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'[EE]: Taking reading from 7-segment BCD (TC4511)'
2001\03\28@110815 by Joe Denehan

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We have a machine where I work which if fairly old. When it jams it reports
the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
capture the BCD input to the display using a PIC and translate this code to
an error message which will be displayed on LCD. I have the circuit working
on a breadboard but when I connect to the trigger LE on the display the
trigger signal distorts ( measured with oscilloscope ) and affects the
7-segment display, I cannot get a reading. I tried a direct input into the
PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and 1M
resistors to limit the current draw but the signal still distorts. Can
anyone suggest a way to get the trigger from LE without distorting the
original signal?

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2001\03\28@122507 by M. Adam Davis

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Try telling us more about the circuit you are connecting your design
to.  What is creating this LE?  How are the LEDs being driven, exactly?

-Adam

Joe Denehan wrote:
{Quote hidden}

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2001\03\28@140127 by Spehro Pefhany

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At 07:56 AM 3/28/01 +0100, you wrote:
>We have a machine where I work which if fairly old. When it jams it reports
>the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
>capture the BCD input to the display using a PIC and translate this code to
>an error message which will be displayed on LCD. I have the circuit working
>on a breadboard but when I connect to the trigger LE on the display the
>trigger signal distorts ( measured with oscilloscope ) and affects the
>7-segment display, I cannot get a reading.

Is it possible you have not set the PIC port pin to be an input?

> I tried a direct input into the
>PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and 1M
>resistors to limit the current draw but the signal still distorts. Can
>anyone suggest a way to get the trigger from LE without distorting the
>original signal?

The LE is just a regular CMOS input to the latch/decoder/driver chip
(latch enable). What is it being driven by?? Even if it comes from some
bizarre high-impedance source the PIC input shouldn't affect it much.
What if you just connnect a regular CMOS gate or inverter to it as a buffer?

Best regards,

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2001\03\28@141349 by Andre Abelian

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part 1 1148 bytes content-type:text/plain; (decoded 7bit)

Using opto isolator is one way to do it.
see attached pdf file and let me know how did you wire them.

Andre Abelian


> We have a machine where I work which if fairly old. When it jams it
reports
> the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
> capture the BCD input to the display using a PIC and translate this code
to
> an error message which will be displayed on LCD. I have the circuit
working
> on a breadboard but when I connect to the trigger LE on the display the
> trigger signal distorts ( measured with oscilloscope ) and affects the
> 7-segment display, I cannot get a reading. I tried a direct input into the
> PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and
1M
> resistors to limit the current draw but the signal still distorts. Can
> anyone suggest a way to get the trigger from LE without distorting the
> original signal?
>
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>
>


part 2 28921 bytes content-type:application/pdf; (decode)

part 3 154 bytes
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2001\03\29@040020 by Roman Black

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Joe Denehan wrote:
>
> We have a machine where I work which if fairly old. When it jams it reports
> the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
> capture the BCD input to the display using a PIC and translate this code to
> an error message which will be displayed on LCD. I have the circuit working
> on a breadboard but when I connect to the trigger LE on the display the
> trigger signal distorts ( measured with oscilloscope ) and affects the
> 7-segment display, I cannot get a reading. I tried a direct input into the
> PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and 1M
> resistors to limit the current draw but the signal still distorts. Can
> anyone suggest a way to get the trigger from LE without distorting the
> original signal?


Try adding a 2k2 pull-up resistor to the LE pin real
close to the latch chip, then add a 220pf cap between the
LE pin and GND. Also, how far is your other circuit,
ie wire length?
-Roman

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'[EE]: Taking reading from 7-segment BCD (TC4511)'
2001\04\01@125209 by Joe Denehan
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-----Original Message-----
From: .....joe_denehanKILLspamspam@spam@esatclear.ie [joe_denehanspamKILLspamesatclear.ie]
Sent: Wednesday, March 28, 2001 7:56 AM
To: Pic Microcontroller Discussion List
Subject: [EE]: Taking reading from 7-segment BCD (TC4511)


We have a machine where I work which if fairly old. When it jams it reports
the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
capture the BCD input to the display using a PIC and translate this code to
an error message which will be displayed on LCD. I have the circuit working
on a breadboard but when I connect to the trigger LE on the display the
trigger signal distorts ( measured with oscilloscope ) and affects the
7-segment display, I cannot get a reading. I tried a direct input into the
PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and 1M
resistors to limit the current draw but the signal still distorts. Can
anyone suggest a way to get the trigger from LE without distorting the
original signal?

Re-posting

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2001\04\02@100154 by Roman Black

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Joe Denehan wrote:
>
> -----Original Message-----
> From: EraseMEjoe_denehanspam_OUTspamTakeThisOuTesatclear.ie [joe_denehanspamspam_OUTesatclear.ie]
> Sent: Wednesday, March 28, 2001 7:56 AM
> To: Pic Microcontroller Discussion List
> Subject: [EE]: Taking reading from 7-segment BCD (TC4511)
>
> We have a machine where I work which if fairly old. When it jams it reports
> the error as a 2-digit code, displayed on 2 7-segment displays. I wish to
> capture the BCD input to the display using a PIC and translate this code to
> an error message which will be displayed on LCD. I have the circuit working
> on a breadboard but when I connect to the trigger LE on the display the
> trigger signal distorts ( measured with oscilloscope ) and affects the
> 7-segment display, I cannot get a reading. I tried a direct input into the
> PIC, I tried an Opto-isolator and also tried an Op-amp as an inverter and 1M
> resistors to limit the current draw but the signal still distorts. Can
> anyone suggest a way to get the trigger from LE without distorting the
> original signal?


Joe, you have been struggling with this
for a while, it really shouldn't be that
hard.:o)

Might I suggest showing us a circuit diagram?
-Roman

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