You need a 125R resistor between the pin 5 and the gate of the FET.You need a reverse bias diode across the relay.You need to connect the -ve of the battery to the arduino ground.
what are you trying to do?
1) How did you calculate the size of the resistor and why is it needed exactly.
2) Do I need a reverse bias diode because of how the transistor is wired to the relay?
and make a 5v regulator for the (+)
Quote1) How did you calculate the size of the resistor and why is it needed exactly.The FET gate looks like a discharged capacitor. A resistor of 125R keeps the peak current below the 40mA that it is "safe" to draw from an arduino.Quote2) Do I need a reverse bias diode because of how the transistor is wired to the relay?No you need it because of the back EMF generated by the coil.Quoteand make a 5v regulator for the (+)You need 12V for the relay, so what is the regulator for?
Use an RFID reader to act as my ignition switch (or kill switch), since I have no key.I guess I could use a smaller Relay, I just have this one laying around.
Quote from: pwnm30rdi3Use an RFID reader to act as my ignition switch (or kill switch), since I have no key.I guess I could use a smaller Relay, I just have this one laying around.cool you should make this into and enter it into the instructables shopbot contesti was going to make something like this. but to start the car i would need to put my wallet in a specific spot.
should always have a 125 Ohm resistor?
Would this work? http://www.radioshack.com/product/index.jsp?productId=2036270
Hopefully it works?
QuoteHopefully it works?Yes it will work but will not provide enough protection. The absolute maximum output current for a pin is 40mA, even that will produce damage if sustained. Your resistor will limit the current to 5 / 120 = 41.6 mA, you are better getting a resistor greater that the 125R you need.The diode is fine.
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