rockon! 2008 1 welcome to day 2 rockon! 2008. 2 announcements: -table set up… -stay close to your...
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2
RockOn! 2008
Announcements:
- Table set up…
- Stay close to your buddy team
- Don’t touch stuff yet
- This is where you will sit for duration of workshop
- Soldering…who has never soldered before
-
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RockOn! 2008
Radiation: Overview
- Radiation is generally viewed as harmful to space payloads.
-While some projects purposely expose parts to the saturated Van Allen belts to investigate the effects of high energy particles, some projects must avoid harmful doses at all costs.
- Sparse data has been collected from suborbital airspace.
- This payload will allow for a large collection of data sets.
Van Allen Belts: www.nasa.gov
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RockOn! 2008
Radiation: Overview
- Radiation is generally viewed as harmful to space payloads.
-While some projects purposely expose parts to the saturated Van Allen belts to investigate the effects of high energy particles, some projects must avoid harmful doses at all costs.
- Sparse data has been collected from suborbital airspace.
- This payload will allow for a large collection of data sets.
Van Allen Belts: www.nasa.gov
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Radiation: Effects
- Single event phenomenon (SEP), burnouts and bit flips can cause damage to solid state devices aboard a space payload.
- An understanding of dose levels is ideal to plan a mission to sub-orbital altitudes, especially with sensitive optics or microprocessors.
SEP diagram: www.aero.org/
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Radiation: Effects
- There are three types of radioactive emissions:
- Alpha - the least penetrating form of radiation, can be stopped with a piece of paper or a few inches of air.
- Beta-rays are more penetrating than alpha-rays
- Gamma-rays are the most penetrating form of radiation. Often produced in conjunction with alpha or beta-rays, they can penetrate several inches of steel or hundreds of feet in air
Particle comparison:
www.freedomforfission.org.uk
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Radiation: A General Trend
- Radiation levels roughly double every 5,000 feet in altitude, so at sea level dosage will be roughly ½ the level observed in Denver, Colorado.
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Radiation: A General Trend
- Radiation levels do depend on the level of cosmic radiation, effective shielding, and any ground or building materials containing radioactive materials
- In general, at sea level; you should see 12-14 counts per minute
- This device has resolution to 2 μs. Which indicates it cannot detect particle events closer than 2 μs to each other
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RockOn! 2008
Radiation: Dosage and Limits
Shielding can drastically reduce the observed dose. Be sure to wear safety glasses when handling the material.
-Max dose for occupational workers (Nuclear Power) 5 Rem/yr (max exposure to retina). [2]
-Max dose recommended for the general public 100 mRem from a high energy source over a short time frame. [2]
- An average American receives 360 mRem/yr from natural background and manmade sources. [2]
[2] http://www.jlab.org/div_dept/train/rad_guide
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Radiation: Comparisons
- A typical radiation dose from a chest x-ray is about 10 mRem per x-ray (Gamma exposure) [2]
- Consumer products contain radiation, such as: smoke detectors, and lantern mantles. This dose is relatively small as compared to other naturally occurring sources of radiation and averages 10 mRem/yr (Alpha exposure). [2]
20th Century Fox ©
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RockOn! 2008
Radiation: Conversions- Generally, 75 counts per minute
(CPM) is equivalent to 1 mRem/hr.
- Therefore, 4,500 CPM is roughly equivalent to 1 mRem
- A source from a smoke detector makes up 2.8% of the yearly average expected dose, which is .027 mRem/day or .0012 mRem/hr
- These numbers shouldn’t alarm you, an average person receives 1 mRem per day.
20th Century Fox ©
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What Are We Building ?
- Basic Geiger Counter
- Audio and Visual Cues for Radiation Detection
- Can detect Alpha, Beta, and Gamma Radiation.
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Prep Step 1: Tool Layout
- Prepare tools for the construction process.
- Put on your safety glasses.
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Prep Step 2: Grounding
- Put on a static strap to remain grounded. Also make sure the strap is tight across your wrist.
- This will protect any parts from electro-static discharge (ESD) and its harmful effects.
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Prep Step 3: Soldering Station
- Turn on the soldering iron
- Set the temperature control on the soldering iron to a temperature less than 700 °F and greater than 450 °F.
- As a general rule use a temperature in the range between 550 and 650 degrees Fahrenheit.
