I am using 1N5226BT/R zener diodes (3.3 Vz, Zz = 28 ohms) and am having trouble getting a constant voltage source...(adsbygoogle = window.adsbygoogle || []).push({});

Silly me, I designed a circuit assuming zener diodes would act ideally... According to the datasheet the minimum voltage reverse breakdown voltage would be 3.1 V. Here's what I've done so far:

1: I have two zener diodes in series with a ~200 ohm resistor. I get about 2.5 V over each diode.

2: I have two zener diodes in series with a ~120 ohm resistor and I get ~3.11 V over each diode. Great! Turns out I actually need ~9 volt instead of ~6 volts so I decide to try again.

3: I keep the 120 ohm resistor and add a third zener diode in series with the others, now I get 2.4 volts over each diode, ugh!

Does anyone know what I am doing incorrectly?

I am using a transformer (wall wart) to supply the initial voltage 12 volt 500 mA (seems to hover at 16-18 volts open circuit).

It seems that supplying more current to the diodes got them in the ideal range. However, I am concerned if I try that again, I will be putting too much current through the diodes (500 mW diodes and 1/4 watt resistors).

3.3 Volts * 18V/120 = .495 Watts --> getting close to the limit...

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# Zener Diode Problems

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