Vermes
Advanced Member level 4
It is a useful current regulation system perfect when you want to warm up small elements or boards. It can be powered from approximately 8-15V. The device has no temperature regulation, so it is only adaptation load, which side effect of heating elements is used. But it does not heat up too much, thanks to placing the current meassurement of mosfet transistor, which is mounted directly on aluminum heated by second bipolar transistor Q1. Resistance of transistor Q2 increases along with the temperature and gives a minimum system which protects against a rapid increase.
Scheme:
Such a system does not provide a good regulation, but operates stable enough for few W. With proper selection of components and isolation of the aluminum channel section, temperature is about 100 degrees Celsius.
Plugging into the circuit of the transistor Q1 collector, you can gain a straight current source. Obviously it is not stable, but may be useful sometimes. If you want to adapt to a stable current source, you should have resistor in place Q2.
LED is used as a reference voltage and as the indicator of connection of the device.
Link to original thread (useful attachment) – Grzanie - regulowane proste obciążenie