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Prep Step 3: Soldering Station
- Turn on the soldering iron
- Set the temperature control on the soldering iron to a temperature less than 700 °F and greater than 450 °F.
- As a general rule use a temperature in the range between 550 and 650 degrees Fahrenheit.
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Prep Step 4: Tinning the iron
- Tin the tip of the soldering iron by melting an inch or so of solder on the tip.
- The iron will now look shiny on the tip.
- Then wipe any excess solder on the golden sponge.
- Now place the iron back into the holder. Tinning your soldering iron in this manner will aid in future soldering.
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RockOn! 2008
Verify Kit Contents
- Open your kits and verify the contents with the provided list and visual layout.
- Find the Geiger Mueller (GM) Tube and set it aside in a safe place.
- You won’t need the GM Tube until the last few steps.
GM TUBE
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Verify Kit Contents: Resistors
-R1 = 4.3KΩ = (YOR)
-R2 = 15KΩ = (BrGrO)
-R3 = 5.6 Ω = (GrBlR)
-R4 = 470KΩ = (YVY)
-R5 = 10 megaΩ = (BrBkBl)
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RockOn! 2008
Verify Kit Contents: Resistors
-R6 = 100KΩ = (BrBkY)
-R7 = 47KΩ = (YVO)
-R8 = 470 Ω = (YVBr)
-R9 = 330 Ω = (OOBr)
-R10 = 1 megaΩ = (BrBkGr)
-R13 = 10 megaΩ = (BrBkBl)
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Verify Kit Contents: Capacitors
- Some capacitors have polarity, while others do not. The majority of capacitors use during this build are not polarized.
- *Note these similar capacitors C4=C5 , C2=C8 , and C3=C10.
- Some capacitors used during this build can carry charge long after power has been disconnected from the circuit (15-30 seconds).
- Use caution especially around the high voltage section of the circuit to avoid a discharge shock.
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Verify Kit Contents: Capacitors
- C1 = Green Ceramic 0.0047 μF
- C2 = Green Ceramic 0.01 μF
- C3(±) = Yellow Tantalum 100 μF
- C4 = Orange Ceramic 0.01 μF 1 Kv
- C5 = Orange Ceramic 0.01 μF 1 Kv
C1 C2 C3 C4 C5
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RockOn! 2008
Verify Kit Contents: Capacitors
- C6 = Green Ceramic 0.001 μF
- C7 = Green Ceramic or Orange Ceramic 0.047 μF
- C8 = Green Ceramic 0.01 μF
- C10(±) = Yellow Tantalum 100 μF
- C12 = Orange Ceramic 120 pF
- C13 = Blue Ceramic 1.00 μF 50v
C6 C7 C8 C10 C12 C13
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Verify Kit Contents: Diodes
- All diodes in this kit have polarity
- *Note these similar diodes D5=D6 , D2=D3=D9
- D1 = 1N914 =
- D2 = 1N4007 1 Kv =
- D3 = 1N4007 1 Kv =
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Verify Kit Contents: Diodes
- D4 = 1N5271 100 V =
- D5 = 1N5281 200 V =
- D6 = 1N5281 200 V =
- D9= 1N4007 1 Kv =
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Verify Kit Contents: Miscellaneous
Q2 (NPN Transistor)Q1 (IRF830) Q3 (7805 Regulator)
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Verify Kit Contents: Miscellaneous
- D7 (Red Led) -T1 (Mini Step-up Transformer)
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Verify Kit Contents: Miscellaneous
- U1 (16 pin 4049 chip and socket)
- U2 (8 pin 555 Timer chip and socket)
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TIPS:
-Make sure the static strap is tight across your wrist at all times.
- DO NOT linger on parts with the soldering iron.
- As a general rule use a 5 second linger time with a 10-20 second cool time for parts.
-Mount and solder components flush to the board unless otherwise stated.
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TIPS:
-Make sure the static strap is tight across your wrist at all times.
- DO NOT linger on parts with the soldering iron.
- As a general rule use a 5 second linger time with a 10-20 second cool time for parts.
-Mount and solder components flush to the board unless otherwise stated.
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TIPS:
- Use caution when clipping leads to avoid flinging metal across the room.
- All soldering must achieve a good solder filet on the pad as shown for circuit reliability.
- Also clip the leads in this fashion.
- Bend resistors and diodes using your plastic tool as shown.
