Cron job every two mintues on my raspberry pi to switch a relay on/off depending on the temperature in my shed. Relay is attached to a 500w heater and 4 old co

Cron job every two mintues on my raspberry pi to switch a relay on/off depending on the temperature in my shed. Relay is attached to a 500w heater and 4 old computer fans blowing the hot air at my feet.