# Can anyone identify the type of diode and its company?

Discussion in 'General Electronics Chat' started by Ashish Agarwal 1, Jan 7, 2018.

1. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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Can anyone identify the type of diode and its company?

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2. ### ericgibbs Moderator

Jan 29, 2010
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Last edited: Jan 7, 2018
Ashish Agarwal 1 and bertus like this.
3. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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I don't believe its a general purpose diode because it is connected in reverse direction in the circuit like Zener diode
and moreover if I give 24Volts to this diode it stops all the voltage and allows only 3.3v to be output across a 100kohm resistor
and if i give 12volts then also the output is 3.3v across a 100kohm resistor

Apr 5, 2008
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5. ### ericgibbs Moderator

Jan 29, 2010
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hi AA,
All diodes do have reverse leakage current, I = 3.3v/100K is only 33u Amps.

If you think it is a Zener, use a 12Vdc supply and a 1k series resistor, post the voltage you measure across the diode and resistor.

E

6. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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Nope this is also not right - as i said its put in reverse condition
Input is 12V ~ 36V
Output is always 3.3v across 100kohm resistance
check the circuit

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7. ### ericgibbs Moderator

Jan 29, 2010
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hi,
If the diode was a Zener type, the Zener voltage would be measured across the Zener diode not the series resistors.
If you always measure 3.3V whatever the voltage input is 12V or 36V, the 3.3V you measure is not from the diode.

Can you tell us what equipment the diode is used in, or a circuit diagram.

8. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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This is an Input to the micro controller pin
It is used for detecting if 12~36 v are applied on the wire, if yes, then 3.3v is output from this and microcontroller receives high input
when voltage is removed it receives low input

9. ### ericgibbs Moderator

Jan 29, 2010
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hi AA,
I am familiar with what you trying to do with the micro, is the micro powered from 3.3V and is the micro input from that circuit set for analog or digital input.?
E

10. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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Commented on the board design

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11. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
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Yes, Dear, Microcontroller is 3.3v Powered, I am actually trying to understand how is this circuit regulating and providing 3.3v from 12~36v without any mosfet, transistor or zener diode

12. ### ericgibbs Moderator

Jan 29, 2010
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hi,
We must be missing something on this circuit layout, I have tried many combinations in the LTSpice simulator.
I cannot get any circuit using that layout that will give micro high input of 3.3v when the inputs are from 12v through 36v.

If I design a circuit using the methods I normally I use to give a 3.3V signal from 12V though 36v, it would be different to what you have posted.

I will keep looking at the problem.
E

13. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
9
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In my opinion the only option possible in this scenario is the constant current limiting diode. If we have a constant current then we can have fix voltage drop across the resistor.
For example if the diode is outputting fix 0.1mA current
then the voltage drop by 100K resistance would be 10v
and if the series unknown resistor is of 33K which is possibly the pull down of the microcontroller as per its datasheet
it will give 3.3 Reference voltage .. no matter whatever voltage you apply on the diode
but i am not 100% sure about all this

14. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
9
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Constant-current diode

Electric symbol
Constant-current diode is an electronic device that limits current to a maximum specified value for the device. It is known as current-limiting diode (CLD), current-regulating diode (CRD).

Internal structure
These diodes consist of an n-channel JFET-transistor with the gate shorted to the source, which functions like a two-terminal current limiter or current source (analogous to a voltage-limiting Zener diode). They allow a current through them to rise to a certain value, and then level off at a specific value. Unlike Zener diodes, these diodes keep the current constant instead of the voltage constant. These devices keep the current flowing through them unchanged when the voltage changes. An example is the 1N5312. Note the negative VGS is required, as an example on the n-type junction-gate field-effect transistor 2N5457.

15. ### ericgibbs Moderator

Jan 29, 2010
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hi,
I have been looking through some datasheets, it could be a CC or a Voltage Dependent Resistor.???
Is there a fault on the micro PCB, that is making you suspect that 'diode'?
E

16. ### Ashish Agarwal 1 Thread Starter New Member

Jan 7, 2018
9
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No, its working fine its the curiosity of how it is sending 3.3v to the microcontroller which is making me work hard over finding the solution of the puzzle

17. ### ScottWang Moderator

Aug 23, 2012
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Please post the pcb with double sides.

18. ### ian field AAC Fanatic!

Oct 27, 2012
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The number sort of looks like a Shottky barrier diode, a bit more research to identify it - or take it out and check the Vf with a DMM diode check.

SB diodes are great for protection because they fail short circuit very convincingly if abused.