Foo - Any way to know what voltage the parallel port is emitting?

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phantomcow2
08-01-06, 07:24 PM
I have an application in which I need to utilize the 5vDC pulses which your parallel port can emit. However I am told that some computers only emit 3v. Is there any way to tell, without a volt meter? THis does not sound like something manufacturers would advertise.

jschen
08-01-06, 07:25 PM
Why not use a voltmeter? They're not that hard to use, and it can't possibly be that hard to get a hold of one for a few seconds.

[EDIT] Given your interests, you probably should get yourself a decent multimeter at some point anyway.
phantomcow2
08-01-06, 07:31 PM
Its not htat I have a problem using my multimeter. But I have a laptop coming sometime soon, and want to know if it emits the 5v I need. If it only emits 3, I have to buy a small electrical circuit which will bump it up to the full 5v, as well as optoisolate my port. I'de like to have these coming at about the same time. Impatient, yes I know :).

jyossarian
08-01-06, 07:33 PM
ever lick a 9v battery? well, 3v will feel 2/3 less tingly and 5v will feel about 1/2 as tingly.
jschen
08-01-06, 07:34 PM
Impatient, yes I know :).
:lol: Yes, and a surprisingly good excuse. If it's a used laptop, I wouldn't trust anything other than a direct measurement. A spec like that may well change over the course of a model line without careful documentation. If it's new, demand an answer from tech support. (Do any new laptops still have parallel ports?)
phantomcow2
08-01-06, 08:17 PM
:(. I hate to say it, but I agree with you. I am just going to measure it. Or to avoid fussing with a voltmeter, test it out. If 5v is present, a stepper motor will go. If not, no go.
It is used, but I dont expect that the 5v would change any. That is just a transformer and bridge rectifier, power supplies last a long time. The 400mhz P2 in my basement still puts out a good 5v.
iluvfreebeer
08-01-06, 08:27 PM
Oscilloscope
phantomcow2
08-01-06, 08:28 PM
Oscilloscope
Oh yea, I forgot about that. I was wanting to buy one of those things.
sabretech2001
08-01-06, 09:06 PM
Check the manufacturer's website. My experience with IBM, hP, Toshiba, Sony, Dell and Compaq is that there will be a chart near the back of the User Manual which will let you know which pin does what. They usually toss that in there instead of really useful information, such as how to upgrade the CPU and/or HDD.

Have you thought about using the USB port to get the voltage you need?
KingTermite
08-01-06, 09:27 PM
Pinout:
http://www.doc.ic.ac.uk/~ih/doc/par/

More pinout and reference that PP uses TTL logic levels:
http://www.interfacebus.com/Design_Centronics_Connector_PinOuts.html

TTL Logic Levels Link (from above):
http://www.interfacebus.com/voltage_threshold.html
phantomcow2
08-02-06, 04:21 PM
Well pons 1-18 will be used to give step and direction pulses, just bursts of the 5v. Two will be used to control a 25amp relay, its okay for these pulses to be 3v. RElay will operate with 3-32vDC.

I could use the USB as a source of 5v, but this will not rectify the signals produced by the parallel port so that they are 5v. I could use the usb as a source for a circuit which will rectify the signals, using the input voltage of the USB to bump it up to the 5. I think its called a hex inverter circuit. I am just going to guess that this produces 5v, its easy to test. I dont want to buy this extra circuit because it optoisolates the printer port.