction so I can avoid smoking the meter or more importantly my Echo. Please remember I am a complete newb so if you provide me with a circuit diagram, I probably won’t understand it, very simple is best and/or YouTube video work great as well. I know so little about this type of connectivity and in respects to correct electronic terminology that I’m not even sure what terms to search for.

Any help is much appreciated.

Thanks

Gordon
 

Yaakov

Joined Jan 27, 2019
1,612
To do this, you need to measure the current at the output form the power supply, not the input to it. There will not be enough difference in the current on the input side to deflect a meter sufficiently for show.

You could build up a little board that has a DC barrel connector matching the Echo supply connection, and with a cord from the other end that matched the input.

On the board would be a shunt resistor, and the meter would be connected across it.

The meter would be a milliammeter, and it might require a resistor in series for scaling.

Alternatively, you could use an active circuit that would drive the meter however you'd like.
 

Thread Starter

owensct

Joined Mar 21, 2019
7
Hello Yaakov,

Thank you for the input, based on that a little searching turned up this. Is this a good example of what your recommending?


Thanks

Gordon
 

Yaakov

Joined Jan 27, 2019
1,612
Hello Yaakov,

Thank you for the input, based on that a little searching turned up this. Is this a good example of what your recommending?


Thanks

Gordon
Yes, and you could even use a big fat old fashioned shunt rated at far too much current for the steam punk effect. Check eBay for "Weston milliammeter" or for shunts rated for high current.
 

Thread Starter

owensct

Joined Mar 21, 2019
7
Yes, and you could even use a big fat old fashioned shunt rated at far too much current for the steam punk effect. Check eBay for "Weston milliammeter" or for shunts rated for high current.
Awesome, thank you so much for your help. I'll check it out. FYI this is the meter I bought, I can't read the rating on it, so your suggestion sounds like the best bet.

Gordon
 

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Thread Starter

owensct

Joined Mar 21, 2019
7
Hello Yaakov,

When I look at the meter with a magnifying glass at the base it reads Westinghouse Style 1159170B Type RX-35. Where can I find the specs for this meter so I can get the correct matching shunt. I looked up the shunts rated for high current and they are a little more than I want to pay as my accountant, (wife) is already giving me grief about budget overruns on my little Steampunk shelving project, lol.

Thanks

Gordon
 

Yaakov

Joined Jan 27, 2019
1,612
Hello Yaakov,

When I look at the meter with a magnifying glass at the base it reads Westinghouse Style 1159170B Type RX-35. Where can I find the specs for this meter so I can get the correct matching shunt. I looked up the shunts rated for high current and they are a little more than I want to pay as my accountant, (wife) is already giving me grief about budget overruns on my little Steampunk shelving project, lol.

Thanks

Gordon
What does your existing meter say below “AMPERES” on the face?
 

Thread Starter

owensct

Joined Mar 21, 2019
7
Hello Yaakov,

Below the word AMPERES it says Direct Current. All the markings I am able to discern on the meter are as follows:

Top of meter face = Made in USA and Westinghouse
Middle of meter face = AMPRES and Direct Current
Bottom of meter face = Style 1159170B and Type RX-35
back of meter looks like 803959, 95 and 855, (see pictures)

Other than the above I can't discern any other lettering. I did a Google search for Westinghouse Type RX-35 and got hits, but non that gave information on the specs for the meter, that I could tell anyways, b ut like I said I'm a newb, the specs could have been there without my realizing it.

Thanks

Gordon
 

Attachments

Yaakov

Joined Jan 27, 2019
1,612
From what I can find, the shunt is built in to that meter, it can be wired in series with the positive lead (input to the + terminal and output from the - terminal). You can test this, but you will have to be very careful. If you have a constant current power supply or some kind, you can try very low input and see if the meter acts as expected. The actual movement is going to be full scale in millivolts.

If you use a DMM to measure the resistance across the terminals, it should be quite low, and the meter should not move. It is bangs against the end when you try, you need a shunt.
 

AnalogKid

Joined Aug 1, 2013
8,493
My guess agrees with his guess, the shunt is built-in. Do you have a DMM (digital multi-meter)? If so, put it on the lowest resistance scale and read the meter's resistance between its main terminals. Your meter might read 0; don't worry, this is good. The internal shunt value probably is less than 1 ohm, too low for your meter but, more importantly, way lower than a meter without a shunt inside.

An ammeter is connected "in series" in a circuit. All of the elements form a long loop. Connection sequence:

Wallwart + to Meter +
Meter - to Echo +
Echo - to Wallwart -

DO ***NOT*** connect the meter directly to the power supply with nothing else in the loop.

ak
 

Thread Starter

owensct

Joined Mar 21, 2019
7
Guys,

Thanks for the input. I have a DMM so I'll run the test you suggest tomorrow. After that I will write out a simple circuit diagram on paper, (try not to laugh too much when you see it) and run it by you guys BEFORE I wire anything up. If it passes muster here I'll wire up the test circuit and if that looks good try to create the same circuit using the Amazon Echo as the load.

Now I just need to look through my various boxes and bins of parts and pieces to find something to use for the circuit.

Thanks

Gordon
 

Thread Starter

owensct

Joined Mar 21, 2019
7
Hi Guys,

Just wanted to touch base to let you know I haven't had a chance to put together a circuit diagram yet, had to help my Brother in-law with a project, hopefully I will have something in the next several days for you to review for me.

Again thanks for all your help, it is really appreciated.

Gordon
 
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