The circuits on this page are for an Infrared - Proximity Detector using the Vishay Electronics - TSOP4830 "IR Receiver Modules for Remote Control Systems".
The detectors are designed for short range - reflected light operation but can also be used for 'broken beam' detection over short distances.
This circuit was designed primarily for Between The Rails detection of model trains.
In this circuit the TSOP4830 Infrared receiver is used as a sensitive detector that does not require shielding from room lighting. The detector will work under almost any lighting condition from complete darkness to full sunlight.
As a guide, if a TV remote control will work in a particular area then so should this circuit as the TSOP4830 would normally used in conjunction with a remote control for a television or VCR.
This circuit will work in almost all light conditions but it can be affected by infrared remote controls. For its designed use this sould not be a problem.
This circuit is more complex than typical infrared or visible light sensitive detectors at this site and elsewhere but will work in a wide range of light conditions.
The following schematic is for a basic version of the Infrared - Proximity Detector used on this page. The circuitboard has 1 LED driver oscillator and 8 detector circuits on it.
In the basic proximity detector circuit, the hand-held remote is replaced by an infrared LED driver that uses a 556 dual timer. The two oscillators in the 556 simulate the pulsed carrier signal of the remote but without the information such as volume or channel that would normally be sent to an appliance.
The upper portion of the circuit uses two astable 556 oscillators, IC 1A and IC 1B to drive an infrared LED. IC 1A operates at approximately 3Hz with a duty cycle of about 9 percent. IC 1B is adjusted to 30 kHz (the design operating frequency of the TSOP4830) with a duty cycle of about 52 percent.
The 556 - LED driver circuit produces an approximately 10 millisecond burst of 30 kHz light 3 times per second via the infrared LED.
The lower portion of the circuit is the IR detector, time delay and output section. The output of the voltage comparator, IC 3, produces a steady LOW - open collector output when infrared light of the correct frequency is detected by the TSP4830 receiver IC.
When the IR Receiver Module receives a sufficiently strong 30 kHz infrared pulse from D1, its output, pin 3, will go LOW for the duration of the pulse. (About 9 milliseconds.)
When the output of the IR detector goes LOW, the voltage at the PLUS input of comparator, IC 3, will be made LOW and the comparator's output will go LOW. As long as the infrared pulses are seen by the receiver module the output of the comparator will remain LOW.
The 4.7uF capacitor provides a time delayed resetting so that the output of the comparator is steady between the IR pulses.
When the 30kHz infrared signal is no longer detected, the 4.7uF capacitor will charge and the output of the comparator will go HIGH.
In typical circuits the output of the comparator would control a LED or drive a relay.
Depending on the circuitboard for the infrared proximity detector circuit, the lower portion of the basic circuit is repeated 4 or 8 times.
The next diagram illustrates a typical model railroad installation method for the emitter and receiver for the proximity detector.
The infrared emitting LED is mounted through a 3/16" hole drilled through the roadbed.
The LED is encased in a section of heatshrink tubing to prevent the light from reaching the receiver directly from the sides of the LED.
The top of the tubing is flush with or slightly higher than the top of the ties. The bottom of the tubing should extend about 1" below the bottom of the infrared receiver IC.
The IR receiver module is mounted through a 1/4" hole drilled through the roadbed.
The top of the receiver module is at the bottom of the ties with the lens of the receiver facing the IR LED.
The TSOP4830 Receivers are very sensitive and will need to be shielded from all sources of IR signal except the LED that is directly across from the receiver when used in a 'Break the Beam' situation.
Mounting of the emitter and receiver depends on the particular situation but many options are possible.
The circuitboard has a dual output - LED driver and eight detector circuits. The eight detector sections of the circuits are identical.
The following schematic for a Octuple - Infrared - Proximity Detector and LED driver circuit.
The individual detector circuits are the same as in the test circuit above. The LED driver circuit is slightly different though, see the "Carrier Frequency Adjustment Notes" section below for details.
The area inside the dashed, gray line is the portion of the circuit that is on the circuit board itself.
The full circuit schematic is too large for practical use so smaller "Terminal" diagrams has been provided that the user can plan, layout and document their own detector systems.
Terminal diagram showing two input and output connections.
The following is a terminal diagram with no input and output connections shown. Print this diagram in the centre of a sheet of paper and use it to plan and document a particular installation.
This circuit uses the TSOP4830 infrared receiver module in a manner for which it was not designed. However, for model train detection the circuit worked very well and is able to sense the uncoupling pin of a Kadee® type automatic coupler.
The infrared LEDs pulse at a rate of approximately 3 times per second. The slow rate also allows the green LED D2 to be seen flashing by the user but is fast enough for model train detection. The slow flash rate can also be helpful for trouble shooting.
The circuit as shown has an output release delay time of approximately 2.5 seconds. The delay can be made shorter by decreasing the values of capacitors at the input of the comparators.
Resistor(s) R5 is given as 1K ohm for an infrared LED current of about 7.5 milliamps. This could be reduced to a minimum of 330 ohms for a infrared LED current of about 20 milliamps.
