UV Tron – Fire Detection Sensor
The object of the fire detection is to navigate the robots through a maze of walls and look into the rooms and see if there is a fire. Using a UV sensor, a flame the size of a single candle can be seen 5 meters away. The Trekker utilizes a Hamamatsu UV sensor that is mounted onto the Trekker sweeping sensor brackets. The Trekker scans the area and finds an open flame.The Hamamatsu UV TRON Flame Detector is lightweight, has low current consumption, and operates as high sensitivity UV Sensor. The UV TRON is an ultraviolet detector that makes use of the photoelectric effect of metal combined with the gas multiplication effect. It has a narrow spectral sensitivity of 185 to 260 nm. Thus it is solar blind, being completely insensitive to visible light. Unlike semiconductor detectors, it does not require optical Visible-cut filters, thus making it easy to use.
-1.jpg "UV Tron Fire Detection Sensor")
The driver for the UV TRON is operated by applying DC low voltage and outputs a high-voltage power supply. It also contains a signal processing circuit on the same printed circuit board. Since background discharges of the UV TRON caused by natural excitation lights (such as a cosmic ray, scattered sunlight, etc.) can be cancelled in the signal processing circuit, the output signals from the C3704 series can be used without errors.UV TRON Flame detector is small, but has a wide angular sensitivity (directivity) and can reliably and quickly detect weak ultraviolet radiation emitted from a flame due to use of the metal plate cathode (e.g. it can detect the flame of a cigarette lighter at a distance of more than 5 m.). The Flame detector 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. To minimize the area the sensor sees the flame, a field of view mask can be used. The shields are useful when you are trying to locate the location of the flame.
The Flame Detector Mask is a piece that slides over the UV TRON Detector to mask the detector so the sensor can only see the UV Flame if its directly in front of the detector. This is ideal when trying to determine where the flame is coming from. The sensor has a very wide viewing angle that is great for detecting the presence of a flame, but without the mask the detector will not be able to determine where the flame is coming from. The Mask is 1″ in diameter with a center hole machined out along with about a 1/8″ slot machined through the side to let the UV in. The field of view is narrowed to about a total of 15 degrees while not significantly impacting its sensitivity. The mask is simply glued to the driver board to allow it to stay on.
A Deluxe Flame Sensor Mask is also available that houses the entire sensor and the board along with masking the sensor and allowing greater sensitivity than the standard mask. The other advantage of the deluxe mask is it protects the detector and protects people from the high voltage of the sensor.
Assembly – Mechanical and Wiring Hookup
1. The UV Tron Bulb needs to be soldered to the drive circuit board. For the Trekker this connection is be done directly with the bulb sitting right on the board. Solder the UV Tron Bulb to the drive circuit board taking care to solder the Cathode (shorter) lead of the UV Tron bulb into the hole marked “K” on the drive board and the Anode (longer lead) into the hole marked “A” on the drive circuit board. Take care when soldering the bulb as it is quite fragile and sensitive to the heat of the soldering iron. See Figure 74 for assembly. Trim off excess leads.
Figure 74: UV TRON Assembly
2. The driving circuit has an input voltage specification of 10 to 30V dc. This requirement is avoided by supplying a reliable regulated 5V supply from the Trekker Expansion board.
- The first thing the unmodified drive board does with the input voltage is to regulate it to 5V. This is done using a small and very common 7805 voltage regulator. This regulator is marked ICI on the board. It has four holes (three are used) and they are marked 0, G, I and O. This stands for Output, Ground, Input and Output.
- The fourth hole on the board marked “0″ is not used. This hole can be used as the input from a 5V regulated supply. This just side steps the voltage regulator completely on the board. Attach the power (5V Red) wire to the hole marked “O”, the Ground wire (black) is then attached to the “-” and the signal wire (yellow) is attached to “2″. See Figure 75 and Figure 76 for installation of the wires.
Figure 75: UV TRON Schematic
Figure 76: UV TRON Wiring
3. This step should be done after the wires are fed through the holes for the deluxe sensor bracket/mask. Place crimps on each wire of the wires (see Figure 14 or Figure 15) and insert them into the connector as shown in Figure 16. The wires should be placed in the order shown in Figure 77 if using a version V.2X OOPic II Expansion board or like Figure 78 if using one of the ultrasonic locations on a version V1.x board.
Figure 78: UV TRON Plug for Ultrasonic U1-U3 Plug on V1.x Boards
4. If using the deluxe scanner bracket and mask, skip to step 11.
5. Place 4 #4-40 x 3/4″ machine screws with washers through the bottom of the bracket fastening them with a washer and #4 nut on the top. See Figure 79.
Figure 79: UV Tron Bracket Mounting
Place 4 #4 x ¼” long nylon spacers over the screws as shown in Figure 79.
7. Place the driver board with UV TRON sensor on the sweeping scanner bracket and attach with 4 #4 Nylon nuts as shown in Figure 80.
8. Attach the UV TRON bracket to the back of the sweeping scanner bracket using the mounting hardware that holds the ultrasonic sensor on. The finished sensor should look like Figure 80.
9. Attach the wires to the sweeping scanner as shown in Figure 81 so they are out of the way.
Figure 81: UV TRON Wire Tie Downs
10. If a mask is being used, install the line of site mask per Figure 82. Apply hot glue or other adhesive product to the board and slide the mask over the sensor. Be careful not to get any glue on the electronics on the board or the UV sensor. You may want to play with the detector some to find the best orientation of the mask, but having the slot face straight ahead works best.
Figure 82: UV TRON Mask Installation
Note: The following steps are for the deluxe bracket and mask, so they can be skipped if you just installed the standard bracket and mask.
11. Insert a #2 x 5/16″ long screw through the top of the bracket. Fasten the servo arm on with a washer, lock washer and nut as shown in Figure 83. The servo arm should be on he unpainted side.
Figure 83: Servo Arm to Deluxe UVTRON Mounting Plate
12. Insert 4 #4-40 x 3″ long screw through the bottom of the bracket. Fasten them with a #4 flat washer and then a #4 nut. Then place a #4-1/4″ nylon spacer on each screw. See Figure 84.
Figure 84: Deluxe UVTRON Mounting Plate Screws
13. Mount the bracket on the servo now. Ensure servo is in its centered position and mount the bracket so it’s oriented the way you want. (The two wire holes are at the rear of the sensor).
14. Feed the wire for the UVTRON sensor through the rear hole closest to the center.
15. Lower the UVTRON board over the 3″ screws and faster with #4 nylon nuts. (This step justifies the cost of a ¼” nut driver…) See Figure 85.
Figure 85: Mounting of UVTRON on Deluxe Bracket
16. This can be skipped if you are not attaching a sensor to the top of the Deluxe UVTRON Bracket. Using the hardware that attached your sensor bracket to a servo arm attach the bracket to the top plate of the UVTRON Deluxe sensor bracket. The unpainted side receives the sensor bracket.
17. Place the round mask over the UVTRON and the 4 screws with the desired width of the mask forward.
18. Feed the wires of the sensor through either hold of the top plate and down through the outer hole on the bottom plate
19. Place the top plate over the 4 screws
20. Faster the top plate on with 4 #4 washers followed by 4 #4 nuts.
21. Tighten nuts. CAUTION: Do NOT over tighten these nuts, it will “tin can” the top plate.
22. The assembled unit should look like Figure 86.
Figure 86: Deluxe UVTRON Final Assembly
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