Switching 12V On or Off (not duty cycle controlled) using an Arduino.

So I want to be able to switch the 12V going to my 12V to 180V booster on and off.

This is to control the 12V to the booster, so I can turn it off for any number of reasons.

The code as far as I know isn't the problem, I have just set a digital output to write high or low depending on the variables in the code.

But when the gate voltage is made to the transistor, the 12V drops to around 5V. Why is this? Is this an issue with the type of transistor I am using. Would a power FET be more suited to this application?

I have included how I am switching on and off below and attached a picture that shows the 'normal' use and desired use of a transistor like this. I am using a BDX53C transistor and a 1kOhm resistor on the gate.

void tempSwitch(){
if (currentTemp < 25){
digitialWrite(tempSwitchPin, 255);
digitalWrite(LED13, HIGH);
}
else {
digitalWrite(LED13, LOW);
digitialWrite(tempSwitchPin, LOW);
}
}

Solved. Relay used.

Anyway, if you choose to use a transistor, it should be a PNP one or a P channel mosfet for this purpose.
Google for: high side switch
The BDX53C is an NPN transistor.

I see from the picture it is a Nixie power supply. Some of these have a shutdown pin. For a recent project I used one which did not have such a pin broken out, so I soldered a wire direct to the pin on the boost converter IC. Six Digit Nixie Clock - Exhibition / Gallery - Arduino Forum

You need to use the normal use always, but with PNP you can invert the polarity and thus do high-side switching.

NPN - low side switching.
PNP - high side switching.

Same applies to p-channel/n-channel MOSFETs.

The "normal use" is the common emitter configuration - the only one to use for switching. You created
an emitter-follower, which is not a switch circuit, but an analog one used for buffering high impedance signals.