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| Where have you actually come across a 555 timer in the wild? |
| << < (9/16) > >> |
| T3sl4co1l:
--- Quote from: magetoo on April 01, 2014, 10:02:11 pm ---Historic note: In the original PC, the timer chip had three separate timers - it generated a periodic interrupt at 18.2 Hz for DOS, drove the speaker with another timer, and also did a third thing I can't remember. --- End quote --- Third is actually the first (timer 0): interrupt for the DMA controller to perform another DRAM refresh. Every couple of microseconds I think. The 18.2Hz is used by the clock (at least when DOS is handling it, I think?). You can hijack the interrupt and use the count for something else (say, an in-game timer to trigger another frame of activity), but don't be surprised if your system time is running slow afterwards. ;D This, by the way, is precisely why, if a motherboard had a 555, it's not used to generate PC tones: the timer has a pin toggle mode which does it directly. Give or take a driver for the PC speaker (2" 8 ohm in the old fashioned models, usually some piss tiny piezo these days). All this stuff was integrated first into a SuperIO chip (along with all the other system functions, and serial and parallel), then into the South Bridge when that become a thing. If your motherboard has a BIOS, it has all of this stuff in it somewhere; UEFI models may not, I don't know. Tim |
| Jarrod Roberson:
Ben Heck finds a 555 timer chip in SOT packaging no less in a drill trigger assembly! http://youtu.be/PUZyzU24Ta4?t=3m53s |
| peter.mitchell:
I've seen a few of them on power supplies for fan failure. The RPM line from the fan triggers it a minimum number of times a second. |
| kolbep:
Saw a 556 in a Barcode Scanner that they use at the Supermarket tills... |
| Anks:
--- Quote from: David_AVD on March 31, 2014, 11:42:13 pm ---I saw two just the other day in a Crown high power audio amplifier. At a guess I'd say the amp design is from about 10-15 years ago. --- End quote --- Crown amplifiers that use the VZ supply (variable impedance) Macrotech 5000VZ and 3600VZ are the most popular. Its very clever in that its quickly switches voltage dependent on the needed output so the transistors don't have to dissipate the extra unneeded energy as heat. |
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