Help With Parallel Port

[hyphenex]

I have found this image (attached) and I have fould that the parallel port on computers can send an output to power say an LED light but the web page doesen't tell me how to connect the LED to the computer. I only have a year 10 basic knowledge of electrical circuts and need to know where the positive and negetive terminals on this port would be.

I also need to know if there is any danger (or damage that could occur) in say connecting flood light to the port. How do I change the voltage.

The last thing I need help with is a quiestion "Is the male port the ones with the pins sticking out or the ones with holes?"

Thanks guys. (This is my first post ever)

 

[falleafd]

I have found this image (attached) and I have fould that the parallel port on computers can send an output to power say an LED light but the web page doesen't tell me how to connect the LED to the computer. I only have a year 10 basic knowledge of electrical circuts and need to know where the positive and negetive terminals on this port would be.

www.lvr.com

Connect the led like with a microcontroller. Connect it directly from data pinouts to ground (pin 18 - 25) via a resistor. Recommends to use 470 Ohm.

The last thing I need help with is a quiestion "Is the male port the ones with the pins sticking out or the ones with holes?"

It's impolite, but male has a cock and female have a hole (sorry). That's why they call it male connector and female connector. The stick out is male, and the other is female.[/quote]

 

[Exo]

I have found this image (attached) and I have fould that the parallel port on computers can send an output to power say an LED light but the web page doesen't tell me how to connect the LED to the computer. I only have a year 10 basic knowledge of electrical circuts and need to know where the positive and negetive terminals on this port would be.

Pins 18 - 25 are ground, This is where the kathode of the led must be connected to, then any one of the dataoutputs (pins 2 - 9) should go to the anode of the led through a resistor (330 ohm or so)...

If you then make your software output to the parallel port (usually 0x378 in the cpu's IO space) the corresponding led will light
pin 2 is the LSB of the data you send, pin 9 the MSB

I also need to know if there is any danger (or damage that could occur) in say connecting flood light to the port. How do I change the voltage.

You'll need to do more then change the voltage, the pc's parallel port can never drive a load like a floodlight. Buffer the parallel ports output with a transistor to drive a relay, the relay would then be capable of switching the floodlight...

 

[hyphenex]

Ok. So the cathod is the negitive and the other pins are the positive.

 

[Exo]

Yes, but you only need one data pin. For example only pin 2 from the parallel port should go to the led, and the other side of the led to ground (pin 18 ).... with a resistor in series

Each of the pins 2 - 9 represents a diffirent bit of the byte on the port. So you can run 8 diffirent leds.

 

[nettron1000]

You can connect the LEDs to the parallel port pins like this :

http://www.hut.fi/Misc/Electronics/circuits/lptleds.gif

 

[hyphenex]

Cool. I know think I have it. I have a question though. How would I go about connecting a flood light to this. Would it wreck my computer drawring that much current?

 

[Nigel Goodwin]

Cool. I know think I have it. I have a question though. How would I go about connecting a flood light to this. Would it wreck my computer drawring that much current?

The port can only supply 5V, at low current - so you would require some kind of interface, which would also need to be isolated. Probably the simplest way would be to use a driver transistor and relay, or an opto-isolater feeding a triac.

Be aware that the parallel port is fairly easily damaged, and as modern ones are part of the motherboard, you would need to replace the motherboard if you kill it!.

 

[hyphenex]

Is there any way to make sure that my port will be safe. I have already spent $1000 replacing the motherboard on my computer and don't want to do it agin. I am a screewie up person (if that word exists) and I will advantually draw to much current so is there any way to "safe guard" this port with any other devices?

 

[falleafd]

This is a clever way to save $1000 (if it costs so). If your board is damaged by using parallel port, you can cut out the protect chip on the mainboard and continue to use the board with no problem.

Most types of mainboards have the protect chip before connect to the db25 connector. Find out that chip (usually next to the connector) and cut it out. Don't worry about it, the board will be oki and work again. It's also effective to P/S2 and serial COM port. I didn't try with USB port yet, because my USB port is still good. ...

The protect chip is usually 14 - 16 pinouts. Find it on your damaged board.

