Build an Infrared Beacon for Robotics
Perfect for Robotic Games and CompetitionsDescription: Infrared Beacon for Robotics
Assembly Time: 2 to 4 hours
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:
|Part Description||Manufacturer Part No.||Component Name|
|LM555CN IC DIP-8||LM555CN||U1|
|Radial Capacitor, 470µF, 25V, 20%||R470/25||C4|
|Switching Diode 1N914||1N914||D1-D3|
|2N3906 Transistor , PNP, GP||2N3906||Q1, Q2|
|Orange, Red, Red Diffused LED 635NM||MCDL-314ED||LED1|
|Miniature Slide Switch SPDT||OS102011MA1QN1||SW1|
|Radial Ceramic Capacitor, 10000PF||SR211C103KAA-VP||C1|
|IC Socket , 08-Pin, Machine Tolled||6100-8-R||--|
|Battery Snap 6 Prong, 6", 26AWG||BC6-R||--|
|Mono Capacitor, .1µF, 50V, 20%||MD.1-VP-R||C2, C3|
|Potentiometer, 20kΩ, 3362P-203||3362P-1-203LF-VP/25PR||VR1|
|Resistor, CF, 10Ω, 1/4 Watt, 5%||CF1/4W100JRC||R4, R5|
|Resistor, CF, 2kΩ, 1/4 Watt, 5%||CF1/4W202JRC||R3|
|Resistor, CF, 27kΩ, 1/4 Watt, 5%||CF1/4W273JRC||R2|
|Resistor, CF, 47kΩ, 1/4 Watt, 5%||CF1/4W473JRC||R1|
|Infrared LED 940nm||TSAL6100||IRLED1-IRLED3|
|Thru-hole Prototyping Board||PAD1||PCB|
Resistor Color Codes
Step 1: Place your components on the circuit board before solderingSome components may have different sizes than the placement guide shown below. Please note that the bottom view is flipped.
Step 2: Solder the components to the circuit boardNow 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.
Step 3: Test and troubleshootNow 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|
|Trigger||6V||Connected to VCC through R1, R2 and VR1|
|Reset||6V||Connected to VCC|
|Threshold||6V||Same as PIN 2|
|Discharge||6V||Connected to VCC through R1|
|VCC||6V||System Power Supply|
Test 1B: Power On Socket
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 performanceTo 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.
• 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