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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Multi-command remote control device on a microcontroller for pyrotechnic shows using electric igniters. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Microcontrollers The proposed multi-command remote control device was developed for pyrotechnic shows using electric igniters. Possessing undeniable advantages over bulky wired remote controls, it is, however, not inferior to them in terms of reliability, thanks to the use of modern element base and digital signal coding. Obviously, the scope of such devices is very wide. The remote control consists of a transmitting part and eight receiving parts (30 commands each). Fireworks are controlled from a standard PC keyboard connected to the transmitting part of the remote control. The transmitting part is equipped with a display for displaying the current mode of operation and the numbers of executable commands. There are LEDs (2 pcs) on the front panel of the transmitter. One is the transmitter power amplifier on indicator, the second is the low battery indicator. If the distance between the receivers and the transmitter does not exceed 20-30m, it is possible to work with the power amplifier turned off. In this case, the current consumed by the transmitting part will be 50 mA. If a longer range is required, the power amplifier must be turned on (on the keyboard it is F12). In this mode, the current consumption will be 150mA. Confident work was observed during tests at a distance of about 1 km in open areas. The radio channels of the device operate at relatively high frequencies - 166,7 MHz (channel 0). The convenience of these frequencies is obvious: with small antenna sizes (40 cm) and low transmitter power (0,3 W), a "decent" range of confident operation is achieved. The device has 10 frequency communication channels, as in a radiotelephone or radio station. The transition from channel to channel is carried out by pressing the F11 key. When switching to the next frequency channel, the receivers react with a "running fire" on the bottom row of LEDs, for clarity of command execution. To stabilize the frequencies of the local oscillator and the master oscillator of the transmitter, frequency grid synthesizers were used, implemented on Sanyo LM 7001 microcircuits, which have proven themselves in many designs at frequencies even higher than the passport ones for this microcircuit. Each of the receivers is provided with a low-frequency monitor (not shown in the diagram) to assess the noise environment at a particular place of use of the device by ear. Modes of operation
Setting
When all the boards are correctly assembled and not yet soldered into their places in the "motherboard", it is advisable to make an approximate adjustment of the transmitter master oscillator and the receiver local oscillator. By applying + 5V to leg 4 of the MC3361, connect the ULF to its ninth leg and make sure that there is noise from the frequency detector. By twisting the core of the phase-shifting circuit, the maximum noise value is achieved. Moreover, the adjustment range of the core should allow you to get the maximum noise approximately in its middle position.
Next, measure the frequency of the local oscillator of the receiver. Until the synthesizer is "flashed" with the controller, the frequency will be very unstable. By selecting the capacities marked in the diagram *, an approximate value of the frequency meter readings is achieved at a level of about 155 MHz. During rough tuning, you should not touch the turns of the local oscillator coil, but you can temporarily solder a capacitance of 1-7 pF in parallel. Then the controller, filter and display boards are soldered into the "motherboard". If everything is correctly assembled and the processor is "flashed", the "running fire" command is initiated on the display board. This test command will be executed every time the power is turned on at the receiving end. Next step. Carefully, on long wires, solder the receiver board with midrange to the "motherboard". Measure the voltage at the test point (2,5+/- 0,5V). Once again, adjust the local oscillator, selecting more accurately the capacitances of 68 and 39 pF until the desired voltage appears. The final adjustment is achieved by pushing the contour turns apart. At the same time, it is undesirable to leave a trimmer capacitor in parallel with it, because with the slightest change in its capacitance (temperature, impact), the local oscillator will leave the PLL capture area. Shielding is a must. We repeat the same procedures with the midrange transmitter with the only difference that the indicator of the normal operation of the controller and other nodes of the "motherboard" of the transmitter will be "0 0 0" on the display and the sound from the piezo emitter. We turn on the keyboard in the slot and make sure that when you press the keys, their numbers are displayed on the display. The display power supply is about 1,3V (it is selected according to the absence of illumination of extra segments). When the midrange of the transmitting part is tuned (at the control point 2,5V +/- 0.5V), set its frequency to 166,7 MHz by accurately selecting the capacitors near the 7,2 MHz quartz marked *. We turn on the receiving part and tune exactly to the transmitter signal (by selecting the same capacitances, only on the midrange of the receiver), controlling the disappearance of noise from output 9 of MS 3361. We carry the transmitter away from the receiver until the receiver makes noise. We adjust the matching loop for connecting the local oscillator with the mixer according to the maximum possible loss of noise. Press any of the alphabet keys on the keyboard. We hear the code in the receiver. We adjust the phase-shifting circuit until the sound distortion disappears, while simultaneously reducing the modulation amplitude in the transmitter. Then set the modulation level to normal, undistorted sound from the receiver on pin 9 of the MC3361. The final adjustment of the receiver is made by adjusting the turns of the URF coils for maximum sensitivity with the antenna turned on (quarter wave). During this setup phase, the transmitter power amplifier is turned off all the time and no antenna is connected to it. Next stage. We control the sound at pin 7 of the LM358 (second order filter output with a resonant frequency of 1,5 kHz). This is the pilot tone frequency generated by the transmitter. The filter does not need to be configured. On the 7th leg of the filter, half the supply voltage (2,5V) must be present during the absence of a signal. When the transmitter is off, the frequency noise after the filter is barely audible, and 1,5 kHz pass with an amplitude of 0,5 V. Next, we check the sound at the "control" port. This is the digital output of the processor's internal comparator. The sound should be clear even if approximately 50% noise is heard along with the code. At this time, the LEDs on the indication board should light up, according to commands from the keyboard of the transmitting part. The processor comparator is software-configured to 2,55V. The reference voltage is taken from the power rail inside the chip. Therefore, if ROLL 5A allows the voltage to drift in either direction, the reference voltage will also change. The main condition is that the filter and the controller are powered by the same bus, then they will "drift" together, which will not affect the comparator response threshold. Pay special attention to the 22k resistors that form the artificial midpoint for the LM358, they should be identical. By selecting a 120k resistance connecting the 9th leg of the MC3361 and the filter input, the comparator achieves the maximum response when the signal passes through noisy conditions. However, you should not reduce the resistance too much. A reasonable compromise is the periodic occurrence of "ones" on the control port (approximately 1 time in 3 seconds) due to RR noise when the transmitter is turned off. Amplifier Before tuning the PA, you should adjust the turns of the bandpass filter circuits at the input to achieve the maximum RF voltage at a load of 50 ohms connected to the FET gate and the common wire. This voltage should be 100 mV. By selecting a voltage divider connected to the gate, the quiescent current of the final stage is set within 100 mA. They connect the equivalent load to the output and, mainly by adjusting the series circuit between the FET and the LPF, they achieve the maximum voltage at the load. Having connected the antenna, you should deal with "excitation" if it occurs. In practice, it was not observed, but if the PA was assembled on a bipolar microwave transistor (there was an option on the BFG 135), it was. In this case, the collector choke is shunted with a resistor of about 100 ohms. It is also necessary to pay attention to the quality of the signal with the PA turned off and when it is turned on. When the PA is turned on, the signal quality (LF from the receiver output) should not deteriorate. This also applies to a folded or deployed telescopic antenna with the PA turned on. The digital part consists of a controller and shift registers. The code received by the microcontroller is converted into data and strobes for shift registers that set log 1 on the legs corresponding to the received commands. The power part consists of powerful keys controlled by shift registers. The scheme of the executive power device for the 23rd team is outlined by a dotted line. The rest of the channels are identical. The lower field-effect transistor on the circuit (resolution of the real shooting mode) is common to all 30 power switches. The shift registers are powered separately from a 6-volt regulator so that their outputs loaded with LEDs have enough voltage to provide a key operating mode for powerful FETs. Details Basically, the device is assembled on foreign SMD elements. MF inverter transistors can be literally any low-power silicon with a gain of at least 100 (for example, a foreign analogue of KT 315 in SMD version). Varicaps are soldered from the Harvest radiotelephone, their brand, according to the scheme 1SV215 (no experiments were carried out with others). All coils, except for the heterodyne and phase-shifting circuits of the receiver, have 4 turns of wire with a diameter of 0,6 mm, the total diameter of the coil is 5 mm. The receiver local oscillator circuit has 5 turns of the same wire, the coil diameter is the same. The phase-shifting circuit is taken, again, from Harvest and has 140 turns of wire, with a diameter of 0,07 mm. This circuit can be made independently by winding 140 turns of wire on the circuit (for example, from imported VHF receivers). At 140 turns it was always possible to get into resonance by selecting a capacitance parallel to this circuit. PCB files are here (not in mirror image). Printed circuit boards may not match the circuit a little (at the level of an extra resistor in the power circuits, or an extra blocking capacitance). There are 2 transmitter boards (there are no significant differences), since 2 options were assembled.
It should be noted that during the development of this device, special measures, both software and hardware, were taken to combat false positives. Download PCB layout files in lay format Demo versions of the firmware for the transmitter controllers and one receiver can be obtained free of charge from the author Author: Sergey, Kremenchuk, 8-050-942-35-95, blaze@vizit-net.com, blaze2006@ukr.net; Publication: cxem.net
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