On this page, you’ll find a 1) power monitor that doesn’t require cutting into your caravan’s wiring, and (at the request of Karl M.) a small 2) alert for power loss.

1) Power monitor. A caravan can contain quite a few power consumers. You'll quickly reach the 6A limit from many campsites. At the heart of our electricity meter is a "KWS-AC301" from China, which measures much more than just current. The 20A version doesn't require an external current sensor. A temperature sensor is included.

We mounted this in a waterproof housing, along with a CEE socket and a standard 230V wall socket. The latter is additionally protected with a 10A automatic fuse.

We don't need the buttons on the display. The housing has a transparent cover that we spray-paint black on the inside so that only the display is visible. The CEE connection is on the front, the fuse, and the additional power outlet are on the side. (This outlet is for the 230V cable leading to the awning.)

Photo on the right shows the result. The CEE connection on top is the input from the campsite supply. The white cable coming out of the bottom right goes to the caravan's 230V connection. The socket on the bottom left side leads a cable to the awning.
 
The display offers a lot of information. Not just your current consumption (in amperes and watts). The kWh indicator on the display also shows how much energy you're using over a given period. This kWh display has a memory, even if the voltage has been off for a year.
 
More and more we're encountering campsites that set a maximum: for example, five kWh per day. In those cases, this electricity meter is especially useful.

2) Power loss alert. Some time ago, Karl M. asked if an audible alarm could be added to the electricity meter to signal a power outage at the campsite. We built something just for fun. You could install it inside the shown power monitor, but instead we glued it onto a small phone charger.

The circuit is not critical. After the power fails, the large electrolytic capacitor discharges across the buzzer, which emits about five beeps using a trick with a blinking LED. If you omit the blinking LED, it is a single beep that lasts for a few seconds. The diode is a Schottky diode due to the lower voltage drop. In this case, the capacitor is 47 mF, which Adrian had in his junk box. (Note: that is not µF but 0.047 F. This is available as a Goldcap and cannot tolerate more than 5.5 volts...)

 

Comments and questions:

Ahmed_B: But what exactly is that extra socket on the lower side, in the last photo? Answer: That socket supplies 230V to the awning of the caravan. This eliminates the need for an unsightly extra connection in the caravan wall. See also: Outdoor cupboard

 

 

 

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