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# How to connect a 10 digit standard calculator display to a large LED display using minimum electronics? Answered

I am interested to display the output from a 10 digit standard calculator on to a large LED display panel that can be read from a distance of 20 meters. I have found instructions in this site on how to make a LED Display pannel. I now need to know how to connect this pannel to the calculator.

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## 6 Replies

AerialGuardian (author)2017-02-03

Why not just use a phone or tablet to calculate and send the output to the LED?

dsolares1 (author)2012-09-14

its easy. LCD is AC. LED is DC. just convert the low ampere AC output from the calculator board to a higher ampere DC. use signal transistors like BC547... for a 10 digit calculator you may need 70 transistors. and 3 separate supply.

steveastrouk (author)2009-09-02

Its pretty difficult to do, without some very low level electronic skills. Calculator displays are usually multiplexed. That means there are 7 lines used to drive all the characters at once, and a line for each single character. A circuit is made between the 7 and 1, then the next character is lit with the same 7 and its unique line. You need to pick off, then amplify the LCD drive signals and use them to drive your other display. Which LED display are you using ? Steve

clarencepinto (author)2009-09-07

Thanks Steve,
Yes I was looking for a way of amplifying the LCD drive signals so that a LED display could be lit up.
I was planning to use a Instructable on this site "LED Matrix using shift Register" https://www.instructables.com/id/SCRTJ2OFH9HU7GR/ with some modifications as the Instructable is for a dot matrix LED board. I will be using the wiring instructions only with modifications for the 7 segments of each digit.
Clarence

john3ab (author)2009-10-24

Hi Clarencepinto,

Did you progress with your project?

I want to do the same but with a VFD panel and I need some ideas about the circuit.
Will you post your project (circuit and photos) here sometime?

thanks
john

steveastrouk (author)2009-09-08

You'll need massive modifications to your suggested design. It is fundamentally unsuited to what you need to do for a 7 seg display. By the time you have only 7 LEDs, and you've changed the display interface....