RE: TI-H: Add LEDs to your link cable!
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RE: TI-H: Add LEDs to your link cable!
The parallel port uses TTL logic which is 0V and 5v. Serial ports use +12v and -12v.
I use parallel port but assume that zener's are being used to drop the RS232 voltages
down to TTL levels.
-----Original Message-----
From: Brad Formby [SMTP:bradformby@mindspring.com]
Sent: Tuesday, September 09, 1997 7:23 PM
To: 'ti-hardware@lists.ticalc.org'
Subject: RE: TI-H: Add LEDs to your link cable!
In the parallel link, no zener's are used? just plain old diodes? I still am not sure what exactly the problem is? I think I'll go play with my multimeter and see the difference with LEDs
-----Original Message-----
From: Tony Do [SMTP:tonyd@execpc.com]
Sent: Monday, September 08, 1997 10:48 PM
To: ti-hardware@lists.ticalc.org
Subject: Re: TI-H: Add LEDs to your link cable!
Brad Formby wrote:
>
> Actually, I believe an LED uses too much current or doesn't switch quickly
> enough, for when I tried that the link simply failed to function. (Unless
> I really did something strange... :) )
Well, for the $4 link, the Zener diodes limit the voltage reaching the
calculator to 5V, and I don't think LED's have any kind of voltage
control, so you may be getting more than 5V to your calc... I think?
Tony
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