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7 segment display connections

pgr2002

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I am attaching one circuit diagram of ESR digital meter using ICL7107. Here in this circuit the 7 segment display, 10th position is shown as "f", but actually the 10th position is "g". Which is correct. (7 segment display is common anode). Will anyone clarify regarding this and which one is correct.
Pin "9" is also interchanged in circuit diagram and the rest of the pins match.
 

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  • Circuit Diagram.png
    Circuit Diagram.png
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  • 7 seg display pins.png
    7 seg display pins.png
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KlausST

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Hi,

There may be differnt displays aournd with differnt pinning.

Thus the only "safe" way is to find the partnumber (usually printed on it) and read the datasheet.
Everything else is guessing and may be false.

Klaus
 

danadakk

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The schematic has f and g connections to 7107 swapped on all 3 digits,
LD1 - LD3.

Regards, Dana.
 

pgr2002

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The connections are not swapped, the display symbol has a typo, f/g letters swapped.

Can I assume that the digits 9 & 10 instead of g & f and proceed accordingly
--- Updated ---

Hi,

There may be differnt displays aournd with differnt pinning.

Thus the only "safe" way is to find the partnumber (usually printed on it) and read the datasheet.
Everything else is guessing and may be false.

Klaus

The part number that I have is HDSP5501 HILITE and this segment has what I had previously attached the 7 segment display file.
And the letters concerning f & g is in the same position as in the file, but letters differ
 

Aussie Susan

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Of course you could always just try it and see. A very simple test rig (power source, resistor and a couple of wires) will tell you in seconds.
However I'd go by the data sheet.
Susan
 

pgr2002

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Hi,

There may be differnt displays aournd with differnt pinning.

Thus the only "safe" way is to find the partnumber (usually printed on it) and read the datasheet.
Everything else is guessing and may be false.

Klaus

Thanks a lot. I just completed the meter with veroboard. The variable resistor in the schematic is 25k. I could not get this but I had 20k.
At the time of calibration R21 i.e. 1K is preset to 0.00 when both the test leads are connected. Upto this it is ok. But when we connect
18 ohms between the leads and adjust R25 (25k) (20k is used) it is not showing and adjusting to 18 ohms but gives more than 53 ohms.
Is it due to this 20k. But when I check with good caps it is showing 0.00 or 0.01 or 0.02 but not further. please clarify.
 

KlausST

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Hi,

I am not surprised that a veroboard design gives wrong reading.
I guess you don´t use a proper GND plane ... and without GND it is more difficult to get it working accurately.

We maybe can give you some wiring hints when you show us your veroboard.

Klaus
 

pgr2002

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Hi,

I am not surprised that a veroboard design gives wrong reading.
I guess you don´t use a proper GND plane ... and without GND it is more difficult to get it working accurately.

We maybe can give you some wiring hints when you show us your veroboard.

Klaus

please see the attached image
 

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  • vero board.png
    vero board.png
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