rockon! 2009 1 geiger counter rockon! 2009. 2 what are we building ?
TRANSCRIPT
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RockOn! 2009
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 5000 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
- However, 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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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 in a year (Alpha exposure). [2]
20th Century Fox ©
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Radiation: Conversions- Generally, 75 counts per minute
(CPM) is equivalent to 1 mRem/hr.
- Therefore, 4500 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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Organization:
The boards may seem like an array of confusing electronics, but one can easily break the board into smaller subsystems of related components.
This build is organized by different sub systems integral to the board.
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Integral Systems:
- Geiger Tube
- MC14049CP Hex Inverter
- LN555C 555 Timer
- Mini Step-up Transformer
- GS 7805 5V Voltage Regulator
- IRF830 Power MOSFET
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Board Safety:
Caution:
Many of the components used in this workshop are sensitive to electrostatic discharge (ESD). Please ensure that you are wearing your protective wrist strap at all times. There will be a warning slide when components are ESD and heat sensitive.
Clipping leads can sometimes cause them to separate in a rapid manner that could cause injury. Please take caution when clipping leads. Wear your safety glasses at ALL TIMES!
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Reading a Resistor:
The resistors in this workshop have already been organized by value.
In the event that your resistors get mixed, please refer to the chart at the left to classify your resistors, or use your multimeter
If you are unsure, don’t hesitate to raise your hand and ask for assistance.
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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 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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Pre-Bending:
Pre-Bending 101:
- Pre-bending is a technique that allows components to be easily inserted into a PCB.
- Pre-bending also allows components to lay more flush with the board.
- Bending components to the correct bend radius takes practice, but mastering the technique will reap rewarding benefits!
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Pre-Bending:
Pre-Bending 101:
- Start with the bending and prodding tool in the position shown in the top picture.
- Choose a location along the length of the tool that will yield the appropriate bend radius.
- Use your thumb to bend the lead such that the component and lead are orthogonal.
90°
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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 = 4.3 KΩ = (YOR)
-R2 = 15 KΩ = (BrGrO)
-R3 = 5.6 KΩ = (GrBlR)
-R4 = 470 KΩ = (YVY)
-R5 = 10 MΩ = (BrBkBl)
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Verify Kit Contents: Resistors
-R7 = 150 KΩ = (BrGrY)
-R8 = 470 Ω = (YVBr)
-R9 = 330 Ω = (OOBr)
-R14 = 220 KΩ = (RRY)
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Verify Kit Contents: Capacitors
- Some capacitors have polarity, while others do not. Majority of capacitors used are not polarized.
- *Note C4=C5 and C3=C10.
- Some capacitors in use can carry charge long after power has been disconnected from the circuit (15-30 seconds).
- Use caution especially around the high voltage (HV) section of the circuit to avoid a discharge shock.
- The capacitors near the HV section have the capability of holding a 1 KV burst and will SHOCK YOU if touched with power connected or shortly after power is disconnected!
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Verify Kit Contents: Capacitors
- C1 = Green Ceramic 0.0047 μF @ 20V
- C2 = Green Ceramic 0.01 μF @ 100V
- C3(±) = Black Electrolytic 220 μF @ 10V
- C4 = Orange Ceramic 0.1 μF @ 1KV
- C5 = Orange Ceramic 0.1 μF @ 1KV
C1 C2 C4 C5C3
- +
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Verify Kit Contents: Capacitors
- C7 = Green Ceramic or Orange Ceramic 0.047 μF @100V
- C8 = Green Ceramic 0.01 μF @ 100V
- C10(±) = Black Electrolytic 220 μF @ 10V
- C12 = Orange Ceramic 120 pF @100V
C7 C8 C10
- +
C12
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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 @ 1KV =
- D3 = 1N4007 @ 1KV =
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Verify Kit Contents: Diodes
- D4 = 1N5271 @ 100V =
- D5 = 1N5281 @ 200V =
- D6 = 1N5281 @ 200V =
- D9= 1N4007 @ 1KV =
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Verify Kit Contents: Diodes
- D10 = 1N75 @ 5.1 V =
- D11= 1N914=
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Verify Kit Contents: Miscellaneous
Q4 (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:
- The ESD wrist strap must be tight on your wrist at all times.
