In today's article we will be able to view multiple applications together to achieve a common goal. A PWM control working 1Khz a LED Blinker , an alert sound (BEEP ), a servo with which to position a powerful set of 36 white LEDs and LED Dimmer to adjust to will light intensity achieved by this source. This development is part of a collaborative project and includes the lighting that will carry a quadricopter (Quad ). Turn signals and intelligent to fly at night and attend this mode transmission system image in real time. Do you like the idea? Watch as we do, we invite you to share the design of this part of the aircraft you see flying here in arg.
Among the thousand and one details that we need to consider when designing a quadricopter find the possibility (sometimes necessary) to provide the development of an illuminated to enhance the possibilities of night flights or low ambient light conditions. A scenario of this kind can occur in the most unexpected time and place and is good to take precautions before regretting this weakness on our ship. In addition, the availability becomes mandatory when using an accounting system transmission of real time images mounted on the engine. But we must be very cautious and careful about everything interesting that we can add to our aerial platform: every screw that we use means " added weight" and that will be noticed in the other when making quick maneuvers or abrupt. If we are guided by our enthusiasm, and added everything that crosses our mind, is likely to achieve our quadricopter not even off the ground.
Peel and the first flight is a challenge
To avoid any headache during the flight tests, it is best to think before construction, practical and effective way of doing things. Of course, the lighting will be based on diodes LED to be mounted on plaques phenolic material. Despite understanding that fiber (FR4 ) plates would look more professional to be evaluated as mentioned at the beginning elementary: total weight increase too for the sake of maintaining a constructive aesthetic . A well-designed work will be as functional and effective in a material or other support. The same applies to the anchor plates. We could have taken an aluminum plate the size of the PCBs that support LEDs while the election was directed toward a small rod of this lightweight material. Ie we support the same function with less than half the weight as possible . Also, do not expect to achieve a strong, impact resistant because we do not expect exactly that impacts. Finally, a servo common feature closes this set with two brackets in the form of "L", also in aluminum. Look at the construction we have adopted in the following video:
We may add, to what we have seen in the video, a better structure might be more solid and reliable, but we must not forget that this advantage we backfires, added weight. It is worth remembering also that the lighting and image transmission system in vivo are not essential to the functioning parts of a quadricopter . We can fly without them or we can build an SUV without lighting or video, but experience to have these "additional " is unique and exciting. Therefore, abandoning the preambles, and moving on the desired system performance, we will address first the overall functioning of the whole and then finished by explaining the prominent features of each particular section. The heart of the system relies on a powerful PIC 18F25K20 which will work as I2C slave at the final moment, when everything is finished. It is for this reason that in the block diagram shows the connection to the bus. Taking advantage of the possibilities offered by the MSSP module , we have seen in the assembly of a display I2C coupled our system, " slave" to the I2C bus main control system of the ship. Thus, we can operate the lights and camera quadricopter from the same system to be used to command the ship.
Basic scheme of assembly carried
Using the PIC as I2C slave be very simple instructions and acted upon a job running which is determined by the times that can handle the main processing system. For now, and before working on the flying drone , use simple soft buttons until you have tested the behavior of full development. This design includes, in the first part we will see today, the movement of a servomotor between two extreme positions and the operation of a MAX16805 PWM using generated by the PIC to control light intensity the main LEDs. When the servo reaches end of travel or the time when the PWM cause low maximum light or a Beep! sound accompanied by flashing a LED (we chose a yellow for now.) The Beep sound can be single or double according to our taste and will only be used at this stage test. In the final assembly will be only the LED indicator will be seen at a distance and the sound of the beep is not very useful there, above the nave. Therefore, to reach the Beep beep ends and will continue once every 10 seconds, indicating that we are working on one end. Coming out of this situation, the Beep is silenced and the LED will not flash more. Observe:
As you observed, up to a 16X2 LCD we have placed on the port B of the PIC to make the task simple initial programming. Of course the code, you'll find at the end of the article, including the LCD so that you too will be easy to work (very useful for control the value of the variables used). Thus, in one assembly met many circuits we have seen separately in arg, but in this development all form a single, with a specific aim: to illuminate the extent necessary, the night journey our ship of exploration. Then recall some fundamental concepts. The MAX16805 in charge of managing the lighting of the 36 white LEDs 10 mm., PWM receive signal at a frequency of 1 kHz. and by varying the duty cycle will adjust the light intensity. For this we use the ECCP module who owns the 18F25K20 and connect the output of channel 1 PWM (CCP1 ) located in PORTC.2 arrive at the entrance of the MAX16805 DIM through a small resistive divider as shown in the following scheme . The rest of the connection required to activate the MAX16805 is the same as we saw in the article Dimmer with Rsense of 1 Ohm and its main power 12Volts.
