How to set full scale of 1.0V on this tool ?

[Externet]

Hi. Seems a nicely made calculator, I can interact to a certain point, but need help to use it from 0V for bottom led lit to 1.0V for the tenth led lit. The dot mode and other selections work fine.

----> https://www.electro-tech-online.com/tools/LM3914V3.php

Where to set the 1.0 Volt upper limit ?

 

[ericgibbs]

Hi. Seems a nicely made calculator, I can interact to a certain point, but need help to use it from 0V for bottom led lit to 1.0V for the tenth led lit. The dot mode and other selections work fine.

----> https://www.electro-tech-online.com/tools/LM3914V3.php

Where to set the 1.0 Volt upper limit ?

hi,
If you look at the attached circuit diagram for the LM3914 you will see it uses an internal 1.25V reference voltage.

If you want a 1 Vin to set LED10 ON, use a +0.9V Vref for Pin #6 [RHi], connect a 1k2 resistor across pins #7 and #8, with Pin #8 also to 0V [ this sets the LED current to approx 10mA].

Lighting the LED on Pin #1, for a 0Vin will be a problem, as RLo, Pin #4 has a internal 1K.

One option would be to apply a +0.25V Offset onto the Vin voltage, this would make Vin appear as +0.25V thru 1.25V.

In that way you could use Pin #6 as normal ie: use the internal +1.25V.

Do you follow that OK.?

Eric

 

[Externet]

Thanks, Eric; understood.

The question was more about the use of the tool; which of its window fields are use selectable and which are calculated results. Found some fields reverting to defaults, and unclear use instructions.

 

[ericgibbs]

Thanks, Eric; understood.

The question was more about the use of the tool; which of its window fields are use selectable and which are calculated results. Found some fields reverting to defaults, and unclear use instructions.

hi,
I will check it out and upgrade asap.

Eric