#Bigclive #electronics #video on an old sound-detecting dusk switch, which turns on a light when you speak near it, but only after dark. In order to be able to switch AC current with a low trigger current, it uses a unidirectional SCR thyristor across a bridge rectifier, which can be triggered with 200μA. He says it’s old, but the main diode is an A7, the microcontroller looks like a SOT23-6, and everything is SMD. But it probably predates RoHS because it has a CdS photoresistor. There’s a 6.2MΩ SMD resistor involved (“625” label on maybe an 0603) which I don’t think I’ve seen before; at first Clive thinks it’s a collector resistor, used to get a high gain out of a grounded-emitter microphone amplifier, but later he thinks it’s being used to supply almost a microamp to the transistor base to just barely bias it into conduction, which would mean that the collector resistor was just the MCU’s internal GPIO pullup. The power supply for the microcontroller is even simpler than a cap dropper: D -- 100kΩ -- (~Z(5.1V) || 100μF || 0.1μF), with a half-wave rectifying diode and only a 100kΩ resistor to limit the bias current for the 5.1V zener, so the peak current is probably (339V - .7V - 5.1V)/100kΩ ≈ 3mA. Which is a very toasty 1 watt peak on the largish (1206? which is ¼W) series resistor, but that’s only some of the time; the RMS voltage across the resistor is only half of that, which would indeed give a quarter watt.
on 02026-08-11#video by #Bigclive from 02025-07-25 about RF-blocking Faraday-cage anti-5G fabric, made of copper, nickel, and polyester. I think this is the stuff that those kids from Yale were laser-cutting at Noisebridge. #materials
on 02026-08-07#bigclive #video on antiparallel green LED tape in series with a 1MΩ resistor as a replacement for a regular neon testing screwdriver
on 02025-12-17#bigclive #video on putting a 1N5187 Schottky diode in series with a TP4056 lithium-cell charger to keep it from charging the battery all the way to 4.2V, potentially significantly extending the battery’s lifetime. The diode drops 350mV at 250mA, over 400mV at 500mA, and 330mV at 110mA. The charger starts oscillating toward the end of the charging process, and in the end the battery charges to 3.89V, which is supposedly 80% capacity. #batteries #electronics
on 02025-10-15#bigclive #video explaining those little electromagnet-powered “perpetual motion” desk toys, showing the circuit consisting of a single npn transistor and the electromagnet, which is actually sort of an autotransformer. A high-resistance winding feeds some current from the emitter into the base, and then a low-resistance winding runs from the base to ground, while the collector is held at 6V. As he explains it, the approaching magnetic target starts switching the transistor into conduction, and then the transistor turns itself the rest of the way on? But then at some point the current stops rising, so the magnetic field stops rising, so the current into the base stops, and the transistor turns off, and the falling current snaps it even more thoroughly off. He reports that it still works if you add a flyback diode across the low-resistance winding, which is what you would normally want to do, but they don’t bother; I assume that drives the emitter-base junction into backwards (zener or avalanche) conduction during turnoff, and I don’t know what effect that has on the voltage. One of them has a duodecahedron I don’t recognize at its center, consisting of quadrilaterals that aren’t rhombuses; maybe it’s a distorted rhombic dodecahedron. #electronics #hardware
on 02025-09-18#bigclive #video dissecting NiMH and lithium AA cells; the NiMH one is mostly empty space in the middle! They’re largely punched metal mesh separated by electrolyte-soaked fibrous separator which looks a bit like thick paper, with lots of powdery paste smeared into the mesh (presumably largely depolarizer). The last battery, a Lidl NiMH cell, caught fire spontaneously as he was disassembling it, but not due to a short circuit; not only was it theoretically fully discharged, but the bits of mesh material that caught fire had no path to the other electrode. I guess it was a pyrophoric metal hydride cathode. Rapid deployment of the Explosion Containment Pie Dish prevents disaster. “There may be a delay between exposure to air and spontaneous combustion.” #hardware
on 02025-08-09#bigclive #video #toread on overcomplicated air freshener #electronics #hardware
on 02024-10-16older #bigclive #video on the #electronics #hardware in an electric #flyswatter, labeled as 1.5kV. It uses a (slightly weird) Cockcroft–Walton voltage multiplier on the transistor output, terminating in an 0.022μF kV cap with a 44MΩ bleeder, and has the primary side of the transformer on the (8050SS) transistor’s emitter (!) rather than its collector but otherwise a similar circuit to the later video.