Example of a good solder filet
workmanship.nasa.gov
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Let’s Start Building
- The board shall be oriented in this manner for the duration of this kit construction unless indicated otherwise.
- Raise your hand for assistance if any issues arise.
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Step 1: C14
-Mount and solder C14 into the appropriate place on the PCB.
- **This capacitor is polarized, note the shorter lead is negative.**
- Also, text on the side of the capacitor indicates the negative lead.
- This capacitor IS electrolytic, but it serves as an audio ground test component only.
- +
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Step 2: R6 (100K BrBkY)
-Mount and solder R6 into the appropriate place on the PCB.
- **This resistor is in a location that was originally designed for a capacitor.**
- The PCB design requires the awkward bending of the resistor.
- Consult the following pictures for examples of this.
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Step 3: 16 pin socket
-Mount and solder the 16 pin socket to the appropriate location on the PCB.
- **This chip socket has a defined orientation note the notch on the PCB as well as the socket itself.**
-Match notch to notch to allow the correct orientation.
- Start by soldering opposite corners of the socket to mount to the board for easier soldering. Also ensure the socket is flush with the board.
Notch
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Step 4: C1 and C2
-Mount and solder C1 and C2 into the appropriate places on the PCB.
- These capacitors are not polarized, so the orientation of mounting will not compromise performance.
C1 C2
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Step 5: D1
-Mount and solder D1 into the appropriate place on the PCB.
- This diode is polarized.
- Orient the diode to match the black line on the diode to the line drawn on the PCB.
D1
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Step 5: D1
-Mount and solder D1 into the appropriate place on the PCB.
- This diode is polarized.
- Orient the diode to match the black line on the diode to the line drawn on the PCB.
D1
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Step 6: R1 R2 R3
-Mount and solder R1, R2, and R3 into the appropriate place on the PCB.
- These resistors are not polarized, so orientation will not effect performance.
- If you haven't already, bend the leads of the resistor around the provided plastic tool.
- This prevents stress fractures from sharp angle bending.
= R2 (BrGrO)
= R1 (YRO)
= R3 (GrBlR)
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Step 7: T1 CAUTION!!!
- Locate T1 (a four pronged transformer) among your parts.
- This component is extremely fragile composed of very small gauge wire twined around a few nodes. The wires are surrounded by brittle plastic connected to four pins.
- If excess force is applied to these metal pins the plastic will break and sever the small wiring within the transformer.
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Step 7: T1 CAUTION!!!
- Use CAUTION! The transformer will fit into the PCB in one orientation only.
- **The transformer may not fit perfectly. Try a dry fit at first to note which leads may need bending.
- If a lead does need bending use care to slowly and gently bend the leads with the plastic tool or a pair of needle nose pliers.
D1
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Step 7: T1 CAUTION!!!
- If you do force the transformer to be flush with the PCB it WILL break and render the kit useless.
-Mount and solder T1 to the PCB.
-Match the dot on the transformer to the dot on the PCB.
T1
Example of flushness to board of T1
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Step 8: D2 D3
- Find D2 and D3 in the parts.
- Orient the diodes to match the grey line with the line indicated on the PCB.
- These diodes are polar, mount and solder these diodes in their appropriate places on the PCB.
D2=D3
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Step 9: C3 C4 C5
- Find C3 C4 and C5 in the provided parts.
- There are two unpolarized capacitors and one polarized capacitor in this step.
- C3 is a polarized capacitor.
- C4=C5 are not polarized ceramic capacitors so their orientation does not matter.
C4=C5
C3
+
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Step 9: C3 (polar capacitor)
“L” Positive lead“107”
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Step 10: Q1
- Find Q1 (IRF830) in the provided parts.
- This transistor must be bent over to lay flat on the board.
-Mount the transistor such that it can be bent and lay flat on the PCB.
- Now solder the transistor in place.
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Step 11: Q3
- Find Q3 (7805 Regulator) in the provided parts.
- This transistor must be bent over to lay flat on the board.
-Mount the transistor such that it can be bent and lay flat on the PCB.
- Now solder the transistor in place.
Q3
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Step 12: C10
- Find C10 in the provided parts.
- C10 is a polarized capacitor.
-Mount and solder this to the appropriate location on the PCB.
- Note the positive hole displayed on the PCB.
C10
+
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Step 12: C10 (polar capacitor)
“L” Positive lead“107”
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Step 13: D9 and Power Bridge
- Find D9 in the provided parts.
