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283 posts

Ultimate Geek
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Topic # 99778 27-Mar-2012 09:56 Send private message

Hi,

I have a home project that I currently have it running on the parallel port.
I have two buttons (for input) that send their on/off status on the parallel port (paper out and busy if I recall correctly, it doesn't really matter) and I have some scripts (mainly call parashell) that will send 5V on other pins of the parallel port if some conditions apply.

As the parallel port will no longer be an option I'd like to get a simple USB controller that can do these tasks. It must have linux drivers.
The idea will be the same. If a button (or two) will be pressed, send a 5V on two wires.
the 5V is not mandatory as the 5V is actually triggering a relay that will close a circuit (effectively pressing a third button).

Please let me know if I haven't described the scenario properly or if you don't fully understand what I'm trying to achieve.
The real life application is quite simple. I have an on/off microswitch attached to the garage door and a PIR in the garage. If the microswitch is open (the garage door is open) too long, send an email: "Hey, you forgot to close the garage door!".
A different scenario is: if the microswitch is closed (garage door closed) and the PIR detects movement then send an email: "Hey, the cat sneaked in the garage again and it's now trapped inside!".
The 5V (output) is to trigger a relay that will open or close the garage door remotely. It can be either 5V triggering a relay or just short-circuiting two wires to close the circuit.

I can find my way around with the soldering iron but I only have basic electronic knowledge. Is there something readily available or something that can be assembled on jaycar or mindkits?

Many thanks in advance.

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5971 posts

Uber Geek
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  Reply # 600612 27-Mar-2012 10:54 Send private message

Hi, i have designed in FTDI devices to a few projects, I think the FT245R FiFo is what you need.

http://www.ftdichip.com/Products/ICs/FT245R.htm

Cheers
Cyril



283 posts

Ultimate Geek
+1 received by user: 2


  Reply # 600620 27-Mar-2012 11:09 Send private message

Hi Cyril,

It does indeed look like it's exactly what I need.
It seems that mindkits can bring it already built: http://www.mindkits.co.nz/store/prototyping/breakout-board-for-ft245rl-usb-to-fifo
which saves me of all the soldering and connectors.

Great stuff, thank you.


2895 posts

Uber Geek
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  Reply # 600788 27-Mar-2012 15:44 Send private message

FTDI also makes a USB cable with the commonly used USB to TTL level serial bridge inside the USB connector and the other end is just a cut wire. The FTDI chip can be reconfigured (and inverted if needed) as digital IO using a free FTDI utility, or you can use the flow control lines as is.




You can never have enough Volvos!




283 posts

Ultimate Geek
+1 received by user: 2


  Reply # 601092 28-Mar-2012 09:14 Send private message

Yes, I found the cable in a tutorial: http://hackaday.com/2009/09/22/introduction-to-ftdi-bitbang-mode/
And I ordered one :)

Cheers

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Uber Geek
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  Reply # 601417 28-Mar-2012 17:13 Send private message

Be aware with the FTDI TTL converters there are 5V versions and 3.3V versions. Not an issue, just be aware of it. The 5V version can take 3.3V input signals, but the 3.3V version cannot take 5V input signals.




You can never have enough Volvos!




283 posts

Ultimate Geek
+1 received by user: 2


  Reply # 601684 29-Mar-2012 08:21 Send private message

Yes, I got the 5V model. Any idea if I can use as an imput a normal on/off switch so I can read from software if the switch is on or off?

Thanks.

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  Reply # 602339 30-Mar-2012 09:34 Send private message

tcpdump: Yes, I got the 5V model. Any idea if I can use as an imput a normal on/off switch so I can read from software if the switch is on or off?

Thanks.


Yes, you can.  But you will possibly need a pull-up resistor.  Either someone will reply, of if I remember I'll have a look at it over the weekend.




You can never have enough Volvos!




283 posts

Ultimate Geek
+1 received by user: 2


  Reply # 602341 30-Mar-2012 09:36 Send private message

Great, thanks for that.

As I mentioned before, I'm not afraid to use the soldering iron but my electronics knowledge is very basic.

Thanks again.

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