light tracker

7/28/2019 Light Tracker

1/8

Light tracker

Light trackerDescripcin:Description : The following robot is a light tracker

Specifically it designed to such effectand its only task is to find a point of

light inside its angle of detection of 180

frontal and to be directed it but quicklypossible toward such source of light.

It has 3 sensors of light LDR arrangedin angle of 60 the some of the otherand put in a horn divided into 3 parts

and throws al effect with blackpasteboard to avoid that the lightenvironment affect to the good

detection of the source of light to find,also has 3 circuits compare analog of

tension around operational amplifiers inway comparador and digital logic programmable (by hand) around integrated

circuits of the series 74, the driver controller of the motors is an ULN2003with what is controlled the lit of the two motors independently, al to use the

ULN2003has turn direction control and the wheels in no case will runbackwards , 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 theymotorized 4x4 to scale 1/32 of trucks of mine that markets TAMIYA, like themotors act on the two wheels of a side and joined two trucks and now eachmotor 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 abattery 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, thesetwo 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 of400mA although the peak of starter is quite high and round 1 Amp.

Operation : Step now to describe the operation of the main circuit of theRobot 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 manualway and without having large know-how of digital electronics , by means of

wiring between the connectors J7 and J6. In this manner we will beourselves the ones that plan the attitude of the robot according to the

conditions or external events grasped by the sensors, as will be seen butahead the configuration optima of the programmable part I describe it andcannot 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 theassembly 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 adjustthe sensibility or histerisis of the level light to detect and in this way be ableto leave out of action to the light environment or other possible sources of

light.
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdf


2/8

The operation of this circuit is like continues; as already we know, the LDRvarious 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 wewill see that what itself to fact is a divisor of simple tension in base to tworesistances, one of them is the LDR that varied its value in function of Thelight 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 betweenthe 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 withanother variable tension this time obtained of a potenciometro, the

operational amplifier what causes is to activate its exit or to defuse it infunction 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 withwhich most minimum value of light its exit was activated.

As also we can observe, in the exit of the operational amplifier itself toarranged 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 externalinstrument 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 handlestwo 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 thecircuits if thus we believe the convenient ( Although keeping in mind thebajisimo 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 logicalsystem of control that will be described in two parts as already you will have


3/8

sensed.

The main problem that was presented me in the design of this robot was theuse of 3 sensors LDR since could not do it as simple as if had been with 2LDR, 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 roleoccurred themselves me (what to everyone with a minimum of digital

electronics jeje) that 3 LDR equalled to 8 possible states at the outset as agroup, well this part already we have it thought, now remains the one that todo 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 thefollowing phase will be to convert the 3 bits binary in 8 independent exits andfor such effect we will use the integrated circuit 74LS138 that is a converterBCD-DECIMAL of 3 bits and its OK for this case, the exits of this integratedare 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 operationalamplifiersLM358do not give but that 3,3 V to its exits and if them to directdirectly al74LS138this 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 thingthat 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 74LS138and 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 controlthat 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 willmaintain a side braked while the other wheels rotated (as a tank) the radio ofturn of this system is but large that causing rotating a side in a sense and the
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74LS14.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/LM358N.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/LM358N.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74LS14.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/LM358N.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdf


4/8

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 motorsULN2003 that is sufficient for small motors of toy store. Wellnow we have it asi; the motor has 2 cables, one of them we carry it to Vccand 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 2motors, 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 therobot.

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 binaryexit 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 Ofpriority they have placed to pull-up by means of resistances and they wereactivated to level low, we recall that the 74138 activated their exits to levellow 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 toregulate 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:
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74ls147.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/uln2003.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74ls147.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdf


5/8

The following part that we have to cause isa species of horn Plan of 180 on the

whole divided into 3 sectors to 60 where

we will locate the LDR. just as can be seenin the photo of the right. In my case thecentral sector it and tightened with you

throw of black pasteboard for thus have abetter detection of what really is the front (in this photo they are not put suchthrow). 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 willhave mounted the robot completely and alone the programming of the circuit

remained you.

The board of the truth of the integrated circuit 74LS138is the following one:

Input OutputState 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 LDRequals to that one of the exits of the integrated take the logical value low. Wewill keep in mind for the programming that the signs originating from the LDRare invested al to pass for the trigger schmitt with what in absence of light we
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74138.pdf


6/8

will grasp all the entrances to high logical level. As it can be seen there aretwo 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 andsatisfactory 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 integratedcircuit 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 ADescription.

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 Stop1 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 dullsince 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 ofwhat will do the motors in all the possible cases and as in the the previousboard will be task of each one to ascertain it:) although in this case is buteasy since having the circuit fed and testing with a cablecito connected tomass we will be able to see what do the motors each time that puncture thecable in a position Of connector J6 (care of put not but of a cable to mass orto 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 beall the pines of J6 al air with what in reality will be to Vcc by the resistancesof polarization and therefore the two motors will move toward before. (if theydid it backwards serious a problem of the wiring of the motors and therewould 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 thatdo what we want but of all forms if someone found too many complicationshe can be put in contact with me and the form he would send him but correctof operation
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74ls147.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/74ls147.pdf


7/8

Line Sniffer

Line SnifferDescription : I Have here a design

super Simple to mount a rastreador of basiclines with 2 sensors CNY70and discretecomponents of easy purchase in anycommerce of electronics.

In the plan shown can be appreciated likethe circuit functions, the led transmitter ofthe sensorCNY70 is fed through aresistance R1 of 680 , when a surfacereflectante as the white color of the surface by where will move the rastreador

, reflects the lightof the ledtransmitter, thefototransistorcontained In thesensorCNY70low its internalresistancebetween Collectorand Transmitterwith whichconducts thecurrent that does

that also amongin conduction thetransistor Q1 thatwas polarized tomass through theresistance R2 of10 K. Q2 servesto invest the sign so that in this way be defused the motor when sees whiteand be set in motion when sees black the sensor, with what al to be activatedQ1 does that be activated Q2 cutting to Q3 with the, since this I finalize wasassets because this polarized by R3 , with which what to past is that the exitof the motor itself to When the sensor to detected a surface reflectante, instate 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 obtained6V, will depend on the consumption of the motors to elect batteries orbatteries but powerful.
http://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdfhttp://personal.telefonica.terra.es/web/x-robotics/downloads/datasheets/cny70.pdf


8/8

Assembly : The robot will be composed of a circuit that we will be able todo easily with a plate of topos or of prototypes or using the fotolitos exposedand this will have two circuitsexactly equals one for each

sensor-motor and Irancrusaders with what the leftsensor acted on the right motorand the right sensor on the leftmotor such As it is shown in theillustration.The motors have to be of directcurrent and there will be that tomanufacture them a reductor ifthey 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 diameterof these because if not in the curves path will leave, some 6 cm. is the idealthing.

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

Operation : we Will Put the robot in the surface of white fund and we willfeed 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 thesensors with the black line this will do that the motor of the contrary lakeharms to function with what the robot entered for if alone in the path, whenhave the two seeing black the 2 motors will be in motion with what the robotadvanced in straight line, now well if the arrives at a curve and we supposethat the left sensor leaves the black line then caused that the motor of thecontrary 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 passesthe same thing but with the other motor and sensor.I expect enjoy this simple design.. I believe that is one of the but simple thatthere is right now by internet by say not the but easy:)

light tracker

Documents