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Project: Solar Dryer Temperature profiler

Concept: we are building a low cost solar dryer and wanted to study the temperature profiles during operation. for this purpose, we decided to connect to LM35 temperature sensors to the analog inputs of the arduino. We will write the captured values onto a microSD card so that we can analyze the data later.

We have also decided to make the arduino run on a 12v solar panel with a 9v battery backup. Cicruit diagram is shown below.

Would love to get your feedback and suggestions. Also, we plan to add a computer heat sink fan to the unit that can be controlled through the PWM output of the arduino. but am not sure of how to connect the fan motor to the arduino. inputs will be appreciated!



regards,
Siddharth

[Reply #1 on:]

If you run the Arduino at 3.3V and 8 MHz you'll save power so you won't need as large a solar panel or battery.  You will also be able to connect the SD card directly to the Arduino pins without level shifters.  You can use a Micro-to-Standard SD adapter as a Micro-SD socket.

[Reply #2 on:]

Why would you need a fan and heat sink? I don't think any of the components get that hot, and it would require a lot more power to drive the fan.

here is a link that you might look at before you go too far. The link also references another link specific to temp logging with the shield.

http://www.planetarduino.org/?cat=343

[Reply #3 on:]

If you don't insist in building it yourself, here you have most of what you wanna have in one package, optimised to use as low energy as possible:

http://www.seeedstudio.com/depot/seeeduino-stalker-atmega-328-p-600.html

You can directly attach the battery and the solar panel, the necessary charging components are on the board.

[Reply #4 on:]

Take a look at the lady ada design; http://ladyada.net/products/usbdcsolarlipo/

She uses a 6V panel, a quasi mppt charging circuit, and a lipo.  The design allows for your circuit to be connected to the charger at the same time as the battery and solar panel.  When the panel is producing an excess of power over powering your circuit, the excess is used to charge the lipo... 

[Reply #5 on:]

Why would you need a fan and heat sink? I don't think any of the components get that hot, and it would require a lot more power to drive the fan.

The fan is not likely for the Arduino circuit, but for the solar dryer function.  I am assuming what he is talking about is something like a solar food dehydrator, where airflow is critical to removing the moisture from the food being dehydrated.  And he probably want to add temperature control to allow the device to maintain the appropriate temperature range for the specific type of food being dried.

[Reply #6 on:]

If that is the case he will probably need something a little more beefy than a heat sink fan, unless it is a pretty small dryer. A convection stack might work better and requires no power.

http://solarcooking.wikia.com/wiki/Solar_food_drying

[Reply #7 on:]

If that is the case he will probably need something a little more beefy than a heat sink fan, unless it is a pretty small dryer. A convection stack might work better and requires no power.

http://solarcooking.wikia.com/wiki/Solar_food_drying

I don't think so, I have an excaliber food dehydrator on my counter and the fan on it looks very much like a standard PC case fan.

[Reply #8 on:]

I don't think so, I have an excaliber food dehydrator on my counter and the fan on it looks very much like a standard PC case fan.

Probably true... but it sounds like  strangeloop is talking about a bigger unit otherwise it would be kind of an overkill to have four temperature sensors in something you could put on your counter. Since it is solar, I still think it is a good idea to look into convection airflow. That way the only thing consuming power would be the data logger.

[Reply #9 on:]

Why would you need a fan and heat sink? I don't think any of the components get that hot, and it would require a lot more power to drive the fan.

here is a link that you might look at before you go too far. The link also references another link specific to temp logging with the shield.

http://www.planetarduino.org/?cat=343

We are using the fan to facilitate air movement along the solar dryer column.

[Reply #10 on:]

If that is the case he will probably need something a little more beefy than a heat sink fan, unless it is a pretty small dryer. A convection stack might work better and requires no power.

http://solarcooking.wikia.com/wiki/Solar_food_drying

Thanks.. will have a look at this idea as well.