Determine mains on/off for boiler burner and pump

lbenson · Nov 11, 2016

I want to monitor on/off on my 120V boiler and shallow well water pump. The boiler aquastat has accessible AC lines for the pump and the burner (individual wires for hot and neutral). The boiler circulating pump is 1/6th horsepower, and the burner is of unknown amperage, but I have read online that it might be as much as 7-8 amps.

I have tested one of these "up to 5 amps" current sensors with 13W CFL and 60W incandescent bulbs, and a picaxe easily detects on/off using ADC. I summed ADC readings for a second, and over a given threshhold (determined experimentally), the light was on.

http://www.ebay.com/itm/162136721044

The circulating pump should be under 5 amps (but I don't know about stalled), but the burner looks to be able to surpass that. I have not done any experimenting yet, and am away from the equipment. What would happen to that sensor (and the picaxe) if the current exceeded 5 amps?

I also have this sensor, rated for 30 amps. The problem with it is that it is too large to fit in the aquastat box. I wish to be as non-invasive as possible. I can probably use this sensor in the large switch box of the shallow well pump. I can enclose the smaller sensor in its own plastic box with the mains neutral fed through the box and through the sensor.

http://www.ebay.com/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-Clamp-Sensor-30A-Good-/281687168935

I'm not trying to measure the current, just whether the pump/burner is on or off. Is there an easier safe way of doing this?

In a related matter, I understand that low-voltage wiring in a box which contains mains voltage must be fire rated. Where is such wiring found and how is it designated in the U.S?

abenn · Nov 11, 2016

Have you looked at measuring the mains voltage, rather than the current, to determine whether it's on or off? I can't offer you any links, but it just seems to me it would be a simpler way of doing things. You could even connect a mobile-phone charger to your pump or boiler AC supply, and then all you need to do is determine whether it's giving out 5v DC.

Jeremy Harris · Nov 11, 2016

I tried to detect a voltage dip in the mains when a bit of equipment turned on (in my case a 1hp air pump) and found that it was much harder than I thought. Mains voltage has a lot of noise on it, from switched mode power supplies through impulse noise from things turning on and off to mains signalling systems, like ethernet over mains. I did try for a while to see if I could make it work, but considered that the only way to do it reliably using voltage-only sensing was to sample several cycles and then calculate the rms voltage, to see if there had been a drop equivalent to the 1hp load.

In the end I used a current sensor, as this was far more reliable, but quite costly. I found some sensors that gave out a 0 to 5V DC output that was proportional to the rms AC current being drawn, and that just clipped over one conductor. The closest I can find after a quick search is this unit from Farnell: http://uk.farnell.com/lem/at10b5/current-transducer-10a-voltage/dp/2664108 but I'm sure I didn't pay anything like that price for it. A good search around may well find something similar at a better price.

hippy · Nov 11, 2016

abenn said:
You could even connect a mobile-phone charger to your pump or boiler AC supply, and then all you need to do is determine whether it's giving out 5v DC.

That's what I would do. Wired in parallel with the pump it then gives you an isolated nothing/5V signal when it's off/on. Just connect 0V of this PSU to PICAXE 0V, 5V into a digital input, with a 10K pull-down from that pin to 0V, a 1K current limiting resistor just for extra protection.

Code:

L ---.
     |                 .-----.               ___
     }----------- L -->|  C  |--- 5V ---.---|___|---> I/P
     |                 |  H  |         .|.    1K
    -^-                |  A  |         | | 
    (O) Pump           |  R  |         |_| 10K
    -.-                |  G  |          |
     |                 |  E  |          |
     }----------- N -->|  R  |--- 0V ---^-----------.
     |                 `-----'                     _|_ 0V
N ---'

For additional isolation you might consider running the 5V output through an opto-coupler into the PICAXE input pin.

darb1972 · Nov 11, 2016

Hello lbenson.

