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Cell Phone Docking Station

ECE 345 Project Presentation. Cell Phone Docking Station. Daniel Finch Mihir Shah David Johns TA: Jeff Cook. Introduction. What Who Where When Why?. What. Design a system to interface a home telephone network with a cell phone.

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Cell Phone Docking Station

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  1. ECE 345 Project Presentation Cell Phone Docking Station Daniel Finch Mihir Shah David Johns TA: Jeff Cook

  2. Introduction What Who Where When Why?

  3. What • Design a system to interface a home telephone network with a cell phone. • Allow incoming calls to a cell phone to ring a home network • Allow audio communications between a cell phone and home network • Provide a seamless environment between the cell phone, the home network, and the subscriber line

  4. Who, Where, When, Why • A person wishing to answer cell calls while at home without the discomfort of a small cell phone • A person wishing to charge a cell phone while keeping the cell’s connectivity readily available. • After work, plug the cell phone in the unit, charge it up and keep connected.

  5. Cell Phone Ring Detector Ring Generator Home Phone Dial tone Generator And Logic Touchtone Decoder Hook Detection Objective - the original plan • What we intended to do: • Provide 100% cell phone functionality through use of the landline phone

  6. BUT… • Motorola has no university support!

  7. Ring Generator -24V DC/DC Converter tip SLIC Ringer Relay Normal line audio ring Ring Signal Detection Circuit Cell Phone Hook detection snd Home Phone Ringing Hook Detection BASIC STAMP Microcontroller End call signal Solenoid Activator What we built SLIC

  8. DC / DC Converter • Uses MC34063A IC • Inverts 5V to -24V • Provides reference voltage for SLIC and ringing off hook detector

  9. SLIC (MC33121) Functionality • Subscriber Line Integrated Circuit • Provides Tip/Ring telephone line conversion to audio I/O. • Audio dB level controlled by network attached to chip • Provides hook status of subscriber line

  10. Cell Phone snd Audio Isolation • 1:1 Isolation transformers used to reduce feedback on audio I/O + SLIC RXI TIP Audio Out - - Audio In TXO RING +

  11. Ring Generator Circuit • 90V, 20Hz AC signal generated by Cambridge “Black Magic” ring generator (12VDC input). • Controlled by logic signals from the STAMP and component network

  12. Ringing Hook Detector • Custom circuit. • Provides signal for the STAMP to switch the relay from the ringing circuit to the SLIC audio conversion circuit. Rectifier And Reference Inverter -24V 12V - 741 1k 1k 20Hz 620 1.3M + - 12V 741 Ring -12V + 270k 20Hz Square Wave (when switched) 0V Else Unity Gain Follower -12V 1k

  13. Ringing Generator Output • Black Magic Telephone Ringing Generator (LS0014) • 20 Hz AC Sine Wave • 90 Vrms

  14. Ring Output Rectifier • Diode -Resistor Network • Remove positive component of sine wave

  15. After Unity Gain Follower • Provides current to drive the ring signal • Makes sinusoid more of a square wave

  16. After Inversion • Provides positive ring signal for Basic Stamp 2 to decode • 20 Hz square wave

  17. Cellular Phone Ring Detection Attempts • Audio out from data connector • Too small (153mV) • Too Fast (900MHz) • Data Bus signals • Not readable by Basic Stamp 2 • Current Sensing IC • Didn’t work for Vin > 5V

  18. Final Cellular Phone Ring Detection Design • Audio out from 2.5mm audio jack on phone (20 Hz, 1V-pp signal)

  19. Amplified Cellphone Ring Signal • Amplified output, compared in Basic Stamp to amplitude level • High amplitude signal (- line noise) = ring.

  20. Stamp functionality • Cell ring detection waitforring2: for reps = 1 to 5 pause 20 if in2=0 then dialtone if in1=0 then noring total=total+1 noring: next if total>1 then ring goto waitforring

  21. Stamp functionality • Ringing off-hook detection pulsin 3, 1, stuff2 ' wait for pickup if stuff2>10000 then goback if stuff2<30 then goback goto pickup

  22. WAIT FOR RING Ring enable off Phone output switched to subscriber line Did Cell Ring? no yes HANG UP CELL Turn off cell phone Turn on cell phone Wait 5 seconds RING PHONE Increment Ring Count Switch relay to ringer Wait 2 seconds no Phone Off-hook? Is Ring Count > 5? yes yes no no DON’T RING PHONE (still calling) Switch relay to SLIC Wait 4 seconds Phone Off-hook? ANSWER PHONE Press SND Using solenoid relay Switch to SLIC Phone Off-hook? yes no yes STAMP flow chart

  23. The Mechanical Finger • STA Push Tubular Solenoid • 5.2V input • Draws ~3A • 12V / 5A Radio Shack Relay - Basic Stamp 2 controlled • Mounted in custom built cradle for cell phone to line up with the solenoid.

  24. Functionality and Testing • Test cell ring detection - no erroneous rings • Test 2 second on, 4 second off ringing - 5 ring maximum • Test hook status functionality • Test solenoid functionality of send button • Test audio I/O between cell and land phone, and also multiple land phones • Test cell hang up when phone goes on-hook

  25. Challenges • Contacting Motorola - for both iDen and Microtac cell phones • Cell phone ring detection • Ringing off-hook detection • Implementing solenoid • Debugging noise from SLIC circuit

  26. Recommendations • Dialtone generator • Databus decoding - Motorola or other brand • Ability to dial land-line phone using cell line connection • Better cell ring detection (using databus)

  27. ?Any Questions??Any Comments? • Where can I buy one?

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