User Manual - Digi-Key
Contents
1. SPREAD pe PIN 9 The burst frequency centers at 100KHz The 2V SPREAD sawtooth causes the oscillator to sweep about 7 around the center frequency If the burst length is adjusted e g by changing the Cs sample capacitors the SPREAD signal may need to be tweaked to maintain the 7 sweep The easiest way to do this is to change C9 For longer burst lengths increase C9 factory default value is 22nF X7R type to maintain a 2V peak amplitude on the SPREAD waveform TROUBLESHOOTER Does Not Work Keys Not Sensitive Enough Noisy or Erratic Operation Power supply too low or connected backwards Keys not calibrated properly Recalibrate or let stand for up to 30 seconds to let drift compensation work on the references Cs values need to be adjusted higher ie if the panel is too thick etc Power supply problem Noisy or unstable power supply Supply voltage is too low Cables or board too close to a strong noise source ie a power line or switcher Increase the distance from the noise source Place a grounded shield between the noise source and the E240 E240 is not mechanically stable gt Prevent board from moving around A 4 4 E I Ri www Qqprox com Corporate Headquarters 1 Mitchell Point Ensign Way Hamble Southampton SO31 4RF United Kingdom Tel 44 0 23 8056 5600 Fax 44 0 23 8045 3939 Email sales1 qprox com Development Team Luben2. THE JUMPER SETTINGS REFER TO THE QT240 DATASHEET 2 2uF 16V 1 2 3 Gnd Vin Vout 8 PCB LAYERS Figure 3 Silk Layer U E240 Evaluation Board Assembly No E240 iss 1 2 3 4 5 6 7 8 2004 ARG Z QUANTUM BOARD OPTIONS g Warning Changing components on the board involves soldering and unsoldering please take care not to overheat the board or to leave excessive flux which can affect signal stability and performance If in doubt clean the board with a commercial flux remover and dry it prior to use Figure 5 Jumper Positions Showing Default Configuration B JMP1A JMP2 B BJMPSA AJMP4B The E240 as shipped is factory configured to operate in fast mode with spread spectrum enabled and with a 10 second recalibration delay The user can re configure the jumpers to change these settings using zero ohm 0603 SMD resistors or bits of fine wire See next page for available jumper combinations 10 OPTION JUIVIPERS Jumpers 1 2 and 3 set the mode to Fast 40msec response or Slow 110msec response Spread Spectrum and external sync Table 2 Jumpers 1 2 3 Fast Slow Spread Spectrum Modes Description JMP 1 JMP 2 JMP 3 Fast amp Spread Spectrum B Yes B v Fast Mode Only None None B Slow Mode Only None None Slow Mode amp External Sync Jumpers 4 and 5 set Normal or Toggle mode and max on duration time delay to recal after prolonged detection Ta
3. Hristov Peter Dennis Matthew Trend North America 651 Holiday Drive Bldg 5 300 Pittsburgh PA 15220 USA Tel 412 391 7367 Fax 412 291 1015 Copyright 2004 QRG Ltd All rights reserved Patented and patents pending 201 220904
4. ation Board ou pootd E240 Evalu 5540 E240 User Manual The New Vision of Touch E240 User Manual OVERVIEW The E240 is designed to let you evaluate and develop with the QT240 4 key QTouch IC It includes four independent touch sensitive electrodes with corresponding LEDs to indicate touch Connections are provided for external interfacing The E240 is powered from an external 7V to 12V DC source such as a common 9V battery For more detailed information about this product please refer to the latest 07240 datasheet at www qprox com datasheets Materials Provided 1 x Clear plastic panel 1 x E240 self adhesive eval board with battery clip 1 x 9V battery 4 x Rubber feet 2 x Sample QT240 ISS chips 1 x QRG product CD ROM with QT240 datasheet but check website for latest 1 x User guide MOUNTING 1 The E240 can be adhered to plastic glass or any other dielectric panel with its peel back adhesive strip You do not have to use the supplied panel if you would rather stick it on your own panel Here s how to mount it 1 Place the plastic panel face down on a table tape down the edges of the panel to the table so it cannot move 2 Remove the peel back paper from the E240 PCB and adhere the E240 to the back of the panel Flex the E240 slightly while pressing down lightly on it to help eliminate trapped air Take care to flex the board only slightly to prevent the delicate SMT parts on the b
5. ble 3 Jumpers 4 5 Toggle Max On Duration Settings Durai 4 10 secs B A Y Normal 60 secs Infinite B B Toggle mode 10 secs Max On Duration is the amount of continuous detection time before the key auto recalibrates SENSITIVITY 11 The sensitivity of the keys has been tailored to match the supplied plastic panel To make a key more sensitive increase the value of its corresponding Cs capacitor see chart below To make it less sensitive decrease it s Cs value Only use 5 or 10 X7R ceramic capacitors most other types will be unstable and give erratic results Key Cs Capacitor Factory Default 1 5 22nF 2 C6 22nF 3 C7 22nF 4 C8 22nF C9 Spread Spectrum Capacitor see next page for details C5 C8 Sample Capacitors Cs increase to increase sensitivity 12 SPREAD SPECTRUM With Spread Spectrum enabled factory default configuration a sawtooth voltage signal is generated on pin 9 SYNC SS of the QT240 this is used to modulate the QT240 s burst frequency As pin 9 ramps up the sample burst frequency increases The effect of Spread Spectrum operation is twofold Peak emissions are reduced by up to 10dB and he E240 s susceptibility to external interference is reduced by a similar amount These benefits are highly significant in all applications The burst and spread modulation waveforms are as shown BURST LEIN d j J
