Shinyi Huang at ITP

What is the UV Tron flame detector sensor?

A flame sensor (UV TRON) made by HAMAMATSU PHOTONICS, Japan, is an ultraviolet light detector.
It has a narrow spectral sensitivity of 185 nm to 260 nm, being completely insensitive to visible and infrared light. Unlike semiconductor detectors, it does not require optical visible-cut filters, thus making it easy to use. In spite of its small size, it has wide angular sensitivity and can reliably and quickly detect weak ultraviolet radiations emitted from flame (eq. it can detect the flame of a cigaret lighter at a distance of 5 meters).

APPLICATION EXAMPLES

The sensor is well suited for use in flame detectors and fire alarms. Compare with the other fire alarm, such as smoke detector, I found that this flame detector sensor can not distinguish how big the fire it is. So I think it more suitable to put in the place which can not even allow a small flame, for example, paper manufacturing factory.

Here are some more common applications for the sensor may include,
• Flame detectors for gas/oil lighters and matches
• Fire alarms
• Combustion monitors for burners
• Inspection of ultraviolet leakage
• Detection of discharge
• Ultraviolet switching
Such as the pictorial example from HAMAMATSU:

Another exemplar use of the sensor is a competition robot in Trinity Firefighting Robot Contest from Ohio Northern University. The robot is to navigate through a model floor plan of four rooms where a candle representing a flame source is randomly placed, locate the candle, extinguish it, and return safely to its starting location.

SENSOR HARDWARE

Operation Theory

The sensor’s theory of detection is actually fairly simple. When ultraviolet rays such as those from an open flame hits the cathode leg of the sensor, electricity or more specifically, photoelectrons, is generated. When the electrons flow toward the anode leg of the sensor combining the applied voltage to the sensor, an electric field is generated and grows stronger over time. This process beings to ionize the enclosed gas inside the bulb and thereby creating more flow of electronics like a tsunami wave building up its energy as it get closer to shore. And finally a discharge occurs like an avalanche effect between the cathode and anode that in turn, result in a voltage drop.
The UV TRON driving circuit board essentially provides the supplying voltage to the tube, look for the discharge effect, and regulate the voltage drop. Then it conditions the signal and provides pulses signal outputs to the users.
Here is the operating theory diagram I drew !

Electronics Characteristics

Detection Characteristics

The effectiveness of the UV TRON sensor lies in its ability to sense a narrow range of light source wavelength.
It is this ability to sense light source between 185 nm and 260 nm below other common light sources like the sunlight and tungsten light allows the sensor to immune to such “noises”. However, there are still other sources of UV light that can cause “false” detection. For example, Halogen lights such as low-voltage home lighting, torchier lights, and lights on video cameras.

Another advantage of its ability to sense ultraviolet rays means it does not need to directly facing the light source. Ultraviolet ray bounces like other lights thus it can bounce off walls or other surfaces to come back to the sensor to be picked up. Thus a flame sensor has a great potential to detecting a flame source anywhere inside a confined space within the detecting range of the sensor.

The viewing ranges of the sensor shows how the sensor has a large range of sensitivity, or a nearly ±45o horizontal and vertical viewing range rather than a narrow focused sensing range directly in front of the sensor.

UV TRON Drive Circuit Board: Layout

The jumper lead for background cancellation is default to 3. It is set such that if UV TRON bulb generates only 3 pulses per every two seconds, the drive board ignores these signals and provides no pulse outputs. It can be set to higher step at 5, 7, or 9.
The power supply input pin is for unregulated power between 10 to 30 Vdc. If a reliable regulated 5 Vdc power is available, it can be connected to a pin 0 shown as my red wire.

The above schematic diagram is a synonym of the board layout discussed earlier with more clear display of how the background noise cancellation filter, power inputs, and the output signals construct.

TEST PROJECT / WORKING EXAMPLE

My orinignal idea to use this fire detector sensor is building an installation when user light up a candle, the projector will project some beautiful pattern on the wall. After I got this sensor and did the research and experinment on it, I found that the sensor is not an analog output sensor, which means it can not distinguish how big the fire it is. I got same amount of the pulse number from the same distance of a candle light and two gas stoves.

So I tested this sensor with different distance. By using the "attachInterrupt" function in Arduino, which can trigger a function when the input to a pin changes value, I got a 0-7 pulses per second depending on the distance of the fire. The first output is a LED, when it detect the fire, the LED will blink. Moreover, I connected the Arduino with processing and drawing the circles which changed the diameter accorading to the amount of the pulse per second.

Arduino code

Processing code

Posted by Shin-Yi Huang at 10:49 AM | Permalink | Comments (0) | TrackBacks (0)

The UV TRON flame detector sensor I chose for final report can detect a match lighting from 5 meters in a sunny room. Since the UV energy emitted by a flame bounces off walls, you don't even need to have a line of sight to the flame to detect it in a room.

