Electrical troubleshooting

This page will have misc. tips, in no particular order.

Voltmeter - get one!

Get one, even a cheap one from Harbor Freight. Do not use test lamps, they will fool you. I won't go into why. Get one with multiple amps scales and multiple ohms scales. I found one at Harbor Freight for about $5.50 and it even has a backlight.

You need one, and there is no excuse with costs that low. Find a friend that can help you use it.

Measuring voltage:

When you measure the voltage of a circuit, it's like getting the pressure of your house watering system. You don't need any water to flow, you just stick the gauge anywhere.

Voltage is like that, except you have to have 2 connections to measure the voltage, you are measuring the potential or difference between 2 points. If you measure DC, there will be a plus and a minus side, and your meter leads are normally black and red. Black is normally minus, and red plus. On a digital meter, if you hook them up backwards, then it usually shows a minus sign "-" on the screen.

Measuring AC voltage, you can use either probe, because the A in AC means alternating. The polarity of the voltage is reversing many times a second. There is a special circuit in the meter to accommodate this.

So, to measure the voltage on a battery, put the two probes on the plus and minus terminals. If you have a light bulb running in a loco, while it is lit, if you connect the 2 probes on each terminal of the light bulb, you can see the operating voltage.

To recap, to measure the voltage, you just put the probes across the part of the circuit where you want to measure the voltage.

Measuring current:

OK, this is way different, and can be dangerous, in that you have to change some wires around, and have the potential of short circuits, or damaging the meter.

Current, in amps, or thousandths of an amp (milliamps) is sort of like how many gallons of water per second is flowing in a pipe. In this case it's the number of electrons through a wire. To measure this, you have to "break" a circuit and "insert" the meter into the circuit, so that all the current flowing goes THROUGH your meter. You have to make sure your meter will handle the current too, some meters can only read thousandths of an amp, and if you wanted to measure the current through a motor, you might need a 5 amp capacity.

The meter will tell you what current it can measure.

All circuits that have power run in a "complete circuit", that is a big loop. You need to put the meter in the loop.

It does not matter where in the loop it goes, because, like a water pipe, the flow at one end is the same as at the other (in gallons per hour).

Finding power problems in powered track:

Basically you want to design things so that you can isolate the power to find a "break" or short. That means if you have a loop of track, one break will not necessarily show up (give clock explanation.

I'm building a high current load to help isolate poor conductivity problems. You cannot just measure voltage with no load on the track.

Basically a poor conducting area or joint is a resistor. The voltage across a resistor is proportional to current flow.

So, many people go out on their rails, and measure the voltage and everything looks fine, but the problem will not show up because there is no current being drawn.

So, to be able to test easily with a voltmeter, you need a significant load at the "far end" of a powered track and then you can easily check the voltage on either side of a joiner.