Build an Infrared Beacon for Robotics

Perfect for Robotic Games and Competitions

Infrared Beacon for Robotics Description: Infrared Beacon for Robotics
Assembly Time: 2 to 4 hours
Difficulty: Intermediate
Designer: MissionPeak

The Infrared Beacon for Robotics Kit is perfect for use in robotics games and competitions. It uses a LM555 timer and a transistor source to drive some infrared diodes. This kit maintains a stable frequency and output through a wide operating voltage (4.5 to 9 volts), simply adjust the low/high switch for a higher infrared (IR) output.

Required tools and components:

Qty.
Part Description Manufacturer Part No. Component Name
1
LM555CN IC DIP-8 LM555CN U1
10
Radial Capacitor, 470µF, 25V, 20% R470/25 C4
10
Switching Diode 1N914 1N914 D1-D3
10
2N3906 Transistor , PNP, GP 2N3906 Q1, Q2
10
Orange, Red, Red Diffused LED 635NM MCDL-314ED LED1
1
Miniature Slide Switch SPDT OS102011MA1QN1 SW1
10
Radial Ceramic Capacitor, 10000PF SR211C103KAA-VP C1
1
IC Socket , 08-Pin, Machine Tolled 6100-8-R --
1
Battery Snap 6 Prong, 6", 26AWG BC6-R --
10
Mono Capacitor, .1µF, 50V, 20% MD.1-VP-R C2, C3
1
Potentiometer, 20kΩ, 3362P-203 3362P-1-203LF-VP/25PR VR1
10
Resistor, CF, 10Ω, 1/4 Watt, 5% CF1/4W100JRC R4, R5
10
Resistor, CF, 2kΩ, 1/4 Watt, 5% CF1/4W202JRC R3
10
Resistor, CF, 27kΩ, 1/4 Watt, 5% CF1/4W273JRC R2
10
Resistor, CF, 47kΩ, 1/4 Watt, 5% CF1/4W473JRC R1
10
Infrared LED 940nm TSAL6100 IRLED1-IRLED3
10
Thru-hole Prototyping Board PAD1 PCB

Digital multimeter
Soldering equipment
Batteries

Resistor Color Codes

Name Value Color Code
R1 47k Yellow-Purple-Orange-Gold
R2 27k Red-Purple-Orange-Gold
R3 2k Red-Black-Red-Gold
R4, R5 10 Brown-Black-Black-Gold

Step 1: Place your components on the circuit board before soldering

Some components may have different sizes than the placement guide shown below. Please note that the bottom view is flipped.

Component Positioning and Wiring

Step 2: Solder the components to the circuit board

Soldering Complete Now solder the components to the circuit board using the diagram above. I recommend starting with the signal wiring before the VCC and GND wiring. SW1 is glued to the circuit board. This kit does not have an on/off switch. You will simply have to unsnap the battery to turn the unit off.

Note: The photos above are given as a reference guide. Your project's appearance will vary depending on the circuit board you are using.

The IRLEDs have a narrow beam angle. For increased area coverage, I slightly angled the first and third IRLEDs after soldering. The angle depends on the beam width of the IRLED; 10 to 30 degrees is typical but you should make sure that you calibrate it with the actual IR receiver.

Angled IRLEDs

Step 3: Test and troubleshoot

Now it's time to test and troubleshoot. Make sure that you resolve any failures before moving on to the tests.

Test 1A: Power On Socket

Remove the LM555 from the socket, apply a 6 volt battery and measure with respect to GND.

LM555 Socket Pin Measured Voltage Note
GND 0V System Ground
Trigger 6V Connected to VCC through R1, R2 and VR1
Output NO TEST --
Reset 6V Connected to VCC
Control NO TEST --
Threshold 6V Same as PIN 2
Discharge 6V Connected to VCC through R1
VCC 6V System Power Supply

Test 1B: Power On Socket

Test 1B IR Emitter Using a piece of wire, connect pin 3 and pin 1 of the LM555 socket to create a short between the two pins. This will simulate the low output of the IC and turn on all of the IRLEDs. Set SW1 to open.

Apply 6 volts of battery power and measure the current consumption and verify that the current drivers Q1 and Q2 are working properly. The result should be 35mA ±20%. If the current is too low, check the polarities of Q1, Q2, D2, D3 and IRLED1-IRLED3. The voltage across pin B and pin E of Q2 should be 0.6 – 0.7 volts.

R3, R4 and R5 may have the wrong value if the current is too large. Close SW1. The measured current should be 70mA ±20%. Also check the values of R5 if it fails – it could be a faulty SW1 switch.

Test 2: IR Emitter Regulation

This is identical to Test 1B. At various points from 4.5 to 9 volts change the applied voltage. The measured current should be within ±10% from the current consumption measure at the 6 volts of the previous test. If the current is too large, Q1 and Q2 have failed. Check the polarities. The Q1 voltage across pin B and E should be 0.6 – 0.7 volts when the VCC is anywhere between 4.5 – 9 volts.

Test 3: IR Emitter Current Off

Use a piece of wire to connect pin 3 and pin 8 of the LM555 socket to simulate the high output of the IC and turn off the IRLEDs. Apply 6 volts of power and measure the current consumption. It should be less than 1mA. This will let you know that Q1 and Q2 are turned off.

Test 4: Complete the Circuit

Install the LM555 and dial VR1 to the center position. Apply 6 volts of power and measure the consumption with SW1 closed. The current should be 25mA ±20%. With SW1 open it should decrease about 45%.

If LED1 is off, check D1 and LED1 polarities – the fault could be the oscillator. Measure the oscillator at pin 3. It should read 70% of the VCC. Pin 4 should be at high and pin 5 should be at 2/3 of VCC for the correct operation.

Measure the oscillator with an oscilloscope at pin 3 and you should see a square wave output between 0 to VCC with 70% output. You can adjust the oscillation frequency by VR1 from 1000 to 1400Hz.

Step 4: Check the performance

Test 1B IR Emitter To house the board you can use a non-conductive box. Use an IR sensor to check the performance of the system. You may also want to adjust the frequency of VR1 for maximum detection range.

Specifications
• Operating Voltage: 4.5-9V
• Operating Current: High IR output 25mA ±20%, low IR output 45% less
• IR Beacon Frequency: 1000-1400Hz adjustable
• IR Wavelength: 940nm
• IR Output Variation: Less than ±10% within operating voltage range