Hello Friends,
Could someone help me out, on a ralais ?
I want to build my own relais (without a board).
What do I need exactly ? Which diodes and resistors do I need ?
By the way: I do not need any LEDs. Only the relais should open/close
It should run with DC 3.3V
saved my day, man ! Thanks 
Make sure you buy a 3V relay, such as:
SRD-03VDC-SL-C
Note that a 3volt sugarcube relay draws more current than a 5volt type. About 125mA vs. 75mA.
Don't you have 5volt available.
The 1k base resistor might not fully saturate that transistor when driven with a 3.3volt pin.
I would lower that to 470 ohm.
Leo..
thanks man, that's an important note. Does @jim-p agree with that suggestion (470 OHM) ?
Are you using an Arduino?
If yes, which one?
I am using an ESP8266-12E (That's why 3.3V)
What's that powered by -- 5V / V_usb ?
(If it is 5V / V_usb then you don't need a "3V" relay.)
it is powered by a 6V VDC, stepped down with an AMS1117-3.3
Something like this?
FWIW, a 5V relay would be OK with 6V. Or you could get a 6V relay (very common).
No. Only the ESP8266-12E on the NodeMCU, it's exactly like this:
Thanks for the clarification.
(But you need not find a 3V relay as a more common sort would do.)
Does the ESP8266-12E output 3.3V on GPIO pins when booting?
Even if it did, how would the 10K keep the NPN from turning on?
I thought the GPIOs were tristated.
Yes, some Pins are booted as HIGH (for appr. a second or so). I should check whether the specific pin (IO12) is booting shortly as HIGH. So, 10K Resistor is okay ?
@KASSIMSAMJI <-- thanks for you too
So how does the 10K keep the transisor from turning On?
I don't know sir I'm just a prof on Coding. Maybe @KASSIMSAMJI could explain it
