Touch Sense Controller

Transcription

1 Touch Sense Controller Paul Boston May 11, 2011 (Modified May 22, 2014) (Modified Dec 28, 2015) The Touch Sense Controller is a microprocessor-controlled circuit designed to provide a switch closure when the touch-sensing pad is touched. The microprocessor senses reflected IR from a sensor located slightly below the Hand and activates a relay to provide both an indication of the touch and an independent switch operation. Power to the control board may be either AC or DC at voltages between 9 and 15 volts. It is highly recommended that a wall wart 12 volt supply be used which will keep the power leads as short as possible. Longer power cables seem to cause erratic behavior, but experience will dictate the installation choices. The circuit board contains a red LED as a necessary part of the power supply. This will indicate that power is being supplied to the entire board. The tally connection is a three-pin connection conditioned to accept a bi-color LED to indicate when the touch sensor has been activated. This allows calibration of the unit after installation. As supplied the touch sense is programmed to hold the on-board relay in the energized state for approximately five (5) seconds after a touch is sensed. During that time the touch pad is ignored by the microprocessor. The relay has two independent contact sets (DPDT) that provide both normally closed and normally open connections. One set of contacts is dedicated to the tally LED while the other set of contacts may be used for any load up to 2 amps.

2 Connections: Power is supplied through a two-pin connector on the top right of the board and labeled as power. Power may be AC or DC and polarity is not important. The status indicator is to be a three wire bicolor LED and is connected with the cathode to the center pin and the anodes connected to the outer pins. The three-pin connector on the top of the board is labeled Tally The touch pad is connected to the circuit board with a cable that is hard wired to the circuit board. (The two-pin connector on the top of the circuit board and labeled Sense and the Trim Pot are no longer used). The 3.5mm stereo plug located on the top left of the circuit board is for programming the PICXE 08M2 chip. See Picaxe.com for specifics. The five-pin connector located at the bottom of the board provides switch closure. The connections from left to right are: 1-Common 2-Unused 3-Normally Closed 4-Unused (Power Option) 5-Normally Open (There is an option that will allow the attached controlled device to be powered by the same power source that is attached to the top right of the board. To use this configuration solder jumper wires between the holes labeled J1 and J2. This links the input power to the Common pin #1 to one wire of the power input and the other wire to the (Power Option) pin #4. By connecting the device to be controlled to pins #3 and #4 the device will be powered whenever power is applied to the main power of the board. If the connection is made to pins #4 and #5 the device will be powered on only when the touch pad is touched)

3 Modification 2. Dec 28, 2015 (PAB) Modifications were made to the circuit board in late 2015 allowing the IR sensor module to be plugged directly into the circuit board (Sensor Connect). Unlike the last modification the IR sensor does not need an in-line resistor to its IR LED. It has been provided for on the board (the resistor just above the Sensor Connector in the photo). The Tally LED is soldered directly to the circuit board eliminating the need to add a remote LED. Some of these board-c builds are still equipped with the 3-pin connector for a remote Tally indication.

4 The other upgrade has been to add the ability to use jumper pins rather than soldering wires to board holes J1 and J2 to provide power as described earlier. Jumper fitted to pins 1-2 (J1) and 3-4 (J2) will provide input power when the device is connected to pins 4 and either 3 or 5 of the Control. Pin 4 is directly connected to the input power while the NC (3-4) or NO (4-5) pins will be relay controlled and connected to the other leg of the power input. Note that whatever power, AC or DC, with voltage up to 25 V and current less than one amp, is provided to the input in the upper right of the board will go to the connected device. Expanded Uses: This board has now been incorporated into a train-detection role and has been installed to control the traffic indicators on the signal bridges. When used as a train detector the sensor is mounted between the ties alongside the center rail of the track with the sensor pointing up. The circuit board is located within the range of the sensor cable length and screwed to the bottom of the HDPE track bed. Power is supplied from any convenient source above 7 volts. Setup: Install the circuit board in a location that is easy to see and fairly close to both the power source and the touch pad. Two to three feet from each is adequate. Attach the bi-color LED to the Talley connector. A three-pin Molex on both ends of a three-wire cable will allow the LED to be inserted in one end and the cable attached to the circuit board with the other end. Again, keep the wire as short as practical since the LED is powered by the same power supply that runs the microprocessor and keeping electronic noise to a minimum is always desirable. Connect the in-line connector from the sensor board to the lead coming from the circuit board. Using a five-pin Molex connector connect the device to be controlled to the circuit board on the lower part of the board. The usual wire configuration is to use pins 1 and 5 for a normal switch closure. This provides a switch closure when the touch pad is touched. Use pins 1 and 3 if a switch opening is desired. See the above chart. Connect the power using a two-pin Molex connector to the pins labeled Power on the upper right of the board. Calibration: During manufacture small deviations in the build process makes each Hand slightly different in its response to touch, requiring mating the hand with the software on the board.

5 It is most convenient to calibrate the Hand sensitivity on the bench before installation. With the power on, confirm the red LED on the bottom right of the board is on. The Talley LED may be either red or green depending on which way it was installed in the holder. On power-up the microprocessor will run its installed program, so the touch pad will be active at all times. Touch the Touch Pad to see if the tally LED changes color. If it does change color it will return to the original color after five (5) seconds (or the programmed time). If this color change does not occur the threshold value in the program will need to be adjusted. This is NORMAL! Programming: The Touch Sense board uses a PicAxe 08M2 microprocessor. The Touch Sense board comes pre-programmed to operate the relay for five (5) seconds when a touch is sensed on the touch pad. The software and instructions needed to program the 08M2 is free and available on-line from PicAxe.com. The 3.5 mm stereo phone jack on the upper left of the board is a serial connection to a computer. It is recommended cable is the AXE027 as configured by PicAxe and available on-line. This cable uses the USB port and is wired to connect directly to the 3.5 mm stereo phone jack. The software from PicAxe is a form of BASIC which is compiled before being uploaded to the PicAxe chip. Below is the program installed on the Touch Sense board after assembly. When the program is uploaded it runs whenever power is present. The Debug line allows the programmer to observe the memory contents so that the sensitivity in line 12 can be adjusted.

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