How to control 12V 70A automobile relay with Arduino Uno

I am using 12V,70A automotive relay to control a starter solenoid. I tried the connections using transistor CL100S and diode IN4007, but couldn’t actuate the relay. I am using 12V car battery for my relay. I don’t know much about these. I used the pic attached as a reference and connected the relay with arduino. But it did not work out. I tried to control the Automotive relay with smaller relay board, but my capacitor got smoked. So please help me out!

What was the value of the base resistor.
I would have used 220ohm.
Did you measure the resistance of the coil.
Leo..

Resistor value is 1k ohm. I contacted some electrician, he suggested me those transistor and diode and resistance. Would 330 ohm be good? Which coil are you asking about? In multimeter 200 scale, the resistance value i got is 80 when connected to terminal 1 and 2 of relay

1Kohm won’t give you enough base current with this transistor.
You should always measure the resistanse of the relay coil, to see if this transistor can handle the coil current.
80ohm is 150mA coil current at 12volt. Ok for this transistor.
A 220ohm (or 330ohm) base resistor should do the trick.
Did you connect Arduino ground to 12volt battery ground.
Leo…

Oh ok. Will try and post my results! Thanks :slight_smile: