Arduino Yun-control different I/O pins at the same time to c

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1

Hi,

I have been trying to control the I/O pins on Yun through Ethernet/Wifi, and have two identical circuits connected on 2 different pins ( Say pin 13 and 11). The circuits that are connected are basic relay circuits to further turn an electrical appliance on or off based on pin 13 and 11 going high or low respectively.

The problem is when I try to turn both the appliances on/off, pins 13 and 11 dont go to ~5V simultaneously. Either 11 or 13 goes up to ~0.6V when turned on, when the relay circuits (load) is connected to these pins, and the other one goes up to ~5V. When I disconnect these external circuits from 11 and 13, these pins work fine and can go up to ~5V when turned on.

The external relay circuits seem to be working fine independently. And they dont require more current than pins 11 or 13 can provide, which is 40mA according to the specs, and as I understand all I/O pins can go up to 5V.

Can somebody suggest how to get ~5V on all I/O pins, so that they can drive an external circuit (in my case an electrical appliance connected via a relay switch).

Thanks.

2

Here’s a graph you should be aware of. It’s from the 32U4 (the MCU in your Yun) PDF file (Google it). The I/O pin output voltage drops rather sharply with current sourced. The graph doesn’t show the voltage @ 40 mA, but IIRC (and damn my old brain for not 'membering) I saw a table of output voltages for a 328p MCU (I suspect the pin drivers are the same) that listed something like 3.5V for a 40 mA draw.

(click on to open)

So now I ask a few questions :

  • what relays (got a link ?) are you trying to drive ? What’s their min pull-in voltage ?

  • have you looked at the physical wiring of the relay “grounds” ? It almost sounds like one relay is pulling the others ground up to some “bad” voltage.

  • does it work when you drive only pin 11 or only pin 13, one at time, not simultaneously ? I am unsure how to interpret the following statement.

The external relay circuits seem to be working fine independently.

- how it the switched load grounded wrt the Arduino 5V return ?