Realize - Terrade Electronique et Logiciels

The need was to create a circuit for students learning electronics for the first year. They will have to study and build the circuit. Capacitor charge was a good applications.

The idea was to build a battery powered flashing LED circuit. Begining with a circuit from William Hudson, I transform all of his idea.

As small as possible, it has to be cheap. In CMS technology, the circuit is less than 1.5 inch diameter, with a possible extension to hang it.

According to chronogramms, the LEDs are flashing in the sequence D1 to D6. But when crossing connections J1 and J2, reverse effect is obtained. Two LEDs are on at a time : good visual effect is achived.

LEDs are to be High Luminosity type, i.e. TLLR 4400. A CMS power switch K1 is added to avoid removing batteries for switching off. The 220 ohms serie resistor limits the current into LEDs as in the MOS gates. The circuit works well down to 3 volts and it's 5 mA current need gives approximatively 50 hours life for two CR2032 lithium batteries.

The cycle time is 1-2 Hz. It is slowered if increasing the value of R1 to R3.

All the components take place on the copper side. LEDs are soldered close to the board, 2 holes for mechanical maintain.

On the other side, only the battery support S1 take place.


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