Original Question:
> Stupid Question of the Day: I have a Need to use a TTL Output to switch
> "Power" (230VAC or 12VDC, still to be determined). I suppose I could
> find Lots of Circuit Schematics how to "just get it to work", however,
> I need this Thing to be RELIABLE (as in: a) breaks rarely; b) prefe-
> rably fails to "Power on", rather than silently; c) is equipped with
> Test Buttons; etc.) [...] Does anyone have a Product, or Circuit
> Schematics I could use, that'ld fit the Bill?
> (In Case it matters, I'm trying to hook Sirens and Flashlights onto
> a RAID SCSI Controller which has a "Disk failed" TTL Signal Line.)
Solutions:
-- Most recommended to use ready-made Relays - I wasn't aware that
there are Relays available that'll take TTL Lines as Input without
overloading them. Good News, I'll check with a local Electronics
Shop!
-- Special Award to Mike Taylor for sending a Circuit Plan that
caters for the Test Switch Requirement, too, and has been used
without Problems.
-- There are Sirens available in the High Availability Market that
will directly connect to RS232 Connectors - but I'm afraid that
that SCSI Controller *really doesn't* have a serial Interface. :-}
-- One Respondent (who asked to remain anonymous :-) reported having
used LEDs and Circuitry from automatic Night Lights for this
Purpose - which basically amounts to a homemade Optocoupler.
Thanks to:
Seth Rothenberg <SROTHENB@montefiore.org>
Mike Youngberg <mikey@synacom.com>
Stan Brown <stanb@awod.com>
Kevin Sheehan <Kevin.Sheehan@uniq.com.au>
Mike Taylor <taylor@syrinx.jeffnet.org>
... and Mr. X. ;-)
Circuit Schematics (redrawn using German (European?) Symbols ;-) :
O U (+5V)
|
o |
|==>=| PB1
o |
|
| |
| | R1
|_| SSR
| +-----------+
|\ | | _ |
Input O---| >---+-------+-| | \ o-+---o
|/ | | |===\ | to Load
U1 +---+-|_| \o-+---o
| | |
| +-----------+
_|_
where (quoting Mike) :
> U1 - Non inverting buffer (or inverting depending on your 'OFF' state)
> PB1 - N.O. Push button (test)
> R1 - 4.7k ??
> SSR - Solid state relay. They come in lots of different flavors, fully
> Isolated. Check with Motorola or GE for part #s and pricing.
> I have used this circuit for a number of different power control
> applications without any problems. Its simple and cheap, however be
> prepared for the relay to cost anywhere between $10 and $50 (u.s.)
> depending on your requirements.
Thanks again,
J. Bern
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