- D9 is a polarized diode.
-Mount and solder this to the appropriate location on the PCB.
- **Save a clipping of one of these leads for the power bridge.
D9
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Step 13: D9 and Power Bridge
- Bridge the left and middle holes of the power section on the PCB as shown using the lead clipping you saved.
- Solder the bridge in place. This removes the need for a bulky switch.
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Step 14: Battery Wiring
- Find the Geiger counter wiring in the provided parts (red, black and blue).
- Solder the red wire to the V+ location on the PCB.
- Solder the black wire to the dot GND location on the PCB.
- Leave the blue wire free for later installation.
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Step 15: 16 pin 4049 chip
- Find the 16 pin 4049 chip (U1) in the provided parts.
- Orient the dot toward the notch as shown in the following pictures.
-Match notch to notch on the chip and socket.
- Either method will work.
U1
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Inspection and High
Voltage (HV) Test
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Step 16: HV Test 1st Powered Check
- Find one 9V test battery and connect it to one of the two 9V connectors provided.
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Step 16: HV Test 1st Powered Check
- Connect power to the circuit using the header and two pin adapter provided.
- Be sure to match the wires of the three pin Geiger header to the correct power and ground wires on the battery wires as shown.
- *note red matches red and black matches black.
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Step 16: HV Test 1st Powered Check
- Locate the provided voltmeter and set the gauge to read the maximum DC voltage.
- Touch the red (positive) lead to the junction of C4 and D2.
- Touch the black (negative) lead to the negative terminal of the 9V battery.
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Step 16: HV Test 1st Powered Check
- The voltmeter should read between 800-550 Volts depending on component tolerances.
- If it does, remove power and prepare for the next step in a few moments.
- If not; check the orientation of the diodes on the board, continuity of soldering joints, and raise your hand.
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Step 17: D4 D5 D6
- Locate D4, D5, and D6 in the provided parts.
-Match the black line to the line on the PCB as shown.
-Mount and solder these diodes in their required locations on the PCB.
- **When bending make note of the wider spacing of the holes for mounting these diodes.**
D4
D5=D6
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Step 18: HV Test 2nd Powered Check
- Locate the provided voltmeter and set the gauge to read the maximum DC voltage.
- Find a 9V battery and apply power to the circuit.
- Touch the red (positive) lead to the junction of C4 and D2.
- Touch the black (negative) lead to the negative terminal of the 9V battery.
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Step 18: HV Test 2nd Powered Check
- The voltmeter should read 500 Volts with little deviation depending on component tolerances and battery charge.
- If it does, remove power and prepare for the next step in a few moments.
- If not check the orientation of D4-D6 and raise your hand.
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Step 19: C6 C7 C8
- Locate C6, C7, and C8 in the provided parts.
- Some kits may have C7 as a orange ceramic capacitor.
- Don’t worry both capacitors are the same value, and interchangeable.
- These capacitors are not polarized.
-Mount and solder these capacitors to the appropriate location on the PCB.
C6 C7 C8
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Step 20: C12 C13
- Locate C12 and C13 in the provided parts.
- C12 is not a polar capacitor.
- C13 is not a polar capacitor although the PCB may indicate otherwise.
-Mount and solder these capacitors to the appropriate location on the PCB.
C12C13
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Step 21: R4 R5 R13
- Locate R4, R5, and R13 in the provided parts.
-Mount and solder these resistors to the appropriate location on the PCB.
= R4 (YVY)
= R5 (BrBkBl)
= R13 (BrBkBl)
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Step 22: Q2
- Locate Q2 (small 3 pin transistor) in the provided parts.
-Mount and solder this transistor to the appropriate location on the PCB.
- Note the flat side of the transistor should match the drawing on the PCB when mounted.
Q2
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Step 23: 8 pin socket
- Locate the 8 pin socket among the provided parts.
-Mount and solder this socket to the appropriate location on the PCB.
-Make sure it is flush with the board, and tack down the corners in the same manner to ease the soldering process.
- Note the notch should match the notch drawn on the PCB.
8-pin socket with notch to top
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Step 24: R7 R8 R9 R10
- Locate R7, R8, R9, and R10 among the provided parts.
-Mount and solder these resistors to the appropriate locations on the PCB.
