Hi everyone, this is my first post.
WOW!!! What an awesome system you've built together. I jumped on the bandwagon a couple of weeks ago and already I've given my raspberry pi full control of my gas central heating and hot water. Remote monitoring, remote control, evironmental feeds, I've zones for upstairs and downstairs with a temperature setting for every hour of the day. This is really awesome stuff! I'm so excited by it.
So, to my question:
I recently added 2x temperature probes to the top and bottom of my hotwater tank, hooked up to a jeenode. My own little python program ensures the boiler heats the water only when required based on the temperature readings. Works great. What I want to do is to calculate the average of the 2 readings on Emoncms with a view to calculating approximate heat flux from my Immersun.
My problem is that each temperature input is in the form 3010 where the actual temperature would be 30.10C. So each input is multiplied by 0.01 to scale them. The trouble is when I try to add them together I end up with one temperature such as 30.1C added to the unscaled input which might be 4050. This is clearly won't compute. So how to I do it? Do I need to create a dummy feed and log the unscaled temperatures just so I can add them together?? Seems a bit wasteful if that's the case. I suppose I could do it in the jeenode too but again it seems a bit obtuse :)
Thanks in advance. Here's hoping I can contribute to the community in the future.
Re: Getting the average of two feeds in Emoncms
Hi.
I'm not so familiar with the processing, but you seem to be in a corner case that was not thought of.
Could this be a workaround ?
Input 1:
x 0.01
Log to feed -> Temp 1
x 100
+ Input 2
x 0.01
Log to feed -> Average
Input 2 :
x 0.01
Log to feed -> Temp 2
Re: Getting the average of two feeds in Emoncms
Jerome,
Brilliant. That works a treat.
Am I using heat flux right? I multiply average temperature by the volume of my tank in litres then apply heat flux? Should I use a long logging interval to better see small changes?
Re: Getting the average of two feeds in Emoncms
Hi.
Glad it works.
I don't know heat flux, I don't see it in the docs. If in doubt, you may have a look in the code...
Re: Getting the average of two feeds in Emoncms
Here is more on the heat flux http://harizanov.com/2012/05/measuring-the-solar-yield/
Re: Getting the average of two feeds in Emoncms
Hi Martin,
Still no luck with it but it's not important. I have 2 of your Funky v2s and they are just awesome. Do you know when you'll have more available?
Re: Getting the average of two feeds in Emoncms
I seem not to have enough time lately and building just one takes me an hour. I was thinking of organizing a batch build of 100pcs of the new v3, but never got there as it requires some investment in both time and money. suggestions on how to move the project forward are welcome :)
Re: Getting the average of two feeds in Emoncms
Ouch, that's a lot of work. I can see how you'll never get rich that way. What you need is for people to preorder and then as you say have a batch made for you. You could do it on a forum, or even better you could start a Kickstarter campaign. I for one would order at least another 5, maybe more.