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UVM CricketSat Manual. What’s a CricketSat? Description Wireless temperature sensor Usually flown on a balloon Simple circuit –Easy to build –Easy to.

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Presentation on theme: "UVM CricketSat Manual. What’s a CricketSat? Description Wireless temperature sensor Usually flown on a balloon Simple circuit –Easy to build –Easy to."— Presentation transcript:

1 UVM CricketSat Manual

2 What’s a CricketSat? Description Wireless temperature sensor Usually flown on a balloon Simple circuit –Easy to build –Easy to modify Low cost (~$10) Operation Produces tone or pulses related to changing temperature Transmits the tone wirelessly over a radio frequency (RF) link Received tone frequency measured with an instrument or computer software Calibration graph used to convert tone frequency back to temperature

3 The CricketSat Program at UVM Freshman introduction to engineering Sensor and system development HELiX / EPSCoR High School Outreach program –2003: Waldorf High School, VT –2004: Milton, VT and JDOB Boston, MA –2005: Milton and Brattleboro, VT University collaboration –Medgar Evers College, City University of New York –University of Alaska Awards (2005) –Massachusetts State Science Fair, 1st Place (JDOB School) –HELiX Symposium Poster Presentation, 1st Place (Shared, Milton and JDOB schools, presenting separate posters)

4 CricketSat Background CricketSat Origins Developed at Stanford University –Space Systems Development Laboratory Part of the NASA student satellite program –Crawl, Walk, Run, Fly –Teach fundamentals of space hardware development –Space Grant Fellowship Program Funded support Vermont Space Grant Consortium (VSGC) Student Satellite Programs CricketSat –Lowest cost - disposable –Live telemetry BalloonSat –Larger balloon –Expensive instruments –GPS tracking system CanSat –Dropped by parachute from plane or rocket –Many instruments –Live telemetry –Test bed for CubeSat CubeSat –Earth-orbit satellite

5 Receiving Station Receiver extracts oscillator frequency from radio signal Oscillator frequency measured by instruments or software Calibration charts used to determine temperature CricketSat Sensor Circuit Oscillator frequency determined by temperature Oscillator output signal modulates RF carrier frequency

6 CricketSat Schematic Diagram Power SupplyTransmitterTemperature Sensitive Oscillator

7 CricketSat Circuit Board Power SupplyTransmitterOscillator Custom Circuit Prototype Area

8 Sensing the Temperature Thermistor Device Resistance changes with temperature as shown in the graph Requires additional circuitry to produce an measurable electrical response Use with an oscillator circuit provides a simple and low cost solution Thermistor

9 Temperature Sensitive Oscillator Produces an oscillation that changes with temperature Circuit based on the popular 555-Timer IC Oscillator frequency determined by two resistors and a capacitor Resistive and capacitive type sensors may be substituted In our case, the upper resistor is replaced with the thermistor Changes in temperature affect the oscillator frequency as shown in the chart Thermistor

10 Frequency vs Temperature Oscillator Frequency –Increases with warmer temperatures –Decreases with colder temperatures Finding the Temperature –A calibration graph, similar to the one shown right, allows the temperature to be determined

11 The Wireless Connection Oscillator output signal enables radio transmitter during charging interval of the timing cycle Oscillator frequency is mixed with radio (RF) carrier frequency to provide the wireless connection

12 Detail Operation – Power Supply

13 Power Supply Operation 9 Volts unregulated supply –Max power to RF transmitter for maximum range. 5.0 Volts regulated supply –5-Volt regulator (U2), Volts input, 5.0 Volts output –Provides constant output as battery discharges (dies). –Required by oscillator circuit for consistent operation. –May be required for student-added circuity. Short-circuit protection –Prevents damage with reverse battery connection. –5-Volt regulator has built-in protection. –Diode D2 added to protect RF transmitter module.