= R7 (YVO)
= R8 (YVBr)
= R9 (OOBr)
= R10 (BrBkGr)
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Step 25: D7-Red Led
- Locate D7 among the provided parts.
-Mount and solder this diode to the appropriate locations on the PCB.
- Note the polarity of the diode: The longer lead is positive, the flat side is negative, the flag points to positive.
- All of these visual cues can be used.
+-
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Step 26: 555 Timer
- Locate U2 (555 Timer) among the provided parts.
-Mount this 8 pin chip to the appropriate 8 pin socket on the PCB.
- Note the dot on the chip and mount as shown in the following pictures.
555 timer (U2)
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Step 27: Audio Bridge
- Find two scraps of leads to bridge two locations in the same manner used in the power bridge.
- Bridge and solder into place a wire across the two leftmost holes in the Audio section.
- Bridge and solder into place a wire across the top two holes in the Headphone section.
Audio Bridge
Headphone Bridge
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Step 28: Speaker
- Find the speaker in the provided parts.
- It is polar note the polarity on the part and the PCB.
-Mount and solder the speaker in the appropriate location on the PCB.
- Now remove the seal over the speaker.
Speaker
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Step 29: Geiger Mueller (GM) Tube
- Find the GM Tube in the provided parts.
- It is polar note the polarity on the part and the PCB.
- On the tube the thin wire is GM negative and the large wire is GM positive.
+
-
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Step 29: Why is there epoxy on the end of the tube?! - The tube is filled with an inert
gas to promote ionization in the presence of radiation.
- The tube also has a very fragile thin mica window to allow alpha particles to pass through.
- This window will blow out in low pressure environments.
- The epoxy prevents blowout, but also eliminates some alpha particles from detection.
- Don’t worry, this won’t impact the merit of the kit as the skin of the rocket will block most alpha radiation.
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Step 29: GM Tube (Precautions)
- Do not overheat the GM tube when soldering it can overheat easily.
- Avoid the glass fill knob at the rear of the tube. Shatter this, and your tube won’t work.
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Step 30: GM Tube-Positive Wire
- Find and strip ¼ inch from each end of Red wire.
- Solder one of the striped edges to the positive end of the GM tube as shown.
- Be CAREFUL! Don’t let the iron linger longer than 5 seconds before giving the tube 10-15 seconds to cool.
- On the tube the thin wire is GM negative and the large wire is GM positive.
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Step 30: GM Tube-PCB Wiring
- Orient the tube on the bottom of the board.
- Solder the free end of the red wire into GM+ coming from the bottom of the board up through the hole.
- Solder the thin wire through the GM – hole in the same manner.
- Be CAREFUL! The thin wire is frail and will snap if bent too much.
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Step 31: GM Tube-PCB Mounting
- Find the small piece of red mounting wiring.
- It is not pre-cut and must be trimmed as desired.
- Strip both ends of the red wiring and solder through two holes on the mounting array.
- ENSURE the insulation is on the wire such that it will not conduct the energy of the GM Tube.
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Step 31: GM Tube-PCB Mounting (after)
TOP
BOTTOM
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Step 32: GM Tube-PCB Lacing
- Find the thin yellow wiring in the provided parts.
-We will use this wire like shoelaces for the mounting array on the GM PCB.
- Run the yellow wire through the first two holes for each end as shown.
- The loose ends of the yellow wire should extend upward through the board.
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Step 32: GM Tube-PCB Lacing
- Begin a cross hatch method above and below the board as if you are lacing a shoe.
-When you get to the end, loop back following a similar pattern until about 6 inches of yellow wire remains.
-We will tie off the wire in the middle of the mounting array, so keep this in mind.
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Step 32: GM Tube-PCB Lacing
- Tie a double square knot when the lacing of the GM tube is complete.
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Step 33: Data wire
- Strip the remaining end of the blue data wire and solder it in place it to the topmost pin of digital out.
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Overview:
- The Geiger counter that you assembled can detect all three types of radiation: alpha, beta, and gamma.
- To test the Geiger counter, we will obtain a radioactive source from the common household smoke detector.
- The common household smoke detector uses a very small amount of Americium 241 to detect smoke particles in the air.
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Safety:
- According to the World Nuclear Association [1], Americium 241 is an alpha emitter that also emits some low energy gamma rays.
- “Even swallowing the radioactive material from a smoke detector would not lead to significant internal absorption of Am-241, since the dioxide is insoluble.” [1]
- Caution: Although the sample is rather benign, do take caution to keep it away from your face at all times.