The infrared LEDs are shown wired in series as this uses the least amount of current. For between the rails type detection the infrared LEDs need very little current as the distance between the LED and the receiver is short, therefore low current, series wiring is sufficient.
The infrared LEDs could also be wired in parallel if R5 is removed from the circuit board and replaced with a jumper. Each LED would then need its own current limiting resistor.
The circuit as shown is designed to control LEDs connected at the outputs through 1K current limiting resistors mounted on the circuit board. The output resistors can be replaced with jumpers or their values changed to drive other devices.
For example; The Base of a 2N3906 PNP transistor could be driven through an external 3.3K resistor or a 4.7K resistor could be mounted on the circuitboard. The transistor would be used to drive a low power relay. See below for a schematic of a relay driver.
There are other TSOP48xx series infrared receivers that operate at carrier frequencies between 30 and 56 KHz. that could also be used with this circuit if the LED driver's carrier frequency was changed to suit. Also there are other receivers with different case styles that should also work.
The TSOP4830 has a wide field of vision and can receive light through the back of its case. In some installations it may be necessary to shield the receiver from stray signals from other emitters.
The infrared LEDs will have to be mounted in a light blocking sleeve. A section of closely fitting heat shrink tubing is ideal for this purpose and in most cases does not NEED to be shrunk.
Moving the IR LED deeper into its heatshrink sleeve will reduce the sensitivity of the detector by reducing the amount of light available without having to change the current through the infrared LED.
This system is not particularly suited to use in tunnels as the infrared may be reflected from the roof of the tunnel and into the receiver causing a false detection. (Inside tunnels, an infrared emitter/detector pair across the track would be more suitable.)
The proximity detector could also be used across the track. In this case the output of the circuit would be LOW until and object breaks the infrared beam. In this case, the time delay would be reversed causing the output to go HIGH about 2.5 seconds after the beam is broken. (Decreasing the value of the 4.7uF timing capacitors would shorten the detection time delay.)
In the beam blocking mode, the distances can be quite large. For long distances it may be necessary to increase the current through the infrared LEDs by reducing the value of resistor R5.
The proximity detector is not limited to model railroad use. Any object that reflects or blocks enough infrared light could be used to trigger the circuit. The proximity detector could also be used by robots to locate walls or obstacles.
This circuit will be affected by some TV or VCR remote controls depending on their operating frequency and might not be suitable for layouts where infrared controlled throttles are being used. On the other hand, a TV remote might be used to see if a particular receiver is working.
Infrared light is not visible to the naked eye, however, a digital camera can be used to view the IR light if it does not have an IR blocking filter on the lens.
The image may not be very bright but close-up or in a darkened area the light should be visible on the camera's display screen.
The TSOP4830 infrared receiver requires a 30KHz carrier frequency from oscillator IC 1B. There are two methods that can be used with the detector circuitboards to set this frequency.
METHOD - A uses five fixed resistors to set the 30KHz frequency of IC 1B. The reason for using this method is so that the user cannot accidentally throw the oscillator out of calibration. Method - A will be supplied with each circuit board unless requested otherwise.
METHOD - B uses two fixed resistors and a 10K ohm potentiometer to set the 30KHz frequency of IC 1B. Method - B can be used if the user has the equipment to set the frequency for themselves.
NOTE: - Assembled circuitboards from this site will be constructed using METHOD - A to set the carrier frequency.
The 8 detector board 2.9 inches by 4.4 inches.
The circuitboards have been commercially produced but have not been tinned.
The IR LED and the IR receiver module will have 5" colour coded leads attached.
1 - 8 - Infrared - Proximity detector circuitboard with no parts is 17.50 dollars US, plus postage.
1 - 8 - Infrared - Proximity detector circuitboard with only the 30KHz oscillator installed is 22.00 dollars US, plus postage.
NOTE - The LM556 infrared LED driver oscillator will be calibrated before shipment.
1 - 8 - Infrared - Proximity detector circuitboard KIT with all parts, including 8 IR LEDs and 8 IR receivers is 62.00 dollars US, plus postage.
- If requesting kits, please ask for... -
KIT 1 - For the kits; To provide the needed accuracy of the IR receiver's carrier frequency the 30KHz. portion of the LM556 oscillator can be installed on the circuitboard and tested before shipment.
- OR -
KIT 2 - If requested, kits can be supplied with the oscillator portion of the circuit not installed and with a potentiometer to set the 30KHz carrier frequency.
1 - 8 - Infrared - Proximity detector circuitboard, ASSEMBLED with 8 IR LEDs and 8 IR receivers is 65.00 dollars US, plus postage.
All IR emitters and IR receivers will have been tested before shipment.
Each input on the detector circuit board can have more than one infrared receiver connected to it. This can reduce costs by allowing one detector input to cover a section of track.
RR-CirKits "TC-64" Tower Controller Web Page.
Other references: -
Ir Receiver Modules.
555 and 556 Timer.
Current Limiting Resistor Calculator information.
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as detectors.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
14 October, 2012