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Author Topic: Parallel LCD question based on winterstick article  (Read 2722 times)

Camay123

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Parallel LCD question based on winterstick article
« on: March 15, 2004, 04:47:30 PM »

Im playing with an LCD display, base on Winterstick article

Im trying to put a led in the circuit and a switch.
When the circuit is on by the switch, the led is suppose to light up.
But im having a problem, in the circuit there is the printer port and and 5v supply coming in. My problem is, the led is always light up when my printer port is plug, even if I dont supply the 5v by having the switch at off.

How can I setup this for the led to light up only when switch is on (5v is supplied ) and the led off when the switch is off ? there seem to be electricity on the printer port. (2,5v DC is coming from the printer port)

I made a graph of my circuit as I tought it would work:

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Skylined

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Parallel LCD question based on winterstick article
« Reply #1 on: March 15, 2004, 06:15:50 PM »

Just a question, why do you want a LED?
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chase!

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Parallel LCD question based on winterstick article
« Reply #2 on: March 15, 2004, 06:27:42 PM »

He just wants it to turn on when the LCD is on. What's the problem?
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Skylined

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Parallel LCD question based on winterstick article
« Reply #3 on: March 15, 2004, 07:25:54 PM »

I think that pin 2 and 15 are feeding the LED, use a diode on that side of the line.

I'm asking why a LED because you'll notice when the LCD is "On", it's not a problem, just wondered.
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Camay123

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Parallel LCD question based on winterstick article
« Reply #4 on: March 15, 2004, 08:46:18 PM »

Quote from: Skylined
I think that pin 2 and 15 are feeding the LED, use a diode on that side of the line.

I'm asking why a LED because you'll notice when the LCD is "On", it's not a problem, just wondered.


Well yeah. The led as really no purpose, but just to add to the project :)
I think it's nice to have a nice high mcp red led.

Pin 2 and 15 are hook directly to the 5v source. But the led stays on even if the 5v source is not present.
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Camay123

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Parallel LCD question based on winterstick article
« Reply #5 on: March 15, 2004, 08:59:20 PM »

You must be right, because I have hookup everything excpt my 5v supply, the printer port was plugged. The led was on. I then cut the wire that goes from my board to the pin 2 and the led was off.

Pin 2 is feeding my led.

Now, what sort of diode do I need.
Please be specific because I only know the basic in electronics.
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Skylined

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Parallel LCD question based on winterstick article
« Reply #6 on: March 15, 2004, 09:09:03 PM »

I only know the basics too, I haven't worked with diodes, so I'll leave this to viridius or linear.
I know both of them are busy, so get a diode that is rated more than 5V and 1A, I think that would do it.
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Camay123

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Parallel LCD question based on winterstick article
« Reply #7 on: March 15, 2004, 10:43:32 PM »

Quote from: Skylined
I only know the basics too, I haven't worked with diodes, so I'll leave this to viridius or linear.
I know both of them are busy, so get a diode that is rated more than 5V and 1A, I think that would do it.


I see alot of diodes on ****.

Would a 100v / 3A rectifier diode be too much or it doesnt matter as long I dont go below 5v/1A ?
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Skylined

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Parallel LCD question based on winterstick article
« Reply #8 on: March 15, 2004, 11:12:20 PM »

I think that's overkill.
Get 10V 1A or something like that.
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Camay123

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Parallel LCD question based on winterstick article
« Reply #9 on: March 15, 2004, 11:22:37 PM »

But would it still do the job ?

I could get for cheap some 50v / 1A diode.
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