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UVM CricketSat Manual

UVM CricketSat Manual. What’s a CricketSat?. 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

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UVM CricketSat Manual

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  1. UVM CricketSat Manual

  2. What’s a CricketSat? 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 Description • Wireless temperature sensor • Usually flown on a balloon • Simple circuit • Easy to build • Easy to modify • Low cost (~$10)

  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 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) CricketSat Background 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 Supply Transmitter Temperature Sensitive Oscillator

  7. CricketSat Circuit Board Custom Circuit Prototype Area Transmitter Oscillator Power Supply

  8. Sensing the Temperature Thermistor 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

  9. Temperature Sensitive Oscillator Thermistor • 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

  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), 5.5-20 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 Thermistor R1 555 Timer IC Vcc LED R2 Digital Output Signal Voltage on capacitor C1 Not Used C1 Capacitor Charge & Discharge Waveform Time Simulation courtesy of Williamson Labs: http://www.williamson-labs.com

  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 Supply Transmitter Temperature 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, http://cbdd.wsu.edu/kewlcontent/cdoutput/TR502/page21.htm

  21. 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 Assembly Equipment List

  22. Safety Use safety glasses while assembling the CricketSat. Hot solder and flying leads caninjure 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. Assembly Preparation

  23. R4: 100 Ohm C1 C2 C3 C4 C5 C6 Negative White Band Non-Polarized Components Brown-Black-Brown-Gold R2: 3300 Ohm 0.1 micro-Farad Capacitors Orange-Orange-Red-Gold Black Band D2 - Diode + - + - + - - + R3: 680 Ohm Longer Lead Notch 47 micro-Farad Electrolytic Capacitors Dimple Blue-Gray-Brown-Gold Pin 1 1234 8765 D1 U3: RF Transmitter DIP Socket U1: 555 Timer IC R1 U2 SW1 Flat Side Up Longer Lead Pins: 1 2 3 Pins: 1 2 3 4 - On/Off Switch 10K Ohm Thermistor + 5-Volt Regulator Light Emitting Diode (LED) Velcro B1: 9-Volt Battery Printed Circuit Board (PCB) - + Red Lead is Positive Battery Snap Connector Antenna Wires - +

  24. Printed Circuit Board • Purpose • To provide mechanical support and electrical connectivity for components. • 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.

  25. Assembly Techniques 45 degree angle is best • 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 ™. Bend lead close to board • Snipping leads • Use safety glasses to protect your eyes. • Hold lead while cutting or point downward. Snip just above solder joint

  26. Power Supply Circuit Assembly

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

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

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

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

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

  32. Oscillator Circuit Assembly

  33. Before Proceeding • Turn off power to the CricketSat • Disconnect the battery • Wear safety glasses

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

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

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

  37. Oscillator Testing (2 of 3) Timing Capacitor Waveform Oscilloscope test probe • This procedure allows the signal on the timing capacitor to be viewed on an oscilloscope. • Turn ON the CricketSat circuit board. • 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. • Touch the oscilloscope probe to the VC1 test point. • Adjust the gain of the oscilloscope to observe a rising and falling voltage signal. • The LED should be OFF while the voltage is rising, and ON while it is falling.. • Animation to the left demonstrates analog signal waveform.

  38. Oscillator Testing (3 of 3) Digital Output Waveform Oscilloscope test probe • This procedure allows the signal on the timing capacitor to be viewed on an oscilloscope. • Turn ON the CricketSat circuit board. • 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. • Touch the oscilloscope probe to the OUT test point. • Adjust the gain of the oscilloscope to observe a rising and falling voltage signal. • The LED should be OFF while the voltage is rising, and ON while it is falling.. • Animation to the left demonstrates digital output waveform.

  39. Transmitter Circuit Assembly

  40. Before Proceeding • Turn off power to the CricketSat • Disconnect the battery • Wear safety glasses

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

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

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

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

  45. Wireless Testing Preparing the CricketSat • Turn on the power switch • The CricketSat should transmit around 433.92 MHz. • It may be as low as 433.75 or as high as 434.25 MHz Testing • 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 • Turn the receiver unit on, and tune through the frequency range specified above listening for the clicks • Adjust the volume as needed • For the UVM CricketSat receiver, just turn the unit on and adjust the volume • Red LED should also flash if CricketSat is nearby

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