Electric soldering iron light prompt and temperature control circuit
Electric soldering iron is a commonly used welding tool that emits heat silently during operation. It only heats up without emitting light. If the user does not try to heat it up, they will not know whether it is working with electricity; Sometimes forgetting to unplug the power plug in a timely manner can cause unnecessary waste of electrical energy, and over time, it can easily burn out the soldering iron tip and even lead to accidents. Sometimes it is necessary to lower the temperature of the soldering iron a little to avoid damaging the components, but generally soldering irons cannot adjust the temperature and often need to be plugged in and unplugged, which is very troublesome. For the above issues, the circuit shown in the attached diagram can be used to improve.
When the soldering iron is powered on, the positive half of the power supply generates a voltage drop across diodes D2, D3, and D4 due to the current. The LED lights up through D1 and the current limiting resistor R; At the negative half cycle (when switch K is closed), the current passes through D5. Due to the voltage drop of the diode being only 0.7v, it is negligible for a 220V power supply and will not affect the normal use of the soldering iron. If switch K is disconnected, the circuit will be in a half wave power supply state, and the decrease in current will cause the temperature of the soldering iron to drop. This not only reduces energy consumption but also achieves the purpose of temperature regulation. In addition, D1 blocks the reverse voltage of the power supply, thus protecting the LED. The entire circuit is very simple, with low component prices and no special requirements. It is not difficult for interested parties to replicate. The D in the circuit is 1N4007. R uses a 1/4W resistor. Due to the current of 1N4007 being 1A, the load current should not exceed this value. Fortunately, commonly used 20W or 35W soldering irons cannot reach this value. Also, it should be noted that this circuit is only suitable for soldering irons and not for incandescent lamps.
