Counting the number of times an appliance was switched on

Thread Starter

gvg

Joined Jul 20, 2012
4
Hi,
I want to build a circuit that would count the number of times an appliance was switched on. In other words I want to count the number of times mains current was on. Ideally I would like to house it into an adapter like this one so that it could count the number of activations of any device connected. Is it doable? I made an extensive Google search with no success.
 

MrChips

Joined Oct 2, 2009
30,458
The design would depend on the type of appliance and the amount of current it draws.

Is the appliance powered by DC or mains AC?
Does the appliance have soft power switch, i.e. does it always draw a small amount of current even when it is “off”?
 

Thread Starter

gvg

Joined Jul 20, 2012
4
Is the appliance powered by DC or mains AC?
Does the appliance have soft power switch, i.e. does it always draw a small amount of current even when it is “off”?
It is for mains AC appliances. Let's assume that the appliance does not draw any current when switched off (a pump, for example).
 

MrChips

Joined Oct 2, 2009
30,458
You could buy a power meter. Maybe it does not count the number of times the appliance is switched on but maybe it will provide the information you are seeking.

1601904013901.png
 

jpanhalt

Joined Jan 18, 2008
11,087
Unfortunately, many or maybe most appliances today have parts that draw a little current while "off." For example, a clock or a microcontroller that goes to sleep.

You could monitor current at the plug and only count when it exceeds a certain level that indicates the appliance has been turned on. A Hall sensor or current transformer (coil of wire around the live wire) can monitor current.
 

Thread Starter

gvg

Joined Jul 20, 2012
4
You could monitor current at the plug and only count when it exceeds a certain level that indicates the appliance has been turned on. A Hall sensor or current transformer (coil of wire around the live wire) can monitor current.
OK, I need to investigate Hall sensor idea. Thank you.
 

AnalogKid

Joined Aug 1, 2013
10,943
One-off or a design for a production unit?

Microcontroller (PIC, Atmel, etc.) or discrete design?

Minimum device on time?

The only way to get the sensor, counter, and display in an in-line housing as shown is with a custom package. Next up after that is a small project box with a panel-mounted plug on one side and socket on the other. With this, the box can be whatever size it takes to hold the circuit board, display, reset button, etc.

To reduce the overall effort, there are many counter/display devices on ebay for very low cost. This reduces the circuit design work to a line current interface and a power source.
https://www.ebay.com/itm/DC-12V-Pow...158731?hash=item2af18cbc4b:g:pJEAAOSwag1fWaFj

An alt-alt-alternative approach is a low-power PIC (or all-CMOS circuit) powered by a lithium battery, that does the counting and display decoding, with the display powered by the current-sense transformer. This gets you a fully-isolated design with multi-year battery life, but the count is not visible when the sensed device is off.

Going with that idea, you could canabalize a little el-cheapo pedometer, the kind health insurance companies give away. Battery lasts years, and they usually have a mechanical switch mechanism that easily can be driven with the output of a current transformer plus some stuff. Hmmm ...

ak
 
Last edited:

Ian0

Joined Aug 7, 2020
9,489
Connect the output of a current transformer to its load "burden" resistor through a bridge rectifier, and put a capacitor across the resistor to smooth the output. Then you can couple that directly to a counter with a schmitt trigger input. Texas still makes the 40110, which will drive 7-segment LED displays and can be cascaded for multiple digits.
The sensitivity (i.e. how much power needs to be drawn before it is detected) can be set by choice of burden resistor.
 

MrChips

Joined Oct 2, 2009
30,458
You can buy something like this Hantek CC-65 clamp meter.
Clamp it on to the power cable and connect the BNC output to a counter.

1601923883484.png
 

Reloadron

Joined Jan 15, 2015
7,447
If it is a simple switched device like a pump all you want is a simple event counter module. Easier bought than built. Google "event counter module". You want one resettable I assume? Look for one with dry contact input and debounce. They are pretty common and should be inexpensive (< $25 USD) give or take. They are also small depending on display you want. Rather than current, which can be done, it would likely be easier to look at voltage across the appliance. Then it is just a matter of simple signal conditioning an input for it. You could likely also use the term "tally counter" for about the same results.

Ron
 
Last edited:

crutschow

Joined Mar 14, 2008
34,027
Going with that idea, you could canabalize a little el-cheapo pedometer, the kind health insurance companies give away. Battery lasts years, and they usually have a mechanical switch mechanism that easily can be driven with the output of a current transformer plus some stuff.
I like that.
It has the counter and the display.
Then it's just a matter of building a circuit to generate the count signal from a Hall sensor or current transformer.
 

soyez

Joined Aug 17, 2020
51
Hi,
I want to build a circuit that would count the number of times an appliance was switched on. In other words I want to count the number of times mains current was on. Ideally I would like to house it into an adapter like this one so that it could count the number of activations of any device connected. Is it doable? I made an extensive Google search with no success.
I have no idea about it...but i actually loved your idea
 
Top