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November 18, 2008
about 2 years ago
My guess is it’s to “key” the chip so it cannot be inserted the wrong way around. If you do an LED backwards it’s only two pins to try to desolder; with the 328 it’s a much bigger deal. Yes, they have all sorts of instructions about the notch and stuff which teaches about the proper way to determine correct orientation, but it’s not a big loss that they took that pin off.
about 2 years ago
There’s a line in the datasheet, though, that reads “Total substrate-terminal current … −2.5 A,” which leads me to believe that you can switch up to 500 mA on each pin, but can’t sink more than 2.5 A total. So if you want to switch 4 A continuous, you cant do it with (just one of) this chip, but if you had 8 loads of 500 mA each, and didn’t turn more than 5 on at a time, you’d probably be OK.
about 3 years ago
Not really. It’s a tool more than a component. It’s like asking what kinds of new projects a new multimeter will bring.
In my (somewhat limited) experience, a function generator is generally used to produce input into circuits to test behaviour. Say: build an op-amp circuit to multiply voltage by 2, feed in a 1.0V amplitude sine wave, and see if you get a 2.0V sine wave out. Or see if it clips at the source voltage for the amp.
about 3 years ago
If you went over a half-inch, it overloaded itself. I think these ramp up the voltage between the sparking electrodes until breakedown, which discharges it, and then it starts again. It’s extremely fast, hence the buzz. If the gap is too wide, the voltage goes over what it can handle, and it kills itself, like an LED without a current limiting resistor.
TRYING TO MAKE A SPARK OF MORE THAN A HALF INCH CAN KILL THESE DEVICES!
Sorry to yell, but I think this is a point which is not adequately made in the product description or the comments to date. I killed mine inside of a half hour playing with the spark gap, accidentally making it too big.
Without a datasheet or even a schematic of a similar circuit, my supposition (based on comments) is that the input end is a coil of wire, and this will burn out eventually with too much voltage and therefore too much current, but may be tolerant for a short time. On the output (sparky) end, the circuit build up voltage until the air breaks down and arcs. There may be an internal capacitor or something to store charge until the spark, but if it is prevented from sparking by a too-large gap, it will ramp up the voltage beyond its own capabilities and it will kill itself, probably within one or two multiples of the (very short given the pitch of the noise) spark-to-spark time.
Unless someone can show me where I’m wrong (and I’m very open to that), I think that these are very capable of overloading themselves if they are not allowed to spark due to a too-large gap.
Mine arrived today. A D-cell will make an arc of ~2-3mm, so no disagreement from what’s been reported here by others getting it to turn on with one alkaline battery. I also have a 6600mAh, 3.7V LiPo pack, which makes a nice arc of ~10mm.
From the comments here, I rather suspect that 4.8V is an UPPER limit. 5V will probably work OK as it’s within 5% of 4.8V, and everything has a tolerance, but I’d be very hesitant to go any higher.
I’ve got a 3.7V, 6600MAh pack that’s supposedly good to 2C, so this should be easy for it, if 3.7V is enough. When my igniter comes, I’ll post whether or not that works.
Also the reported failure mode seems to be rather boring - they just stop working.
That’s awesome, thanks. I’ll just have to wait until mine arrives and I can do my own testing. ;)
Current was 3A at 3V? It will operate as low as 3V? If so, I suspect one should be able to operate it nicely on 3 D cells, but probably best with that capacitor you suggest.
Edit: Nevermind. On further reading, looks like Ds (alkaline at least) shouldn’t go much beyond 1 amp.
I’ve bought one and I’m just wondering what the risks are, if anyone knows, of accidental shorts between the blue and grey wires, or leaving it powered without it being able to spark for periods on the order of minutes. Thanks!
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