 

[Exo]

On most modern motherboards the super io chip (wich includes the pport) is integrated into the chipset (one of the 2 square shaped chips). So if it's broke then its broke. Never saw a P+ motherboard with a 'protect' chip...

The only way to make sure the parallel port won't be damaged is to make the circuit right...
But I would suggest you get yourself a nice 2nd hand pc ,a Pentium 1 class machine will do nicely and cost virtually nothing. And you can experiment with it all you want...

 

[hyphenex]

I think you have got it all wrong. My motherboard broke down by it's self (No idea what was wrong with it.) and it had to be replaced. I just don't want to have to replace it agin.

What I was asking is there an electrical thing I can put into a circut to stop it from drawing to much current (volts, whatever!) or draw electricity from another source (a battery or something) and make sure it has no chance of damaging my port if i make a short circut or something.

 

[falleafd]

Come to the site I suggested above, and you will find many helpful circuits even protection. Don't worry. But if you are trying something difficult or strange, why don't you use an old old old PC? With an MMX CPU, you can run Win98 and do many stuffs on it without worries. PC is now cheap enough, and some old ones are cheaper than a programmer.!!!!!!

I have no problem with the circuit, but once, I connected the wrong pins, and it damaged my protect chip. I cut it out an continue to use until now. I don't know bout new modern mb, simply because I don't have money ...

 

[Electric Rain]

Guys guys guys... why can't he just get a cheap PCI card with a parallel port on it? Then, rather than replacing his whole motherboard, he can just replace that card if something goes wrong. Problem one solved.

About the flood light; you will need an external power supply, but to control it with your P-port, the best thing to do would be to use a relay. Here: http://www.hut.fi/Misc/Electronics/circuits/parallel_output.html This should help a lot. For that relay, look for "Building your own relay controlling circuit" on the page. Problem two solved. Let me know if you still have some unanswered questions. :wink:

Rain

P.S. Welcome to the forums! :wink:

 

[Exo]

I think you have got it all wrong. My motherboard broke down by it's self (No idea what was wrong with it.) and it had to be replaced. I just don't want to have to replace it agin.

What I was asking is there an electrical thing I can put into a circut to stop it from drawing to much current (volts, whatever!) or draw electricity from another source (a battery or something) and make sure it has no chance of damaging my port if i make a short circut or something.

As far as i know you can't buy pre-made parallel port protectors, so you wll have to make something yourself, but then we are back to the same problem... If you make an error while building the protection circuit it too may damage the port... That's why i say you should buy a old pc to experiment with if you don't want to damage your good pc.

Once you got it up and running on the old pc, you can use it on the good one

 

[falleafd]

The circuit to protect parallel port is as simple as 330 Ohm resistors. Don't use high voltage at this port, and use 330 resistors is enough.

If you scare of short circuit, try a pull up for example. pp is difficult to damage. You know, I damaged my port by applying 36VDC to the port. If you don't get this stupid mistake, your port is safe.

 

[ivancho]

If you want to protect your port just use a 74245 chip. Then if anything goes wrong it's that chip that suffers and not the port.

Ivan

 

[falleafd]

74254 is only the shift register chip, so how can we protect the inputs? We have to use 2 x 74254? That is we need another pin to enable output of 74254. 74HC573 is the same type. I usually use 74HC573 as shift register and use nSTROBE to enable outputs. That is the basic and perfect circuit.

In some cases, we dont need to care about the enable bit, but I recommend to use nSTROBE to enable outputs. As using parallel port, I always design it as identical with the printer communication as possible.

 

[ivancho]

The chip protect the inputs because the parallel port is only dealing with known impedances from the IC. This is what is calleds a buffer. So the current taken from the port will be only the one stated on the data sheet of the IC. At the other side of the chip, where you connect your inputs/outputs you will have more current available, and if you screw up you will damage the chip and not the port, had the chip not been there. Now if you want to completly not risk it, then you would need to add on top of that, a opto-isolator :wink:

You can use the direction pin to control if you read or write. Or you could just hard wire it to always output or always read the pins.

Good Luck

Ivancho

 

[hyphenex]

Thanks for all your help. I'm going to have to say good day untill I get a new (old) PC