- DO NOT linger on parts with the soldering iron.
- As a general rule use a 3-5 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 as shown in the solder filet example with little excess wire above the top of the filet.
- Bend resistors and diodes using your plastic tool as shown.
Example of a good solder filet
workmanship.nasa.gov
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Schematic Overview – Part Highlighting:
- Blue highlights indicate parts will be added to the board in the current step.
- Green highlights indicate components already on the board but relevant to the current step.
Part added previously
Part to be added
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Schematic Overview – Coordinates (A1):
- All schematic close-ups include coordinates so they can be easily located in your schematic printout.
- The coordinates correspond to the letters across the side of the schematic and the numbers across the top.
Coordinates given here
Numbers across top
Letters along side
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Current Sub System:
Geiger Counter Sub Systems:
Oscillator
High Voltage (Unregulated)
DC Voltage Regulation
High Voltage Regulation
Output Pulse
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Oscillator Circuit – Coordinates (A1):
Acts as an invertin
g buffer fo
r oscilla
tor output
Current li
miting re
sistor
- This circuitry creates an oscillatory square wave to switch the primary windings of the mini step-up transformer on and off.
- The speed of this oscillation is determined from the RC circuit design.
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Oscillator Circuit – Coordinates (B1):
Rectifying Diode
Pull Down Resistor
- Here the capacitor C1 acts like a switch. Because of the setup of the inverting buffer pins, the circuit will form a rectified oscillating square wave at U1D.
- This circuit oscillates at a frequency according to the time constant from the RC circuit. (~50 KHz)
Timing Capacitor
Timing Resistor
Inverting Buffe
r
Inverting Buffe
r
Allows Oscillating High Freq Voltage to pass
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Special Resistors – Coordinates (B2 and B4):
Current li
miting re
sistor
- This includes the odd footprint soldering at the beginning of the board construction.
Current li
miting re
sistor
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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: R7 (150KΩ BrGrY)
-Mount and solder R7 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 2: R14 (220KΩ RRY)
-Mount and solder R14 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 (0.0047 μF @ 10V)
- C2 (0.01 μF @ 100V)
C1 C2
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Step 5: D1 (1N914)
-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 (after close up)
- Notice the black line on the diode matches the PCB silkscreen.
- It is very important to mount all diodes in the proper orientation!
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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.
- Bend the leads of the resistor around the provided plastic tool.
- This prevents stress fractures from sharp angle bending.
= R2 (BrGrO)
= R1 (YOR)
= R3 (GrBlR)
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Oscillator Circuit – Coordinates (A1):
Acts as an invertin
g buffer fo
r oscilla
tor output
Current li
miting re
sistor
- This circuitry creates an oscillatory square wave to switch the primary windings of the mini step-up transformer on and off.
- The speed of this oscillation is determined from the RC circuit design.
Highlight your schematic
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Oscillator Circuit – Coordinates (B1):
Rectifying Diode
Pull Down Resistor
- Here the capacitor C1 acts like a switch. Because of the setup of the inverting buffer pins, the circuit will form a rectified oscillating square wave at U1D.
- This circuit oscillates at a frequency according to the time constant from the RC circuit. (~50 KHz)
Timing Capacitor
Timing Resistor
Inverting Buffe
r
Inverting Buffe
r
Allows Oscillating High Freq Voltage to pass
Highlight your schematic
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Special Resistors – Coordinates (B2 and B4):
Current li
miting re
sistor
- This includes the odd footprint soldering at the beginning of the board construction.
