can Zenner 5 V1 to replace 4.3 V diodes????

You have the zener diode in back-to-front.

Ken

detect

0.636

No, it won't work (the power supply is 5V and the zener is there to detect a lower voltage...). My guess is that anything between 3.9 and 4.3V will work, but not 5.1... Robert

"Mylinux" a écrit dans le message de news:bjmokb$ snipped-for-privacy@imsp212.netvigator.com...

a

work,

I measure the 5V1( becuase it is marked ) via a digital multimeter is 0.636 V. Is there something wrong with this component?

however

I have four other diodes a. 0.659 V b. 0.658 V c. 0641 V d. 0.659 V

I may guess they are the same group.

which side is positive in circuit and actual component?

my guess is on circuit

+ve is non -"twisted" bar side on component +ve is non flat-bar side

I mixed up the "back to front" , the multimeter will not show a voltage.

I could only see that zenner in the brown-out circuit. A brown out circuit is used to detect very brief partial power failures (eg where the supply voltage falls from 5V to say 4.5V rather than all the way to 0V). Most applications don't bother to detect this kind of brief power failure and they use a simpler RC circuit on the Reset pin. Perhaps you don't need such high reliability either? If not check the data sheet for the AT90S4433P and see what circuit they recommend for the Reset pin.

Or..

If you had a lot of small signal diodes (like the 1N4148 or 1N4149) you could use a lot in series instead of one zenner. eg 6 would give approx 6 x

0.65 = 4V which is close enough. Remember though that ordinary diodes would need to be used the other way round eg "pointing down" rather than "pointing up".

Colin

such

and

x

would

"pointing

I always prefer this url epecially for diodes, my class mate told me zenner diodes are just opposite direction for cathode and anode.

In article , snipped-for-privacy@My.com says... | I measure the 5V1( becuase it is marked ) via a digital multimeter is 0.636 | V. Is there something wrong with this component? | | however | | I have four other diodes | a. 0.659 V | b. 0.658 V | c. 0641 V | d. 0.659 V | |

You are measuring them the wrong way and you can't check the zenor point just with a multi meter... You need to set it up in a circuit with (for instance) a

12 v supply -1k resistor- zenor - ground Then measure the DC voltage across the zenor diode.

--
Regards,
         Harry (M1BYT)...

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In article , snipped-for-privacy@My.com says... | see the component list. | | I do not have 4.3 V but 5V1. | | help, please. | |

A 5v1 zenor will not work. 4v3 is about the ideal voltage (4.3 + 0.6 for the transistor junction = 4v9), just a touch lower than the 5v supply, so it will detect the first droop of the 5v from a power loss.

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         Harry (M1BYT)...

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anode.

What you should have said is that a zener is used in the reverse-bias mode. Its avalanche knee voltage is much greater than its 0.6V forward-bias knee. | / | / | / | /

-----==========----- / |+0.6V / | / -5V | / |

(1st figure. Cached; original link is 404)