If you say about current limiting resistor on the gate i assume maybe you are right.
I did this a lot of times, in practice 2V is no problem, no resistor needed.

What you suggest ?

 

Although the input is a gate, but in bjt normally we don't call it gate, you might say b or base, when you keeping say gate, other members may think about the gate in MOSFET which you are talking about.

Rb is needed, you can use that way by youself, but you can't tell other members it is no need.

This forum is for education, so, when we talking everything in ee then we should according to the ee theories.

 

Ok , but this is also a projects forum that maybe will be build. I know well what is in theory and what is on PCB.
So forgive me about the "gate" , as on BJT it's base. But still there is no need for resistor @2V on that specific 2N2222. I had issues biasing this transistor with series resistor on base on this low voltages. I had also a measurement and the current was under normal ranges without resistor. So if someone intend to build this please try 200 ohm resistor and lower until transistor biasing ok.
I hope that will be educational and practical also.

Cheers

 

as you have the 2-2,5 V on the transistor gate you have 12V on the load.

You show a bipolar transistor, so that is the base, not the gate. And it needs a current limiting resistor in series of the transistor will fail.

ak

 

djb. you need current limiting into the base of the transistor. Just don't make it too high, or Scott will tell you about it

If you are going to use a relay, why use the regulator? Relays have a wide voltage tolerance and dont need a "regulated" voltage. If a relay, then use a 12Vdc one...

 

Ok , but this is also a projects forum that maybe will be build. I know well what is in theory and what is on PCB.
So forgive me about the "gate" , as on BJT it's base. But still there is no need for resistor @2V on that specific 2N2222. I had issues biasing this transistor with series resistor on base on this low voltages. I had also a measurement and the current was under normal ranges without resistor. So if someone intend to build this please try 200 ohm resistor and lower until transistor biasing ok.
I hope that will be educational and practical also.

Cheers

Now we are calculating the values for your circuit.

The specs of EMR021A03 reed relay, I=3V/(450~550Ω)=5.45~6.67 mA


The current of spec for relay is :
I_ry = V_ry / (R_ry)
= 3V/ (450~550Ω)
= 5.45~6.67 mA.

You used this:
I_ry = V_ry / (R_ry)
= 5V/ (450~550Ω)
= 9~11 mA.

The watts of spec for power is 18 mW

You used this:
W_ry = V_ry * I_ry
= 5V * (9~11 mA)
= 45 ~55 mW

Your circuit:

Q1 = 2N2222.
Ib = (Vin-Vce1)/Rb
= (2V-0.7V)/200Ω
= 1.3V/200Ω
= 6.5mA

Ic = Ib*10 = 6.5mA*10 = 65 mA (Ic capable of sinking)

So the relay of spec needs current 5.45~6.67 mA, but you supported 65 mA.

Yes, many values may not damaged quickly, but the designation is to get the circuit working properly, and also considering the problem of components replacement.

I just calculated, you just need to see and think.

If you felt that is not enough then maybe Mike could give you the examples of LTspice ...

 

OK OK! use a current limiting resistor It's really amazing what is happening now

now i understand what it takes to get people involved on a design!!
Why i didn't had the same "help" on my other post on step up converter??
You people are so judgmental on a small mistake that doesn't really matter. (no fence, nothing personal)
Where is the thread starter anyway? ))

I could use some help of your brilliant brains please on : http://forum.allaboutcircuits.com/t...it-3-7-li-po-cell-to-5v-regulated-psu.112570/
I'm using multisim 12.

 

OK OK! use a current limiting resistor It's really amazing what is happening now

now i understand what it takes to get people involved on a design!!
Why i didn't had the same "help" on my other post on step up converter??
You people are so judgmental on a small mistake that doesn't really matter. (no fence, nothing personal)
Where is the thread starter anyway? ))

I could use some help of your brilliant brains please on : http://forum.allaboutcircuits.com/t...it-3-7-li-po-cell-to-5v-regulated-psu.112570/
I'm using multisim 12.

The thread starter as posted before has ordered all of the recommended parts and will post an update once I receive them and build the circuit. Thanks again for everyones thoughts, time and experience with helping me with this.