Current li
miting re
sistor
Highlight your schematic
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Current Sub System:
Geiger Counter Sub Systems:
Oscillator
High Voltage (Unregulated)
DC Voltage Regulation
High Voltage Regulation
Output Pulse
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High Voltage (Unregulated) – Coordinates (A2):
Power MOSFET
- This circuitry uses the oscillator circuit output through a mini step-up transformer to create the high voltage (HV) needed for the operation of the Geiger counter.
- The power MOSFET (Q1) stabilizes the voltage switching on the primary windings of T1 better than the output of the oscillator circuit can provide.
- D2 and D3 rectify the HVAC output to HV DC with some voltage ripple.
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HV
AC
OU
TPU
T
- Rectified HV is received after the HV AC passes through the two rectifying diodes.
- The circuit is now nearing the desired HV DC supply for the Geiger Tube! But why is there still voltage ripple present?!
Voltage R
ipple N
OT DC Y
ET!!!
High Voltage (Unregulated) – Coordinates (A2, A3):
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- The circuit is now nearing the desired HV DC supply for the Geiger Tube!
- Using a HV capacitor on each output line for the proper voltage, the voltage ripple is smoothed.
- Each discharges with a falling peak and recharges with a rising peak.
Voltage R
ipple C
apacitors
Rectifyin
g Dio
de
Rectifying Diode
High Voltage (Unregulated) – Coordinates (A2, A3):
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- The circuit is now at the desired HV DC supply for the Geiger Tube!
- This technique is used frequently in power electronics, and most electronics can handle a small variation in voltage!
High Voltage (Unregulated) – Coordinates (A2, A3):
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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 polarized, mount and solder these diodes in their appropriate places on the PCB.
D2=D3
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Step 9: C4 and C5
- C4=C5 are not polarized ceramic capacitors so their orientation does not matter.
C4=C5
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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 10: Q1 (bending)
- Pre-bend Q1 in the depicted manner using the plastic tool.
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High Voltage (Unregulated) – Coordinates (A2):
Power MOSFET
- This circuitry uses the oscillator circuit output through a mini step-up transformer to create the high voltage (HV) needed for the operation of the Geiger counter.
- The power MOSFET (Q1) stabilizes the voltage switching on the primary windings of T1 better than the output of the oscillator circuit can provide.
- D2 and D3 rectify the HVAC output to HV DC with some voltage ripple.
Highlight your schematic
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HV
AC
OU
TPU
T
- Rectified HV is received after the HV AC passes through the two rectifying diodes.
- The circuit is now nearing the desired HV DC supply for the Geiger Tube! But why is there still voltage ripple present?!
Voltage R
ipple N
OT DC Y
ET!!!
High Voltage (Unregulated) – Coordinates (A2, A3):
Highlight your schematic
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- The circuit is now nearing the desired HV DC supply for the Geiger Tube!
- Using a HV capacitor on each output line for the proper voltage, the voltage ripple is smoothed.
- Each discharges with a falling peak and recharges with a rising peak.
Voltage R
ipple C
apacitors
Rectifyin
g Dio
de
Rectifying Diode
High Voltage (Unregulated) – Coordinates (A2, A3):
Highlight your schematic
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- The circuit is now at the desired HV DC supply for the Geiger Tube!
- This technique is used frequently in power electronics, and most electronics can handle a small variation in voltage!
High Voltage (Unregulated) – Coordinates (A2, A3):
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Current Sub System:
Geiger Counter Sub Systems:
Oscillator
High Voltage (Unregulated)
DC Voltage Regulation
High Voltage Regulation
Output Pulse
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DC Voltage Regulation (5V) – Coordinates (C1)
- Using Q3 as a 5V voltage regulator VCC is maintained. C3 and C10 serve as circuit protection in addition to the voltage rectifying provided by D9.
Power Filt
er Capacito
r
Rectifying Diode
Power Filt
er Capacito
r
5V VREG
5V VCC OUTPUT
- The output VCC powers the ICS and other components on the board
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Step 11: C3 and C10
- Find C3 and C10 in the provided parts.
- C3 and C10 are polarized capacitors.
