Advice for a newbie

[fetster]

Hi All,
I've just come across the Moteino boards and this forum which seems to be full of very helpful people.

I'm looking for a low power Arduino compatible board that can be connected to sensors (temperature or LDR depending on use case)

I'd like the temperature device to power up every hour, take a temperature reading from a DS18B20, send it wireless to a receiver connected to a Raspberry Pi (in same building) and then go to sleep until the next hour. Possibly send over battery data to alert when low batteries. I'm looking to power this with 2 x AA batteries (any other suggestions?).

I've got a few newbie questions sorry-
Is the above use case suitable for a Moteino baord?
What would you suggest? I was thinking of a Moteino with RFM69HCW 433Mhz transciever - I live in UK
In the above application approx what kind of battery lifespan am I likely to achieve?

I'm also looking at the Moteino to be used as an LED pulse counter using an LDR to count the pulses from my electricity meter (similar to EmonPI project). I've managed to achieve this with a Pi Zero but need to look at a battery powered alternative. The Moteino would need to be powered continuously to allow it to count light pulses on the LDR and I was looking at sending the counts wirelessly every hour.
Again, would this be a suitable use case for the Moteion board and approx what kind of battery lifespan could i achieve (bit of a how long is a piece of string question I suppose).

Thanks for taking the time to read this.

[TomWS]

I'd like the temperature device to power up every hour, take a temperature reading from a DS18B20, send it wireless to a receiver connected to a Raspberry Pi (in same building) and then go to sleep until the next hour. Possibly send over battery data to alert when low batteries. I'm looking to power this with 2 x AA batteries (any other suggestions?).

I've got a few newbie questions sorry-
Is the above use case suitable for a Moteino baord?

Absolutely.  It's a natural for this along with the libraries available for it.

What would you suggest? I was thinking of a Moteino with RFM69HCW 433Mhz transciever - I live in UK

I'll let our UK comrades address this one.  They'll know the regulatory requirements.

In the above application approx what kind of battery lifespan am I likely to achieve?

With a couple of AA batteries, you'll achieve well over 1 year (should be more than 2, but then you run into issues like corrosion, etc).  If temps go below freezing, then I suggest you use Everready Ultimate Lithium as these will work down to -20F.  Note that you will want to use Moteino 8MHz for this project due to the voltage being lower than 3.3V.

I'm also looking at the Moteino to be used as an LED pulse counter using an LDR to count the pulses from my electricity meter (similar to EmonPI project). I've managed to achieve this with a Pi Zero but need to look at a battery powered alternative. The Moteino would need to be powered continuously to allow it to count light pulses on the LDR and I was looking at sending the counts wirelessly every hour.
Again, would this be a suitable use case for the Moteion board and approx what kind of battery lifespan could i achieve (bit of a how long is a piece of string question I suppose).

There are others who have done this so I'll let them address this question.  Just be aware that, to continuously monitor your moving dial, you'll need a continuous light source and this will be your biggest overall power drain.

Welcome to the forum.

Tom

[Sergegsx]

Quote

I'm also looking at the Moteino to be used as an LED pulse counter using an LDR to count the pulses from my electricity meter (similar to EmonPI project). I've managed to achieve this with a Pi Zero but need to look at a battery powered alternative. The Moteino would need to be powered continuously to allow it to count light pulses on the LDR and I was looking at sending the counts wirelessly every hour.
Again, would this be a suitable use case for the Moteion board and approx what kind of battery lifespan could i achieve (bit of a how long is a piece of string question I suppose).

There are others who have done this so I'll let them address this question.  Just be aware that, to continuously monitor your moving dial, you'll need a continuous light source and this will be your biggest overall power drain.

If the meter has a LED blinking on every WH then there is no need for a continuous light.
I have this node implemented, the problem is that to get accurate power consumption you need to keep track of the time between blinks. To do this I have not found a way to make the node sleep so I have to power it without battery.
What i am doing is reading an interrupt and calculating power based on the time in ms between pulses (Wh). Then increase another variable to accumulate and be able to calculate consumptions.

i would be happy to hear of an alternative where batteries can be used.