I'm away from my office and doing a reply via a tablet so this will be fairly breif.

Check out this IC. HCPL-3700. I don't have a direct link for you. www.avagotech.com. Please Google it. I purchased some from Element14. Their site is down for maintenance so I can't link the part number. It's an affordable (and safe) way of sensing voltage across your devices. Totally isolated. Deals with various mains levels. Can produce square wave or DC results from detection. Output levels are compatible with logic/PICAXE. Input/mains/line levels are "programmable" via external resistors/components. Please download and read the application notes. Very informative. Great little devices. I'm using a couple to detect mains switching on an old Clipsal "Star Serve" system. Can be used for many different sensing applications.

As for the cable, look for "zero smoke, low halogen". There is also various cables on the market that are completely fire rated. Again, check out Element14 web site. Cables used in heaters/electronic start gas heater might also be of use. Many are sheathed in a flame proof fibre/cloth.

I hope this helps.

Regards
Brad

grim_reaper · Nov 11, 2016

This is a problem I've been (very occasionally!) trying to solve for many years now!
The issue IBenson describes is the same as my own - detecting whether power is flowing (or even just voltage is present) inside a sheathed cable without interfering with the sheathing. Or as IBenson puts it, being as non-invasive as possible.
Please correct me if I'm wrong, but the opto-coupler idea, although notionally very good, would definitely involve cutting the feed and wiring it into the detector circuit? Also, if the length of mains wire available is short, the phone charger idea may not be possible if no standard socket can be inserted for the charger to be plugged into!

The ideas I've come across over the years, but still haven't experimented with, are;

Hall effect IC - Theoretically able to detect change in magnetic density within the wire. The usual problem I've read about is that the Live(Hot)/Neutral 50Hz (60Hz!) signals cancel each other out. This might not be an issue in this case, because IBenson mentioned the wires are separated anyway. The theory for this detector is to connect a fairly high-scale Op-Amp circuit to the Hall effect IC and calibrate it to get a 'no magnetic flux' reading and a 'something is happening' (i.e. digital compatible) output.

Simple counter - I won't take credit for this, all the details are on this page. It's a simple mains detector based on a floating input to a counter going crazy when it's near 50Hz (60Hz!) mains. I'm very sure that it could be adapted into a PICAXE compatible detector, but the experiment I was planning on doing was trying to get a PICAXE input to natively response (e.g. count, pulsin, or touch input(?)). Either way, this is in my mind the easiest route to chase.

For anyone else interested in Home Automation (or rather monitoring) and this particular non-invasive methodology, the reason I want to solve this problem is simple monitoring of which lights or appliance are on in the home. I have a loft/attic full of lighting cables, and although in easy reach of many monitoring devices, I obviously don't want to cut into any of them due to the many (ever changing) regulations that says we shouldn't. External sensing through a short bit of wire wrapped round the cable would be ideal.

Food for thought anyway!

stan74 · Nov 11, 2016

Tried these? http://www.ebay.co.uk/itm/like/142129462749?lpid=122&chn=ps&adgroupid=33170564523&rlsatarget=pla-257284464120&adtype=pla&poi=&googleloc=9045370&device=c&campaignid=661219804&crdt=0

rq3 · Nov 11, 2016

lbenson said:
I want to monitor on/off on my 120V boiler and shallow well water pump. The boiler aquastat has accessible AC lines for the pump and the burner (individual wires for hot and neutral). The boiler circulating pump is 1/6th horsepower, and the burner is of unknown amperage, but I have read online that it might be as much as 7-8 amps.

I have tested one of these "up to 5 amps" current sensors with 13W CFL and 60W incandescent bulbs, and a picaxe easily detects on/off using ADC. I summed ADC readings for a second, and over a given threshhold (determined experimentally), the light was on.

