Hey folks! I'm diving into a project where I'm trying to control traditional 12V automotive turn signal bulbs with a Bosch 0332 019 150 relay and a CF14 JL-02 flasher unit. The power source is a Bosch 18V battery which I'm stepping down to 12V using a 10A DC buck converter. My challenge is getting a 5V microcontroller (Arduino Nano) to control the relay via a 2N2222 NPN transistor and struggling with a few issues. The transistor gets super hot and fails, and the relay either doesn't click or just doesn't activate properly. I'm looking to figure out how to properly interface my 5V components with this 12V setup without damaging anything or losing signal integrity. I'm also wondering if switching to a logic-level MOSFET (like an IRLZ44N) would be a better option. Any advice on what might be going wrong or what components might work best? I'm based in Germany, so finding stuff via EU distribution would be ideal. Thanks in advance!
2 Answers
Switching to a logic-level MOSFET could be a solid upgrade. You might want to use a 1kΩ gate resistor inline and add a pull-down resistor (like 10kΩ) from the MCU output to ground to keep the relay off during start-up or resets. This will help ensure stable operation without pulling too much current when you're transitioning states. Give it a shot!
It sounds like your transistor might not be saturating properly due to the 1kΩ base resistor. You could try lowering that to around 300-500Ω, which will allow more current to flow through and ensure it saturates enough to activate the relay. Right now, it seems like the transistor isn't able to handle the load well enough, leading to it heating up and failing.
Good point! I checked the relay specifications, and with a coil resistance of around 85Ω, it would need about 150mA at 12V. The 2N2222 can handle that, but if the setup isn't optimal, it might be getting too hot. If the transistor is incorrectly wired in a high-side configuration, it might be the culprit too!
Thanks for the suggestion! I'll try that and see how it works out.