Light Tracker Line Sniffer    

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Easy robots with all the instructions of assembly of the circuits and mechanical (if thus were necessary) so that any can mount it to him without too many problems.




Light tracker

Light tracker

Descripción: Description : The following robot is a light tracker Specifically it designed to such effect and its only task is to find a point of light inside its angle of detection of 180º frontal and to be directed it but quickly possible toward such source of light.

It has 3 sensors of light LDR arranged in angle of 60º the some of the other and put in a horn divided into 3 parts and throws al effect with black pasteboard to avoid that the light environment affect to the good detection of the source of light to find, also has 3 circuits compare analog of tension around operational amplifiers in way comparador and digital logic programmable (by hand) around integrated circuits of the series 74, the driver controller of the motors is an ULN2003 with what is controlled the lit of the two motors independently, al to use the ULN2003 has turn direction control and the wheels in no case will run backwards , by I finalize and to finish with the description, and used a mobile base with direction of turn Differential (type tank) built from 2 kits they motorized 4x4 to scale 1/32 of trucks of mine that markets TAMIYA, like the motors act on the two wheels of a side and joined two trucks and now each motor of each truck acts on a side with what already we have the differential system of direction. The diet of the logical part of control is by means of a battery of 9V and the part of power and motors is by means of the same batteries that brings each composed truck for 2 batteries LR6 of 1,5 V, these two groups of batteries the and connected in parallel to have but current and that be exhausted for an equal the two groups of batteries, as can be deduced the motors they are Of 3V each one and they spend an average of 400mA although the peak of starter is quite high and round 1 Amp.


Operation : Step now to describe the operation of the main circuit of the Robot that contains the composed digital logic by integrated circuits of the series 74xx, the design of the circuit is such that can be planned in a manual way and without having large know-how of digital electronics , by means of wiring between the connectors J7 and J6. In this manner we will be ourselves the ones that plan the attitude of the robot according to the conditions or external events grasped by the sensors, as will be seen but ahead the configuration optima of the programmable part I describe it and cannot be seen in none of the plans, nevertheless will be explained of a complete and very simple form the way to do it and each which will have to be planned the robot Flavor since in this manner will be but satisfactory the assembly of this robot and in transit we will learn a little on simple digital circuits.

Sensors: The following plan sample the circuit utilized to be able to adjust the sensibility or histerisis of the level light to detect and in this way be able to leave out of action to the light environment or other possible sources of light.

The operation of this circuit is like continues; as already we know, the LDR various its internal resistance in function of the light that impacts on her, to but light less resistance and vice versa, if we set us in the previous circuit we will see that what itself to fact is a divisor of simple tension in base to two resistances, one of them is the LDR that varied its value in function of The light and the other is a fixed resistance of 10K, al to vary the LDR of value what will also cause is to vary the tension in the intermediate point between the two resistances, with what already we have a level of proportional tension to the light. Continued what causes he is to compare the level of tension provided by the joint one divisor of tension LDR-RESISTANCE with another variable tension this time obtained of a potenciometro, the operational amplifier what causes is to activate its exit or to defuse it in function of if the values in its positive entrance is equal or greater al of its negative exit, in this way we can adjust the level of histeris That is to say with which most minimum value of light its exit was activated.

As also we can observe, in the exit of the operational amplifier itself to arranged a diode LED to have an indication of visual of the state at the outset of the circuit and in this way be able to adjust easily without external instrument some, also itself to arranged a jumper in the case that we do not want that the leds light up once adjusted the circuit.

The robot is comprised of two identical circuits as this, like each one handles two LDR on the whole serian 4 but as in this so alone case we need 3 sensors LDR we can leave without mounting average part of one of the circuits if thus we believe the convenient ( Although keeping in mind the bajisimo price of the components that form it does not be worth while).

Logic of control 1/2: Here we have the half of the heart of the logical system of control that will be described in two parts as already you will have sensed.

The main problem that was presented me in the design of this robot was the use of 3 sensors LDR since could not do it as simple as if had been with 2 LDR, although neither that to say of the advantages to use 3 sensors in it practices. Therefore well al to think a little and to do some sketchs on role occurred themselves me (what to everyone with a minimum of digital electronics jeje) that 3 LDR equalled to 8 possible states at the outset as a group, well this part already we have it thought, now remains the one that to do with these 8 possible states, in binary form they are not us very useful to be not that we use a microcontrolador or complex system with what the following phase will be to convert the 3 bits binary in 8 independent exits and for such effect we will use the integrated circuit 74LS138 that is a converter BCD-DECIMAL of 3 bits and its OK for this case, the exits of this integrated are pull-up and they are activated to level low (always they are to 5V less when themselves active the exit that Being 0V or GND).