View attachment 20456
http://www.ebay.com/itm/162136721044

The circulating pump should be under 5 amps (but I don't know about stalled), but the burner looks to be able to surpass that. I have not done any experimenting yet, and am away from the equipment. What would happen to that sensor (and the picaxe) if the current exceeded 5 amps?

I also have this sensor, rated for 30 amps. The problem with it is that it is too large to fit in the aquastat box. I wish to be as non-invasive as possible. I can probably use this sensor in the large switch box of the shallow well pump. I can enclose the smaller sensor in its own plastic box with the mains neutral fed through the box and through the sensor.

View attachment 20457
http://www.ebay.com/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-Clamp-Sensor-30A-Good-/281687168935

I'm not trying to measure the current, just whether the pump/burner is on or off. Is there an easier safe way of doing this?

In a related matter, I understand that low-voltage wiring in a box which contains mains voltage must be fire rated. Where is such wiring found and how is it designated in the U.S?

A small, home-made Rogowski coil clipped around one of the pump AC wires should easily trigger a Picaxe input directly. I'll have to go try it to make sure I'm not talking through my hat!

lbenson · Nov 11, 2016

Thanks to all for responses. I guess that the suggestion of abenn and hippy may be best. I can take 2 short pieces of bx cable out from the aquastat, connected to the pump and burner leads and feed them into separated outlets of a 2-gang outlet. A phone charger (or the like) plugged into each will give me two 0/5V signals for the picaxe.

Here is my aquastat:

I also found this 30A current sensor with pot adjustable threshold for a digital on/off signal.

http://www.ebay.com/itm/282198624208

I've ordered one of those and will test it.

The bear · Nov 11, 2016

@Ibenson,
From your previous posts, I know you are a clever chap.
This may sound too simple, how about connecting a mains clock/timepiece to your problem area.
It would 'record' how long it was on for a given period.
Good luck, Bear..

abenn · Nov 11, 2016

lbenson said:
Thanks to all for responses. I guess that the suggestion of abenn and hippy may be best. I can take 2 short pieces of bx cable out from the aquastat, connected to the pump and burner leads and feed them into separated outlets of a 2-gang outlet. A phone charger (or the like) plugged into each will give me two 0/5V signals for the picaxe. . . .

Come to think of it, why do you need a PICAXE? If all you want is confirmation that power is there, just connect an LED with a suitable resistor to the output of the phone charger.

lbenson · Nov 11, 2016

stan74, bear, abenn--this is for remote monitoring (sometimes from upstairs rather than in the basement, sometimes from 2,000 miles away). My current system logs events and temperatures around the Nova Scotia house, including temperature on 3 outbound boiler zone pipes and on the return pipe--using picaxes and small routers.

I get daily emails when I'm away, and instant emails and text messages in case of an out-of-bounds situation. The boiler pump can run when the burner is not on, and the burner can run when the pump is not running--because the boiler provides domestic hot water. Knowing those on/off times just satisfies curiosity, but monitoring the shallow well pump could warn me of a leak if the pump runs continuously or more often than expected.

Actually, monitoring the boiler pump could also flag a leak. I had one such two winters ago, which I detected from Florida because of a rising temperature over hours in the basement. I was able to get a plumber to go to the house before any damage was done.

I keep the house heated (minimally) over the winter because I've been told that repeated freeze/thaw cycles are bad for 170-year-old plaster.

SteveDee · Nov 12, 2016

lbenson said:
... I was able to get a plumber to go to the house before any damage was done....

It seems to me that if this monitoring is important, you need to give yourself the best indication of what is happening.

Just measuring the voltage applied does not confirm that the pumps are running. Measuring the current draw on each circuit is a much better indication.

Probably a crazy idea, but how about measuring vibration at/near each pump, is that practical? It would overcome voltage isolation issues.

You could also measure the temperature at the boiler pump outlet pipe (before the zone valve). Again there would be no HV isolation problem.

rossko57 · Nov 12, 2016

Going back to your first post, the 5A rated current sensor won't be damaged by overload, although you wont measure high currents accurately. For your go/nogo situation that would be fine.

