Subject: Re: Digital circuit help needed
Date: Mon, 16 Dec 2002 20:29:44 +0100
Organization: Wanadoo, l'internet avec France Telecom
NNTP-Posting-Date: 16 Dec 2002 19:29:45 GMT
X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.20 i686)
Why not one UCN5811A /UCN5812A /A6812 ? May even get rid off the Darlingtons.
(okay, it looks expensive..)
Spehro Pefhany wrote:
> On Sun, 15 Dec 2002 19:08:22 GMT, the renowned "Bob Pierfelice"
> >I have a 8 bit input that I need to use to control 12 relays. The relays in
> >use will all be turned on and off at the same time. They may be randomly
> >selected like 1,4,6,12.
> >I looked at the 4 to 16 latching decoders but they only select one output
> >line. I'm thinking I may need some sort of storage (flip-flop?) at the
> >output of the decoder and "walk" through the desired 1..12 channels, storing
> >the active ones. The relays are controlled with Darlington transisitors.
> A few ways come to mind immediately:
> Two 8 bit parallel latches, use 6 bits out of each, 6 data lines + 2
> clocks.Eg. 74HC374 (not expandable)
> Two 8 bit serial in parallel out SRs with output latches. 1 data
> line, 2 clocks (expandable indefinitely, and you get 16 lines for the
> same complexity as 12 with this setup) Eg. 74HC595. This methiod is
> nice if you have hardware SPI available, and is easily opto-isolated.
> Two 8 bit addressable latches- two data lines, one clock (or one data
> and two clocks, or one data and one clock and one additional address
> line plus an inverter) and 3 address lines. Eg. 74HC259 Expandable.
> Random access. You get 16 lines with just the two 74HC259s.
> Best regards,
> Spehro Pefhany
> "it's the network..." "The Journey is the reward"
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