Drive 5v relay with 2N2222

Other Hardware General Electronics
1

Hi there,

I'm trying to build a soft-starter circuit with 2N2222 transistor.
But I'm struggling to get a fix on the R1, R2 and C1 values.
Now the relay engages as soon as the power up (I see no delay).
I'm trying to come up with 300~500milliseconds delay from power-up to relay engaging.

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Datasheet for the relay

  • Nominal operating current - 80mA
  • Coil resistance - 62.5Ω
  • Nominal operating power - 400mW

Could anyone shed some ideas?

2

Hi @dinesha77
Are you operating a 5V relay with 12V power?

RV mineirin.

3

I’ve done similar.

A MOSFET (IRFZ44) was used, the resistors were 100k and the capacitor was 10uF. (need to confirm)

The time was ≈ 1 second.

Add a 68 Ω resistor to your relay if you only have a 5v coil.

Your capacitor is wrong way up.

Maybe experiment with a base resistor added.

4

Oh dear I'm so sorry. it's all 5v. Corrected in the original post.

5

Oh sorry again. corrected it.

6

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This I tried and worked. But unfortunately I do not want to use a 12v relay as I do not have any and I have plenty of 5v relays. It is impossible to buy a 12v relay nowadays where I live.

7

As stated, if your 5v relay coil is 62.5 ohms, add a 68 ohm series resistor to the relay.

That looks correct, just add the 68 ohm resistor.

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8

@LarryD so you are suggesting to use 12v circuit with a series resistor added to 5v relay?
But my circuit runs on 5v.

9

Yes but, I’m confused now.

Is the inverter/charger 12v ?

If so, use 12v, not 5v.

10

@LarryD so sorry to confuse you and all,
12v circuit was a sample circuit which I found in here. Since you have mentioned on your first post.

My test circuit is this;

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On my first post, circuit had 2 type errors. Which you and @ruilviana had pointed out.

  1. Showed 12v voltage. which is wrong. Should be 5v.
  2. Capacitor was wrongly placed.
11

Did you try adding a base resistor ?

12

No. This soft started is for a mains voltage 230v AC appliance. 5v relay, when switches on, it by passes the shunt resistor and supply the full current to the main voltage appliance.

13

Did you try adding a base resistor ?

Do you have a 555 timer ?

When does the 5v appear ?

14

Thanks @LarryD
Let em try your suggestions and update later.

15

For 5 V, an IRLZ44.

Transistor (BJT) circuit will not work.

1 Like
16

thanks @Paul_B
thin I have a logic level mosfet somewhere.
Let me try that.

17

IRLZ44 logic level MOSFET worked.
Thanks @Paul_B

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18

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