Discovering the normal working current for your equipment would be useful, as you can then detect three states for monitoring - off, running, overload (fault). I suspect a pump running dry might be detectable by lighter than normal current load too.

Circuit · Nov 12, 2016

Surely the best solution is simply to install a water flow switch in the pump pipeline; should be an easy cut and shut job. There are many water flow switches available - google your favourite supplier. This will give you precisely the data that are required.

lbenson · Nov 12, 2016

SteveDee--I get confirmation that the pump is running and the zone valves are working by monitoring the temperature rise on the far side of each zone valve. I have a picaxe with an RTC which turns on the pump and opens the zone valves (by shorting out the 3 zone thermostats) for one minute in the am and for 5 minutes late in the evening. If I don't see that temperature rise, I know something is amiss. I will look into sensing the current with the 30A sensor--that will, as you say, provide more information.

Circuit--Installing a water flow switch may be "an easy cut and shut job", but at least for now I'd like to avoid involving a plumber and introducing one more thing that can fail.

rossko57--Thank you for the information that the 5A current sensor (and picaxe attached to it) won't be damaged by overload, even if it won't measure a high current accurately. The similar 30A sensor may solve all the problems. If I wire up a plug-in outlet box with the sensor, I will be able to test current measurement at 12.5A using a 3-position 1500W 120V electric heater (also about 4A and 8A).

grim_reaper · Nov 14, 2016

SteveDee said:
Probably a crazy idea, but how about measuring vibration at/near each pump, is that practical? It would overcome voltage isolation issues.

I don't think that's crazy at all - measuring vibration (on it's own merit) would give you an indication of pump wear/bearing failure/etc. in advance of an actual pump breakage.
I assume you're recording the total time the pump is active for it's maintenance schedule?

lbenson · Nov 14, 2016

grim_reaper said:
... I assume you're recording the total time the pump is active for it's maintenance schedule?

"

" noted, but my mode of operation seems to be "use until failure".

Buzby · Nov 14, 2016

lbenson said:
"" noted, but my mode of operation seems to be "use until failure".

If it ain't broke, don't fix it.

novolts · Nov 14, 2016

120 volt relay across the supply cable to the pump then you have volt free contacts to switch to your monitor Cct
Regards
Novolts

Reloadron · Nov 16, 2016

I generally just use these little sensors.
CR2550 Low Cost Remote Current Indicator
I have used them in large banks with pumps, heating elements and just about anything drawing AC current. They come in a variety of shapes and designs and cost about $11.00 USD each. When I retired about three years ago I had some which had been in service over 20 years. Anyway, something else to consider. The simple LED output can be modified to drive other circuits, for example opto-couplers or modified for remote monitoring situations.

Ron

lbenson · Dec 11, 2016

Neither of the two new currents sensors I tried gave me any variation whatsoever. One always read 0, the other 128.

For the left one, the digital output gave no joy no matter where I set the pot. The analog reading never changed no matter what I turned on or off.

For the right one, the SCT-013-030, I used the following circuit (replace "Ard..." with "PICAXE").

I had left my original modules, which worked for OFF/ON by simply adding up the ADC values for a second, in Nova Scotia, to which I won't return before April. I ordered a couple more of those and rigged up a test outlet box. They worked fine for discriminating between off, a 300W heater, the "low" setting of another heater at unspecified wattage, and the "high" setting, 1500W (also both heaters on, 1800W).

