wiring and diagram

Some sorts of electronic gear do  no longer provide any indication that they are  in fact on when they're switched on.  This situation can occur when the back-light of a show is switched off. In addition, the otherwise mandatory majors  power  indicator  is  now not  required  with  tools  that  devours  less  than  10 watts. As a outcome, you can simply forget  to modify off such gear. If you want  to grasp whether or not gear continues to be drawing power from the mains, or in case you want  to have a sign that the gear  is switched on without needing to switch the equipment, this circuit offers an answer. 

One way to realize AC power current and  generate a reasonably consistent voltage  impartial of the load is to attach a  string of diodes wired in reverse parallel in collection with some of the AC supply  leads. Here we chosen diodes rated  at 6 A that may just handle a non-repetitive  peak current of 200 A. The top current  score is vital in connection with  switch-on  currents.  An  advantage  of  the selectedn diodes is that their voltage  drop will raise at high currents (to 1.2 V  at 6 A). This method you may roughly  estimate the energy consumption from  the brightness of the LED (at very low  power degrees). The voltage across the diodes serves as  the supply voltage for the LED driver. To  raise the sensitivity of the circuit, a  cascade circuit (voltage doubler) which incorporates C1, D7, D8 and C2 is used to double  the voltage from D1–D6. Another benefit  of this association is that each halve- waves of the AC present are used. We use  Schottky diodes in the cascade circuit to  minimise the voltage losses. 

Circuit diagram :

Power On Indicator Circuit Diagram

The LED forcer is designed to operate the LED  in blinking mode. This increases the amount  of current that could float though the LED when  it's on, so the brightness is sufficient even  with small hundreds. We selected a duty cycle of pproximately 5 2ds off and zero.5 2d  on. If we assume a current of 2 mA for excellent  brightness with a low-current LED and we can  tolerate a 1-V drop in the supply voltage, the  smoothing capacitor (C2) must have a worth of  a thousand µF. We use an astable multivibrator built around two transistors to put into effect a  high-efficiency LED flasher. It is dimensioned to minimise the pressure current of  the transistors. The average current consumption is approximately zero.5 mA with a  provide voltage of three V (2.7 mA when the  LED is on; 0.2 mA when it is off). C4 and  R4 resolve the on time of the LED (0.5  to zero.6 s, depending on the availability volt-age). The LED off time is determined by  C3 and R3 and is fairly lower than 5 seconds. The theoretical value is R × C × ln2,  however the real price ranges reasonably due to  the low provide voltage and the selectedn  component values.

 

Diodes D1-D6 shouldn't have to be special  high-voltage diodes; the reverse volt-age is simplest a couple of volts right here due  the reverse-parallel association. This  voltage drop is negligible in comparison to  the worth of the principles voltage. The most effective  thing you must take now note of is the  maximum load. Diodes with a excessiveer  present rating need to be used above 1 kW.  In addition, the diodes may just require cool-ing at such excessive power stages.  Measurements on D1–D6 indicate that  the voltage drop throughout each diode is  approximately 0.4 V at a present of 1 mA.  Our purpose was once to have the circuit give a  affordable indication at current levels  of 1 mA and excessiveer, and we succeeded  effectively. However, it's essential to make use of a  excellent low-current LED.

 

Caution: the entire circuit is at AC power doable. Never work on the circuit with the primarys cable plugged in. The  best possible enclosure for the circuit is a small,  translucent field with the identical color as  the LED. Use reliable pressure aids for the  primarys cables getting into and leaving the  box (connected to a junction box, for  example). The LED insulation does now not  meet the necessities of any outlined insulation category, so it should be equipped such that it  can't be touched, which means that it cannot  protrude from the enclosure.