AXON II and Sensors

[Sensor Guy]

I would like to use the Axon II to read some sensors and record these data.
Here is an example of the sensors; Can I hook them up directly to the AXONII? and read and record
the data? What would I need to make the Sensors work with the Axon II?

Thank you
 1- Soil moisture sensor
Dielectric Measurement Frequency:    70 MHz.
Measurement Time:    150 ms
Power: 3.6 - 15 VDC, 0.3 mA quiescent, 10 mA during 150 ms measurement
Output: Serial TTL, 3.6 Volt Levels or SDI 12 (contact Decagon for
information on SDI-12 mode)

2-Light Sensor:
Range:Full Sunlight: 400 mV (2000 μmol m-2s-1) Linear Range: 0 μmol m-2 s-1
(0 mV) to 5000 μmol m-2s-1 (1000 mV) note that full sunlight is about 2000
μmol m-2s-1
3-Humidity and Temp
Humidity Resolution:0.1% RH
Temperature Resolution: 0.1°C
Humidity Range:    3 to 100% RH
Sensor Type: Digital capacitance and thermistor
Output: I2C

[TrickyNekro]

You may need a level shifter for the first one to get from 5V to 3.6V and vice versa...
I can't recall if Axon can recognize the 3.6V signal...
I think that all signals above 2.7V are recognized as logic 1 but I'm not sure for that "2.7V"
Better check the datasheet of ATMEGA1260 or wait for a more descent reply....


Things are easier for the axon output... A voltage divider would be more than enough... to get the voltage
from 5V to 3.6V...
But first check if the input of your device is 5V tolerant... if so... a 4K7 to 10k current limiting resistor is ok ;-)

[Admin]

Sensor Guy, yes, the Axon can work with both sensors. The first one uses UART, and the second uses I2C.

The basic tutorials:
http://www.societyofrobots.com/microcontroller_uart.shtml
http://www.societyofrobots.com/member_tutorials/node/35

Next, read the WebbotLib manual for instructions on programming it.

You may need a level shifter for the first one to get from 5V to 3.6V and vice versa...
I can't recall if Axon can recognize the 3.6V signal...
I think that all signals above 2.7V are recognized as logic 1 but I'm not sure for that "2.7V"
Better check the datasheet of ATMEGA1260 or wait for a more descent reply....

Yeap, it'll recognize 3.6V no problem. And its the ATmega640

edit: (but you'll still need a level shifter the other way or it'll fry something)

[TrickyNekro]

Still can't fill that 64kB anyways... :-p

[Sensor Guy]

Hi

Thank you for the reply; Excuse my questions, but I am trying to understand things a little more.

What would I need a level shifter for? is it for the moisture sensor?
How many of these sensors can I read with the Axon II? do I need a level shifter for each one?

The sensor that uses the I2C (light sensor); do I need to buy a chip to connect the sensor to it? or do I connect it directly?

My intention is to use many sensors at the same time (2 or 3 of each sensor).

Sorry for the beginners questions (I don't think I am up to a beginners level yet)

Thank you

[Admin]

Level shifters are needed when two devices of different voltages need to 'talk' to each other.

The Axon is 5V, and if it talks with a 3V device, there will be a 2V short (5V-3V = 2V). The shifter fixes that short.

The Axon can interface up to three UART based devices (plus the USB), up to 127 (128?) I2C devices, and up to 16 ADC based sensors. You can connect everything directly. The UART on the Axon has protection resistors so it'll work with 3V devices.

[Sensor Guy]

What would I need to have the AXON II control a Solenoid Valve that requires 24 V ac.
Here are the specifications
• Inrush volt-amp: 24 V ac-9.6 VA
• Inrush current: .4 amp
• Holding volt-amp: 24 V ac-4.8 VA
• Holding current: .2 amp

[Admin]

You'll need a motor driver that can handle no less than 24V, and have a big heat sink on it.

This will probably work, assuming the voltage never spikes above 30V:
http://dimensionengineering.com/SyRen25.htm


The Axons can interface with any motor driver, no problem.

[Soeren]

Hi,

A TRIAC circuit would be cheaper and take less board area (assuming it is to be driven from a 24VAC supply).
If there's only DC available, a transistor should do (an AC solenoide will draw on DC as well).

[Admin]

A TRIAC circuit would be cheaper and take less board area (assuming it is to be driven from a 24VAC supply).
If there's only DC available, a transistor should do (an AC solenoide will draw on DC as well).

Correction, ignore what I said above, Soeren is right. A MOSFET would be better, however

[Sensor Guy]

Where would be a good place to buy these electronic parts like the TRIAC and any other items?

[Admin]

http://www.societyofrobots.com/robot_parts_list.shtml

[Sensor Guy]

Hello;

I would like to thank you all for posting the replies. I really appreciate the help; I was wondering how much data does the AXON II hold?
How would I go about adding more memory to the AXON II?

Thank you

[Hawaii00000]

64KB Flash, 4KB EEPROM, 8KB SRAM

Unless you have to to log something for a long a
amount of time you should be good to go. I think upgrading th memory would just be too impractical. Just get something that will meet your memory needs the first time around. 

[Sensor Guy]

I  have 50 sensors that will be logging once every 15 minutes. The data will be downloaded once a week, this makes 126000 readings every week. Do you think I have enough storage for that?

Thank you

[Hawaii00000]

Oh I see. I don't know how you'd go about calculating that, but some of the other members do. If its not enough you could try using an external memory such as an sd card. I found  this article on Hack a Day and I think it would work: http://hackaday.com/2010/03/14/storage-for-your-hacking-needs/

[Soeren]

Hi,

I  have 50 sensors that will be logging once every 15 minutes. The data will be downloaded once a week, this makes 126000 readings every week. Do you think I have enough storage for that?

How did you arrive at that number (126,000 reads)?

7 days of 24 hours, with 4 readings an hour, of 50 sensors: 7x24x4x50=33,600 readings/week
Assuming two bytes for each read, you'd "only" need 67,200 bytes.

You won't find a microcontroller with that amount of (non-program) storage, but even the smallest SD card sold currently will hold an incredible amount of weeks worth and will have the added benefit of being able to be simply swapped (by unskilled persons if needs be) when collecting, and the actual reading can be done later - this method needs two cards for each unit of course.

[Sensor Guy]

Thank you for the correction; I don't know how I got to that number. Your number is correct.