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Rick H Parker

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Reply with quote  #21 

The Lux meter is an artist's tool. A Pyranometer is a scientific tool.

The Lux is analogous to radiometric unit watt per square metre but, the Lux is based on human perception not Physics. 

Good luck in converting between Human perception and Physics.

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Rick H Parker
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stmbtwle

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Reply with quote  #22 
Back to the speed control: my Arduino nanos (about $5) came in yesterday so I spent most of today putting one together to drive a 15 amp dc speed control. The biggest job of course was writing the software.

Anyway, IT WORKS!
I get full temperature regulated speed control from dead stop to wide-ass open. The fan pulls something over 3 amps at full speed and so far no problem. I have a slightly bigger fan in the junk box I'll try. I get a bit of pulsing at low speeds that I don't know the cause of but I think I'll get to the bottom of it.

Anyway a couple of questions... what temperature do you like your air collectors to run at, and do you like a wide or narrow speed band? Currently it's set up to start the fan at 80F and ramps up to full speed at 90F. I'll try and put a routine in that will allow use of a trim knob for temperature control, and an output for a display.

Other suggestions welcome.

Once I get that I'll post all the details here...


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Willie, Tampa Bay
stmbtwle

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Reply with quote  #23 
Rick,
This low-speed pulsing seems to be a conflict between the PWM output from the Arduino and the speed control, which is "expecting" an analog input.

The only connections are the ground and the variable voltage to the control's input. Do you think a capacitor across those two leads would help?

Aside from that it appears to be working fine.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
stmbtwle

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Reply with quote  #24 
The capacitor did the trick! A 100uf was just right, though different setups might require a different value.

I'm guessing the whole thing came in around $20.

Now to put together a schematic...

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
stmbtwle

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Reply with quote  #25 
Here's the diagram on the Arduino version:

  Spd Ctrl2.jpg Parts:
https://www.ebay.com/itm/DS18B20-Stainless-Steel-Waterproof-Digital-Thermal-Probe-Sensor-100cm-Arduino/121952945591?
https://www.ebay.com/itm/6-90V-15A-DC-Motor-Speed-Controller-Pulse-Width-PWM-Speed-Regulator-Switch/253056259652?
https://www.ebay.com/itm/MINI-USB-Nano-V3-0-ATmega328P-CH340G-5V-16M-Micro-controller-board-Arduino/222543127037?
https://www.ebay.com/itm/Screw-Terminal-Expansion-Adapter-Board-Shield-4-Arduino-Nano-V3-0-AVR-ATMEGA328P/322349808192?

Code attached in TXT format.  Paste it into your arduino sketch.

 

 
Attached Files
txt AutoSpeed Ctrl.txt (2.24 KB, 1 views)


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

stmbtwle

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Reply with quote  #26 
Well not so easy but still cheap enough.  With a little more programming I now have it so it will not only control the fan, but actuate a servo to open or close a vent.  Now for the display...
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Willie, Tampa Bay
gbwillson

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Reply with quote  #27 
Willie-

Thanks for working on this. I would love to have a simple and cheap way to control my fan power and speed. Will you also be able to log data? 

Greg in MN
stmbtwle

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Reply with quote  #28 
I'm sure it can be done, but that's a whole 'nother ball game. I'll leave that part to someone else.

It uses I2C to send data to the display, you could use that output for whatever you like. Or use the USB connection. But for logging you'd also need mass and velocity, and irradiation. Temperature alone doesn't tell you much, especially when you're varying the fan speed.

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gbwillson

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Reply with quote  #29 
Probably right-

You would need the input and exhaust temps and CFM at the various fan speeds. So the speed and temps would have to settle before a reading could be taken. But, if the fan speed updated only every minute or two as opposed to continuously, it might be possible.

Greg in MN
stmbtwle

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Reply with quote  #30 
Oh it's possible all right. One could install an anemometer or pitot in the duct for velocity, and with the duct diameter calculate the CFM. That with the temperature gain would get the BTU/hr or watts. A pyranometer would get you the incoming energy and you can calculate the efficiency. But all that takes equipment and time to calibrate and adjust the calculations. And we haven't even STARTED with the data logging.

As this is a DIY site and no two collectors are identical, a "plug & play" approach would be difficult. So I'm taking the easy way out and letting Y'all D I Y. This particular unit is for my own use, I'm simply sharing, though I do think I'll put provision in the software for a second temperature sensor.

The latest version will control fan speed according to temperature, and will actuate a servo to open a vent. Setpoints are adjustable via software and a trim pot for the fan speed. Display will show output temp, set temp, fan percent, and vent status.

I'm open to suggestions. Feel free to make adjustments, corrections, or improvements, but please post what you do.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
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