Wireless sensor data transmission.

[Alhazar]

Hi First timer here. I used to make very simple robotic kits a long time ago and i recently saw something that re-sparked my robotics spirit lol. i'm working out the practicality of it all and have run into quiet a little road block and have been trying to tackle this issue have had a few possible ideas.

Ok to the point, my sensors (most likely going to be the basic assortment of bump sensors, sonic and IR sensor I was thinking of including a camera but that kinda of obstacle avoidance would be quiet above me at the moment and I can always add it later) will not be able to be directly connected to the MCU of the robot and would need some kind of wireless transmission(Very short distance) to send their data. I was thinking IR at first but would each sensor need its own IR emitter and collector, then i was thinking of using RF or Bluetooth or WiFi to send the data but with the same question would I be able to combine the sensor data into one bluetooth connection then separate it back into its separate signals (the would be digital signals and analog as well.)

Any ideas or suggestions?

[izua]

Gather all sensor data with a microcontroller, then transmit it. You won't be able to connect sensor directly, anyway, since most of them have some kind of formatted output that's not going to be accepted by the transmitter. So even for one sensor, a microcontroller is still required.

[Alhazar]

So it would need a separate CM on the "outside" then have it go through the wireless to the "inner" MCU? I was thinking at least with the digital sensors I could have it use IR LED on the "outside" that would be turned on when the sensor was activated and a IR photo transistors "inside" that would that would relay the signal to the "inner" MCU. The Barrier between the outer and inner systems would just be clear plastic, maybe polycarbonate, bubble. But couldn't the IR also be used for the analog signaling also be done the same way but using a photo resistor so the signal would be based on the intensity of the IR beam. Maybe the term "wireless" might have been the wrong choice implying long distance, I just need to send the signal through a thin plastic clear barrier. Would it still need a separate MCU's 

[pomprocker]

build the $50 robot and add the BlueSMiRF from sparfun.com

[Alhazar]

build the $50 robot and add the BlueSMiRF from sparfun.com

I'm not looking at the $50 Robot, and I need a way for sending the sensor data through thin plastic to the MC of the robot not to a computer system.

[izua]

Why would you want that?

[Alhazar]

Part of the design requirements and the locomotion system, battery and the "brain" will be inside a contained unit while the sensors are going to be in the outside environment

[krich]

So, what you need is a wireless point to multipoint arrangement.  I think ZigBee is designed for that kind of thing.  Although, it seems that might be overkill and $$$ when we're talking simply transmitting through a thin plastic barrier.

IR may be the way to go if you're only transmitting very short ranges and if the plastic barrier is IR transparent.

I thought I saw a project recently that was a "benchtop wireless" solution, where RF was used in a rather crude, but sufficient way to create a reliable and short range wireless connection.  I'll see if I can't find that again and post the link.

[Alhazar]

Awesome i was thinking that IR should work and with my first post i think saying wireless came across as implying long distance, the other question i've have been working around with would be inductive power transmission to the sensor array, i have built Tesla Coils and should be a similar task but much smaller voltages being used and it should just be a simple tuned set of coils and Rectifiers and DC to AC converters for the power transmission portion
 

[izua]

Inductive transmission might be a solution, but, you must somehow ensure that a given magnetic coupling will be extremely local, and it won't be influenced by other sensors' magnetic coupling.

ZigBee is one solution.
Adding a small IR led to each sensor, along with a microcontroller, to modulate the data would be another idea. IRDa might be another solution.

Or you could use the nordIC RF chips, or something like CC1000.

[Alhazar]

Inductive transmission might be a solution, but, you must somehow ensure that a given magnetic coupling will be extremely local, and it won't be influenced by other sensors' magnetic coupling.

ZigBee is one solution.
Adding a small IR led to each sensor, along with a microcontroller, to modulate the data would be another idea. IRDa might be another solution.

Or you could use the nordIC RF chips, or something like CC1000.

So each Sensor would need a micro controller on the send and receive side? How would I go about implementing that? Would the straight digital signal sensors need one since they are just a On Off signal? I couldnt really find any example of something like this(sensor data transmitted over IR) being done. I'm Planning one IR send receive Circuit for each sensor currently. As for the Magnetic interference from the Inductive powering, i was planning on having that shielded but thats just something i'm toying with and will need to experiment with to see if its fesible, i could go the easy route and just toss some batteries into the sensor array but wheres the fun in that

[Alhazar]

Inductive transmission might be a solution, but, you must somehow ensure that a given magnetic coupling will be extremely local, and it won't be influenced by other sensors' magnetic coupling.

ZigBee is one solution.
Adding a small IR led to each sensor, along with a microcontroller, to modulate the data would be another idea. IRDa might be another solution.

Or you could use the nordIC RF chips, or something like CC1000.

Oh No, i didn't mean using induction for sending the sensor data i just meant using one induction power transfer to provide power to the external systems as they would be separated from the main battery

Looking at using the Axon for this project

[izua]

TBH, unless you have the sensors wide apart, this is a very brutal requirment. I hope you asked for the proper funding.
Digital sensors rarely output data as 1/0. Digital sensors encode their data using a digital method - such as i2c, spi or rs232.

[Alhazar]

what i'm calling a digital sensor would just be bump sensors just switches that complete the circuit when they are depressed like hitting a wall or such so they wont be sending a digital signal just a 1 On 0 Off and the IR sensors would be blocked from each other and spread over the dome so there shouldn't be to much of a possibility of cross talk.

[Admin]

In order to transmit data wirelessly, you first need something that can generate a data signal that can be transmitted.

A sensor alone cannot, so you need a microcontroller to convert the sensor signal into data, then a wireless transmitter to actually transmit that data.

check these out:
http://www.sparkfun.com/commerce/product_info.php?products_id=7813
http://www.sparkfun.com/commerce/product_info.php?products_id=872
http://www.sparkfun.com/commerce/product_info.php?products_id=7816
http://www.sparkfun.com/commerce/product_info.php?products_id=7815

You'd also have to find a microcontroller.