Therefore well this part of the circuit already we have throws it , or almost.. you will have set you in which and placed some trigger schmitt type 74LS14 in the entrances , therefore well this due to that the operational amplifiersLM358 do not give but that 3,3 V to its exits and if them to direct directly al 74LS138 this neither would be informed of the logical levels and would take all as 0, there are other that they give to their exit the same thing that their diet but good this already this I throw and functioning:)

Logic of control 2/2: Therefore well here we have the second part of the circuit of control and the problem now is that we have 8 exits of the 74LS138 and alone 2 motors that to act, so they exceed us some as many exits not?, and as we are going to be able to do that in a determined state of entrance such motor be activated?

We are going to analyze it now of the reverse, we have 2 motors, the control that are going to have on them is going to be such that Alone we can activate them or to defuse them in a direction with what to rotate the robot will maintain a side braked while the other wheels rotated (as a tank) the radio of turn of this system is but large that causing rotating a side in a sense and the other side in another sense , but like is but simple we will use the first thing. To control the motors we will use an integrated circuit driver I specify for model motors ULN2003 that is sufficient for small motors of toy store. Well now we have it asi; the motor has 2 cables, one of them we carry it to Vcc and the other we cause we pass it for the driver that acted as a switch and activated or not the motor, now we have 2 cables for the control of the 2 motors, 2 cables are 4 possible states; Ahead, right Turn, left Turn , Stopped, in this manner we have a simple control of all the possible Actions of the robot.

To solve the problem presented previously on the 8 exits and the 2 motors.. therefore nothing but easy that an encoder of priority or converter Decimal-BCD, in this case a 74LS147 that has 9 independent entrances and a binary exit of 4 bits equivalent to the active entrance, for activate the motors we will use (just as is seen in the plan) only the exits TO and B, the entrances Of priority they have placed to pull-up by means of resistances and they were activated to level low, we recall that the 74138 activated their exits to level low also, with what the 2 integrated they adapt among if to the perfection.

In the plan also we can see the regulator of tension around a 7805 that to regulate to + 5V the + 9V obtained of the battery that feeds the circuit.

Assembly : The robot is evident on the whole of 3 plates of printed circuit , two for the sensors and a with the logic of control , connected among if just as can be seen in the following figure:

The following part that we have to cause is a species of horn Plan of 180º on the whole divided into 3 sectors to 60º where we will locate the LDR. just as can be seen in the photo of the right. In my case the central sector it and tightened with you throw of black pasteboard for thus have a better detection of what really is the front (in this photo they are not put such throw). This it should be tested on the march once the robot already function and we do different tests.


Programming: They Arrived at this phase I suppose that already you will have mounted the robot completely and alone the programming of the circuit remained you.

The board of the truth of the integrated circuit 74LS138 is the following one:

Input Output State of the sensors
C B A /Q=L
0 0 0 1 Light in all
0 0 1 2
0 1 0 3
0 1 1 4
1 0 0 5
1 0 1 6
1 1 0 7
1 1 1 8 Total darkness

And as it can be seen each combination of entrance of the sensors LDR equals to that one of the exits of the integrated take the logical value low. We will keep in mind for the programming that the signs originating from the LDR are invested al to pass for the trigger schmitt with what in absence of light we will grasp all the entrances to high logical level. As it can be seen there are two fields filled pertaining to darkness and light in all the sensors, the others they owe to fill them each which since in this manner will be but amusing and satisfactory the work. The numbers at the outset equal to each pin of the connector J7 of the circuit of control.

In the following board of the truth we can see the equivalent one al integrated circuit 74LS147 encoder of priority, that as we see removes an equivalent binary value to the entrance that has put to level low.