(same thing with a water meter with a reed contact)

[fetster]

Thanks for your comments and advice, I've ordered a few boards which will hopefully be delivered today

Sergegsx - very interesting that you mentioned about keeping track of the time between blinks, i wasn't aware that this needed to be tracked, looking at the meter it says 1KwH = 100 imp which I just assumed that 100 blinks was 1Kwh. The raspberry Pi setup simply counts the number of blinks and outputs the count for 5 min intervals which is then processed to give hourly / daily / specific period usage (only been in operation for a few days and not done a comparison with actual meter readings yet.

Whats the variance likely to be between just counting the number of pulses and counting pulses and interval between pulses?

The meter in my house blinks probably 5 times a minute on average but meter in my parents house could blink every second if not faster at times(different imp / kwh ratios) so I'm worried about accurately counting time interval between pulses.

Thanks again for your comments - you have made me more comfortable buying the Moteinos as I can see there is great community support here.

[Sergegsx]

Whats the variance likely to be between just counting the number of pulses and counting pulses and interval between pulses?

The meter in my house blinks probably 5 times a minute on average but meter in my parents house could blink every second if not faster at times(different imp / kwh ratios) so I'm worried about accurately counting time interval between pulses.

Thanks again for your comments - you have made me more comfortable buying the Moteinos as I can see there is great community support here.

Well i wanted to be able to see a value of instante power (W). To do this I had to measure the time between blinks. If the consumption is very low then you get a blink at a longer interval but still a valid value. So for example, if each blink is 1 wH and you measure 1 second between two blinks:

1 wH / (1sec/3600) = 3600 W

That way you can display the value in a dashboard, app or whatever.
Additionally I have a variable which is an accumulator of "wh". Every time I get a blink I increase the value by 1.

Then for example if I want to know how much power I used from 7am to 8am I get the value at each of this times and subtract them: 3333 (8am) - 1111 (7am) = 2222 Wh

[ChemE]

Is it possible to rig up a photodiode to wake a sleeping mote using INT0 or INT1?  Basically, any pulse of light hitting the photodiode generates a wake signal and then the mote could just count wakes and go back to sleep?

[Sergegsx]

It is possible but in my case I want to know the power consumption every 10 seconds, so not much sleep there.

[TomWS]

Is it possible to rig up a photodiode to wake a sleeping mote using INT0 or INT1?

You don't need to use those pins specifically.  All the digital pins are capable of generating an interrupt if you use PinChange interrupt code.  What you do need is to have a reliable level comparator & filter so that you don't get any 'accidental' trips and this could consume some power.

Tom

[fetster]

Thanks for all the suggestions and advice guys.

I've taken your advice on board and purchased a few Moteinos with the RFM69HCW 433Mhz transceivers.

I'm still picking up the basics of Arduino coding and had a play around with some examples I have found on here for DS18B20 sensors. Managed to get a few sensors working around the house and they have been talking to the Raspberry Pi gateway. First few readings when the device is powered on have been 0C and 0.5C but then after a few min they are displaying correct temps and have been sending readings successfully for a week or so.

Last day or two they are starting to 'disappear' and I'm having to remove / reinsert battery to get them going again, for them to disappear again some time later - I'm assuming the batteries are dying so I'm obviously using the wrong code / not optimised it correctly - still learning and don't understand it much yet.

I'm just wondering if anybody on this forum offers advice / solutions on a freelance basis? - with me being a newbie I don't want to pester people for advice on this forum (i'd only insult you all with my limited knowledge and silly questions).  I noticed there is a Jobs / Freelancing thread but thought i'd keep the post in this topic for now.

[akstudios]

I don't think the questions would be silly. Post your setup and code -- this community is quite helpful.