14 Detail Operation - Oscillator

15 Oscillator Demo Capacitor Charge & Discharge Waveform LED Digital Output Signal 555 Timer IC Time Not Used R1 R2 C1 Thermistor Vcc Voltage on capacitor C1 Simulation courtesy of Williamson Labs:

16 Oscillator Circuit Operation Based on the popular 555 timer IC design. Timing components –Capacitor C1 is the electrical charge storage vessel. –Resistors R1 and R2 behave as electrical conduits for the charge to flow into and out of the C1 capacitor. –R1 is a thermistor whose resistance (conductivity) varies with temperature. –The timer, U1, monitors the operation and the discharging of the C1. –Timing is completely controlled by R1, R2 and C1 represented by the formula:

17 Oscillator Circuit Operation Oscillator operation –Voltage level on C1 oscillates between 1/3 and 2/3 of the supply voltage (5 Volts). –Charging interval Voltage increases on the capacitor with charge entering from the series combination of R1 and R2. The timer IC monitors the voltage on the capacitor waiting for it to rise to 3.33 Volts. Once it does, it begins to discharge it through R2 alone. –Discharging interval The timer now monitors the voltage on the capacitor until it drops to 1.67 volts. At this point, it ceases the discharge and allows the charging cycle to repeat.

18 Oscillator Circuit Operation Timer Output –The timer also provides a digital output relating to capacitor charging and discharging. –The output pin is high during the charging interval and low during the discharge interval. –The output drives an LED for visual cue as well as the RF transmitter. Temperature Relationship –The resistance of R1 increases with colder temperatures causing the charging interval to increase, and thereby reducing the oscillator frequency. –The opposite effect occurs for warmer temperatures.

19 Detail Operation – Transmitter Power SupplyTransmitterTemperature Sensitive Oscillator

20 RF Transmitter Operation Purpose –Modulate (mix) 434 MHz “carrier” signal and 555-Timer output signal –Amplify and transmit signal through antenna sized for 434 MHz Common Types of Modulation –FM: Frequency Modulation –PM: Phase Modulation –AM: Amplitude Modulation Analog –Ex: Audio Digital (CricketSat) –Amplitude Shift Keying (ASK) –Also known as…. –On-Off Keying (OOK) AM and FM Waveforms: Washington State University,

21 Assembly Equipment List Assembly and Repair –Soldering iron and solder. –Wet sponge or paper towel to clean the soldering tip. –Diagonal cutters for snipping excess wires and leads. –Small portable vise to hold board while working. –Solder wick or a solder sucker for removing excess solder. Testing –Digital multi-meter –Oscilloscope (optional) –UHF radio receiver

22 Assembly Preparation Safety –Use safety glasses while assembling the CricketSat. Hot solder and flying leads can injure your eyes. –Most surfaces of the soldering iron are very hot, will burn you and leave a blister. Hold the soldering iron by the handle. Follow the directions –There are plenty of opportunities to mess up this project by rushing the assembly or winging it on your own. –Components that are soldered in place incorrectly are nearly impossible for an untrained person to reinstall correctly. Component orientation –Many components are polarized or have pin-outs requiring proper orientation in the circuit board. –Pay close attention to instructions concerning the proper placement of those components –The components outlined in Blue on the following page are not polarized, and may be installed in either direction. Organization –Make a hard copy print-out of the following page to assist your CricketSat assembly. –Placing the actual components on top of the corresponding images will help identify components and orientation markings.

23 C1C3C2 C4C5C6 U2 R1 D1 DIP Socket Notch U1: 555 Timer IC Dimple Pin 1 Flat Side Up U3: RF Transmitter 5-Volt Regulator 10K Ohm Thermistor Printed Circuit Board (PCB) 47 micro-Farad Electrolytic Capacitors Longer Lead Light Emitting Diode (LED) 0.1 micro-Farad Capacitors + - Black BandD2 - Diode + - B1: 9-Volt Battery Pins: Antenna Wires Battery Snap Connector + - Red Lead is Positive R4: 100 Ohm R2: 3300 Ohm R3: 680 Ohm Brown-Black-Brown-Gold Orange-Orange-Red-Gold Blue-Gray-Brown-Gold Negative White Band On/Off Switch SW1 Velcro Non-Polarized Components

24 Printed Circuit Board Composition –Circuit board composed of metal layers (conductors) on epoxy (insulator) board. –Metal traces provide the wiring connections between electrical components. –Via holes connect the two metal layers –Green insulating layer covers metal, except at pads and holes. Front side of board –Install components on this side of board. –White silkscreen Component placement outlines. Reference designators to associate components to schematic diagram. Back side of board –Most of the soldering is done on this side of the circuit board. Purpose –To provide mechanical support and electrical connectivity for components.