The UV TRON is a bipolar tube with a structure similar to that of a phototube. the inside of the UV TRON tube is filled with a special gas. It is only sensitive to ultraviolet rays. When UV glass due to the photoelectric emission effect. Then a large current is rapidly generated between the anode and the cathode and electricity is discharged. The strength of UV rays which pass through the UV glass is monitored by electronic circuitry which triggers the detector unto the alarm state.

The UV TRON sensor is well suited for use in flame detectors and fire alarms, and also in detection of invisible discharge phenomena such as corona discharge of high-voltage transmission lines.

When I search this flame sensor I found that there is "The Trinity Fire Fighting Contest" which takes place every year in Hartford, CT on the Trinity College campus. this annual event has become something of a rite of spring for engineering students and hobbyists from around the world. The basic challenge is to build a robot and enter a small maze, navigate around without hitting walls or obstacles, and find a lit candle placed randomly in the maze. Once the candle is located, the robots are charged with extinguishing the candle and then exiting the maze. The competition simulates many of the challenges that would be faced by a real-world fire fighting robot. The UV TRON sensor was a kind of sensor that usually used as a fire detection.

One of the more colorful robots included revolving firemen design for Trinity!

Posted by Shin-Yi Huang at 05:16 PM | Permalink | Comments (0) | TrackBacks (0)

Last time I had a Sharp GP2Y0A02YK IR Sensor for the datasheet report, so I use the same IR sensor to record the value this time.

Since I have no idea about the mySQL, so I chose the way: Arduino -> Processing -> PHP -> txt file. and I follow the steps of the code sample.

At the first, I use Arduino to get the value from sensor and produces the serial sensor data stream.
The sencond step, I used Processing to take in serial from the Arduino and then call a PHP script on the network, like this:

finally, uploading a writeable datalog.txt file and a php/cgi script which writes that data to a textfile on the network when passed data.

Wala~~ It's done!

Posted by Shin-Yi Huang at 01:45 PM | Permalink | Comments (0) | TrackBacks (0)

I choose photocell for this sensor and time assignment. Actually at the first I want to play with the sensor that I never try. I chose temperture sensor (LM34) , but it start smoking and burned when I connect to the power!! So I came back to my favorite - the photocell...

The circuit of photocell is simple, just hooked it on Arduino board analog pin as below:

To visualize the serial vaule of the sensor, I used Arduino to get the values from photocell and communicate the Processing serially. At the same time, I used a potentiometer to compare the different values in time and get the result as below:

The purple circles in the bottom are the values of the photocell and on the top are the potentiometer. The photocell values are low but not the zero because it's not completely dark by covering with the hand. The sensors booth seem pretty stable and keep the value track almost a line.

when the hand uncover the photocell, it will go up immediately to the greatest value (0.894), and than keep staying at the value. In the bottom, the lowest value of the potentiometer keeps in zero fixedly.

The track of two different sensor.(purple circles are photocell, pink circles are potentiometer.)

Arduino code
Processing code

Posted by Shin-Yi Huang at 06:04 PM | Permalink | Comments (0) | TrackBacks (0)

This time I decide to choose Sharp GP2Y0A02YK IR Sensor as my sensor datasheet report assignment.
This sensor takes a continuous distance reading and reports the distance as an analog voltage with a distance range of 20cm (~8") to 150cm (~60"). The interface is 3-wire with power, ground and the output voltage and requires a JST 3-pin connector.

The Features:
1. Less influence on the colors of reflected objects and their reflectivity, due to optical tringle measuring method.
2. Distance output type(detection range:20-150cm)
3. Analog voltage corresponding to distance
4. An external control circuit is not necessary, output can be connected directly to a microcomputer.

Applications:
for detection of human body and various types of objects in home appliances, OA equipment, etc.

How it work? (from Acroname):
The basic idea is this: a pulse of IR light is emitted by the emitter. This light travels out in the field of view and either hits an object or just keeps on going. In the case of no object, the light is never reflected and the reading shows no object. If the light reflects off an object, it returns to the detector and creates a triangle between the point of reflection, the emitter, and the detector.

The angles in this triangle vary based on the distance to the object. The receiver portion of these new detectors is actually a precision lens that transmits the reflected light onto various portions of the enclosed linear CCD array based on the angle of the triangle described above. The CCD array can then determine what angle the reflected light came back at and therefore, it can calculate the distance to the object.

Analog Output Voltage and Distance to Reflective Object

Because of some basic trigonometry within the triangle from the emitter to reflection spot to receiver, the output of these new detectors is non-linear with respect to the distance being measured.
Detecting distance of 20 to 150 cm. Thing to notice in the above graph is that once you fall inside of the stated distance range (less than 20cm), the output drops rapidly and starts to look like a longer range reading.

Download datasheet

Posted by Shin-Yi Huang at 10:38 AM | Permalink | Comments (0) | TrackBacks (0)