Re: [CAD_CAM_EDM_DRO] Parallel port relay blues

On Sunday 30 January 2005 01:14 am, codeSuidae wrote:

> Roy J. Tellason wrote:
> >On Saturday 29 January 2005 09:30 pm, Alan Marconett wrote:
> >>Are you tying one end of the relay to +5, and the collector to the other
> >>end? The output gate of the parallel port is "sinking" current in this
> >>case.
> >
> >If it were a circuit configuration
> >with say the inversion of the above arrangement, using a PNP transistor
> >(2N2907 comes to mind as the opposite number of the 2N2222),
>
> If you don't have a PNP you can also just use a second NPN as an
> inverter, something like the circuit below should work.
> (view in non-proportional font, or copy to notepad)
>
> VCC
> +
>
> +------o
>
> .-. o_ +---------->
>
> | | ) o
>
> 1k| | Relay ) / Relay Contact
> '-' o_) o---------->
>
> | |/
>
> +----| 2N2222
>
>
> ___ |/ |
> In >--|___|--| 2N2222 |
> 1k |> |
>
> +------+
>
> ===
> GND
> (created by AACircuit v1.28.4 beta 13/12/04 www.tech-chat.de)
>
> Hope that helps
> CS

This doesn't address the issue of the port being expected to source current,
though, rather than sinking it...