C3 C10
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Step 11: C3 and C10 (polarized capacitors)
White stripe marks negative lead!
Also the negative lead is shorter!
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Step 11: C3 and C10 (close up before)
Note the proper orientation of the polarized capacitor by the + printed on the silkscreen.
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Step 12: Q3
- Find Q3 (7805 Voltage Regulator) in the provided parts.
- This transistor must be bent over to lay flat on the board.
- Leave enough space to allow a digital out wire to pass underneath this part in a later step!
-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: Q3 (bending)
- Pre-bend Q3 in the depicted manner using the plastic tool.
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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 13: D9 and Power Bridge (before close up)
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DC Voltage Regulation (5V) – Coordinates (C1)
- Using Q3 as a 5V voltage regulator VCC is maintained. C3 and C10 serve as circuit protection in addition to the voltage rectifying provided by D9.
Power Filt
er Capacito
r
Rectifying Diode
Power Filt
er Capacito
r
5V VREG
5V VCC OUTPUT
- The output VCC powers the ICs and other components on the board
Highlight your schematic
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Step 14: Battery Wiring Schematic
Black Battery Wire Connects Battery Negative Terminal to Ground
Red Battery Wire Connects +9V to the Power Bridge
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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.
BlackRed
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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.
- You may have to bend the leads in slightly. Do so carefully.
U1
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Step 14: Battery Wiring Schematic
Black Battery Wire Connects Battery Negative Terminal to Ground
Red Battery Wire Connects +9V to the Power Bridge
Highlight your schematic
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Step 15: 16 pin 4049 chip Full Schematic
Highlight your schematic
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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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Inspection and High
Voltage (HV) Test
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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 to 1,000 V DC (depicted next slide).
- 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 550-850 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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Current Sub System:
Geiger Counter Sub Systems:
Oscillator
High Voltage (Unregulated)
DC Voltage Regulation
High Voltage Regulation
Output Pulse
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High Voltage Regulation – Coordinates (A3):
- The circuit is regulated to the needed 500V DC for the Geiger tube by 3 Zener Diodes.
Regulating Z
ener Dio
des
Voltage S
mooth
ing C
apacitors
Rectifyin
g Dio
de
Rectifying Diode
- Zener Diodes provide cheap voltage regulation.
- Conduct, if and only if the voltage across them is > than their rated voltage.
- Dissipate enough power to keep voltage at the appropriate value.
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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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High Voltage Regulation – Coordinates (A3):
- The circuit is regulated to the needed 500V DC for the Geiger tube by 3 Zener Diodes.
Regulating Z
ener Dio
des
Voltage S
mooth
ing C
apacitors
Rectifyin
g Dio
de
Rectifying Diode
- Zener Diodes are a cheap voltage regulation.
- Conduct to a certain voltage.
- Dissipate extra voltage as current.
Highlight your schematic
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High Voltage (HV)
Regulation Test
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Step 18: HV Test 2nd Powered Check
- Locate the provided voltmeter and set to the 1,000 V DC setting.
- 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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Current Sub System:
Geiger Counter Sub Systems:
Oscillator
High Voltage (Unregulated)
DC Voltage Regulation
High Voltage Regulation
Output Pulse
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Output Pulse Circuit – Coordinates (B2-C4):
Regulating Zener Diode 5.1V
555 Timer M
ono
Inverting Buffer Pin
Current Sourcing Buffer
Indicator LED
VCC 5V Supply
Timer Setup Capacitors
Cur. Limit R
Current Limiting Resistors
General Purpose Amplifier NPN Transistor
Rectifier Diode
VCC Supply
Current limiting resistorCurrent Limiting Resistor
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Output Pulse Circuit – Coordinates (A3 & A4):
Current limiting resistor
Geiger Tube
Current spike filter
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Output Pulse Circuit
- Output is sent through many different indicators for each radioactive particle detected.
- Audio is sent through a multi stage inverter to give extra current push through the speaker amplifier transistor Q4. This will turn Q4 on and result in an audible click.