- Caution: Also make sure that you wash your hands before eating if you handle the sample.
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Step 1: Opening the detector housing
Opening the detector housing and remove the lid.
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Step 1: Opening the detector housing
Opening the detector housing and remove the lid.
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Step 2: Visually inspect the detector
Speaker Radiation Source
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Step 3: Peel back the Black cover over the Detector
Peel Back and remove
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Step 3: Peel back the Black cover over the Detector
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Step 4: Remove PCB
Remove the PCB from the protective housing by bending the four plastic prongs to release and pulling the PCB.
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Step 4: Remove PCB
The PCB is glued to a middle prong. Pull until it releases from this prong, which may require a little additional force.
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Step 5: Remove Radiation Source
Note the two metal notches holding the radiation source to the PCB.
Bend these with a provided screwdriver as shown so the source will slide out of the PCB.
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Step 6: Clipping attachments
Clip the attachments on the radiation source with the pliers until the source is free.
Use brute force to extract the source, and don’t worry about damaging the remainder of the detector as it is not needed.
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Final Product Testing
- Attach power to the circuit again.
- The Geiger counter should randomly blink detecting usually 12-14 counts per minute depending on sources in the area and shielding.
- Acquire the provided alpha particle source (taken from a smoke detector).
- Notice a large jump in the frequency of counts.
- Each count represents the detection of a radioactive particle by the Geiger counter.
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Coronal Discharge: An Overview
- Coronal discharge occurs in low pressure environments with high voltages present.
- The air around a high potential (high voltage) will become a conductor and emit a bluish glow (plasma).
- This plasma will cause adverse effects for the component as well as neighboring parts.
- The plasma is a bluish-purple and is visible under normal lighting. (see images)
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Coronal Discharge: An Example
RockOn! Geiger counter seen through a vacuum chamber.
Area of interest near back of D4-D6
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Coronal Discharge: An Example
Geiger counter seen through a vacuum chamber
Glow of coronal discharge
Close-up
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Coronal Discharge: The solution
- Coronal discharge is detrimental to parts.
- Dangerous to other payloads on the rocket.
- To mitigate these risks, we will add conformal coating to the board to prevent coronal discharge.
- **Note: We will be in a pressurized environment on this flight so this is not necessary, but is a good practice especially with space applications.
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Step 1: Board Prep
- Take the board to a well ventilated area (we will be outside).
- Put on safety glasses and rubber gloves.
- Place the board face up on the prepared protected surface.
- Shake the bottle lightly and open it.
-MAKE SURE there is no power on the board.
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Step 2: Begin Coating
- Dip the brush in and begin application coating the entire top side of the board with an even layer.
- Re-dipping the brush every 2-3 strokes is recommended.
- The board should look glossy under lighting where coating has been applied.
- If any safety concerns occur consult the MSDS provided.
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Step 3: Detail Coating (chips in sockets)
- Coat the chips as well as long as they are secured in their sockets.
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Step 3: Detail Coating (underneath components)
Apply underneath closely oriented parts like diodes, capacitors, and resistors in this manner.
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Step 4: Detail Coating (between components)
Apply between closely oriented parts
Use smooth strokes (about 3 per dip)
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Step 5: Backside Coating
- Flip the board over using minimal contact with the currently curing coating.
- Coat the entire backside as desired using the same 3 stroke per dip rule.
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Step 5: Backside Coating
Apply across the whole board, make sure the whole PCB is coated thoroughly.
Note glossy look of coated board.
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Step 6: Touch-ups
- Visually inspect the board to ensure it is coated thoroughly.
-Make any touch-ups as necessary, ensuring there are no bubbles underneath parts.
- You may add additional coating to the HV section if you desire, but one coat is enough to do the job.
HV Section
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Step 7: Drying and Clamping
- Flip the board over and attach to helping hands where shown.
- This area is not HV and won’t affect the cure if clamped here
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RockOn! 2008
Step 7: Drying and Clamping
- Allow the board to cure in a controlled environment for 24 hrs to achieve a full cure.
- Tack free cure is about 10 min. The coating wont stick to your hand as readily after this stage.
- Handling cure is about 4-6 hrs depending on the humidity.
- Cure time can be decreased by using a convection heater at low heat (100 °F) and low humidity.
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