Instead of adding up the ADC values, I looked for the high value in all the readings I could get in 4 seconds after the heater had been on for 10 seconds (fewer than 4 seconds did not give me numbers as reliable, and I think there was inrush current when I first turned on a heater--as there likely will be with a burner or pump first turning on). I got the following ranges with somewhere around 90 readings in 4 seconds, repeated 10 times (the theory being that you are going to get readings at random points on the sine wave, and the highest will be closest to the actual peak):

Nothing: high of 4

300W: 26, 27, or 28

???W: 75-81

1500W: 112-123 with an outlier of 166

1500W+300W: 115-192, with most between 136 and 144

There appears to be an approximate linear progression: 5 times my 300W reading of 26 would give 130, as compared to the 112-123 range for the 1500W heater. The boost to 1800W is close to another 5th. The unknown "low" setting would appear to be around 900W.

Here is a sample of 4 seconds worth of readings for 1800W:

Code:

0 134 120 100 75 0 0 0 26 0 0 0 0 0 0 115 93 0 0 0 39 0 0 0 2 0 0 
126 108 87 0 0 0 35 0 0 0 0 0 0 123 104 82 0 0 0 31 0 0 0 0 0 0 119 99 0 0 0 44 
0 0 0 6 0 0 131 114 92 0 0 0 38 0 0 0 1 0 0 124 106 84 0 0 0 33 0 0 0 0 0 0 121 
100 78 0 0 0 28 0 0 0 0 0 0 115 94 0 0 0 40 0 0 0 3 0 0 127 110 88 0 0 0 36 0 0 
0 0 0 0 123 104 82 0 0 0 32 0 0 0 0 0 0 120 100 78 0 0 0 28 0 0 0 0 0 0 116 94 
0 0 0 41 0 0 0 4 0 0 129 111 90 0 0 0 36 0 0 0 0 0 0 123 105 83 0 0 0 32 0 0 0 
0 0 0 121 100 78 0 0 0 28 0 0 0 0 0 0 116 94 0 0 0 41 0 0 0 4 0 0 128 111 89 0 
0 0 37 0 0 0 1 0 0 125 107 85 0 0 0 35 0 0 0 0 0 0 123 104 82 0 0 0 32 0 0 0 0 
0 0 120 99 0 0 0 44 0 0 0 7 0 0 132 115 94 0 0 0 40 0 0 0 4 0 0 128 111 89 0 0 
0 37 0 0 0 0 0 0 124 106 84 0 0 0 34 0 0 0 0 0 0 122 102 80 0 0 0 31 0 0 0 0 0 
0 119 99 0 0 0 44 0 0 0 6 0 0 132 114 93 0 0 0 39 0 0 0 2 0 0 126 108 86 0 0 0 
35 0 0 0 0 0 0 123 103 81 0 0 0 31 0 0 0 0 0 0 119 98 0 0 0

The max reading was 134.

So my question is, is there something I can do to get better / more consistent readings for calculating current? Perhaps what I need to do is average the reading for as long as the pump/burner stays on, throwing away the first several where there is inrush current, and the last before a return to 0 which might be cut short.

Reloadron · Dec 11, 2016

lbenson said:
I want to monitor on/off on my 120V boiler and shallow well water pump. The boiler aquastat has accessible AC lines for the pump and the burner (individual wires for hot and neutral). The boiler circulating pump is 1/6th horsepower, and the burner is of unknown amperage, but I have read online that it might be as much as 7-8 amps.

I have tested one of these "up to 5 amps" current sensors with 13W CFL and 60W incandescent bulbs, and a picaxe easily detects on/off using ADC. I summed ADC readings for a second, and over a given threshhold (determined experimentally), the light was on.

View attachment 20456
http://www.ebay.com/itm/162136721044

The circulating pump should be under 5 amps (but I don't know about stalled), but the burner looks to be able to surpass that. I have not done any experimenting yet, and am away from the equipment. What would happen to that sensor (and the picaxe) if the current exceeded 5 amps?

I also have this sensor, rated for 30 amps. The problem with it is that it is too large to fit in the aquastat box. I wish to be as non-invasive as possible. I can probably use this sensor in the large switch box of the shallow well pump. I can enclose the smaller sensor in its own plastic box with the mains neutral fed through the box and through the sensor.

