Infrared Car

This article shows an infrared car that has two infrared sensors and two gear motors on each of the two sides of the car. Each infrared sensor activates to motor on the opposite side that will allow the car to follow the infrared transmitter.



The circuit for this toy is not hard. It is simply a BJT transistor motor driver that amplifies the current from infrared microchip TTL (Transistor Transistor Logic) output. The TTL receiver is 5 V in OFF state (no infrared signal)  and 0 V in ON state (infrared signal received).


You can see how my car works in those videos:

Turning Left:


Turning Right:



Step 1: Design Receiver

I have drawn the circuit via PSpice simulations software to reduce drawing time:


You can use four 1.5 V AA/AAA batteries connected in series to obtain a 6 V supply for the receiver circuit.


Find the maximum and minimum power supply output:

VirPowerSupply = Vs - Vd - VceSatMax - VceSatMax

VirPowerSupplyMin = 6 V - 0.7 V - 0.25 V - 0.25 V = 4.8 V
VirPowerSupplyMax = 6 V - 0.6 V - 0.2 V - 0.2 V = 5 V


Usually, the TTL receiver output fluctuates between 0 V and 5 V. The infrared receiver components that I purchased were faulty. This is why I had to implement a transistor amplifier. Thus you would not need the optional transistor amplifier if your receiver component is worked properly. However, you might need a TTL inverter because remember that the TTL output is 0 V when ON and 5 V and OFF. The transistor amplifier is also useful for motor speed control. The motor speed control will bypass the receiver control.


Step 2: Receiver Simulations

Simulations show that the transistor driven TTL power supply voltage is 5 V as predicted:

The receiver output is above 2 V.


Step 3: Design Motor Driver

You can use four 1.5 V AA/AAA batteries connected in series to obtain a 6 V supply for the motor driver circuit.


Step 4: Motor Driver Simulations

Simulations show that the output transistors are saturating.


Step 5: Make the Receiver

I attached the LED to the output of the receiver.


The LED current is very small for such a big LED. This 10 mm LED needs 20 mA of current, 5 mm LEDs need 10 mA and 3 mm LEDs require 5 mA current.


I asked the authors of the Instructables article:



to ship me their motor driver circuit so that I can use it for my infrared car design to avoid wasting money on purchasing additional components.


Step 6: Make the Car

I used metal wire to attach the motors to foam packaging:


Here is another photo:


Step 7: Testing

An infrared transmitter can be a TV remote control or any other remove control (eg toys or security systems). You can also make your own transmitter with a 555 timer oscillator.


Testing showed the car will work well in open spaces because the infrared receiver on the opposite side was receiving infrared light due to reflections from furniture and nearby walls. However, the car was still able to follow the transmitter.

Turning left:

Turning right:


Conclusion

You can try implementing a different motor driver circuit if your motors have a maximum voltage of 3 V. However, usually, 3 V motors might not have enough torque to move the car.

Also, this circuit is only useful if you are using the same battery power supply for the receiver and motor driver circuits (6 V). Otherwise, you can simply use the circuit with fewer batteries connected in series.


Motor driver 2 simulations:


You can also connect a MOSFET driver directly to the TTL receiver.  However, you will need the right TTL receiver and the right MOSFET transistor. The TTL receiver must saturate to 0 V when it receives the infra red signal. MOSFETs have threshold gate voltages at which they turn ON. This threshold voltage needs to be approximately 2.5 V. Enhancement MOSFET is OFF at zero gate voltage and depletion MOSFET is ON at zero gate voltage. In simple circuits, n-Channel MOSFET sources is usually grounded (negative terminal) while p-channel MOSFET is usually connected to the power supply (positive terminal). and Thus you must not mix them up. Also, it is easy to mix up the pins of MOSFET transistors if you do not have access to datasheets (the base-emitter pins of a BJT transistor are similar to a diode).

You will need to drive the motors with a p-channel enhancement MOSFET, one transistor for each motor. The p-channel will need to be connected to an idea TTL infrared receiver (one that saturates).

This is why using BJT transistors (although they require more complicated circuits) could be a better option for hobby electronics.


Click on this link:

https://instructables.com/Light-Drivers

Comments

Post a Comment