temperature sensor on quadcopter

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sensor
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temperature sensor on quadcopter

Post by sensor » Mon Jul 28, 2014 3:11 pm

Hi,

I saw the blog entry for 6/30/2014 talking about the proposed work relaying sensor measurements from the crazyflie quadcopter to a ground array. Not sure if that has gotten off the ground or not. Along those lines though, I was wondering if a sensor, such as the one (see link) below for temp/pressure/rel humidity, could be mounted on a quadcopter, or is it just too large or too heavy? Then the other part, how to send the sensor information back to the user? Could the CrazyRadio handle this?

http://www.seeedstudio.com/depot/TPH-Bo ... -1895.html

Didn't want to just buy the quadcopter and this sensor board, then find out they couldn't work together.

Let me know what you think about this.

Best,
steve

arnaud
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Re: temperature sensor on quadcopter

Post by arnaud » Wed Jul 30, 2014 8:18 am

Hi,

This board looks like it will fly, the size fits the Crazyflie battery and the weight of a single PCB should not be too much (we have flown things like neopixel rings that are bigger). The thing to make sure is the sensor voltage: the Crazyflie is running at 2.8V which seems to be OK for both sensor (I quickly looked at datasheets but it is worth double-checking that they work correctly at 2.8V ...).

As for the data collection you will have to do some soldering to connect the sensors to the expansion connector I2C, and to implement the driver into the Crazyflie Firmware. The Crazyflie contains a log subsystem that makes getting data to the ground very easy. We have made two video that walk throw the process of getting data from within the firmware down to displaying them into the Crazyflie client on the PC: https://www.youtube.com/watch?v=chWrNh73YBw and https://www.youtube.com/watch?v=cutgIMfHwyQ. The crazyradio is used for all communication between the copter and the PC (control and telemetry).

Best regards,
Arnaud

sensor
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Re: temperature sensor on quadcopter

Post by sensor » Thu Jul 31, 2014 12:44 am

Thanks Arnaud. I was taking a brief look at the first video you cited and in the code I noticed there was mention of temperature (via barometer?), which I assume could mean the derivation of temperature assuming a standard lapse rate and a barometer value from which one could derive an altitude. I guess my question is, is crazyflie already measuring any atmospheric parameters and communicating that data via crazyradio? Just trying to get things straight before I try to reinvent what already exists.

Again, thanks for the detailed info you outlined below. I have a lot to bone up on.

Best regards,
Steve

arnaud
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Re: temperature sensor on quadcopter

Post by arnaud » Fri Aug 01, 2014 9:02 am

Crazyflie 10DOF is measuring pressure, temperature and altitude (asl) from the pressure sensor. It makes available via the log framework these variable: https://github.com/bitcraze/crazyflie-f ... zer.c#L459
This is currently used for altitude hold (which is still pretty shaky, there is still some work to do to filter sudden pressure change).

The log values can be fetched at any rate (multiple of 10ms, limited by radio bandwidth ...) with Crazyradio and the log framework using the PC client and/or the python library. Our wiki contains some info about the log framework and the videos describes how data are fetched in the client (https://www.youtube.com/watch?feature=p ... 3YBw#t=363)

Best regards,
Arnaud.

sensor
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Re: temperature sensor on quadcopter

Post by sensor » Sat Aug 02, 2014 11:23 pm

Hi Arnaud,

Thanks again for the additional information you provided. I'm starting to go through some of the videos now.

I took a closer look at the temp/pressure/humidity (TPH) sensor from seeedstudio.com, and it says it is only 3.3V compatible. When I checked the specs for the Crazyflie, I saw this:

+BATT 3.0-4.2V
VCOM 3.0-5.5V
VCC 2.8 or 3.3V
VCCA 2.8 V

I wasn't sure which value is the key one here as I try to determine whether I could use this TPH sensor or not. Will this TPH sensor (that has to run at 3.3V) work with the Crazyflie?

Also, I think I understand now that Crazyflie, measures pressure via barometer. Then temperature and altitude are derived from this measured pressure. In other words, there are no temperature or humidity sensors on Crazyflie. Do I have that right?

thanks much.

Best regards,
Steve

arnaud
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Re: temperature sensor on quadcopter

Post by arnaud » Mon Aug 04, 2014 7:58 am

Hi,

Yes it is right, the temperature measurement of the Crazyflie is just a by-product of the pressure sensor which is used to measure altitude. It is used in the videos as an example of a simple sensor value that one would want to get to the ground. There is no humidity sensor on-board.

The way to connect electronic to the Crazyflie is via the expansion header: http://wiki.bitcraze.se/projects:crazyf ... ion_header

The main MCU is on VCC power domain, at 2.8V during flight (3.3V to be compatible with USB when charging).

Seeeds specify 3.3V for the sensors but this is just a breakout board so you should look at the data-sheet of the sensors. They both work at 2.8V, I checked earlier, but you still need to verify thing like if the accuracy would be affected by the voltage (this is what can happen with sensors: they work over a wide range of voltage but best at one smaller range).

Best Regards,
Arnaud

sensor
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Re: temperature sensor on quadcopter

Post by sensor » Mon Aug 04, 2014 4:38 pm

Hi Arnaud,

Thanks for the additional information. The only thing I see at seeedstudio is this:

Specifications:

Size: 26 * 19 mm
3.3 volt compatible
Grove compatible
Sensirion SHT21 humidity sensor
Bosch Sensortec BMP180 pressure sensor
Double temperature sensor (SHT21 & BMP180)
Operating temp: -40 .. +85 degrees Celcius
I2C pull-up resistors with cut-trace

Where are you finding the "data-sheet" that you mention for this sensor?
http://www.seeedstudio.com/depot/TPH-Bo ... -1895.html

It does sound like you are saying this sensor can work with crazyflie.

Thanks.

Best regards,
Steve

sensor
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Re: temperature sensor on quadcopter

Post by sensor » Wed Aug 06, 2014 3:09 pm

Hi Arnaud,

I greatly appreciate all of the info you have provided. Just ordered a quadcopter and can't wait to test it with the TPH sensor.

When you get a chance, let me know where you saw datasheets for: http://www.seeedstudio.com/depot/TPH-Bo ... -1895.html. I only see a small block of specs on that page - is that what you are referring to?

Had one more really basic question. I take it the 80m range limitation of the crazyflie is due to the limit of the radio transmission. What would it take to increase this limit? Just wondered because it would be nice if I could measure higher.

Best regards,
Steve

arnaud
Bitcraze
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Joined: Tue Feb 06, 2007 12:36 pm

Re: temperature sensor on quadcopter

Post by arnaud » Thu Aug 07, 2014 9:28 am

Hi Steve,

Great, I hope you will have some fun with your Crazyflie.

The board contains 2 sensors, Google helps to find the manufacturer datasheets: https://www.adafruit.com/datasheets/BST ... 000-09.pdf and http://cache.freescale.com/files/sensor ... /SHT21.pdf

As for the range the limit is the radio power. Both Crazyflie and Crazyradio emit at 0dBm and the sensitivity is best at 250Kbps. If you are flying in only one direction (for example mostly up or mostly north), a directional antenna connected to the Crazyradio could help having an higher range. Though we have not tested that yet, but I would be really interested by hearing how it works if you happen to test it.

Best regards,
Arnaud

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