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I have a 4026 counter chip controlling a seven segment LED display.

The current set up is every time I press a button it advances by one digit on the display. See circuit below.

This circuit runs on 9v so I haven't been too adventurous in my testing from fear of frying the Raspberry Pi.

How can I control this with an Raspberry Pi, regarding 9v vs Raspberry Pis 3,3 volt ?

Example circuit.

enter image description here

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Since there are only output from the Raspberry Pi that should drive the 4026 7-Segment Counter there are only need for a driver circuit.

This can be done with transistors, MOSFETs or a driver IC.

A simpler way is to change the voltage for the 4026 from 9 volt to 3,3volt its within the IC's working parameter (3-15v).

And then replace the current limiting resistors to the 7-segment LED display to fit the new voltage.

And now you can interface the 4026 directly to your Raspberry Pi.

Ref.: https://components101.com/sites/default/files/component_datasheet/CD4026%20Datasheet.pdf

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    I tried with 3 V but it isn't consistently bright, i ended up using 2N2222 transistors to interface. – euan Nov 11 '20 at 15:06
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    @euan Nice, that is a appropriate solution. Did you change the current limiting resistor when you changed the voltage ? – Mats Karlsson Nov 11 '20 at 15:43
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    @MatsKarlsson No, I mean displays with several LEDs in series, which need higher voltage regardless of the current-limiting resistors. Running a single led per segment display with 9V results in incredibly poor efficiency. – Dmitry Grigoryev Nov 11 '20 at 15:51
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    @MatsKarlsson For instance SC23-12EWA is a 12V part with 4 LEDs in series in each segment (except the dot). – Dmitry Grigoryev Nov 11 '20 at 17:16
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