25 Assembly Techniques Inserting Devices –Bend leads at a right angle on diodes and resistors to allow insertion into board. –While pressing component to board, bend leads outward at 45 degree angle. –This will hold components in place while soldering. Soldering –Soldering iron must touch component lead and metal pad on circuit board. –Apply solder to intersection of all three. –Once solder melts, feed liberally for about one second. –Remove the solder first, then the iron last. –Do not dab or paint with the soldering iron. –The soldering iron should stay fixed in position while feeding the solder quickly. –The finished solder connection should look like a shiny Hershey’s Kiss ™. Snipping leads –Use safety glasses to protect your eyes. –Hold lead while cutting or point downward. Bend lead close to board 45 degree angle is best Snip just above solder joint

26 Power Supply Circuit Assembly

27 Power Supply Assembly (1of 3) Gather these components (parts). Insert socket at location U1, notch end up. All eight pins must pass through the holes. Solder the socket into place. Tape socket flat to board to prepare for soldering. Notch up Thread battery clip wires through center holes as shown. Red lead closer to center of board. Poke bare ends of wires up through B+ and B- holes. Bend bare leads outward to prepare for soldering. D2 Printed Circuit Board (PCB) 9-Volt battery clip U2 DIP Socket C2 C3 Switch Step 1 Step 2 Step 3 Step 5 Step 4 Step 6

28 Power Supply Assembly (2 of 3) Pull center wires up until small loops remain as shown. Make sure that all of the bare wire extends up through the holes. Solder the bare leads on the topside of the board. Clip wires close above solder joints. Place switch onto the circuit board as shown. Pull remaining wire through board. Only insulated wire should pass through center holes. Tape the switch flat to board to prepare for soldering. Solder all eight switch pins into place. Step 7 Step 8 Step 9 Step 10 Step 11 Step 12

29 Power Supply Assembly (3 of 3) Insert U2 as shown. Push into board deep enough so that wire leads are below top of switch. Solder into place and clip the leads close the solder joint. Push capacitors tight to board and bend leads. Solder in place and clip leads above solder joint. Install two blue capacitors, C2 and C3. C2 and C3 are Polarized. White stripes face the outside edge of board. Bend the leads on D2 diode and insert into board as shown. Diode is polarized. See note to the left. Bend, solder and clip leads close to board. Leads Top of switch Flat side faces this way. White stripes. Black band lines up with white band on the board. D2 U2 Step 13 Step 15 Step 17 Step 20 Step 19 Step 18

30 Power Supply Testing (1of 2) 1)Slide the CricketSat power switch to the ON position. 2)Set the multimeter to the Ohms setting. 3)Touch the meter leads to the terminals of the battery clip as shown. 4)Wait a few seconds for reading to stabilize. 5)Meter should display O.L or O.F for overflow. 6)Reverse the leads and repeat the test 7)If meter indicates a near-zero reading, check for solder shorts or incorrectly installed components. 8)Do not connect the battery to the CricketSat until the short circuit has been resolved. Short Circuit Test 1)Set the meter to the VDC setting (Volts DC). 2)touch the red meter lead to the positive (+) battery terminal and the black lead to the negative (-) terminal. 3)A fully charged 9-Volt battery should read between 9 and 10 volts. 4)Reversing the leads should indicate a negative voltage of the same value. Why? 9-Volt Battery Test

31 Power Supply Testing (2 of 2) 1)Connect the battery to the CricketSat. Make sure the switch is in the ON position. 2)Set the multimeter to the VDC setting. 3)Touch the meter leads to the GND and V+ test points on the CricketSat board as shown to the left. 4)The meter should indicate nearly 9 volts for a fully charged battery. 5)If the voltage is absent, check to make sure that nearby diode D2 is installed with the black band oriented to the left.. 9-Volt (V+) Test 1)Now touch the red meter lead to the 5V test point directly below the V+ test point. 2)The meter should display around 5 Volts. This voltage is derived from U2, a 5-Volt regulator. 3)It has an accuracy of 4.75 to 5.25 volts. Everything is fine if your measurement is in this range. 4)If the voltage is out of this range, check to make sure that U2 is oriented with the flat face towards the left. 5)Also, check that the negative end (white stripes) of the capacitors C2 and C3 face the top of the board. 5-Volt Regulator Test Test Points

32 Oscillator Circuit Assembly

33 Before Proceeding 1.Turn off power to the CricketSat 2.Disconnect the battery 3.Wear safety glasses

34 Oscillator Assembly (1of 2) Gather these parts. Install the three resistors (R2, R3, and R4). Bend, solder and clip the leads. Install the LED at location D1. The device is Polarized. The longer lead is positive. Install the yellow capacitors, C4 and C5. Bend, solder and clip the leads. Longer lead (+) Resistors are not polarized. Orientation does not matter. These capacitors are not polarized. Orientation does not matter. U1 C4 C5 R1 D1 R2 R3 R4 C1 Step 1 Step 3 Step 4 Step 5 Bend the resistor leads at right angles to the body. Step 2

