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Practical Electronics Editorial offices Electron Publishing Tel +61 2 9939 3295 (Australia) Email pe<at>pemag.au Web www.electronpublishing.com Address mail to: Electron Publishing (Australia) PO Box 194, Matraville NSW 2036 Australia Advertising enquiries +61 2 9939 3295 pe<at>pemag.au Editor Nicholas Vinen Publisher Nicholas Vinen Digital subscriptions Stewart Kearn Tel 07918 614662 Online Editor Alan Winstanley Web Systems Kris Thain Production Bao Smith Technical staff Tim Blythman, John Clarke Print subscriptions Practical Electronics Subscriptions PO Box 6337 Bournemouth BH1 9EH Tel 01202 087631 United Kingdom Email pesubs<at>selectps.com Volume 54. No. 7 July 2025 ISSN 2632 573X Editorial ChatGPT can analyse circuit diagrams I took a circuit I had drawn in CorelDraw and removed anything obvious regarding how it functioned (it’s reproduced below). I then fed the image to ChatGPT and asked it what the circuit did. I thought it would get it wrong as it requires quite a few logical inferences to figure out but it described its function almost perfectly! Its only mistake was with the function of the diodes; they’re necessary because the two outputs drive some of the same LEDs. Here’s an abbreviated version of what it said: This is a high/low voltage indicator circuit using an LM393 dual comparator and a 7-segment display (LTS542R) to visually indicate the input logic level — high or low. IC1a and IC1b are configured as voltage comparators. Each comparator compares the input to a reference level (likely derived from resistor networks and diode drops). When the input crosses a threshold, the corresponding comparator output changes. Technical enquiries We regret that technical enquiries cannot be answered over the telephone. We are unable to offer any advice on the use, purchase, repair or modification of commercial equipment or the incorporation or modification of designs published in the magazine. Questions about articles or projects should be sent to the editor by email: pe<at>pemag.au Projects and circuits All reasonable precautions are taken to ensure that the advice and data given to readers is reliable. We cannot, however, guarantee it and we cannot accept legal responsibility for it. Some projects and circuits published in Practical Electronics employ voltages that can be lethal. Do not build, test, modify or fix any mains-powered equipment unless you fully understand the safety aspects involved and you use an RCD (GFCI) adaptor. Component supplies The outputs of the comparators drive specific segments of the 7-segment display to show either “H” (High) or “L” (Low). The series resistors limit the current through each segment. The arrangement of resistors and wiring determines which segments light up based on which comparator is active. Diodes D1 & D2 provide voltage drops to slightly offset the comparator thresholds — possibly giving hysteresis or creating slightly different high/low switching points. If input is LOW (0V), one comparator activates and the display shows “L”. If the input is HIGH (5V), the other comparator activates and the display shows “H”. Silicon Chip Publications may offer kits or other parts for making our projects, but not in all cases. When kits are not available, readers will need to find and source parts themselves. We advise readers to check that all parts are still available before commencing any project in a back-dated issue. Advertisements Although the proprietors and staff of Practical Electronics take reasonable precautions to protect the interests of readers by ensuring as far as practicable that advertisements are bona fide, the magazine and its publishers cannot give any undertakings in respect of statements or claims made by advertisers, whether these advertisements are printed as part of the magazine, or in inserts. The Publishers regret that under no circumstances will the magazine accept liability for non-receipt of goods ordered, or for late delivery, or for faults in manufacture. Transmitters/bugs/telephone equipment We advise readers that certain items of radio transmitting and telephone equipment which may be advertised in our pages cannot be legally used in the UK. Readers should check the law before buying any transmitting or telephone equipment, as a fine, confiscation of equipment and/or imprisonment can result from illegal use or ownership. The laws vary from country to country; readers should check local laws. 2 +5V 100nF 1kW +4V 3 INPUT 10MW 100kW 2 1.5kW +2.5V 1.5kW +5V 8 IC1a 1kW 1 1kW IC1: LM393 1kW 5 +1V 6 IC1b 7 4 1kW K D1 K A A D2 750W 750W 1kW 7 a 6 b 4 c f 2 d 1 e 9 e f 10 g 5 dp 3 A a b g c d dp DISP1 LTS542R D1, D2: 1N4148 Nicholas Vinen, Electron Publishing (Australia)* Publisher & Editor, Practical Electronics Magazine * a division of Silicon Chip Publications Pty Ltd. Practical Electronics | July | 2025