# I cant get the sparkfun relay PCB to work with Arduino.

**URL:** <https://community.sparkfun.com/t/i-cant-get-the-sparkfun-relay-pcb-to-work-with-arduino/22184>\
**Category:** Arduino\
**Created:** [October 9, 2011, 12:09pm UTC](https://community.sparkfun.com/t/i-cant-get-the-sparkfun-relay-pcb-to-work-with-arduino/22184 "2011-10-09T12:09:23Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![fableman](https://avatars.discourse-cdn.com/v4/letter/f/b9bd4f/32.png) [@fableman](https://community.sparkfun.com/u/fableman)\
**Post date:** [October 9, 2011, 12:09pm UTC](https://community.sparkfun.com/t/i-cant-get-the-sparkfun-relay-pcb-to-work-with-arduino/22184/1 "2011-10-09T12:09:23Z")

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Hi, first time trying to use relays.

Got this PCB: [http://www.sparkfun.com/products/9096](http://www.sparkfun.com/products/9096)

All components are as the PCB tells me.

When I connect the board to my arduino uno I can only see a very dim blink on the diod and no click sound from the relay.

Code: digitalWrite(7, HIGH); //connected to CTRL pin

Connected GND to arduino GND

and 5V to 5V

If I connect the CTRL pin to 5V the relay works

Is the current to low from the arduino pin7 to controll the relay board?!?!

I power the Arduino from USB and I tried external 5V aswell (1A)

What should I try or fix, iam stuck.

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<div class="post-metadata">

**Author:** ![fableman](https://avatars.discourse-cdn.com/v4/letter/f/b9bd4f/32.png) [@fableman](https://community.sparkfun.com/u/fableman)\
**Post date:** [October 9, 2011, 3:59pm UTC](https://community.sparkfun.com/t/i-cant-get-the-sparkfun-relay-pcb-to-work-with-arduino/22184/2 "2011-10-09T15:59:04Z")

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The problem was I missed to define the PIN as output.

Under setup()

pinMode(7,OUTPUT);

Now works like a charm.