ULN2803 question

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#1
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Hi there,

I would like to connect to the same ULN2803 ic 3 different types of relays, simultaneously:

1st type: 5Vdc relay
2nd type: 12Vdc relay
3rd type: 24Vdc relay

My problem is that I never did this before and I really don't know where to connect the PIN10 (Internal Clamping Diodes) ???

1st connection: 5Vdc ???
2nd connection: 12Vdc ???
3rd connection: 24Vdc ???

This connection must be done in order to protect the internal Darlingtons and also to avoid any reverse current because of the different voltages.

Does anybody have any experience on this issue ?

Thank you in advance.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer

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Total votes: 0

You will have to connect it to the highest rail or the voltage, say for the 24V relay pin, will swing between ~5.6V and GND ie the relay will be always on.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Thank you.

Michael.

User of:
IAR Embedded Workbench C/C++ Compiler
Altium Designer