Converter K1003PP1 in automation devices. Encyclopedia of radio electronics and electrical engineering

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Devices designed to control linear LED scales are now produced in the form of relatively inexpensive microcircuits, for example, domestic K1003 series or imported LM315, KIA6966S, etc.

In the article below, the author talks about some options for non-standard applications of these microcircuits.

Chip analog-to-code converters are designed to operate the LED scale in one of two modes - either a "luminous line" (its length is proportional to the displayed parameter value), or a "luminous dot" (the parameter value is proportional to its distance from the beginning of the scale). A number of microcircuits - K1003PP1, UAA180, LM314-LM316 are capable of operating in both modes.

Unusual ways of using transducers are known [1, 2], which mainly implement visual indication. At the same time, displaying the value of the input signal in a particular mode, the device performs only an informative function. You can expand the scope of its application if you use the properties of the transducer as a multi-threshold device. By removing signals from its outputs, which are switched very clearly and in a certain sequence, it is possible to control various external devices, while maintaining its basic functions.

Consider, as an example, a twelve-level indicator circuit on a common K1003PP1 microcircuit (Fig. 1). It is assembled on an analog-code converter DA1, resistors R1-R4 and LEDs HL1-HL12. The LEDs are connected in series in three groups of four and operate in the "luminous line" mode [1]. With an increase in the constant voltage at the input of the device - pin 17 of the microcircuit - from the level set by the voltage at pin 16 to the level set by the voltage at pin 3, the LEDs turn on in series, forming a continuous light-emitting line.

To implement control functions, you have to take signals from the outputs to which the LEDs are connected. A step made on transistors VT1, VT2 allows you to get a switching characteristic with a high steepness. Transistor VT1 with "over-amplification" (h21e = 400...800) is connected in series with transistor VT2 - current amplifier, which provides a high overall transfer coefficient, as well as low output impedance.

The operation of the stage is controlled by a signal taken from one of the outputs of the converter relative to the positive power wire. In this case, the change in voltage across the resistor R5 depends on the voltage drop across the LED and is already 1,6 ... 2 V, depending on its type. The current drawn by R5 is small (and can be reduced by increasing R5), so it has no effect on the operation of the converter and LEDs.

The voltage drop across the load (on the winding of relay K1) is almost equal to the supply voltage with a large switching slope. The output of the device - the open emitter of the transistor VT2 - has a high load capacity, limited only by the allowable current through the transistor. That is, actuating elements with an ohmic resistance of at least 120 Ohms (at Upit = 12 V), in particular, the winding of an electromagnetic relay, can be included as a load.

If the input signal Uin is smoothly increased, at some point the HL11 LED will turn on in the output circuit 5 of the DA1 converter. The LED, from the cathode of which the control signal is removed, will be called the control LED.

When the control LED is turned on, the transistor VT1 opens, followed by the transistor VT2 opens to saturation. Relay K1 (or another load) is triggered, including external devices with its contacts - household appliances, electric motors, heaters, etc. The trimming resistor R5 sets the current for reliable opening of transistors. When the input voltage decreases, the control LED goes out, the transistors close and the relay releases the armature.

To change the response threshold in such a system, it is enough to switch the output A of the resistor R5 to another LED and adjust this resistor. Thus, the response threshold changes by a multiple of the scale step. Of course, a more accurate setting is not excluded - with resistors R2, R3 or the input divider of the converter.

In any case, the control LED highlighted in the scale, for example, in a different color, acts as a visually convenient indicator of the threshold level. If feedback on the controlled parameter is introduced into the device, we will get a ready-made automatic control system.

In practice, quite often a sound signaling device is required to warn of the value of some controlled parameter going beyond the permissible limits. To do this, it is convenient to use a simple device instead of relay K1, made on a blinking LED HL13 (for example, L-56BID) and an active capsule BF1 (Fig. 1, right). Such capsules (НСМ1206Х and the like) contain a built-in audio frequency generator. When the LED is on, it emits a rather loud signal with a frequency of 2 kHz. Resistor R6 is selected so that the voltage on the capsule with the LED on corresponds to the last two digits of the marking (for the specified type 6 V). Other active capsules can also be used [3].

