Re: Configurable circuit boards (straps and jumpers)

On Wed, 22 Feb 2006 11:16:37 -0800, the renowned "Joel Kolstad"
<JKolstad71HatesSpam@xxxxxxxxx> wrote:

"Kenneth Porter" <shiva.blacklist@xxxxxxxxxxxxxxx> wrote in message
news:Xns97726FD5B1D3Cshivasewingwitchcom@xxxxxxxxxxxxxxxxx
What's the current practice to make circuit boards configurable?

For systems that already have plenty of digital smarts, 8 pin serial EEPROMs
are quite common. For just setting a few configuration "jumpers," you can buy
"solid state DIP switches" which are a handful of analog switches controlled
by a tiny bit of non-volatile memory (all built into the IC); software running
on a PC and a small program header are used to "flip" the switches' positions.
I was going to suggest Maxim as a source, although I'm only finding digital
pots there... and an application note on using it as a DIP switch. Still, I'm
sure I've seen such things.

None of these solutions are directly applicable (without additional circuitry)
at 24V. If you don't mind the extra manufacturing hassle, the zero ohm
resistor approach works quite well. A step up from there is, of course, a
mechanical DIP switch. While I understand you don't want customers
misconfiguring the board, if the board is enclosed or otherwise difficult to
physically access (i.e., takes enough effort that a customer can't
realistically claim they accidentally bumped it and it changed!), there is
great value to field service personnel as well as your own stock room to only
requiring having one physical version of the board kicking around.

If you have a number of similar cards that you're thinking of jumpering,
sometimes you can instead make all the cards the same and isntead build the
back panel that they plug into differently so they know who they.

---Joel Kolstad

Here's yet another solution that is cheap in high volume- a flat cable
(perhaps 0.1" or 2mm pitch) stripped and soldered into one position or
another (.. or another..). (formed into a U). This can configure lines
of several amperes and relatively high voltage (or microvolt level
signals) for under a penny a pin.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
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