What voltage and current to control 1 segment of LCD ?

Hi..

How high is the current needed to switch ON one segment of a seven segment number on a LCD screen ? What is the voltage needed for this ?

Is the current enough to light up a small LED ?

Thanks.

Hi..

How high is the current needed to switch ON one segment of a seven segment number on a LCD screen ? What is the voltage needed for this ?

Is the current enough to light up a small LED ?

Thanks.

The current is usually in the nA "nano-Ampere" range. The voltage can be anything from about 1 to 3 volts or so, depending on the design of the unit. The voltage is not DC, but is usually at 15 to 30 Hz, depending on the design necessity for the display and application.

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Jerry G. GLG Technologies GLG ==========================

How high is the current needed to switch ON one segment of a seven segment number on a LCD screen ? What is the voltage needed for this ?

Is the current enough to light up a small LED ?

Thanks.

-- Email address: hihihi wanadoo nl Replace the spaces with @ and .

l though the current available from an LCD driver may be sufficient - not sure why you would want to thoiugh...

I found a Philips PM 2544 Logic multimeter on a secondhand market. Problem is the LCD is partly black. One number and the volt/amper/ohm indicators are unreadable.

I thought about connecting the signal from the LCD driver to a external 7 segment number and a few leds. That way i could read the measured info, missing from the LCD.

But it looks like i found a new way :-) The signal to the LCD driver is a serie of pulses. Which contain all the data which would be displayed on the LCD.

I am trying to connect this signal, via a opto-coupler, to a serial or parallel port on a computer. Then make a prog which converts the pulses to a number on screen.

Who needs a LCD screen when you can have the measured data inside a computer :-)

Its easier then that. You do not need to mess with the LCD or its drivers. Here is a picture of the signal to the drivers.

It contains all the info displayed on the lcd. Its like a I2C or SPI signal.

I have allready connected it to the pin 13 of the parallel port. Now i have to figure out what the signal says :-)

I am making progress :-) Here is a picture of the signal for different range selections. The data has been actually read by the computer from the pin 13 of the parallel port. So that part works.. I had never done it before..

Good second hand ones seem to be around 160 Euro but perhaps you can get a new meter that will do what you want a lot cheaper. Is it really worth spending a few hours trying to fit it?

CWatters casted

Yes.. There is now way i am going to spend that much money on a meter. This one costed 3 euro on a secondhand market :-)

I do not need such a meter. But i am having fun trying to make it work :-)