I disassembled a LED lamp and it's circuit. My intention is to rebuild that circuit within EveryCircuit app, to understand how it is working.

On this circuit I found two elements that are rising questions to me.

A) I couldn't find a reference for “CY40(0|D)474JE“ To me it looks like a capacitor but it have no idea about the numbers to use?

B) I also found a so-called varistor. I understand that as a variable resistor? But the data sheet that I found did not specify any ohms. enter image description here The lamp was driven by 230V AC. The lamp's circuit did drive 30 LEDs in series. From my measures I saw 300V DC coming out of the circuit and going to the LEDs.




This is a variable resistor but not like potentiometer. In potentiometer , resistance variation is linear . But for varistor , it's resistivity changes is non linear, it mainly works like diode , specially zener diode and mainly use to protect the device. It has a threshold voltage below which, varistor's resistance remain so high as it is non conducting. When voltage crossed the threshold voltage, it became conducting. For your better understanding , you can go to wiki .

So what you are looking here is not resistance value but voltage and you may need to replace varistor with zener diode in EveryCircuit app as it do not have varistor (as far as I know).For this varistor maximum allowable voltage is 470V

CY400 474JE

this is CY400 model capacitor with value 470nF. This link will teach you how to read capacitor code information .and JE most probably manufacturer's name. Some write it at the end of the code or model name.



This component is a metal-oxide varistor, or MOV. They are used to suppress surges and other transients -- they present a high resistance at their terminals normally, but switch into a low-resistance state when a high voltage is present, suppressing/absorbing the surge. It likely is a 470V unit based on the part number -- such would be seen in 240V mains applications like yours.


This is a capacitor -- a 470nF, 400V metallized film capacitor to be precise. Capacitors like this are used in AC circuits as they have benign failure behavior and provide reasonably high capacitance at high voltage while being non-polarized.

One thing to note is this capacitor lacks any safety ratings -- while it has enough voltage rating to survive mains exposure, its surge withstanding abilities are not known.

  • \$\begingroup\$ From parts number I also think that it is a 470V. But according to the datasheet , it says maximum allowable voltage is 30V AC(rms) and 38V DC. It make me confused but I go with the datasheet. \$\endgroup\$ – Anklon Jun 20 '16 at 4:38
  • 1
    \$\begingroup\$ @Anklon -- You are looking at the 470KD07's line entry in the datasheet...the 471KD07 is 300VAC/385VDC \$\endgroup\$ – ThreePhaseEel Jun 20 '16 at 11:41
  • \$\begingroup\$ oh, I found my mistake . thnx \$\endgroup\$ – Anklon Jun 20 '16 at 17:16

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