I am using a HK19F relay in a simple wiring circuit. Pin 2 is connected to the Arduino is coded so that it goes to 5V/GND and switches the transistor on and off.
However, when I bring pin 2 to 5V, the relay doesn't click and it doesn't seem to be on.
Could anyone take a look at my wiring and suggest what might be wrong? [The resistor in the circuit is 1k ohms]
What is the part number of the transistor?
The transistor is an NPN BC547.
When replacing the diode and relay with a resistor and LED it works so not too worried about that.
It's a 3V relay but I must have put the wrong one on the diagram, apologies.
What is the entire relay part number?
Depending on the power spec it could draw up to 165 mA and that will damage the Uno.
Ok. Anyway, I wouldn't drive a relay with any Arduino power output because it can't give the required current.
Power the relay directly from the adaptor you use for Arduino if using a 5V relay, or you need another power adapter or add a step-down.
It is a HK19F relay and I think needs about 50-70mA for the coil to switch on.
That is too much for the Uno 3.3V output. You need a separate power supply
Alright, I'll probably try that then. Just curious, how much current can the Arduino supply for 3.3V?
Not more than 50 mA.
Max of 50mA but best is you stay below 40mA.
What is the value of the resistor 10K or 1K?
1k ohms
That's good
If you put a 47Ω resistor in series with the relay coil, you can power it with 5V from the Uno 5V output.
All of the above and…
Are you sure you are connecting to the relay coil? The picture looks like you are not.
Are you sure your transistor EBC is accurate? Not all TO-92 packages are the same.
LED tested, I see, good.
a7
The cathode of the diode and the wire connecting to 3.3V are supposed to be in the same row as pin 1 [the small green wire at the top is only because I couldn't resize the diode.]
are my pins 1 and 8 correct? I had thought pin 1 is the bottom right, and pin 8 is the bottom left
No.
You can't put the relay on the board like that because you are shorting all the pins.
Turn it 90 degrees and place it over the slot in the middle breadboard.
like this
Thank you for informing me about that.
I've turned it around now, however it still doesn't seem to work.
As the current to be drawn for the relay is 67mA and the Arduino can only supply 50mA, I most likely am going to use another power source.
