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HiLetgo 2pcs PCF8574 PCF8574T IO Expansion Board I/O Expander I2C Evaluation Develop Module

Q: Is there a wiring schematic for the pull-up resistors to trigger a relay from a esp8266. the pcf8574 wont put out voltage to trigger?

What kind of relay? Need to know voltage and current for the relay coil. Best bet is to use an fet to drive the relay. Still need to know your relay specs to answer completely.

Q: Are these only digital I/O or also analog?

These are discrete only, no analog. Best to use them as active = low. I follow them with a 74LVC14A when I need active = high. Note the chips come in 2 address ranges. I have been receiving the low range with consistency.

Q: Leds connected with vcc = 3.3v to board make them too dim. is this usual?

There are a couple of reasons this could happen. The pins on the PCF8574 can only sink 25 mA of current and, if I'm reading the datasheet correctly, can source much less. So you'll want to put the LED from Vcc to the output pin (so that low = on) and use at least a couple hundred ohms of series resistance.

Q: Where should the pullup resistor be placed to trigger a relay from an mcu?

You can use any of the I/O pins of the Device. Do not exceed rated current!

4.1/5

Product ID: 316555261

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Details

Brand
HiLetgo
Connectivity Technology
I2C
Included Components
[2 x IO
Compatible Devices
Arduino Pi and
Processor Count
1

Frequently Bought Together

HiLetgo 2pcs PCF8574 PCF8574T IO Expansion Board I/O Expander I2C Evaluation Develop Module

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Description

HiLetgo 2pcs PCF8574 PCF8574T IO Expansion Board I/O Expander I2C Evaluation Develop Module

Specifications

Manufacturer	HiLetgo
Part Number	3-01-1150
Item Weight	0.634 ounces
Package Dimensions	5.39 x 3.82 x 0.51 inches
Item model number	3-01-1150
Is Discontinued By Manufacturer	No
Size	Small
Color	Blue
Item Package Quantity	1
Included Components	[2 x PCF8574/PCF8574T IO Expansion Boards]
Batteries Included?	No
Batteries Required?	No

Have a Question? See What Others Asked

Is there a wiring schematic for the pull-up resistors to trigger a relay from a esp8266. the pcf8574 wont put out voltage to trigger?

Are these only digital I/O or also analog?

Leds connected with vcc = 3.3v to board make them too dim. is this usual?

Where should the pullup resistor be placed to trigger a relay from an mcu?

Common Questions

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