- on Test & Measurement
- Published in issue 12/2003 on page 0
The idea behind this economical flashing LED indicator is very simple: it uses a very low frequency oscillator to drive two LEDs. As can be seen in the circuit diagram, the LEDs are connected in anti-parallel. At every change in level there will only be a current flow for a short time, due to the large capacitor (C3) that is connected in series with D1 and D2. When C3 is charging D1 lights up and when it is discharging D2 lights up. The current through the LEDs is limited by R4.