Greetings, and thanks for looking!
I apologize in advance - I'm very new to electronics and so this might be ridiculously simple. As part of a circuit I'm creating, I need to use a relay. I've been able to test most parts of my circuit using an Arduino board and various stand-alone items, including a relay board. However, to finalize the project, I intend to design a PCB containing all of the necessary elements on one board for neatness.
In trying to move the relay board setup to my PCB design, I've run into a problem. From what I can tell, the relay board is set up similar to the following schematic, with 3.3 - 5 VDC acceptable input and a 3.3 VDC signal entering through R1 to switch the relay (and also activate the LED showing the state of the relay).
When I set it up according to that schematic, switching the signal that enters through R1 did not activate the relay or the LED (nothing happened at all).
I simplified the design to the following for testing, and substituted an LED for the relay. This works fine:
However, placing the relay back in it's place and changing nothing else, I again get no action whatsoever:
The relay works fine without transistor Q1 in the circuit:
So my questions are the following:
1. What is wrong with my design that is causing the relay to not function with the transistor in the circuit?
2. If the relay activates correctly with the 3.3V signal being applied directly to it, is there a reason to bother with the transistor at all?
Thank you in advance for your assistance!
I apologize in advance - I'm very new to electronics and so this might be ridiculously simple. As part of a circuit I'm creating, I need to use a relay. I've been able to test most parts of my circuit using an Arduino board and various stand-alone items, including a relay board. However, to finalize the project, I intend to design a PCB containing all of the necessary elements on one board for neatness.
In trying to move the relay board setup to my PCB design, I've run into a problem. From what I can tell, the relay board is set up similar to the following schematic, with 3.3 - 5 VDC acceptable input and a 3.3 VDC signal entering through R1 to switch the relay (and also activate the LED showing the state of the relay).
When I set it up according to that schematic, switching the signal that enters through R1 did not activate the relay or the LED (nothing happened at all).
I simplified the design to the following for testing, and substituted an LED for the relay. This works fine:
However, placing the relay back in it's place and changing nothing else, I again get no action whatsoever:
The relay works fine without transistor Q1 in the circuit:
So my questions are the following:
1. What is wrong with my design that is causing the relay to not function with the transistor in the circuit?
2. If the relay activates correctly with the 3.3V signal being applied directly to it, is there a reason to bother with the transistor at all?
Thank you in advance for your assistance!