6. n be left floating as the board has its own internal reset circuit To reset the E240 externally for example to force all keys to recalibrate connect RESET to GND for at least 1ms then release it the board will restart recalibrate and be ready to detect touches again after about 180ms 7 8 POWER GND Use 7 to 12VDC connected between the POWER and GND to power the E240 board The battery snap feeds the same two connections and can also be used for power input BOARD LAYOUT 5 Figure 1 Board Layout Battery Connector Electrodes Connector CN1 on user side Table 1 Connector CN1 Pinout Pin Description Pin Description 1 SYNC 5 OUT A 2 OUT D 6 3 OUT C 7 GND Ground OV 4 OUT B 8 POWER 7 12V SCHEMATIC VDD C2 Figure 2 Schematic Diagram m VOD SYNC SPREAD t R6 JMP1 kevi D SPEED C5 R3 R31 4K7 10nF 2K2 ER VDD R23 1K l 1M R4 C6 R5 4K7 10nF 2k2 IO SOLDER PADS T CN1 B 1 e RS R32 4K7 4 10nF 2K2 E 8 VD R26 1K j zu 1M KEY4 A R9 OPT2 C8 R10 R33 T 4K7 o n R29 10nF 2K2 1K an peo 1M i R13 100K 01240 SSOP FACTORY JUMPER SETTINGS SYNC SPREAD JMP1 B SPREAD2 JMP2 Fitted Is o 8 _ Conon ws a COMPONENT FOOTPRINTS nc U2 nc 1 HT7158 1 5v BATTERY PADS SUPPLY VOLTAGE 7 15VDC Q1 Q4 FOR A DETAILED DESCRIPTION OF
7. oard from cracking and failing Tip Line up the PCB with the alignment marks on the back of the slider panel The PCB must be positioned as shown below so that the keys line up with the graphics SKOG A d iii 3 Un tape the board from the table and mount the four rubber feet as shown above to make the E240 mechanically stable in use 2 RUNNING THE E240 To run the E240 simply 1 Place the E240 on a table touch side up 2 Connectthe 9V battery while making sure your fingers are clear of the touch areas to allow proper no signal calibration The E240 is now ready to use Touch the keys to see the LEDs light up continuous touch of 10 seconds will cause the key to recalibrate Releasing the key after such an event and waiting a few seconds will cause the key to recalibrate yet again and the key will function normally thereafter THEORY OF OPERATION 3 The E240 scans the keys using bursts of charge transfer pulses Immediately after power up the signals from these bursts are used to calibrate the baseline reference values of the keys This makes the device highly adaptive to mechanical differences i e varying panel thicknesses The QT240 chip also performs drift compensation on a continuous basis so that the signals are constantly being adjusted at a slow rate to accommodate drift The calibration process done at power up should be performed in a not disturbed neutral condition i e all fingers awa
8. rate independently The 10s timeout can be changed to 60s or infinite with jumpers see page 10 for details 4 BOARD DETAILS The E240 is a simple double sided PCB on industry standard FR4 material All parts are standard surface mount types Here is a brief description of some of the parts and features Keys Keys consists of capacitive electrodes formed using copper areas on the E240 which project a capacitive field through the overlying dielectric panel material Electrodes Copper areas on the PCB which define the touch keys LEDs The board has one Power LED which remains on as long as the board is powered plus one LED per key to indicate touch Connector CN1 The main interface connector is located at one end of the E240 board The pinout of this connector is shown in Table 1 next page The pin functions are as follows 1 SYNC Not used in fast mode the default setting SYNC is available in slow mode only and is used to synchronize the E240 burst with an external falling edge signal usually derived from a 50 or 60Hz source to suppress mains interference or to allow two or more QT240 chips to synchronize to to each other to prevent cross interference effects between the adjacent keys of different chips 2 5 OUT A OUT D OUT pins are low when the corresponding key is inactive and high when active and are controlled by the QT240 chip These lines also control the LEDs 6 RESET Ca
9. y from the keys and with the board situated in the location where it will be used Changes in location can alter the amount of signal coupling from the board back to the local environment and thereby change the sensitivity of the keys If the calibrations are in error just leaving the board alone for up to 30 seconds will allow the drift calibration process to settle the keys into the correct calibration values The QT240 features spread spectrum pulse modulation which heavily suppresses external noise effects while also suppressing radiated emissions This powerful feature provides for highly reliable compliant operation under a wide variety of operating conditions The QT240 chip also uses a Detect Integrator to protect against false detection reporting by verifying that a key is reporting touch for 6 bursts in a row if the device fails to detect a touch during any of these 6 signal samples the chip will refuse to report a key touch on an Out pin Combined with spread spectrum operation the detect integration process provides a powerful mechanism to suppress false detections from external noise sources If a key is touched for longer than 10 seconds the key is flagged as a stuck key and the QT240 recalibrates it so that the corresponding LED will go out and the key will operate again normally while suppressing the object ie a touch that caused the prolonged detection Only the stuck key is recalibrated as all electrodes ope
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