The Tech Blog

Back to Basics(With a Twist): SIDAC

Posted under Back to Basics, Educational, Technology on December 11th, 2022 by Amaldev

SIDAC is a specific type of thyristor that is designed to switch on when the voltage applied to it reaches a certain threshold. It is often used in high-voltage applications, such as in power distribution systems. To understand how a SIDAC works, it’s helpful to think of it as a switch that has three states: off, on, and holding. When the voltage applied to the SIDAC’s gate terminal is below its threshold, the SIDAC is in the off state and does not allow current to flow through it. When the voltage applied to the gate reaches the threshold, the SIDAC switches on and allows current to flow through it. Finally, once the SIDAC is on, it remains in the holding state until the current flowing through it drops below a certain level, at which point it switches off again.

It is similar to a DIAC but with higher voltage breakdown regions and current-carrying capabilities(SIDAC = Silicon Diode for Alternating Current). Its a 5-layer PN junction device as shown in pics. Once breakdown voltage(VBO) is reached, it goes to a negative resistance region when current conduction happens. SIDACs are used in relaxation oscillators which are used to create non-sinusoidal waveforms like triangular waveforms. Here a SIDAC is connected in parallel to a capacitor. Initially, the capacitor charges up and when the voltage reaches the threshold of the SIDAC, it makes the SIDAC discharge to obtain your sawtooth waveform whose timing can be adjusted via RC time constants.

Now for the twist, the first paragraph wasn’t written by me. It was generated automatically by the Chat-GPT3 AI service(built on 175 billion parameters). I just gave it an input to explain what a SIDAC is and it gave me the first paragraph as is. An AI model gave me an answer instantly which would have taken me a couple of hours to read up from different papers and books. I am totally mind-blown by what can be done with the tool. It’s going to be used as a companion tool to improve your efficiency drastically(Think GitHub CoPilot). It’s not correct always, it usually gives plausible-sounding but sometimes incorrect answers. If I ran it a few times, I can clearly see it getting some stuff wrong. But possibilities are endless with this tool and I can’t even imagine what it will become 3-4 generations down the lane. All the low-hanging jobs in future will be taken over by AI, in a similar way to how automation killed a large part of manual labour. Start upskilling yourselves in whatever field you are in or you will struggle in a decade or so.

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Repair Tips for a Laptop

Posted under Hacks, Repair on December 4th, 2022 by Amaldev

When ICs & PCBs became smaller and smaller, thermal management became a big deal in circuit design. It’s one aspect that heavily impacts the lifetime of the product you are designing. The reliability of a product drops in an inverse-squared fashion as temperature increases.

Last week my laptop was showing the classic Windows Blue screen of death intermittently. Initially, I thought it was a Windows software issue, but a bit of snooping around made me realise the processor cores were heating up. This is a common problem with laptops as it ages. What usually happens is that the thermal compound which is used to transfer heat from the processor to the heatsink dries up and its thermal resistance increases drastically.

Thermal resistance, as the name implies, is the amount of hindrance a part provides for heat dissipation. It is measured in Kelvin per Watt. What it means is that, for 1 Watt of power passing through the device, how much will that part heat up on the Kelvin scale. A larger number means it is pretty bad at conducting heat. All processors will be connected to a heatsink for heat management. These two are 2 solid surfaces that won’t have flush mating surfaces. The thermal compound is the key element that facilitates this gap-filling and helps in the efficient transfer of heat. In the PC build domain, there are tons of info online on which thermal compounds you must use, so I won’t go into details about that. In the end, it mostly boils down to a factor mentioned as thermal conductivity. Larger the conductivity, the better the heat transfer. It’s measured in Watts/Kelvin. When buying thermal compounds, pick the larger one in your budget.

Back to the laptop heating problem. Well, the solution to the problem is fairly simple. You need to dissemble the laptop and remove the heatsink. Thoroughly clean the old thermal paste with isopropyl alcohol, then apply the new thermal compound and put everything back. I saw all my CPU cores running at approx 10°C cooler after I changed the thermal compound and no more crashes. If you are having performance issues, this may be something you can try.

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