From the point of view of the reliability of switching the load, it is advisable to use thyristors instead of relays. On fig. 2 shows a diagram of the output node with a switch on the triac VS1. The node works to turn on the load - an EL1 incandescent lamp (or a heater). The opening field of transistors VT1, VT2 through the control transition of the triac VS1 begins to flow the opening current, limited by resistor R6. The triac opens and turns on the load. If the triac is installed on a heat sink, the load power can reach 1 kW.

The scheme of the node operating in the inverse version, i.e., disconnecting the load when the threshold input voltage is reached, is shown in fig. 3. In the absence of a signal at terminal A of the converter, transistors VT1, VT2 are closed, and triac VS1 is opened by current flowing through resistor R6, terminal 1 of the triac and the control electrode. When a signal appears at terminal A, transistors VT1, VT2 open, transistor VT2 shunts the output section 1-control electrode of the triac VS1, as a result of which it closes, turning off the load EL1.

Applying the node according to the diagram in Fig. 3 in the mains voltage voltmeter [1], you can get a device that automatically disconnects the load - household equipment, etc. - with an unacceptable increase in mains voltage. Moreover, such a device will combine the functions of an indicator and a circuit breaker, which distinguishes it favorably from other similar ones.

The device works with self-return, which is undesirable with multiple power surges. If you enter into it a node on the transistor VT3, shown by dashed lines in Fig. 3, then due to the deep positive feedback through the transistor VT3, the device will operate in latch mode. The load will be disconnected as indicated above, and to return to its original state, it is necessary to turn off and turn on the 12 V supply voltage. The same "latching" node can also be added to the device according to the diagram in fig. 2.

We draw the attention of readers that if the device is made transformerless [1], the nodes whose circuits are shown in Fig. 2 and 3, the entire indicator as a whole and the source of the measured signal will be under mains voltage. Therefore, certain precautions must be observed when working with the device. It is impossible to ground the common wire of such indicators!

The considered nodes work correctly when using the "luminous line" mode. In the "luminous point" mode, all LEDs on both sides of the luminous one turn off and, ultimately, a failure occurs. To achieve correct operation in this case, you can use, for example, a counting trigger that changes its state every time it passes the threshold level.

However, there is a simpler and more universal solution (see the diagram in Fig. 4) In this device, the indicator works in the "luminous dot" mode as a result of the corresponding switching on of the HL1-HL12 LEDs [1]. On diodes VD1-VDN, a logical node WIRED OR is assembled. If there is a signal at any of the outputs of the DA1 chip, to which the VD1-VDN diodes are connected, the signal at point A will be present. If a device assembled according to the scheme in Fig. 2, his triac VS1 will be open.

Since the VD1-VDN diodes are turned on so that they control a continuous section of the scale, the device will turn off outside the section, i.e. when the Uin signal drops below the level displayed by the first LED (HL3) of the section, or when it exceeds the level displayed by the last LED (HL9). In other words, now the device works similarly to a two-threshold comparator - in a certain "corridor" of values. By changing the number of diodes and the points of their connection to the outputs of the converter, it is possible to change the width of the "corridor" and even organize several "corridors".

In some cases, a full twelve-level indication, which the K1003PP1 chip is capable of providing, is not required. In this case, the extra LEDs can be excluded from the scale or, if necessary to preserve the operation of the rest, replaced by resistors with resistance R = Usd / Isd, where Usd and Isd are the voltage on the LED and the current through it (for the device according to the circuit in Fig. 1 Icd = 15 mA) In conclusion, we note that the considered devices also work with other analog-to-code converters mentioned at the beginning of the article. Their circuitry allows the use of much more powerful triacs that require a control current of up to 1 A. To use them, it is enough to replace the KT315G (VT2) transistor with any of the KT815 series, and replace the limiting resistor R6 (see Fig. 2, 3) with another one of lower resistance , so that the triac stably opens at both half-waves of the switched voltage. Of course, the power supply must provide the required current without reducing the voltage, which is important for maintaining the accuracy of the converter.

Literature

1. Biryukov S. Two voltmeters on K1003PP1. - Radio, 2001, No. 8, p. 32, 33.
2. Pakhomov A. LED scale on K1003PP1. - Radio, 2001, No. З.с.43.
3. Butov A. Signaling generators. - Radio, 2002, No. 7, p. 59.

Author: A.Pakhomov, Zernograd, Rostov region

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