robot brain diagram

Robot Brains Circuit and Theory

All robots have brains, even the insect size ground rovers do a remarkable job of negotiating rough terrain with nothing more than a few switch sensors. These small robots are fun to construct and demonstrate basics of robotics.

robot circuit breadboard

Advanced robot brain

More advanced robots have something called non-sensory activities. These activities are programmed and are performed in a given order or agenda. To accomplish this it is necessary to sequence the order of duties. What is required of such a sequencer is quite demanding. Aside from basic functions (Moving, avoiding collisions, negotiating terrain), there are a number of complex processing commands that the sequencer must accommodate.

  1. Any non-sensor unit must be allowed to hold the clock count until the normal processing function is complete.
  2. There must be an access allowing any non-sensor activated unit to advance the clock count to the next stage.
  3. The sequencer must provide any non-sensor unit to reset the clock count.
  4. The sequencer must provide the ability to change the order of the functions performed.

These four elements assure that the robot is efficient and performs procedures in the proper order. The brain described here has access ports to advance to the next stage, to hold the stage, to reset the clock and even control the speed of the clock. A sequencer chart has been provided to show the operational relationship between the clock and the 4017-decade counter.

robot brain diagram

Flow chart

A flow chart has also provided to illustrate the function order of operation. Two power supplies are necessary to keep the glitches, created by motors or other high current drawing components from interfering with computer function. Since no robot operates continually, an external switch system can set predetermined operation time. Both a master switch and a sound operated switch should be included. A sound switch gives the robot a sense of hearing and makes it more connected to the world around. Light switches will also make your robot more responsive to the surroundings.

Although a 10-stage sequencer is used, only 5 are required for the prototype robot, so the stages are doubled up. Stage 1 is head control and moves the head from side to side. Next is the mobility base, which enables your robot to get around. Besides feeler switches, the mobility base should also have three visual sensors, a left and right sensor and a ground continuity sensor. This last sensor was installed after a very expensive robot fell down a flight of undetected stairs. A ground continuity detector is illustrated to detail this lifesaver. Light display is little more than a fancy display element but we all want our robots to look impressive.

The arm system is next on the sequencer list and is driven by its own computer and sensor system that should be capable of suspending the sequencer count until the arm and manipulator have completed their task. Stage five of the sequence is a voice and again can be some kind of voice recorder but I personally prefer a random tone generator, which seems more interesting. Three voice altering elements can give the voice enough variety to keep it interesting. First is a voice sensor that stops the chatter when it hears loud sounds. A proximity detector that makes it aware of people and light sensors that control the quality of the voice.

Pictorial diagram

A 22 terminal, edge connector computer board was selected for the primary board. The clock trimmer and timing access port enable any device connected to determine basic drive speed


the brain, to hold the clock until the prescribed duty is performed. The 4001 quad nor gate was chosen for the clock drive because of its versatility. It can also be advanced by an external signal, and it can be reset by an external signal. Sequencer duties were assigned to the 4017-decade counter because of its stability as well as its versatility. The custom programmer is nothing more than a hard link between the sequencer and the drive unit.

Operation pulse chart

operation pulse chart

It can, however, provide a different order of sequence (With different custom modules), and with a ribbon assessed device, be expanded to more advanced programming units. Since the circuit board is a computer type, it can be easily removed and tested. A distribution barrier strip is used with the edge connector to assure maximum flexibility when adding new circuitry.


Relay 1 applies a 6-volt lantern battery to the main mobility drive motors. Obstacle sensing and ground continuity circuitries are a part of the mobility base. The 10-stage display indicates which mode of operation the computer is in at a given time. Relay 2 controls the head movement, which, in the prototype, is just to enhance demonstration, as is the light display. More elaborate modules can be added, as you become more familiar with the brain.


Nothing unusual or fancy is required in the construction of this circuit and you should of course observe good circuit building practices. Because of the complexity of the circuit it is a good idea to come to the project with some wiring experience. All ICs are mounted in sockets as well as the 10-stage programmer and relay number 1. Stages 5 through 9 are fed to access ports that can be distributed as you see fit. All transistors and relay 2 are soldered to assure reliable operation.

robotic brain schematic


Access ports enable units to control their own operating time. Added circuitry can take the form of remote controlled cameras, arm and hand manipulation control, or any other circuitry you can imagine.

P-T 100 Programmer

A programmer IC is provided for the purpose of selecting the desired circuits and the order of performance. The P-T 100 is a device that is constructed from an IC sized circuit board and small staples. When the circuit was completed, it was placed in a small mold filled with sealing wax to form a workable package. Empty IC shells are also available at your suppliers, which can make this process simpler. Make sure that when you make several of these programmers that you label them to indicate the different functions.

Another programming device can be made by attaching 10-conductor ribbon cable to each side of an IC shell that leads to a more expansive interface. A few of the expanded functions are remote control function, camera, remote controlled arm, and alarm and timed surveillance. This makes your brain uniquely versatile and capable of continual upgrading and expansion.

t-100 programmer types


The sequencer is easily tested. Just apply a 9-volt power source to the operating terminals of the unit. Turn the speed trimmer to a fast rate and the ten stage LED display should advance at a rapid rate. Slow the speed and check the voltage at the output terminal of each function. Stages that activate relays can be heard clicking. A positive probe can be used to trigger the port access to see if they are responding

Event cycle

An event cycle timer determines how long the robot is active. It can be set to provide one cycle or several, what ever you need. Resistors R2 and R3, and capacitor C1 will provide several

event cycle times sound switch

minutes of operation, but if you require more or less time than the circuit can provide, just change the value of any or all of these components. Keep in mind that you may need to spend some time experimenting if you need an accurate time base. A bypass switch should also be included to accommodate specific duties.

light switch

Sound switch

A sound switch allows the robot to respond to sounds around it. When the robot detects a sound it resets the sequence. To customize the reactions and make your robot more sophisticated you may program the sound switch to activate any of your input ports. A bypass switch should also be included to focus attention when important functions must be completed.

Light switch

You may want a light sensor to activate your robot. This kind of triggering, when combined with an alarm system, is useful for sentry robots and is effective as a deterrent against burglary.

Head control

Head controls are primarily designed to aim cameras or light sensitive devices. Remote control devices can be auto engaged to enable the operator to observe dangerous situations, such as bomb defusing.


Robots controlled by this type of sequencer can operate independently, by remote control, or by a combination of both. With input ports like advance, hold, and reset, any remote control system combined with the right custom programmer, can be easily adapted to operate the robot. Very elaborate systems can be controlled with the

Arm systems

There are many arm systems that can be adapted to the brain. Even arms with complex sub-systems can function as long as the proper arm programmer is in place.

Voice system

For the prototype, the voice was just a series of tones controlled by three different input ports. This arrangement was primarily a demonstration element, but other systems such as alarms or instruction voice can be used.

Light display

The flashing lights in the prototype, signifying nothing, were also used for demonstration purposes. More informational light displays can be substituted.


Robot configurations can be programmed in an infinite variety of functions and duties. Despite the simplicity of this circuit it is so versatile that a large number of sophisticated function circuits can be operated because of the sequencer-input facility. You can determine the way your robot will function. Almost anything can be added, your own response sensors, work functions, surveillance cameras, and with Hall effect motors it can even be used in hazardous conditions, such as explosive gas environments. Whatever your choices, you will be able to produce a robot with sophisticated capabilities that you can modify to accommodate today’s needs as well as tomorrow’s.

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