on 02024-05-09#bigclive #video on the #electronics #hardware in an electric #flyswatter. The circuit is extremely simple! A transformer, a transistor (C2328A 30V 2A 1W), a 560Ω resistor, a diode, an 0.33μF 630V film storage capacitor, a 2.2MΩ bleeder resistor for it, and a probably unnecessary LED (with its own 560Ω resistor) and power button. It all runs off 3 volts from two AAs. It’s a blocking oscillator, basically a Joule Thief with a high-voltage secondary which is half-wave rectified into the storage cap; the resistor limits the current into the base of the transistor. Although I think I may have misunderstood how the Joule Thief works — he says the feedback winding turns the transistor on more until the core saturates, at which point it starts turning off. The two primary-side windings attached to the transistor are 1.5Ω each, and the high-voltage secondary is 150Ω. A commenter says his is 1500V, and he altered the output to 1μF 10MΩ for a “nice loud bang”.
on 02024-05-09#bigclive sex toy teardown, clitoral suction stimulator (“Nooky” brand from Poundland). It’s built around an unidentified 8-pin microcontroller and an outboard MOSFET (“A2SHB”) to PWM the motor, which pushes a rubber suction cup up and down with a crank. The microcontroller is powered at 3.6V with an E36F boost converter shunt controller running a diode, capacitor, and inductor, all of which are surface-mount, and then there’s an LC filter to low-pass filter the micro’s power. #mechanical #hardware
on 02024-04-14#bigclive inside an ozone room deodorizer #hardware #video #toread
on 02024-04-06#bigclive inside a nasty high-voltage ozone-generator power supply #hardware #video #toread
on 02024-04-06#bigclive high-power shady £16 #ozone generator teardown with schematic #electronics #hardware #video. Arrived with a broken ceramic plate through which it arced. Operates around 4000V and uses the “ridiculously high power” of 155 watts with a power factor of 94%. He says it really needs to be mounted in an enclosure with a fan so it doesn’t overheat. The wires to the high-voltage conductive-ink grids (very hard ink, harder than his box cutter) are silicone-insulated for high temperature, and the solder connections are silasticked over, presumably to prevent lower-voltage corona discharge. He explains that capacitive coupling through a high-dielectric-strength insulator gives you lots of tiny little sparks when you’d get an arc without the insulator. The input bridge rectifier is made out of 1N5399 1.5A 1kV diodes. An interesting oscillator design using a sort of totem pole of two npn transistors, perhaps FJP13009 (700V 12A; they’re labeled J13009-2), driven from (opposite-sense?) feedback windings on a high-current toroid, only used for feedback; its primary is in series with the primary of the resin-potted high-voltage transformer (2Ω primary, 100Ω secondary). Surprisingly to me, there’s a diac in the oscillator, which he says is the “start circuit”. The transistors are mounted on a giant aluminum heatsink through an insulating film (mica?). The primary of the toroid is tied to both rails of the power supply through rather large (0.47μF 400V) film caps, which discharge through the transistors when they come on. There’s no storage cap, so the oscillation dies down when the 50Hz signal is close to its zero-crossings. Originally I thought it was a blocking oscillator, but apparently the feedback through the toroid is positive, not negative; what terminates a pulse is when the film cap, discharging through the two transformers, runs out of charge, and thus stops turning on the transistor it was discharging through. “Normally, with transistors to a positive rail, you’d have a pnp transistor, but in this instance, because it effectively has its own transformer-coupled supply to its base here from the emitter, you can use standard npn transistors for both of them. (...) Much simpler circuitry than I was expecting.” The diac to the base of the negative-rail transistor is activated by a .01μF cap charged up through a 470kΩ resistor pulling it up toward the positive rail, though I’m not sure why you need the cap. The size of the heatsink makes me think it can’t be dissipating more than 5–10W, which means better than 92% efficiency.
on 02024-04-06#bigclive random high voltage eBay thing #hardware #video #toread
on 02024-04-06“easiest free street-lithium yet” #bigclive #hardware #video about disposable cylindrical “blu” vapes with 16300-sized #lithium-ion cells of 520mAh, 13g, 1.92Wh, that drop right out when you unscrew the endcap, with coaxial contacts on one end. It looks a lot like an electrolytic cap.
on 02024-04-05