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 Solar thermal controller on a chip
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By: Anonymous: Matt A. () on Saturday, February 21 2009 @ 11:13 AM PST (Read 8755 times)  
Anonymous: Matt A.

Hi Windell, Lenore & Chris,

After Obama's recent visit to Denver and seeing him wander around the solar panels on the roof of the Museum of Nature and Science, I got that glassed over, green and googly-eye look of an environmental do-gooder.

I've been piecing together a solar hot water system for my home off of Craigslist and just had 15 collector panels dumped in my driveway last night (gulp). So I guess I'm committed now.

I did pick up some pumps and controllers, but most everything that's out there is analog relics from the early 80's (during the last energy crisis). Seems to me that there should be a relatively simple digital solution these days. Here's where you and your big brains come in...

Would it be possible to make a DIY controller on a chip similar to your Atiny projects?

Here's what I'm envisioning (will be using a "drain back" type system):
Required:
2 temp sensors (solar collector temp, and storage tank temp)
1 pump switch (120 VAC)
High Limit set point

When Tank temp reaches a low point AND Collector temp is high enough, turn on Pump to send water to the collectors for heating. When High Temp limit is reached in the storage tank OR Collector temp is too low, turn off pump.

Optional (but why wouldn't you?):
USB/wireless connection for programming and datalogging on home computer
Web based display of data
(my inspiration: http://www.instructables.com/id/Real_time_Web_Based_Household_Power_Usage_Monitor/)

What do you think?

THANKS





       
   
By: Windell (offline) on Saturday, February 21 2009 @ 04:29 PM PST  
Windell

Sure, why not? Grab an Arduino and make it happen. Smile


Windell H. Oskay
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By: Anonymous: Matt A. () on Tuesday, February 24 2009 @ 04:55 PM PST  
Anonymous: Matt A.

Ah, I see. An Arduino sounds like a fine Italian sausage, so your suggestion was more than suggestive.

So uh, ok, let me rephrase the question: Would you be willing to take on such a project? Or at least provide enough guidance that I, a rank amateur, could start piecing it together?

The goal is a low cost DIY controller that could shared with the larger community.

Thanks!






       
   
By: Windell (offline) on Tuesday, February 24 2009 @ 05:11 PM PST  
Windell

No, seriously-- you're looking for "a low cost DIY controller that could shared with the larger community." That already exists, and you should check it out. By pointing you in the direction of Arduino, we are giving you enough guidance to start piecing it together. Go learn what's out there.


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By: Anonymous: Duncan () on Tuesday, March 10 2009 @ 02:34 AM PDT  
Anonymous: Duncan

I agree with Matt A, I'm setting up a solar system with 1 set of panels and 2 tanks. I want the primary tank to supply hot water to the house and the second tank will act as a thermal store and heat exchanger for the swimming pool.

It seems simple enough, but the available solar controllers are all over 200, $200, 200. and the pump stations are all over $250-300.

I found 1 sample circuit on reuk.co.uk, and looking at the component prices all are under 1.

They updated this using a PIM, but this had to be factory programmmed, and so a simple comparator circuit with a few pot adjusters seems simpler.

To supply 2 stores, I can either have 2 pumps or 1 pump and a 3way valve, the 2 pumps seems easier and cheaper.

some people have 2 sets of panels split east and west, so having 2 solar temp inputs would be nice

It ought to be simple and cheap to add a temp display, but may be easier to get a cheap off the shelf seperate digital temp display.

So my ideal spec would be......

4 temp sensors, solar array A and B, and store A and B
4 output relays, Pump1 for Array A, Pump 2 for Array B, Pump 3 for Store A and Pump 4 for Store B.

Logic....
2 Array opton
turn on Pump 1 if Array A is above temp of Store A, and Store A is not over max temp.
turn on Pump 2 if Array B is above temp of Store B, and Store B is not over max temp.

2 Store option
Turn on Pump 3 if Array A is above temp of Store A, and Store A is not over max temp.
Turn on Pump 4 if Store A is a max temp limit, and Array A is above temp of Store B, and Store B is not over max temp.


The requirement and logic seem simple, I'm not an electronics expert, but can understand the logic of the sample circuits the components are cheap.

So why are the commecial units soooo expensive.





       
   
By: Anonymous: greg () on Tuesday, March 08 2011 @ 10:33 AM PST  
Anonymous: greg

Try looking for industrial controlers.

These may be of use and much cheaper than anything "green" as suppliers raise prices when rebates are possible.

SOLO Temperature Controllers -- simple one is $89 US

Best regards

G





       
   
By: Anonymous: pauldusa () on Thursday, May 19 2011 @ 10:52 PM PDT  
Anonymous: pauldusa

Good for you to put together a thermal solar system - the controller is to read (ADC) or compare voltage with a op amp just by crossing a set point, you can take ( 2 ) 10 thermistor tie them together as a 3 leg voltage divider, connect one leg to Gnd - the other far leg to +5 ref voltage and the center leg to a op amp as LM741
or
the center leg being a input port on a micro as set up IF commands on input and THEN on a out port, with code in the middle, a very simple of micro to use is a PicAxe 08M 8 pin chip - BASIC Code, and a relay for the output to on/off the pump, you can build program your solar controller in 1 hour, Really. I have built very many of these for yrs. thermistor H go up to the roof, and thermistor extends to the storage tank just to complete the design. Good luck





       
   



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