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Basil
07-22-2009, 05:39 AM
Hi All,

Sorry this is not really a Prop centered question!

Can anyone suggest an alternative to the 1N4157 diode? (Which I could source from RS components)

Thanks :)

Alec

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)

Mike Green
07-22-2009, 05:55 AM
The 1N4157 seems to be a low voltage Zener diode (actually called a Stabistor). There seem to be some that you can find with Google. The National Semiconductor LM385-ADJ is an adjustable voltage reference that can be used in place of a Zener in many circuits. You might look at the datasheet on National Semiconductor's website. There are some more recent similar parts, also in a TO-92 case, on the same website.

Basil
07-22-2009, 06:32 AM
Thanks Mike,

Is a stabistor a specific type of zener, or simply a name for a zener which meets a set of electrical specs?

Reason I ask is i'd prefer to use a drop in replacement (i.e. another stabistor) rather than an alternative.

Thanks for the help!

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)

Bob Lawrence (VE1RLL)
07-22-2009, 06:38 AM
Basil,

Re:source from RS components)

They carry NTE parts but if it's not a stock item they can probably order it for you.


Replace part.... With NTE part.... Product Line
1N4157 NTE177 Semiconductor

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Aka: CosmicBob

Basil
07-22-2009, 06:48 AM
Thanks Bob,

I must be blind! I can't find NTE177 anywhere on RS's website? :/

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)

Basil
07-22-2009, 07:44 AM
Would one of these this work?

docs-asia.electrocomponents.com/webdocs/0733/0900766b8073397e.pdf (http://docs-asia.electrocomponents.com/webdocs/0733/0900766b8073397e.pdf)

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)
Post Edited (Basil) : 7/22/2009 12:50:27 AM GMT

viskr
07-22-2009, 08:58 AM
Stabistors are multiple diodes stacked in a single package. The 1N4517 is 3 diodes in series.

In some transistor amplifiers they were used as a temperature compensator for the transistors, trying to track the Vbe of in this case 3 transistor drops.

If that's what it's doing, then 3 vanilla diodes in series might be what you need. They are still available from Arrow, but good luck if you need just 1, you might be able to get a sample out of them.

If its being a voltage reference, there are better options these days.

Basil
07-22-2009, 09:36 AM
Hmmm. I didn't actually design this circuit, i'm just building it :)

This being the case, I haven't got a good understanding of its operations so couldn't tell you what the purpose of the stabistor is.

The circuit is a DC speed controller for a model railroad.*

The output from the stabistor is being fed into the THRESHOLD input of a 555. Heres a snippet from the circuit description:


said...
The threshold input to the 555 is a voltage dependent on the back EMF of the motor and controls, with the control voltage input, the pulse frequency and period


I wonder if anyone could suggest the purpose of the stabistor with this info?

*Note: My plans of prop based DCC controller have been defered due to the cost associated with fitting my already very expensive German loco's with a very expensive DCC decoder :P

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)

Philldapill
07-22-2009, 09:54 AM
From what I can tell, a few diodes in series would work just fine. Looks like a stabistor is basically used as a low voltage Zener, but with a more vertical I-V curve.

Basil
07-22-2009, 09:56 AM
Excellent :) I have a ton of both zeners (1n4004) and signal diodes at home :) Thanks!

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)

Leon
07-22-2009, 08:37 PM
1N4004 is a rectifier, not a zener!

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Basil
07-23-2009, 03:40 AM
You are quite right :D I was having a moment...been looking for Zeners all day!

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-Alec

Velden in N scale
(http://veldeninn.blogspot.com/)