View attachment 20457
http://www.ebay.com/itm/SCT-013-030-Non-invasive-AC-Current-Sensor-Clamp-Sensor-30A-Good-/281687168935

I'm not trying to measure the current, just whether the pump/burner is on or off. Is there an easier safe way of doing this?

In a related matter, I understand that low-voltage wiring in a box which contains mains voltage must be fire rated. Where is such wiring found and how is it designated in the U.S?

Back to the beginning. My understanding here is you only wish to know if a pump or heater is on or off, would that be correct? Should that be correct all you need is a sensor with a yes or no output, as in 1 or 0. I used those little current sensors I linked to, if you read the data sheet most will read as low as an amp. The LED can drive a home brew opto coupler or the LED removed and use a factory opto coupler. Either way the sensor out can drive a PICAXE or similat digital input. It seems like you are using an analog signal which would be fine if you wanted to measure the actual current levels. The pump is either drawing current or it isn't and likewise for the heaters.

Ron

hippy · Dec 11, 2016

lbenson said:
I used the following circuit (replace "Ard..." with "PICAXE").

View attachment 20594

If that were working as shown, I would expect an average of sequential readings to come out at 128, $80, 2.5V.

Catching the high values should work, but it is not clear why you are getting any zeroes in your results because it should never get that low.

I personally wouldn't worry about balancing the voltage about some virtual 0V, I'd go for half wave rectification and use an RC to track the peak ...

Code:

 .-----.---|>|---.------.---> ADC
 |     |         |      |
(     .|.      __|__   .|.
(     | |      =====   | |
(     |_|        |     |_|
 |     |         |      |
 `-----^---------^------^---- 0V

I've got a handful of current transformers from various energy consumption monitors and for clamp-on ammeters but have never got round to trying it myself.

lbenson · Dec 11, 2016

ron--detecting on/off is not a problem with the module I have. Posters encouraged me to go further and determine current, so I'm now trying to figure out the best way to do that. The good news is that my "5A" sensor seems to give good and useable (if variable) readings for 15A at 120V (thanks rossko57)--especially if I throw away outliers. 15A is well above what my pump and burner will draw.

hippy--it's not an average of 128, $80 that I'm getting on the module which doesn't work, but a constant whenever I do the ADC read (or as many as I can in 1, 2, or 4 seconds). I should have mentioned that the SCT-013-030 includes a "burden" resistor of, as I recall, 16Ohm (not the 33 shown in the schematic), so my circuit was just what was to the right of that resistor. (Note that my zero readings (along with many above that) shown for 1800W did not use that circuit--just the picaxe readadc of the "Sample" output (with 0V connected) of the TA12-100 module (the first one I tried).)

What R & C values would you recommend I try for the half wave circuit, and what readings should I expect?

Reloadron · Dec 11, 2016

Ibenson:

ron--detecting on/off is not a problem with the module I have. Posters encouraged me to go further and determine current, so I'm now trying to figure out the best way to do that. The good news is that my "5A" sensor seems to give good and useable (if variable) readings for 15A at 120V (thanks rossko57)--especially if I throw away outliers. 15A is well above what my pump and burner will draw.

OK, now I understand. Knowing the current can be useful especially with a pump as it can help with a locked rotor situation or similar problem.

Ron

hippy · Dec 11, 2016

lbenson said:
hippy--it's not an average of 128, $80 that I'm getting, but a constant whenever I do the ADC read (or as many as I can in 1, 2, or 4 seconds).

Might be worth posting your code so it's clearer how you are doing it and calculating your result because I can't see how you are getting that constant, why it varies and why there are zeroes in your sample readings in post #22.

If the raw readings are plotted out they should be giving something like a sine-wave.

You seem to have 400 readings for a 4 second period which suggest reading every 10 ms. You really want to sample as many times and as quickly as possible for at least 20ms to catch the peak value ..

