Re: 5V+ Supply for Gecko? Still confused!

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers <rogersmach@y...>
wrote:

> Abby,
>
> If you use the Sound logic Mach2 breakout board between the PC

and the drives, it has a 5 volt transformer on board to power the
opto-isolators of the Geckos. Bob Campbell sells them. It makes the
whole thing plug and play practically. It also handles all the table
travel limits (proximity sensors) and outputs for the spindle,
coolant etc. Makes everything work together really well.

>
> Ron
>
> Abby Katt <cnc@a...> wrote:
> Hmm.. myabe I'm having a brainworm day, but I just don't get this
> still.
>
> Okay, since we've established that the gecko has it's own internal
> bus which is powered from the 18-80V motor supply, and we know this
> powers the encoders....
>
> The Step/Dir pins and the 5V+ pin of the gecko make up two opto-
> coupled LED's emitters. From looking at the circuit diagram, it

looks

> like the step-dir pins are triggered by negative voltage on the
> parallel port. Am I correct in assuming that when the parallel port
> pulses, it is negative?
>
> Now surely, if this is going to be negative, then there wil be a
> positive pin, or two in the parallel port, as I don't see
> lineprinters needing the PC power supply connected. All we need to

do

> is light up two opto-isolator LED's from the parallel port - surely
> there is going to be enough power/connections for that?
>
> Sorry if this is painful.... there just seems to be something I'm

not

> getting here.
>

printers don't use opto isolators.

LED's consume power. Logic chips don't need nearly as much.

But the question of will an opto work directly from the parallel
port ? The answer is some will, some won't and the ones that will
will not with 100% certanty.

The output current from the parallel port is rated for 2.5mA at 2.5
volts. As long as it meets that, it meets the specs. Your old IBM
PC would way outperform that spec. You 3.5 volt laptop will meet it,
but not excced it.

Add to the problem that if something goes wrong it will be your
parallel port. If it is on the motherboard, that means you may lose
your mother board.

Are we paranoid ? yup.
Are we overly cautios ? nope.

Is the loss risk greater than the benifit ?

Run down to Radio Shack and buy parallel port breakout box. it
looks like a small cable coupler. you can solder your wires to that.

While you are there, get a 15 pin wide DB shell for your game port.

With that, you have all you need for under $20.00. Almost all the
risk goes away.

While you are there, check the price of an add-in parallel port card
for your PC. compare which is cheaper and then make your decision.

Dave


notes on parallel port spec.
http://www.circlemud.org/~jelson/software/parapin/docs/node2.html

Quote from that page

"Output pins can assert either a TTL high value (between +2.4v and
+5.0v), or a TTL low (between 0v and +0.8v). The port can not source
much current. Specs for different implementations vary somewhat, but
a safe assumption (staying within spec) is that the voltage will be
at least 2.5v when drawing up to 2.5mA. "


picture of a breakout box

http://www.buytester.com/breakout_loopback/images/detail/2520.jpg

Dave