TM AccessTouch Touch sensitive keyed access controller Summary AccessTouch is an integrated combination key access controller featuring tough-sensitive keys for vandal-proof operation. An accompanying design blueprint is available for a complete low cost, access control product. AccessTouch uses capacitive touch sensing technology. The PCB keyboard shown can be overlaid by a non-metallic covering. It automatically calculates signal averages to compensate for track capacitance, water splashes, etc. A buzzer output provides audio feedback as buttons are pressed. AccessTouch is firmware for the PIC16F631 microcontroller and is available as a pre- programmed chip from electronics distributors or as a firmware download from www.hexwax.com. User Operation When the correct code is entered, the door release output is activated for a fixed time delay. The sequence of keys pressed prior to entering the code is unimportant. Typical Application Circuit To change the access code, an electrical switch is Figure 1 closed and the new code is entered twice. LEDs Vss C3 R12 indicate Open, Closed and Set Code states. All . J1 R2 R3 R11 BZ1 LEDs turn off when the device enters a sleep . Vdd state. Set Vdd LED1-3 Touch3 . Features . SetLED . Touch2 R8 . Touch1 . OpenLED Access Tiny volume BOM cost R9 . Touch0 Touch ClosedLED R10 Vandal-proof design, no parts need to be TouchD physically exposed To lock Lock TouchA driver Lock Codes may be up to 8 digits Audio feedback on touch press . Vss TEAclipper 1 2 3 4 5 connector Safe Controller mode available C2 C1 20-pin SSOP package Vdd . Vss R1 Electrical Specifications Vss Table 1. Electrical Specifications 1 2 3 Supply voltage Vdd 2.0 5.5 VDC . Touch0 Touch1 Current, sleep scan mode, 3V Vdd ~50A 4 5 6 Operating Temperature 40C to 85C Touch3 Touch2 7 8 9 Firmware Factory Ltd rd Vss 2 Marshall St, 3 Floor 0 Typical touch London W1F 9BB, UK Touch1 pad layout sales firmwarefactory.com support firmwarefactory.com p1 of 4 7-Sep-08 Access-Touch HW140-1 www.firmwarefactory.com Click1 Click2 Vdd TouchB PGD Touch0 TouchC Rst Vss R4-R7oscillator which scans the contacts in turn. When a Device Pinout finger is placed close to the contacts, the capacitance will increase, reducing the frequency of the oscillator. A sudden drop in capacitance is interpreted as a button press. The touch pads measure changes in capacitance relative to a recent moving average. This provides some resilience to changes in humidity and water splashes. In order to achieve reliable operation, keys do not need to be pressed hard, but they must be held for approximately 250ms. When power is applied, all three LEDs light for approximately 15 seconds while the average capacitance is initially measured. After a period of inactivity, an optional sleep state Table 2. Pinout Table reduces the key scan rate to once every 500ms. If this Name Description Click 1, 2 Buzzer driver mode of operation is used, the first key must be held for ClosedLED Closed LED output this time in order to wake the device. Rst / Vpp Reset input, active low / Vpp programming input Vss, Vdd Lock Lock release, active high Lock Lock release, active low Vss is the power supply ground reference. Vdd should OpenLED Open LED output be connected to a DC supply of 2.0V 5.5V. PGD PGD programming input SetLED Set Code LED output TouchA Touch D SetSw Set Code input control, active high The TouchA to TouchD pins configure the relaxation Touch0 Touch sensor input 0 (Keys 1, 2, 4, 5) PGC programming input oscillator and should be connected as shown in figure 1. Touch1 Touch sensor input 1 (Keys 0, 2, 3, 6) Touch1 Touch4 Touch2 Touch sensor input 2 (Keys 0, 4, 7, 8) Touch3 Touch sensor input 3 (Keys 5, 6, 8, 9) The Touch1 to Touch4 pins are capacitance sense TouchA Relaxation Oscillator Drive Output inputs. They should be connected to the touch pads as TouchB Relaxation Oscillator Reference Voltage Drive shown in figure 1. TouchC Relaxation Oscillator Reference Voltage Input TouchD Relaxation Oscillator Counter Input Vpp, PGC, PCD Vdd 2.0V 5.5V supply TEAclipper programming pins. Refer to the Delivery Vss Power supply ground and Programming section for details. Note that the Vpp pin may be subject to voltages as high as 12V during Bill of Materials programming. The Table 2 shows the recommended components for RST the bill of materials. The table does not include components for providing power or driving the lock The pin is an active low reset input. It is important that release, which will be application specific. Package this is connected to a 22k pull-up to Vdd, the TEAclipper sizes apply to the gerber files in the product blueprint. connector, and nothing else. Table 3. Suggested component values Open LED Label Component Outputs high when the lock release is triggered. This C1 100nF capacitor 0402 pin can drive up to 25mA. C2 1uF capacitor 0402 C3 1nF capacitor 0402 Closed LED J1 Jumper or switch for set code control LED1-3 Light emitting diodes, e.g. HSMx-C265 Outputs high when the lock release is not triggered and R1 22k resistor 0402 the device is not in a sleep state. This pin can drive up R2 3k3 resistor 0402 to 25mA. R3 1k resistor 0402 R4-R7 120k resistor 0402 Set Code LED R8-R10 470R resistor 0402, adjust for LED brightness Outputs high when the SetSw input is high. This pin can R11 10k resistor 0402 drive up to 25mA. R12 10k resistor 0402, adjust for buzzer volume U1 PIC16F631-SS with AccessTouch preloaded SetSw X1 Piezo buzzer, e.g. CMT-1603 Set Code input control. Set to Vdd to enter a new code. The code must be entered twice and is acknowledged How It Works with a beep. This minimizes the chance of entering in The touch pads measure the capacitance of the an incorrect code while keeping user operation simple. interleaved touch contacts using a relaxation oscillation It does mean, however, that codes made up of repetitive p2 of 4 7-Sep-08 Access-Touch HW140-1 www.firmwarefactory.com