Code:

SetFreq M[i]fast[/i]
b0 = 0
For w1 = 0 To ?
  ReadAdc ADC, b1
  b0 = b0 Min b1
Next

lbenson said:
What R & C values would you recommend I try for the half wave circuit, and what readings should I expect?

No idea I'm afraid. It will depend on what voltage you are getting and you will need to adjust it to give you a reasonable hold from peak-to-peak but with enough decay to be responsive. I would probably start with a diode and cap see how that goes. Put a scope on it and you can easily tell how well it's working.

Reloadron · Dec 11, 2016

Looking at your sensors and thinking about this do your sensors output a DC level proportionate to the AC current or do those sensors output an AC voltage proportional to the AC current? If it is the latter your readings would make sense. I would be curious to see the data sheets on the sensors.

Looking at this sensor the Vout is going to be 0 - 1 VAC which could be the problem. Note the drawings on this PDF. Looks like a CT (Current Transformer) with an internal burden resistor giving a 0 - 1 VAC output proportional to the AC current.

The problem with rectification is using a peak detect circuit I think the forward voltage drop on the diode will be about 0.7 volt and anything below 0.7 I doubt will pass.

Looked at the other drawing in post #22. The idea of R1 & R2 is to get the zero above a zero reference to 2.5 Volts so the AC level will swing above and below 2.5 VDC as it is drawn. The problem with the AC is wherever the level is when the PICAXE samples is what you get. What you really want to cut down on external circuitry is a current sensor that gives you a DC voltage out proportional to the sensed current. That is my guess anyway.

Ron

lbenson · Dec 12, 2016

Using the TA12-100 module and modifying hippy's code to do readADC as many times as possible in one second @ 16mHz, I got the following:

I used a Kill-A-Watt type monitor, and two different heaters, and measured wattage as follows, with two consecutive readings of the sensor (120V, 60Hz in the U.S).

Heater1:

Nominal 300W heater started at 250W, after 2 minutes stabilized at 196W +/- .4.
1168 reads in one second; max = 28
1168 reads in one second; max = 27

Heater2:

Low setting on heater: started at 250W, climbed and stabilized around 622.5W
1168 reads in one second; max = 82
1168 reads in one second; max = 82

High setting on heater (Nominal 1500W): started at 550W, climbed quickly and stabilized around 1330W
1168 reads in one second; max = 177
1168 reads in one second; max = 177

Both heaters (Nominal 1800W); stabilized around 1496W
1168 reads in one second; max = 204
1168 reads in one second; max = 203

Picaxe code:

Code:

' 08ADCfast does as many adc reads as possible in one second
#picaxe 08M2

SetFreq M16
w13 = time
do while w13 = time : loop
w13 = time
b0 = 0
w12 = 0
do until w13 <> time
  ReadAdc 4, b1
  b0 = b0 Min b1
  inc w12
loop
sertxd(#w12," reads in one second; max = ",#b0,cr,lf)

So by extrapolating, I think I can get fairly close to the current readings for my boiler pump and burner using the TA12-100 module when I get back to them in April.

Using the nominal 300W heater, I put the code in a loop and in 25 sets of reads, got only values of 27 and 28, so pretty good repeatability.

I don't know if my Kill-A-Watt clone is accurate, so am not sure about absolute wattage values.

lbenson · Dec 12, 2016

@Reloadron--all three of the sensors are supposed to put out a voltage proportional to the AC current. One of them also has a digital output for which in theory you can set a threshhold using a pot. I got nothing I could make sense out of from that "30A" module using either the analog or the digital pin.

Likewise, with the SCT-013-030 I got no variation when I changed the load.

Maybe I did something wrong, but I managed to get it right twice with the TA12-100 module. Maybe I got 2 bum sensors. Maybe I didn't understand how the other two were supposed to work (documentation is sparse to non-existent).

Determine mains on/off for boiler burner and pump

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