This circuit was devised for the sole purpose of AUTOMATICALLY turning off the burner on a homemade glass crucible vaporizer.
The FINAL circuit also contains:
- a thermister attached to a red led/resistor combo to indicate "HOT"
- a green led/resistor conbo to indicate "POWER"
- a yellow led/resistor combo to indicate "ON" (when thle heating element is active)
It is activated via a momentary switch.
It utilizes
Switch
1. Momentary switch
1. IRFZ44N mosfet
1. C3420 transistor
1. 10k Ohm 1/4 watt pull down resistor
RC net (these are adjusted to affect time delay)
1. 100uf Electrolytic capacitor
1. 470k Ohm 1/4 watt resistor
Indicators (not shown)
3. LEDs in diff colors (see above description)
3. 1/4 watt resistors 510-560 Ohms resistance
1. Thermister
POWER
1. Class 2 wall wort power supply. 120v AC. To 12v 1.5A DC
Heating element .
2 inches of salvage NiCr (Nickel Chromium or Nichrome) space heater coil
1. Ceramic light socket with the metal removed (the heater coil enclosure).
All inserted inside an aluminum container the size of a soda can and insulted with fireplace sand (silica) and sealed with foil tape.
I've built two of these and they are both still going strong. Give it a try. This entire project (both times) was completed using items already in my garage left over from other projects.
