Simple LED Flasher with 2N2222

This would be the most simple LED flasher circuit ever. But the theory behind the operation is not that simple. The principle behind this circuit is the negative resistance of a transistor.

Negative Resistance is the way a transistor behaves Voltage and Current are inversely proportional to each other. While a usual circuit follow the Ohm's law. However there is no such thing called minus resistance but the term came based on the negative slope of the relevant V-I curve.

In this configuration the base of the 2N2222 is open the C? should be 330uF 16V. The 1K resister is charging the capacitor the capacitor until the Base-Emitter voltage is set to trigger the transistor to operate in the negative slope of the V-I curve, thus the the current starts flow through Emitter to Collector and the LED lights. This discharges the capacitor and drop the Base-Emitter voltage and again the transistor will off, and the capacitor starts charging again. This continues and the LED will stay blinking.

Just to increase the LED blink frequency I have changed the C? to 220uF and also used 15 Ohm resistor between the Q1 and the LED for protection.

Couple of Zero Ohm has also been used instead of jump wires (this is very useful when constructing on a breadboard, will be discussing more about zero ohm resistors in a later post)

This circuit requires exact 12V DC, and it is better to experiment with other general purpose NPN transistors and PNP ones doesn't work with this. Since the voltage is important, make sure to measure the supply voltages (in my case, the 12V supply was throwing 18V :( and the circuit didn't work)

You can try adding a 10K pot between the +Ve supply and the 1K resistor for voltage adjustments as well.

AN6610 Motor Speed Controller.

I been collecting some NOS stock of good old Linear ICs and found a couple of AN6610 ICs. It's been pretty hard to locate a data sheet (In English) however managed to construct a simple motor speed controller within 5 minutes of effort (on a breadboard)

The IC,

AN6610

AN6610 comes in TO-126 Package and pretty easy to use.

The data sheet I found from here


As per the data sheet, the schematic would be,

The quick and dirty construction worked well, except there is a start-stop-start pattern observed at low speeds.


Rs, I have used a 5K POT and worked fine.

Here are some pics I have taken while playing around and quick and dirty construction of the above circuit.

Components:

Unfortunately I couldn't find 470 Ohm resistor and the 22uH Inductor. I used 330 Ohm resistor instead. However it is good to do experiments by changing the value of this.








The construction on a breadboard: