Cybernetic planetary rover. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Microcontrollers

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That was the title of the article by P. Alyoshin, published in the Radio magazine No. 2 for 1987. It told about a toy machine that was able to bypass obstacles encountered on the way. Its electronic part was assembled on four digital microcircuits of the K561 series and 16 transistors. The use of a modern element base made it possible to reduce the number of parts to a minimum: three microcircuits, a quartz resonator, four capacitors, one resistor and an LED - that's all that is needed to assemble the planetary rover described in the article.

The proposed toy, like the prototypes [1, 2], colliding with an obstacle, drives back, turns away from the obstacle and moves forward again until a new obstacle is in front of it. The direction of the maneuver is determined by the state (closed/opened) of two microswitches mounted behind the bumper located at the front of the toy.

Schematic diagram of the electronic part of the planetary rover is shown in the figure. Its basis is an inexpensive and affordable microcontroller (MK) AT90S1200 from Atmel. The presence in its composition of the Flash-memory of programs with a volume of 1 KB with a resource of 1000 write / erase cycles allows you to improve the program, as well as create new devices using the same MK.

Conclusions 18, 17 MK DD1 serve as inputs to which microswitches SA1 and SA2 are connected, located in the front bumper of the toy. Logic levels from pins 13, 14 and 15, 16 (programmed as outputs) control threshold devices and bridge power amplifiers DA2 and DA1 (TA7291S), loaded respectively by the right (M2) and left (M1) motors. To pin 12 DD1 connected LED HL1. The clock frequency is set by a ZQ1 quartz resonator at a frequency of 2 MHz.

After power is applied, the device maintains a pause (6 ... 15 s) necessary for the user to install the toy in the desired direction. The burning LED HL1 indicates the presence of power. After a pause, it goes out and the model starts to move forward. In a collision with an obstacle, as already mentioned, it stops, drives back and turns away from the obstacle. The HL1 LED is on at this time, indicating a change in direction of movement. At the end of the maneuver, it goes out again and the model starts moving forward.

The assembly language program with detailed comments is given in Table. 1, hex-file - in table. 2.

(click to enlarge)

It should be especially emphasized that in a specific version of the device, the duration of the delays depends on the frequency of the resonator and the speed of the toy, so they are selected experimentally. The duration of the delay t (in seconds) is calculated by the formula t- 393216X / fres, where 393216 is the number of cycles of the delay subroutine; fres - frequency of the quartz resonator in hertz; X is the value of bigpause, pause1, pause2, pause3 constants. For example, if a quartz resonator is used for twice the frequency (4 MHz), then the corresponding constants should also be doubled (bigpause=200, pause1=30, pause2=l00, pause3=100). If the frequency of the resonator is the same as in the author's version, but the speed of the toy is too high, and the duration of the delays must, for example, be reduced by 1,5 times, then the values ​​of the constants must be reduced by the same amount (respectively, to 66, 10, 35 and 35).

When repeating the design, you can use the MK AT90S1200 with any numeric and alphabetic indices. The easiest way to program the MK is to connect it directly to the LPT port of an IBM-compatible computer (this is how the MK was programmed when the described toy was made). More details about this method can be found at [3] and in the series of articles [4].

The TA7291S chip was developed by TOSHIBA to control the electric motors of VCRs. It has a large input impedance (about 150 kOhm), built-in protection against simultaneous operation (when both control inputs are set to log. 1 levels) and overload protection. The microcircuit is available in three versions: for conventional (with indices P and S) and for surface mounting (F). They differ in size, number and purpose of pins, maximum operating current and power dissipation (for the variant with the P index, it is the largest). In the author's version, a microcircuit with the index S is used (in brackets on the diagram, the pin numbers of the P version are indicated).

The frequency of the quartz resonator can be from 1 to 4 MHz. It is convenient to use a three-pin ceramic resonator (the middle pin is connected to a common wire), in which case capacitors C1 and C2 are not needed.

Literature

1. Aleshkovsky S. Cybernetic all-terrain vehicle. - Radio, 1977, No. 7, p. 49, 50 and 3rd p. tabs.
2. Aleshin P. Cybernetic planetary rover. - Radio, 1987, No. 2, p. 49, 50 and 3rd p. tabs.
3. .
4. Dolgy A. Programmers and programming of microcontrollers. - Radio, 2004, No. 1-6.

Author: M.Potapchuk, Rivne, Ukraine

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