Circuit used in this trial
For the movement of LED panels, as already announced and we saw in the videos, use a conventional servomotor (in our case, a Hitec HS-311) to which we feed 5Volts. These 5Volts also use for the adapter formed impulses to activate the servo control signal. Trivia: During the start of the trials observed erratic movements in the servo to the direct instructions from the PIC is powered with 3.3 volts. Although the technical talk that the servo can work with pulses from the amplitude 3Volts decided to put an adapter levels (3.3 V 5V). After this, the servo response was always correct and accurate.
Distribution feeds tested
These feeds 5Volts 12Volts and is complemented by a 3.3-volts, which is destined to PIC and the circuit is that we show in the picture above. It is worth mentioning that for convenience and technical practice, we refer to 12Volts stress values \u200b\u200balong the entire explanation, but to be more precise we should clarify that batteries used in radio are the Lithium - Polymer ( Li-Po) of three cells that have a rated working voltage of 11.1 volts. For practical purposes, the voltage delivered is as effective as if we were working with a battery Lead-Acid of 12Volts. In addition, all tests were done with these batteries and for this reason that throughout the text and the circuit shown, the supply voltage is referred to 12Volts. It is important to clarify this issue to know when riding all over the ship, the available voltage shall be that of 11.1 Volts.
The trial and fundamental parts
The program developed for the PIC is very simple and is based on generating a set of conditional statements which question the entire time the keyboard. Of course, when we come to work in slave mode I2C this situation will change dramatically, but while we perform the tests, 4 soft touch buttons did the work to activate the mobility and lightness of the system. Returning to the protruding parts microcontroller program highlight the main loop constant attention to the potential action buttons. In case of detection, the program executing powerful instructions provided by Amicus to operate servo PWM outputs and . In the case of the servo, an indication of the output pin and the desired position. The latter value is between 500 and 2500 by type of servo used and the desired stroke length. In our case, the limits were 975 and 2140. The management and PWM generation is just as simple through a single statement, as in the case of the servo, you just have to define the cycle work (Duty-Cycle ) ( PVVM ) and the desired working frequency ( fPWM ). These values \u200b\u200bare obtained variables, each touch of a button, increase or decrease the variable unit employed. That is, generating a PWM control a servomotor and activate your job from four buttons is a task that Amicus allows you to summarize it in 20 lines of program. Thus:
main loop status polling of the buttons
Another interesting part to watch is the generation of Beep. Do not forget that this sound will be accompanied by the activity of a diode LED (in this case yellow) and both indicate that the variables for the PWM servo and reached their maximum or minimum value. "Why a yellow LED ? Because the drone will be full of red and green LEDs performance indicators of different stages, hence the yellow LED may be varied smoothly and effortlessly you will notice the operating state of the lighting system. To generate the Beep then only need a single instruction on a single line of program: FREQOUT . Then the on / off LED indicator complete "audio-visual "
FREQOUT instruction, useful to trigger sound alerts
Finally, another sequence of instructions useful and effective are those that are responsible for generating the delivery of a beep every 10 seconds when any of the variables reaches its extreme value . Using a simple code, implementing a delay 10 seconds, then turns the LED , Beep is issued, you control the keyboard and closed loop program. However, 10 seconds would be held in a time-delayed " useless" while the situation may require some movement or change in intensity of light before they are completed within 10 seconds. For this, an elementary For-Next loop solve this scenario to be mindful of every moment of the action of the keyboard, although we are within the counting time of 10 seconds for Beep . Does the TMR0 ? No, this:
be useful for routine attentive during a timeout
In line 93 conditional verify the activity of the buttons every 2 milliseconds (the duration of the delay) and if any are active GND, I leave the For-Next loop and I go to the instruction that I needed at that time. The instructions " OR " equivalent to what we know as "or" in our English. This "or" one. Today "or" tomorrow. That is, if one of all controlled inputs has a logic low, the program shares routed to the code where change has occurred in states. In our example the action of pressing a button on the final development will be a statement received by the I2C bus . The rest of the CIP program are variable declarations, assignment of initial values \u200b\u200bto these variables and, with these values, determine a starting position set by the servo and a level of enlightenment, also original, through the PWM MAX16805 .
This will complete the development phase and initial test the lighting module of quadricopter . The next phase will be doomed to start working with the I2C bus from another microcontroller and lay the foundation of communication and the operation of PIC 18F25K20 in slave mode. After completing this process, the challenge will to optimize the energy . Then, the weight reduction in construction of bounded size will result in the final step: mounting the camera on the same arm that manages the LEDs ( Or in another set of independent servos?, Do you think? ) and the TV transmitter that deliver live images of every flight, every adventure. Want to be part of this experience? Join the Electronics Forum arg; works by providing advice, suggestions and ideas to this part of development. Would you do it otherwise, how?, Why? Tell us your opinion matters. Source
+ large circuit Download
Source:
http://www.neoteo.com/led-control-pwm-servo-y-led-dimmer
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