/input /output
1 2 3 4 5 6 7 8 9 D C B A Description.
1 1 1 1 1 1 1 1 1 1 1 1 1 no input
0 1 1 1 1 1 1 1 1 1 1 1 0  
1 0 1 1 1 1 1 1 1 1 1 0 1  
1 1 0 1 1 1 1 1 1 1 1 0 0 Stop
1 1 1 0 1 1 1 1 1 1 0 1 1  
1 1 1 1 0 1 1 1 1 1 0 1 0  
1 1 1 1 1 0 1 1 1 1 0 0 1  
1 1 1 1 1 1 0 1 1 1 0 0 0 Stop
1 1 1 1 1 1 1 0 1 0 1 1 1  
1 1 1 1 1 1 1 1 0 0 1 1 0  

As we can observe the exits C and D are represented in a color but dull since in they are used in this assembly for nothing and do not they keep in mind themselves. Also we can observe that is not filled the description of what will do the motors in all the possible cases and as in the the previous board will be task of each one to ascertain it:) although in this case is but easy since having the circuit fed and testing with a cablecito connected to mass we will be able to see what do the motors each time that puncture the cable in a position Of connector J6 (care of put not but of a cable to mass or to do contacts among pines adjacent). The first position whose description is "all al air" corresponds al case in which we have no calecido placed and be all the pines of J6 al air with what in reality will be to Vcc by the resistances of polarization and therefore the two motors will move toward before. (if they did it backwards serious a problem of the wiring of the motors and there would be that to invest the these to invest the turn of these)

I believe that is quite easy to find the combinations to plan the robot and that do what we want but of all forms if someone found too many complications he can be put in contact with me and the form he would send him but correct of operation.


Plans for the construction of the horn

Printed Circuit Boards

Video of operation (2.5 Mb) Codec Divx.5





Line Sniffer

Line Sniffer

Description : I Have here a design super Simple to mount a rastreador of basic lines with 2 sensors CNY70 and discrete components of easy purchase in any commerce of electronics.

In the plan shown can be appreciated like the circuit functions, the led transmitter of the sensor CNY70 is fed through a resistance R1 of 680 Ω, when a surface reflectante as the white color of the surface by where will move the rastreador , reflects the light of the led transmitter, the fototransistor contained In the sensor CNY70 low its internal resistance between Collector and Transmitter with which conducts the current that does that also among in conduction the transistor Q1 that was polarized to mass through the resistance R2 of 10 KΩ. Q2 serves to invest the sign so that in this way be defused the motor when sees white and be set in motion when sees black the sensor, with what al to be activated Q1 does that be activated Q2 cutting to Q3 with the, since this I finalize was assets because this polarized by R3 , with which what to past is that the exit of the motor itself to When the sensor to detected a surface reflectante, in state of rest the exit will be always active and Q3 conducting. The 2 circuits can be fed with 4 normal batteries of 1,5V put in series with what are obtained 6V, will depend on the consumption of the motors to elect batteries or batteries but powerful.

Assembly : The robot will be composed of a circuit that we will be able to do easily with a plate of topos or of prototypes or using the fotolitos exposed and this will have two circuits exactly equals one for each

sensor-motor and Iran crusaders with what the left sensor acted on the right motor and the right sensor on the left motor such As it is shown in the illustration.

The motors have to be of direct current and there will be that to manufacture them a reductor if they do not have she to move the wheels, against but large be the wheels, but velocity reached the robot, although not one must pass with the diameter of these because if not in the curves path will leave, some 6 cm. is the ideal thing.

The sensors Iran arranged looking at al floor and to some 2 or 3 mm of separation since the floor to the surface of the sensor and the separation among both sensors will be so that remain inside the black line that we be going to use as path. In my assembly I have utilized two servos trucados so that they remain alone the motor CC with the reductora osea without circuit of control but any motor can be used of CC of some 5 or 6 volts and that does not consummate too much for exhaust not the batteries or batteries too much fast. The layout we will be able it to do on a white pasteboard and to draw the lines to use black insulating tape, to be careful in do not curves too much closed since if the robot is very fast (large wheels) will leave the path by inertia and al to remove the 2 sensors out of the line will not enter again (we recall that this system is not microcontrollated) for which we will do some tests before To draw the final road.

Operation : we Will Put the robot in the surface of white fund and we will feed it, as the two sensors are assets the motors they will remain stopped , now we will push the robot to the line of black path, al to enter one of the sensors with the black line this will do that the motor of the contrary lake harms to function with what the robot entered for if alone in the path, when have the two seeing black the 2 motors will be in motion with what the robot advanced in straight line, now well if the arrives at a curve and we suppose that the left sensor leaves the black line then caused that the motor of the contrary side (motor right) is defused with which the robot rotated to right (as a tank) entering of this way in the black line again ... for Contrary case passes the same thing but with the other motor and sensor.

I expect enjoy this simple design.. I believe that is one of the but simple that there is right now by internet by say not the but easy:)


eschematics and circuit board

Video of operation (1.72 Mb) Codec Divx.5







Robotica & µControladores Pic


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 Daniel C. Martin "ionitron" ··· Barcelona (Spain) ··· 2001-2006