Schemes of alternating present comparators with an adjustable switching threshold are introduced, which permit utilizing color-dynamic indication to manage the above- and sub-threshold values of alternating voltage of symmetrical and uneven form.
Wow the engineering world together with your distinctive design: Design Concepts Submission Information
The AC comparators, Figures 1 and Determine 2, assist you to visually monitor the degrees of AC enter alerts. Beforehand, for categorical evaluation of the degrees of managed alerts, a technique of color-dynamic indication was proposed [1–4], the essence of which is diminished to visible or instrument management of the whole shade of the glow of multi-colored light-emitting diodes when the enter sign degree modifications.
The AC comparator, Determine 1, comprises two comparators U1.1 and U1.2 of the LM339 chip, the non-inverting enter of the primary of them and the inverting enter of the second are related to the enter of the gadget.
Determine 1 AC comparator with color-dynamic sign degree indication.
The comparator comparability inputs are provided with voltages of reverse polarity and are regulated by way of a twin potentiometer R5.1, R5.2. The outputs of the comparators are loaded on LED1 and LED3 with a pink glow. The anodes of those LEDs are related to the anode of LED2 with a inexperienced glow, the cathode of which is related to a typical energy bus. The present from the facility provide is provided to the LEDs by means of a current-limiting resistor R2.
When an alternating voltage of the pre-threshold degree is utilized to the enter of the gadget, LED2 lights up. When the enter voltage degree is additional elevated and the comparator switching threshold is exceeded, they start to modify alternately in accordance with the polarity of the enter voltage, LED3 – LED2 – LED1 – LED2 – LED3, and so forth.
Because the enter voltage will increase additional, a type of pulse-width modulation shall be noticed within the glow of the LEDs: the length of the glow of the pink glow LEDs will improve, and the inexperienced glow LEDs will lower. All it will trigger a easy change within the complete shade of the glow of a set of LEDs, which can allow a visible evaluation of the change within the degree of the enter sign.
Determine 2 exhibits a diagram of a two-threshold AC comparator, which is distinguished by a comparability voltage adjustment node. The variety of switching thresholds of comparators is doubled as a consequence of using an enter resistive divider R1, R2. The switching thresholds of the AC comparators U1.1 and U1.2 could be easily adjusted by the twin potentiometer R5.1, R5.2, Determine 1, and the potentiometer R8, Determine 2, from 0 to ±10 V.
Determine 2 A two-threshold AC comparator with an adjustable switching threshold and a color-dynamic indication of the over-threshold degree of the enter sign.
To offer galvanic isolation of the enter circuits of the gadget, you need to use the node proven in Determine 3. The enter sign from the alternating present supply E1 is provided to the enter of the alternating present comparator by means of a separation transformer Tr1, diodes D1, D2 and a bridge resistive voltage regulator R1–R3. With the assistance of the R3 potentiometer, you may easily change the ratio of the degrees of constructive and adverse polarity alerts getting into the comparator enter. This makes it attainable to detect the asymmetry of the waveform, in addition to to shift the general radiation spectrum LED1–LED3.
Determine 3 A variant of the enter circuit with galvanic isolation.
A noticeable drawback of the only LED energy provide scheme proven in Figures 1 and a couple of is that the present by means of all LEDs is ready by resistor R3 (or R9). The voltage drop on LEDs of various glow colours is noticeably completely different, as are the sunshine flux ranges of those LEDs. Due to this fact, so as to present a suitable shade notion, it’s higher to make use of particular person present limiting resistors for every of the LEDs.
On this regard, it’s fascinating to make use of a present stabilizer to energy the LEDs, Determine 4, made on the U1 LM317 chip. The resistance worth of the resistor R1 units the present by means of the LEDs: at R1 = 240 Ω, the output present of the stabilizer and, accordingly, the present by means of any of the LEDs is 5.3 mA. As light-emitting RGB LEDs LED1–LED3, Determine 4, it’s needed to decide on LEDs with roughly equal luminous flux on the identical present passing by means of the LED.
Determine 4 A variant of the RGB node of the colour dynamic show, powered by a steady present generator.
AC comparators can be utilized for fast visible evaluation of AC voltage ranges, in addition to units for shade and music accompaniment of audio packages.
Michael A. Shustov is a health care provider of technical sciences, candidate of chemical sciences and the creator of over 750 printed works within the discipline of electronics, chemistry, physics, geology, drugs, and historical past.
Associated Content material
References
- Shustov M.A., Shustov A.M. “Colour-dynamic measuring devices”, Radioamateur (BY), 1998, No. 4, pp. 32–33.
- Shustov M.A. “Sensible circuit engineering. 450 helpful schemes”. M., Altex-A, 2001, Ebook 1, 352 p.
- Schustow M.A., Schustow A.M. “Farbindikatoren – Alternativen für Zeigerinstrumente”, Funkamateur (DL), 2005, Bd. 54, Heft 11, S. 1146.
- Shustov M.A., Shustov A.M. “Digital Circuits for All”. London, Elektor Worldwide Media BV, 2017, 397 p.; “Elektronika za sve: Priručnik praktične elektronike”. Niš, Agencija EHO, 2017; 2018, 392 St. (Serbia).
