Re: [CAD_CAM_EDM_DRO] Hp 7475 Plotter Servo's

----- Original Message -----
From: "Stephen Wille Padnos" <spadnos@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, October 04, 2005 9:33 AM
Subject: Re: [CAD_CAM_EDM_DRO] Hp 7475 Plotter Servo's


> Victor A. Estes wrote:
>
>>Tom H.,
>> I have negative voltage coming off of pin 3 of the computer's com1
>> port.
>>But I'm not convinced that the computer is sending out any data from the
>>com1 port. When I send a sting of commands through the port using DOS, I
>>did not get any change in the voltage across the pin. In fact when I send
>>the string, my curser hangs up and does not let me type any more commands
>>without first exiting the DOS window and then opening back up and starting
>>over.
>>
>>
> Try using HyperTerminal. You can cut/paste text into it if you want to
> send data quickly. If you were opening the port with ",p" at the end,
> try not doing that - it turns on XON/XOFF handshaking, which you don't
> want for testing purposes. You should use something like "mode
> COM1:9600,N,8,1".
> -12V is correct for the "mark" state = logic 1, +12 for "space" = logic
> 0 (unless I've got them backwards :) ). The port should be toggling
> rapidly (depending on the baud rate) between -12 and +12 V. You won't
> be able to see it on a multimeter, you need a scope for that. What you
> may be able to do is pick some character that has 4 bits on and 4 off
> (try "f" - make sure it's lower case - that's 01100110 binary), and see
> if you get a DC voltage near 0.
> You could also try setting it to 110 baud, and put the meter on AC -
> sending 'f' characters at 110 baud would give something close enough to
> 60 Hz to be detectable.
>
>> I think at this point I am going to try and find a DOS only computer
>> (No
>>Windows) laying around and try it.
>>
>> Still trying to get the plotter to work.
>>
>>Victor A
>>
> Good luck with that
> - Steve
>
>
>
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