Best I/O serial expander?

[fuzzzy]

serial expander

Hi,

according to your experience, could you tell me wich is the best I/O I2C serial expander to drive 15 automotive relays? I tryed to use PCF8575 interfaced by ULN2003 but It doesn't work.

Do you think PCA9555 could work? is there a better device to do this job?

thanks

 

[tjalps]

pcf8575 problem

You have several drivers from Maxim, Motorola, Philips, Microchip...

Did you consider use of SPI and not only I2C...

What is the power consumption of your relays?

Regards!

 

[jdhar]

Your limitation sounds like it's the current required by the relays. I have used the PCA9538 no problem, but they can only put out so much current. You may have to use a transistor to turn on your relays.

 

[fuzzzy]

I had problems driving Automotive relays through a darlington array(uln2003).
and I had same problems driving leds directly using a PCF8575.

NOW I found PCA9555, that i think is more suitable for this job. i'm asking you if according to your experiences this expander can work to drive relays or do you think there is a better device ?


reading datasheet, i can say that these device cant' drive directly relays.only (10mA sink)

 

[Bingo600]

I had problems driving Automotive relays through a darlington array(uln2003).
and I had same problems driving leds directly using a PCF8575.

NOW I found PCA9555, that i think is more suitable for this job. i'm asking you if according to your experiences this expander can work to drive relays or do you think there is a better device ?


reading datasheet, i can say that these device cant' drive directly relays.only (10mA sink)

If your wire length to the relays are more than a couplt of inches , you still need protection diodes on the relays , the ones in the ULN2003 is not enough

/Bingo