Hello, I am an absolute beginner both with Arduino and electronics. At least I have some programming experience...
I am trying to connect a ready-made relay shield to my Arduino UNO without success. It is this one: Click And in the attachment picture it is shown how to connect it.
But I cannot make it work. Please, could someone tell me what I am doing wrong. Here is what I do:
I have a strong power supply at 5V, that I connect to VCC an GND of the relay shield.
Then I connect the "Signal" to a digital output e.g. at PIN 13 of the Arduino.
That it, no? Then, when running the "Blink" example, I was expecting the relay to switch forward and backward. But it doesn´t. Please, does anyone have an idea what I am doing wrong?
Please, with my beginners ideas I was thinking that connecting the Relay shield to the 5V power supply with VCC an Ground, the connecting the "Signal" to + at the power supply too should make the relay witch, no? It doesn´t do even that... I suppose I should hear such big relay switching, no?
Unfortunately this doesn´t change anything... I was trying like this now: connect the shields VCC and Ground to the power supply, connect the shields "Signal" to PIN 10. Connect the power supply "Ground" to "GND" at the Arduino too.
Still nothing happens. Any idea? Thanks a lot!
PS.: When connecting ONLY the relay shield to the power supply and then connect the signal to VCC of the power supply too, the LED on the relay shield is lit shortly, but I cannot hear the relay switch.
The LED is not lit when the signal comes from the Arduino...
PS.: When connecting ONLY the relay shield to the power supply and then connect the signal to VCC of the power supply too, the LED on the relay shield is lit shortly, but I cannot hear the relay switch.
Do you have some specs from the relay shield?
it sounds like the Arduino (power supply) just cannot supply enough juice...
That´s what I thought too... That´s the reason why I was trying to get the signal from the power supply too, just for testing. Even then the relay doesn´t do anything, and I am quite sure the supply has enough juice...
After trying around some hours more I examined the relay shield somewhat closer. Since I am not an electrician in any way I cannot really judge the circuit, but there is nothing really hard to unterstand. The seller of the relay sent me this link to a relay circuit: Relay
Okay, since this circuit is exactly what is made on the shield I bought, I was thinking that maybe something is broken on the shield. Thus I unsoldered the transistor, which is a "2N3904 B 331". I replaced this with a "BC547 B 011", actually without really knowing what I am doing. I cannot say what the difference is between the two transistors, because I am starting to learn what a transistor is.
Nevertheless: Now it works! Unbelievable! I am so happy I fixed it myself! Now I would really like to know:
1.: Was the original transistor broken or was it the wrong one?
2.: Does using the BC547 instead of the original one is in any way dangerous for the Arduino? I suppose not, since the power for the relay comes from a big 5V power supply, am I right? But just to be sure, is it dangerous in any way?
No, it is cool after running more than 5 minutes switching every second the relay on off...
Now I was metering the voltage at the output of the transistor, it is 4,27V.
Since the shield is two channels, I was trying to replace the second transistor too, but I don´t have a BC547 any more... So I tried BC557 and BC337. Both won´t work. The output is 0,9V respectively 1,9V. Did I have so much luck when trying with the BC557?
You'll need good professional help, but finding a good repair shop is becoming tougher every ... Dealer service departments are probably the most expensive. ..