35 Oscillator Assembly (2 of 2) Install the thermistor R1 as shown. Solder and clip the leads. Press the timer IC, U1, into the socket. Pin 1 up towards notch in socket. Pin 1 Dimple U1 Notch Dimple Install capacitor C1. Capacitor is polarized. Orient C1 with white stripe as shown. R1 C1 White stripe Step 6 Step 7 Step 8

36 Oscillator Testing (1 of 3) 1)Connect the 9-Volt battery. 2)Slide the CricketSat power switch to the ON position. 3)Observe the red or green LED. 4)It should be flashing on and off about once or twice per second. Flashing LED 1)This measurement can only be made by a multimeter that can measure frequency. 2)Set the meter to the frequency measurement setting, Hertz (Hz). 3)Touch the red meter lead to the OUT test point. 4)Touch the black meter lead to the GND test point. 5)The meter will indicate the frequency in Hertz. 6)One Hertz = 1 cycle per second or in our case, flash per second. Frequency Measurement

37 Oscillator Testing (2 of 3) 1)This procedure allows the signal on the timing capacitor to be viewed on an oscilloscope. 2)Turn ON the CricketSat circuit board. 3)Connect the oscilloscope ground lead to one of the four corner holes in the CricketSat board. These are connected to the ground (GND) wiring plane. 4)Touch the oscilloscope probe to the VC1 test point. 5)Adjust the gain of the oscilloscope to observe a rising and falling voltage signal. 6)The LED should be OFF while the voltage is rising, and ON while it is falling.. 7)Animation to the left demonstrates analog signal waveform. Timing Capacitor Waveform Oscilloscope test probe

38 Oscillator Testing (3 of 3) 1)This procedure allows the signal on the timing capacitor to be viewed on an oscilloscope. 2)Turn ON the CricketSat circuit board. 3)Connect the oscilloscope ground lead to one of the four corner holes in the CricketSat board. These are connected to the ground (GND) wiring plane. 4)Touch the oscilloscope probe to the OUT test point. 5)Adjust the gain of the oscilloscope to observe a rising and falling voltage signal. 6)The LED should be OFF while the voltage is rising, and ON while it is falling.. 7)Animation to the left demonstrates digital output waveform. Digital Output Waveform Oscilloscope test probe

39 Transmitter Circuit Assembly

40 Before Proceeding 1.Turn off power to the CricketSat 2.Disconnect the battery 3.Wear safety glasses

41 Transmitter Assembly (1) C6 U3 Gather these remaining parts. Step 1 Bend the bare ends of the antenna wires at a right angle. Step 2 Antenna Wires Insert bare wire ends from the back side of board. Use masking tape to hold in place. Step 3 Solder and trim exposed wires. Step 4 Use outer holes. Route free ends of antenna wires up through the center holes. Step 5 Pull remaining wire tightly through board. (See following photos for final antenna detail.) Step 6

42 Transmitter Assembly (2) Install capacitor C6. Bend, solder and clip the leads. Step 7 Install the RF transmitter module U3, facing the metal can towards the antenna as shown. Step 8 Bend, solder and clip the transmitter’s leads. Step 9

43 Final Inspection Black band All component leads clipped shortInsulation through holes. White bands up Flat face Wire clipped close to board Metal can facing outward Dimple on IC

44 Final Assembly 1)Turn off power switch 2)Connect snap connector to battery terminals 3)Affix battery to bottom of CricketSat using the Velcro 4)Secure the connection with a plastic tie-wrap as shown above

45 Wireless Testing 1)Turn on the power switch 2)The CricketSat should transmit around MHz. 3)It may be as low as or as high as MHz Preparing the CricketSat Testing 1)Use an amateur radio transceiver such as the Kenwood THD-7A or a low-cost UHF receiver similar to the UVM CricketSat unit shown right 2)Turn the receiver unit on, and tune through the frequency range specified above listening for the clicks 3)Adjust the volume as needed 4)For the UVM CricketSat receiver, just turn the unit on and adjust the volume 5)Red LED should also flash if CricketSat is nearby


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