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Showing posts from March, 2024

HDMI standard and functions

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HDMI stands for high-definition multimedia interface. Since it has HD in the name, it should be easy for anyone to guess when it was first introduced and implemented, raising 'HD' on the flag is so early 2000s. HDMI is a digital interface that was and still is competing with DisplayPort. The crucial thing in this standoff was that DisplayPort was always meant for computers and all the alike. At the same time, HDMI was developed by a consortium of consumer tech manufacturers, including TV makers. Historically, this meant a much greater spread of the technology, so any new type of device should have HDMI if it supports an external display for any purpose. HD am I, image source: Reddit, r/puns Just to keep this explanation fair, DisplayPort still has one undoubtedly significant advantage—native support for Thunderbolt USB-C. Thunderbolt and USB-C are complex standards, so I won't dive deep into this. It should be noted that if you have a fairly recently produced laptop compute

PWM frequency in Shelly RGBW2 controller

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  I received an interesting email from a reader of my post: https://teardownit.com/posts/shelly-rgbw2-controller-and-shelly-duo-rgbw-bulb-dangerous-light-pulsations ===== After having some bloody eyes and reading your article I decided to change the firmware on shelly rgbw2 with ESPHome so I can modify the pwm freq to 1500 Hz like you recommended. Don't know if placebo or not but I feel better :) . I can test only with camera from phone with shutter speed at 1/1500 and no flicker (and sub multiples like 1/500). With PWM freq at 600 Hz I could see flicker on camera at anything above 1/600. Don't know if this is the same you have tested but I was curious if you can test with a modified Shelly with ESPHome to be able to put higher frequency. I also don't know if there is a limit on the maximum frequency  (the shelly or the COB LED strip it's dimming ) it will work and if is there any benefit in increasing any further. Thank you for publishing this extensive tests online. C

Finding water damage in a cable using a reflectometer

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  Despite all the hard efforts to keep IT cables dry, water remains the most likely cause of cable failure. Water introduction into the cable leads to various types of damage, often resulting in a high-resistance short circuit. Signs of cable water ingress change over time. Usually, the first symptom is the appearance of noise on the line. Interference occurs due to the flow of microcurrents between conductors. Suppose the service personnel do not take any measures. The problem may grow in that case, so communication will be blocked entirely. Cables with some water inside them can be categorized into two types: wet and waterlogged. Most of the time, the cable is simply soaked. In cables with filler, water can accumulate in existing voids and in overhead cables in sagging sections. In warm weather, it evaporates, and in cold weather, it condenses back again. As a result, the copper wires corrode, increasing resistance and causing poor cable performance. Water ingress occurs when water p

Review, teardown, and testing of RSP-320-24 Mean Well power supply

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  The RSP-320-24 is a 24-volt power supply with a maximum current of 13.4 amps. The supported mains voltage is from 100 to 240 volts without an additional switch. The supply measures 8.5 × 4.5 × 1¼ inches (215 × 115 × 30 millimeters), made on a printed circuit board fixed to the base's case. The top cover is perforated at the back near the connection terminals and on the front, where the cooling fan is installed. The fan starts spinning even if there's no electrical load. As the load increases, the fan speeds up, following the load current value. The fan sucks in the air and pushes it through the internal case volume to the perforated holes, including those on the side walls. The input and output circuits are connected to a standard screw terminal block (1), from right to left: 3 terminals for the input line, neutral and ground wires, and 3 in parallel for common and +24V output. The input voltage from the terminals goes to the fuse (2), then to the pulse limiter (varistor), fo

VGA videocard for microcontrollers. Part 2

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  First of all, you should pay attention to the ROM used. The flash-ROM chip from an old computer motherboard has a finicky parallel interface where the address is written in two runs. This complicates the operating logic and increases access time. Additionally, the PLCC housing it comes in can be expensive and challenging to install manually. In this regard, it was decided to replace it with a more modern 39-series microchip from SST. These chips, such as the SST39LF and SST39VF, have faster access times (55 ns and 70 ns, respectively) compared to 270 ns for the 49 series chip. This allows one to reduce data preparation time to one cycle. The SST39VF010-70-4C-WHE chip has been ordered. It is also necessary to replace the RAM. To save money, I picked one that operates precisely at 3.3 V and has TSOP housing. The IS62LV256AL-45TLI chip was ordered. The CPLD chip remains unchanged. These updates improve overall efficiency by reducing memory access times and using more convenient and mode