On 8 May 2013 23:09, john d norton <[email protected]> wrote:

> I would have too much io on the intended machine for just the p port
>
> I was wanting to use the Mesa 5i25 7i76 png kit

In that case you might want to discuss with Mesa. it is entirely
possible that there is an easy way to make the 7i76 24V-compatible.

> Then the strip board with uln chip - is there anything else to go with
> the chip apart from the required connectors
> Is it just a case of field power to the chip signal to the chip and
> output from the chip

Pretty much, yes. The ULN is a switch-to-0V device, though, which
requires a bit of mental gymnastics if you are used to thinking about
+5V = yes 0V = no.

You need to think in terms of current flow through the optos on the
drive inputs. So +24V from your PSU goes to the + terminal of the
input, the relevant pin of the ULN connects to the - terminal of the
input, and the common ULN Earth/ground pin connects to the PSU 0V.
When there is 5V on the ULN input pin, then there is current flow into
the output pin to earth, the LED in the opto lights up, and a signal
is seen by the drive.

The ULN2003 is capable of 50V and 0.5A per output.

-- 
atp
If you can't fix it, you don't own it.
http://www.ifixit.com/Manifesto

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