Relay doesnt work toggling GPIO Output? how can pull it down

[acidguy]

Hi triying to drive a Relay with Output but have tried every functon in "nrf_gpio.h"

this works with a LED perfectly : nrf_gpio_pin_toggle(23);

in the main i configure :

nrf_gpio_cfg_output(23); nrf_gpio_pin_write(23, 0);

but the relay dont change state with Toggle, with STM32 i change the pullup, pulldown configuration and it works, i have to send a "0v" signal for the Relay to change state to off, and a voltage to go on.

how can output configuration be change in a output pin? thanks.

[Jørn]

Hello acidguy

When a pin on the nRF51822 is configured as an output, setting it high will source current, and setting it low will sink current. The exception to this is if you specifically configure it to disconnect on either high or low. As long as you haven't done that, there is no need to use any additional pull-up or pull-downs.

As RK mentioned driving a relay straight from a GPIO may not be the best idea. The GPIO are limited in how much current they can source/sink, as well as how large voltage they can withstand. See page 38 and 66 of the nrf51822 product specification for the absolute maximum ratings and the electrical specifications of the GPIO respectively.

I found the datasheet for the relay in your picture. Its markings indicate that this relay has a nominal coil voltage of 12VDC, and a nominal coil current of 30mA. Both of these are far beyond what the nRF51 is capable of producing, and I would recommend you use a proper relay driving circuit.

You mention it is already driven by a transistor, do you have a link to the specification of the specific module you are using?

Best regards

Jørn Frøysa

[acidguy]

Hi, the Relay is activated all the time because the Voltage of NRF51822 is enough to do it, the deactivate it i need 0v or ground, for example in STM32 i dot this : i65.tinypic.com/291m80n.jpg

how can the pin23 made "output push/pull" thanks.

[Jørn]

Pin 22 is configured as push-pull by default. Your configuration of the pin seems to be correct so it should not be necessary to do anything more. Could you measure the pin, with a multimeter, logic analyzer or oscilloscope, to ensure it is toggling as intended?