Hi all, I've a Rasperry Pi that is connected to an 8-Bit IO-expander (PCF8574) over I2C. The IO-expander should control a Solid State Relay Board from SainSmart. The name of the Relays is "Omron G3MB-202P". But when I connect the Relayboard to the IO-expander (pins configured correctly as output) the pins will change to HIGH in the console and are not controllable anymore until I disconnect the RelayBoard from the IO-exapnder. The setup works for me, when I connect a normal Relay board (like the Board from SunFounder that is made for Arduino) to the IO-expander. Thanks in advance, Michael Mayerhofer
Michael_mhr wrote: > But when I connect the Relayboard to the IO-expander Show a schematic of the complete wiring including the supply/supplies.
There is no special wiring. I have a breakout board from Waveshare with the PCF8574 on it that is directly connected to the relay board from Sainsmart. The RelayBoard Power-in is wired to the RaspberryPi 5V. The Power supply and I2C of the breakout board is also directly connected to the RaspberryPi. As I wrote above, this setup works perfectly with a normal RelayBoard. Michael_mhr
Michael_mhr wrote: > As I wrote above, this setup works perfectly with a normal RelayBoard. Anyway: electricians talk to other electricians by using schematics. So just draw 2 schematics. One of the working configuration and one of the faulty. Add as much information to those schematics. It will help you further on... > I have a breakout board from Waveshare with the PCF8574 on it that is > directly connected to the relay board from Sainsmart. Add information and/or a link to those boards also. There is more than 1 relay board availabe from sainsamrt. No one of those relay boards can be directly connected to the IO expander. There must be done some wiring. Maybe you can post a photo of that.
Michael_mhr wrote: > But when I connect the Relayboard to the IO-expander (pins configured > correctly as output) the pins will change to HIGH in the console You can't configure a PCF8574 pin as output (there is no direction register). Reading the data register just returns the pin state. If you set the pin to LOW, the chip will strongly pull down the line. If you set the pin to HIGH, the chip will weakly pull up the line. So if you output a LOW and you see a HIGH, then something is driving against the PCF8574, and is stronger than that chip. This might already have killed the PCF8574. Check your wiring for shorts.