Arduino wireless datalogging

[bryanncy1999]

I'm planning to build a data logging system that uses 2 arduino's (one for reading sensor, one for logging) The reason I planned to use 2 Arduinos is because the data I want to log is indoor and outdoor. The outdoor sensor arduino will transfer the sensor data to the indoor arduino, which will read the indoor sensor and process all the data and log it into a SD card.

I'm planning to use a LM35 temperature sensor and a humidity sensor that I got from Cytron for the outdoor arduino and also the same for the indoor arduino. The data will be shown out on a 16x2 LCD and a button on the indoor arduino controls the data logging.

For the outdoor arduino I want to use solar and li-on battery to power it 24/7, the indoor one is powered via a wall adapter. The problem I have is I can't find out what kind of charging circuit for the li-on battery should I use and what kind of amplifying circuit should I use. Anyone here can suggest me some circuits that all the components can be bought from Cytron and is low cost.

I am just a 14-year old student in Kuching so I don't have much knowledge about electronics engineering(though I'm quite interested in it)

The components that I plan to use (all from Cytron)

2 arduino's (a simple atmega328 clone or arduino pro mini)
LM35 temperature sensor
16x2 character lcd
solar cells
Li-on rechargeable battery(ies)
water sensor brick
hr 202 humidity sensor
RF Transceiver 2.4G
piezo disk

I started planning for this project after I thought of making a door knock sensor. (That's why there's piezo disks in the list above)

My budget is very low since I'm just a 14-year old teenager

Thank you for reading my post and i hope you all can reply me on what I should add or remove in this project.

[robosang]

Good that you are interested in electronics and microcontroller.

I would suggest you to power the whole project with power supply first, solve the power later on

[bryanncy1999]

So that means I only use one microcontroller first? Then in the future change it into wireless? I'm going to use a simple atmega 328 clone so should I use 3.3v or 5 v for it?

[yonghui]

not sure, but from the reading on atmel website, seems the voltage can be from 1.8v to 5V.
u will need to buy a voltage regulator for your microcontroller and circuits.
the operating voltage should take consider of all others devices. example, if u are goin to use SD card, i think it will be better 3.3V.

[ABSF]

I am just a 14-year old student in Kuching so I don't have much knowledge about electronics engineering(though I'm quite interested in it)

I thought 14 y.o. are too busy playing Angry Birds games. May be you are the exceptional one.....
BTW which school are you from? St Joe, St Thomas or KHS?

2 arduino's (a simple atmega328 clone or arduino pro mini)
LM35 temperature sensor
16x2 character lcd
solar cells
Li-on rechargeable battery(ies)
water sensor brick
hr 202 humidity sensor
RF Transceiver 2.4G
piezo disk

From your list of devices, I guess you're going to connect the sensors LM35, water sensor & HR202 to one arduino and the LCD display to another arduino. And link the 2 srduino with RF modules, right?

Where & how are you going to store the data collected? To SD card or PC harddisk?

To simplify your project, I think it is easier to do it in 4 steps:.

1. Connect all the sensors and LCD to one arduino and make sure each sensor is working properly one at a time before adding the next sensor.
2. Transfer the LCD to the second arduino. Link the 2 arduinos with physical wires between the 2 UART and make sure that the data captured are displayed on the LCD.
3. Connect in the mass storage media like SD card or PC HD. and write the data into them and read from them are working well.
4. Finally replace the physical link with wireless link using your transceivers and make them work properly.

I have bought 2 arduinos but still have not have time to play with them yet. Recently I am busy playing with PIC and MSP430 launch Pad. I still have a project going on with PIC. It's a RPM project for express boat engine shaft.

Allen

[bryanncy1999]

I am just a 14-year old student in Kuching so I don't have much knowledge about electronics engineering(though I'm quite interested in it)

I thought 14 y.o. are too busy playing Angry Birds games. May be you are the exceptional one.....
BTW which school are you from? St Joe, St Thomas or KHS?

I'm from SMK DPHA Gapor at Stampin.

2 arduino's (a simple atmega328 clone or arduino pro mini)
LM35 temperature sensor
16x2 character lcd
solar cells
Li-on rechargeable battery(ies)
water sensor brick
hr 202 humidity sensor
RF Transceiver 2.4G
piezo disk

From your list of devices, I guess you're going to connect the sensors LM35, water sensor & HR202 to one arduino and the LCD display to another arduino. And link the 2 srduino with RF modules, right?

Yes

Where & how are you going to store the data collected? To SD card or PC harddisk?

To a SD card on the receiver

Now I'm just finding a way to power the outdoor arduino without maintaining it. Like putting a circuit that charges at morning and uses batteries at night non stop. I plan to use Li-ion batteries and four 5v solar cells.

I also have problems using the HR-202 humidity sensor as I can't find out the calculations needed for it.

Lastly, Is there any way to convert 4 - 5vdc to 3v3 stable voltage? Is it possible to charge Li-ion battery using arduino analog output safely?

[ABSF]

Now I'm just finding a way to power the outdoor arduino without maintaining it. Like putting a circuit that charges at morning and uses batteries at night non stop. I plan to use Li-ion batteries and four 5v solar cells.

That should be doable.

I also have problems using the HR-202 humidity sensor as I can't find out the calculations needed for it.

In the datasheet of the HR202 module, there is a table showing the resistances of RH in percentage against the temperature. You can use the ADC of Arduino to connect the AO of the HR202. Using the data from the temp sensor and the resistance from the HR202, you can create an array of RH for indexing to get the nearest RH.

Here is a link from Arduino forum that discuss about this...

http://forum.arduino.cc/index.php?PHPSESSID=uajknlrqtuksr7j916jpqgu8g6&topic=143815.0

Lastly, Is there any way to convert 4 - 5vdc to 3v3 stable voltage? Is it possible to charge Li-ion battery using arduino analog output safely?

You mean the 3.3V for the Vcc to run the MCU? There are LDO regulator that converts 5V to 3.3V just like the 7805. You should be able to get the easily from Cytron or E14.

What is the capacity of your Li-ion battery? Normally we charge battery based on 10 or 20 hour rate calculation.I dont think the Analog output has an output of more than 25mA. And why do you want to risk the life of an expensive AVR atmega328 just to charge a battery.

Allen