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Topic: What is the best way for controlling array of 8-16 relays? (Read 2 times) previous topic - next topic


I2C port expander to a pair of ULN2803As to your relays should be enough. The relays don't require regulated power and their current needs are in their datasheet. Get a supply that has at least 50% more current then you need.

What are you switching and which relays are you planning on using?

What he said. Use a PCF8574N 8-bit IO expander. Its the easiest to work with.
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Oct 12, 2012, 08:00 am Last Edit: Oct 12, 2012, 09:01 am by Boffin1 Reason: 1
thats 3 chips when its all in the 2 TPICs...  although the specs say the PCF can drive an LED , and the total output is 100mA, so it might be OK for 8 x  5v relays drawing less than 12mA ? 

The TPIC can sink 150mA per latch, and handle up to 50v relays, and uses just 3 pins of the micro.
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