On May 30, 2009 at 12:07, Gizmologist09 said...
The professional AV presentation industry has thousands of devices that use flip/flop circuitry for power up/down sequencing. This is not a new or unique concept.
No, it's not, but in professional custom installation remote programming, the first thing we look for is ZERO TOGGLES, instead relying on discrete codes for control. Toggles give us action, discretes give us control.
I totally forgot an important detail last time I wrote: If you charge up that capacitor, then leave the system on for, say, two days, it's very likely that the capacitor won't have enough charge to bounce the relay once and turn off the amp.
It's not a big deal to engineer something so that a variation in capacitor value of as much as 50% doesn't materially affect how something works when you're supplying electrons on a regular basis and depending on its time constant, but it's a bad idea to depend, really depend, on a disconnected electrolytic to maintain a charge for more than about five minutes. If it works all the time, you're lucky, and I'd expect it not to work for too many years. If you really want to make a circuit like that and have it work perfectly, use 600 volt oil-filled caps (2 mfd is about the size of a pack of smokes) and enclose them in a low humidity encasement. I am now not in favor of that circuit due to self-discharge of the electrolytic.
On May 30, 2009 at 00:22, Gizmologist09 said...
If the relay concept was as reliable as a solid state circuit which delivers a stable time constant and bounce-free response, why have manufacturers superceded the use of relays with monolithic circuitry in even the simplest devices?
The debouncing part of this is supplied by the switched unit, that requires, what was it, 130 msec to respond, so no, it's not inherently bounce-free.
Manufacturers can do this function IN QUANTITY at much lower costs than we can, using a 555 or whatever. Those cost less than the relays, are smaller, but require a PC board, assembly, and power that it would cost us more to implement if doing one or two.
Not to mention the fact the the 555 version would be about 1/10 the size of the relay concept shown with a cost parity using Rad Shack parts.
Maybe 1/10 in volume, but a 555 on a PC board has a footprint as large as that relay.