- The original pulse is fed into a 555 timer configured in monostable mode.
- This mode allows for a lengthening of a short pulse width to a wider, more detectible pulse for the speaker setup and digital output.
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Step 19: 555 Timer Socket
- Locate the 8-pin socket in the parts
- Note the Notch on the socket must match the notch printed on the PCB silkscreen.
- Solder opposite diagonal corners of the socket first to allow ease of soldering the remainder of the pins.
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Step 20: R4 and R5
- Locate R4 and R5 among the provided parts.
- R4 = 470KΩ (YVBr)
- R5 = 10MΩ (BrBkBl)
-Mount and solder these capacitors to the appropriate location on the PCB.
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Step 21: C12
- Locate C12 in the provided parts.
- C12 is an orange ceramic capacitor
-Mount and solder these resistors to the appropriate location on the PCB.
C12
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Step 22: R8
- Locate R8 470Ω (YVBr)
-Mount and solder this resistor to the appropriate location on the PCB.
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Step 23: C7 and C8
- Locate the remaining green ceramic capacitors.
- C7 = Green Ceramic or Orange Ceramic 0.047 μF @100V
- C8 = Green Ceramic 0.01 μF @ 100V
-Mount and solder these components to the appropriate location on the PCB.
C7 C8
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Step 24: 5.1V Zener Diode
- Locate the D10 1N75 diode.
- This diode serves as a pulse limiter for the Geiger counter.
-Mount and solder this component to the appropriate location on the PCB.
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Step 25: D11 1N914 Zener Diode
- Locate the D11 1N914 diode.
-Mount and solder this component to the appropriate location on the PCB.
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Step 25: D11 1N914 Zener Diode (after close up)
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Step 26: R9
- Locate R9 among the provided parts.
- R9 330Ω (OOBr)
-Mount and solder this resistor to the appropriate location on the PCB.
+
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Step 27: Q4: 2N3904
- Locate Q4 among the provided parts.
- Q4 is an NPN transistor with one side rounded while the other is square.
- This transistor serves as a general purpose amplifier to drive the speaker.
-Mount and solder this resistor to the appropriate location on the PCB.
+
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Step 28: 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 29: Speaker
- Find the speaker in the provided parts.
- It is polarized 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 30: 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 31: 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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Output Pulse Circuit – Coordinates (B2-C4):
Regulating Zener Diode 5.1V
555 Timer M
ono
Inverting Buffer Pin
Current Sourcing Buffer
Indicator LED
VCC 5V Supply
Timer Setup Capacitors
Cur. Limit R
Current Limiting Resistors
General Purpose Amplifier NPN Transistor
Rectifier Diode
VCC Supply
Current limiting resistorCurrent Limiting Resistor
Highlight your schematic
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Output Pulse Circuit – Coordinates (A3 & A4):
Current limiting resistor
Geiger Tube
Current spike filter
Highlight your schematic
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Step 32: Geiger Mueller (GM) Tube
- Find the GM Tube in the provided parts.
- It is polarized. 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 32: What’s that 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 32: 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 33: 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 33: 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 34: 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 34: GM Tube-PCB Lacing
- Begin a cross hatch method above and below the board as if you are lacing a tennis 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 34: GM Tube-PCB Lacing
- Tie a double square knot when the lacing of the GM tube is complete.
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Step 35: 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. Use the side cutters as a fulcrum.
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Step 2: Visually inspect the detector
PCB Radiation Source
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Step 3: Separate the PCB from the detector housing
Clip wires Bend inward and remove PCB from housing.
Close up
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Step 3: Separate the PCB from the Detector Housing
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Step 4: Cut PCB
Cut the PCB removing the radiation source portion. Remove and
discard
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Step 5: Remove Radiation Source
The PCB is glued to a middle prongs.
Also release the source from these plastic holders.
Cut the PCB as necessary! Be an animal!!!
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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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Step 6: Clipping attachments
Remove the remnants of the PCB from the radiation source.
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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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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.