[HH] cheapest/simplest way to control a relay from a PC

[Mark Woodward]

On 11/18/2012 01:28 PM, Tom Metro wrote:
> Mark Woodward wrote:
>>>> Tell us what you choose, and how it works for you in your application.
>>> I wanted to prototype this using my desktop machine, rather than the
>>> target server, and it doesn't have a parallel port.
>> I've been following this thread for a while and I'm confused.....
>>
>> I originally thought you wanted to drive a relay from a parallel port...
> Correct. That's still the plan.

So, did you see the schematic I posted? It is a standard TTL interfacing 
circuit. 2 resistors, a diode, a 2n2222 and a relay. Excluding the relay 
and connector, its probably 50c worth of stuff and you can build it onto 
the connector.

>
>
>> and I'm reading that you have a USB parallel printer interface, which
>> you have seen is not the same thing. Let's put the engineering caps on!
> It was a lengthly post, so you may have missed it, but I explained that
> the only reason why I was exploring the USB option was for the
> convenience of prototyping the interface using my desktop, rather than
> the MythTV server located in my basement. (See quote above.)
>
> I also noted that I anticipated issues with a USB parallel adapter.
> Still, I was curious to find out what those issues would be. Now I know.
> And so I shared that.
>
>   -Tom
>
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