The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Gary Tait
Subject: Re: LCD Question
References: <email@example.com> <firstname.lastname@example.org>
X-Newsreader: Forte Free Agent 1.92/32.572
Date: Sat, 02 Nov 2002 10:29:11 -0500
NNTP-Posting-Date: Sat, 02 Nov 2002 10:29:30 EST
Organization: WorldCom Canada Ltd. News Reader Service
On Fri, 1 Nov 2002 19:08:17 -0500, "Jack B. Pollack"
>Thanks Wafer & Gary ,
>Both of your posts were helpful. From Wafer's post I envisioned the whole
>process as a data and address type of scenario for each digit, but was
>baffled when I masked out with tape one of the contacts to find what
>appeared to be random segments disabled.
>Gary's post was right on the money 'it is not even on a digit basis'.
>Now that I understand how this works let me try to ask a little more
>We have a really nice Jacob Jensen digital clock that only displays time in
>24 hour format, this drives my wife crazy. When I opened the clock I found
>a hardwired jumper to set the time format.
>The clock now displays time in 12 hour format, but the display lacks a PM
>indicator making the alarm function useless.
>I am sure that the 'blob' is outputting a signal for PM, but how do I find
>it (In a data/address scenario I would have looked for it on the 'digit'
>with the other indicators ('Alarm on', time set, etc)? But since segments
>are 'random' how do I find it?
Is there an AM indicator? If so, you could wire in a circiut (I think
an XOR gate), to figure if that segment is active, and use that signal
to drive your PM indicator, when it is "not" AM.
>Secondly, I was going to drive a small low current LED for the PM indicator.
>I dont think this will work based on the explanation of the 2 square waves.
>I guess I could NAND them and then use the NAND as a driver for the LED (I
>dont know if the square wave voltage is too low to drive TTL). Any
>suggestions on indicate PM would be appreciated.
I think an XOR gate is what you want. You can use other elements of
the chip as an invertor, if needed. I suggest a CD4070
>"Jack B. Pollack" wrote in message
>> I have several questions about a LCD display in a portable clock that I
>> There are 13 'pad' connections on the PC board that connect the LCD
>> to the PCB and 'blob chip'. If I look at these connections with a scope
>> there is a square wave on each of them.
>> The display has no electronics in it, how is the data transferred to the
>> display and decoded? How are the individual segments on the display
>> The second question is about the LCD backlight:
>> There is a thin film (looks like a piece of paper) with 2 contacts on it.
>> When 50V AC is applied the film glows blue and backlights the LCD. I would
>> like to find out more about this type of backlight technology and how to
>> build a similar driver circuit for the backlight.
>> Any insight would be appreciated.
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup