PC Parrallel Port

[demestav]

Ok i done a bit of reading. The Parallel Port uses TTL (hopefully :lol: ) while the RF MODULE uses CMOS levels. According to http://www.interfacebus.com/voltage_threshold.html the output level of the PC could vary between 3.3 and 5V. BUT since the RF MODULE is CMOS it detects signals higher than 3.7V. SO if the PC outputs 3.4 for example as output, the RF module will not detect it. And i guess the solution would be a 10kohm pullup resistor to all the lines. Is this correct? or i should do something else? Thank you

 

[Nigel Goodwin]

Ok i done a bit of reading. The Parallel Port uses TTL (hopefully :lol: ) while the RF MODULE uses CMOS levels. According to http://www.interfacebus.com/voltage_threshold.html the output level of the PC could vary between 3.3 and 5V. BUT since the RF MODULE is CMOS it detects signals higher than 3.7V. SO if the PC outputs 3.4 for example as output, the RF module will not detect it. And i guess the solution would be a 10kohm pullup resistor to all the lines. Is this correct? or i should do something else? Thank you

As far as I'm aware it should work regardless, CMOS and TTL 5V logic levels are compatible. I'm pretty sure the logic switching level for CMOS (running from 5V) is far lower than 3.7V - in fact the site you refer to above says it's 2.5V!.

Try it and see!, why worry about something which most probably isn't going to be a problem - I've never even measured the voltage out of a parallel port, nor do I have any intention of ever doing so.

 

[demestav]

Yep i am trying tomorrow morning... Thnx for replies.

 

[demestav]

Well, I came to uni got the RF modules, but it is really hard to connect them with any way on a testing board. I searced in RS Components and FARNELL Electronics for something that maybe could convert the pin layout to DIL, but i could not find any. Could you plz suggest me something?? Anything??
Thank you.

 

[Nigel Goodwin]

Well, I came to uni got the RF modules, but it is really hard to connect them with any way on a testing board. I searced in RS Components and FARNELL Electronics for something that maybe could convert the pin layout to DIL, but i could not find any. Could you plz suggest me something?? Anything??
Thank you.

I'm presuming you're wanting to plug them into a breadboard?, this isn't a good idea! - breadboards and RF don't mix!.

A couple of modules I've just got even say not to use veroboard!, though I don't really see the difference between that and a PCB - if you remove the unused tracks!.

 

[demestav]

hello nigel and thnx for your reply. Well i just got back from the uni and i am really dissapointed. I used small insulated crimp terminals to connect the RF module on the breadboard ( it was before i read your post). Well i quickly constructed the testing circuit shown on their datasheet (http://www.radiometrix.co.uk/products/sp2.htm) and try to test it. Unfortunately (as always) i rushed to do that, connecting both the RF Modules with 10V instead of the standart 5V and 5 seconds passed before i realised that. I saw no LED light. Actually i saw nothing. I was testing for about 5 hours with no result. And now i dont know what should i do. Are they destroyed? or i just dont manage to operate them. The thing is that the debug circuit is very simple leaving small margins for errors. Is there anyway to test whether they are blown up? I measured the current passing through and is about 4.5mA while it should be about 10mA. i would hate to tell my supervisor that i have blown £120 in one go!! I feel terrible..
Thank you for reading.

 

[Nigel Goodwin]

hello nigel and thnx for your reply. Well i just got back from the uni and i am really dissapointed. I used small insulated crimp terminals to connect the RF module on the breadboard ( it was before i read your post). Well i quickly constructed the testing circuit shown on their datasheet (http://www.radiometrix.co.uk/products/sp2.htm) and try to test it. Unfortunately (as always) i rushed to do that, connecting both the RF Modules with 10V instead of the standart 5V and 5 seconds passed before i realised that. I saw no LED light. Actually i saw nothing. I was testing for about 5 hours with no result. And now i dont know what should i do. Are they destroyed? or i just dont manage to operate them. The thing is that the debug circuit is very simple leaving small margins for errors. Is there anyway to test whether they are blown up? I measured the current passing through and is about 4.5mA while it should be about 10mA. i would hate to tell my supervisor that i have blown £120 in one go!! I feel terrible..

It sounds to me rather like you may have blown the modules :cry:

If they quote 5V maximum, they usually mean it, and it's for good reason, certainly doubling their supply is likely to be fatal to them!.

I can only suggest connecting them to 5V and testing them, if you feed a 5V squarewave signal in to the transmitter (try at least 1KHz), you should be able to see a similar output on the receiver with an oscilloscope.

You may have been 'lucky' and only killed one of the modules, but you will probably need another pair in order to test this.

 

[demestav]

Hello and thnx for the reply...
I am still trying to get them to work..The one of the two shows some signs that is alive. I have two questions if you know the answers

(1) The are two RF GND pins, where are these connected if the antenna is just a simple wire?

(2) How can i detect if signals are transmitted from the antenna?

Thank you.

 

[Nigel Goodwin]

Hello and thnx for the reply...
I am still trying to get them to work..The one of the two shows some signs that is alive. I have two questions if you know the answers

(1) The are two RF GND pins, where are these connected if the antenna is just a simple wire?

You would connect them to a metal case, assuming you used a metal case!.

(2) How can i detect if signals are transmitted from the antenna?

With some kind of receiver that covers that frequency range, a spectrum analyser would probably do the job!.

 

[dustinpruente]

adding to that, i would also be interested in using the com port on my laptop to emit a rf frequency equivelent to that of a cell phone, so i can jam my neighbor who is always outside the house screaming at her boyfriend (ex?) on her cell. can anyone help me out with that, so i can get some sleep? also, am interested in using the same com port to make a cordless phone scanner, or a cell phone scanner. that would be fun.

 

[demestav]

Well suprisingly enough, after some hours i managed to find out what went wrong. Right now i sent a test message with the one module and the other one connected on my PC Parallel Port ( ), indicates that it receives it. I dont have enough wires to completely connect the module to the PP and receive the message on the PC, but i am optimistic that everything will be fine. It seems that they survived the 10V shock i gave them :roll: :lol: (hopefully!!!!!)

Thank you for your replies so far.