A friend, who is a lot better with electronics bought a volt-ammeter to hook up so we can see the the volt and amp readings as we run trains. Unfortunately he is sick and I am trying to figure out how to wire it. The diagrams I find on line for this part I can't translate to using it on my MRR.
It has 3 wires, black-red-yellow. Trying to figure out how it works I hooked it to a 3 volt battery with the neg. battery connected to either the yellow or red wires I get 3 V and .01A. Negative to yellow I get nothing.
When I hook it to the track I do not get meaningful readings. If I hook neg track to the black lead and the positive tack to the yellow lead it causes a short. When I hook the negative track to the black lead and the postive to red I get a reading of 0.45 V and 0 amps. When I hook the positive track to the red lead and the negative track to the yellow lead I get .43 V and no amps.
I know from using a meter designed to read DC voltage there are 14 volts.
Any idea how to hook this up so I get volt and amp readings as I am running my trains?
Patience please with an electronics neophyte.
Need some kind of diagram or instructions, if there are 3 wires, then one pair goes in series with one rail's power, and the third wire would go to the rail. I wouldn't randomly try wires too much, you may burn it out.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Found this link. These devices are fairly common on ebay and Amazon. I have a couple but not this model and I use them only for voltage.
I believe this is what you have. Nifty little volt ampmeters.
https://www.youtube.com/watch?v=1mpuF2Ss7J8
Also.
http://diyprojects.eu/how-to-wire-digital-dual-display-volt-and-ammeter/
A search for,
using three wire volt ampmeter
will bring up more links.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
No idea if you need a shunt for reading amps. I would suspect maybe one amp when running a DC loco.
As you can see, these meters are only for DC. More images in the below link for those who like projects like this.
http://tinyurl.com/z9gc9o3
I use a single display version for the 36 volt motor assist on my bicycle. Helps on hills and keeping track of battery power.
I use several of these nifty readouts. Follow Rich's links and you will figure it out.
If you are trying to read track voltage in DC and you slow your train to a stop you will no longer be powering the meter. There are other meters with a separate power input that will read down to 0 volts.
Red = DC + in
Black = DC common — also load common —
Yellow = DC + load
You need a model like this to read voltages down to 0
https://www.amazon.com/DROK-DC0-100V-voltmeter-Multimeter-Monitoring/dp/B00BYKRETK/ref=pd_sbs_469_5?ie=UTF8&pd_rd_i=B00BYKRETK&pd_rd_r=89P2ARM5XPM0DBWSDSHX&pd_rd_w=Awgld&pd_rd_wg=hyBWF&psc=1&refRID=89P2ARM5XPM0DBWSDSHX
Another thing to keep in mind is that if you have the meter after the reversing switch you will be giving the meter the wrong polarity half the time.
You have to wire it ahead of the reverse switch.
Good Luck,
Ed