I am just new to the electronics field. basically I am a software developer but currently my job profile changed and I have to teach students some electronics subject and electronics project.

Currently me with my team decided to develop the project over here.

enter image description here

but as shown in the part list of that project, I couldn't find component D3 = 1N5819 here in my local area. So could any one suggest me the compatible/equivalent/substitute for that diode?

enter image description here

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    \$\begingroup\$ Put a small cap - say 1 NF from top of R4 to wiper of P1. This improves stability and step load response by passing the AC load change to the reference directly. | D1 protects agaunst supply reversal but wastes power. If this is from mains power pack then no problem. If from battery then considr removing. D1 or D2 useful but both together make one or other redundant. \$\endgroup\$ – Russell McMahon Mar 16 '12 at 7:26
  • \$\begingroup\$ thank u so much for such a nice comment and information....it is very knowledgeable comment.....thank u so much... \$\endgroup\$ – Aryan SuryaWansi Mar 16 '12 at 12:50
  • \$\begingroup\$ @RussellMcMahon, could u please tell me,, what is TP1 and TP2 in above image? \$\endgroup\$ – Aryan SuryaWansi Mar 16 '12 at 12:54
  • \$\begingroup\$ @AryanSuryaWansi TP1 and TP2 look like they are test points. \$\endgroup\$ – Renan Mar 16 '12 at 13:15
  • \$\begingroup\$ @Russell McMahon - If the input is from a replaceable battery pack, that uses commodity cells (like AAs), D1 is absolutely essential. If it's not there, and someone installs the batteries backwards, it will destroy the circuit (or at minimum, blow up D2). It would be a good idea to make certain you are using a schottky for D1, though. \$\endgroup\$ – Connor Wolf Mar 17 '12 at 7:39

A 1N5819 is a 40V 1A Schottky diode.

Any Schottky diode with a similar rating will be acceptable (see below)

BUT in fact a 1N5817 or equivalent would be slightly superior here. The difference is small but there is no point in throwing away efficiency for no resultant benefit. The 1N5817 has a SLIGHTLY lower forward voltage drop when conducting so cause very slightly less losses overall. You may get a percent or two extra efficiency by using it.

1N5817 - 20 V 450 mV drop at 1A
1N5818 - 30 V 550 mV drop at 1A
1N5819 - 40 V 600 mV drop at 1A

For 5V output (5 + .450) / (5 + .6) = 0.973
ie notionally at 1A you need to make about 2% more voltage at thesame current with the higher voltage diode.

1N5817, 1N5818, 1N5819 data sheet

The output voltage is 5V so a diode of 10V and above rating will be notionally OK for D3.
A 20V rating will be very safe.
Looking through tables and checking forward voltage drops would allow you to select a Schottky diode that was best suited, but most of similar ratings will be OK.

1N5819 is axial leaded through hole mount - but you could easily solder an SMD part on the board bottom if one had especially good specs. One does, if you can get it - see below.

You don't say where you are and that affects availability somewhat, but using memory & digikey as a guide:

  • Generic SMD: SS12 = 20V, SS14 = 40V

  • ST STPS1L20MF 1A 20V 430 mV at 1A

  • Microsemi LSM115JE3/TR13 15V 1A 220 mV at 1A !!!!!!!!!! Datasheet

Digikey's component database selector guide is a powerful design aid.

  • \$\begingroup\$ @Russell..is there any website or link...which suggesting us diode...as per i giving ratings or values? thank you so much for answering \$\endgroup\$ – Aryan SuryaWansi Mar 16 '12 at 8:27
  • \$\begingroup\$ @Russell..is there any website or link...which suggesting us compatible/equivalent diode...as per i giving ratings or values? thank you so much for answering \$\endgroup\$ – Aryan SuryaWansi Mar 16 '12 at 9:08
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    \$\begingroup\$ @AryanSuryaWansi - yes - use Digikeys component selection system as I notes above. [Digikey](digikey.com}. Search eg for schottky diodes and then select "Diodes, Rectifiers - single" and use their filtyers. Vf = say 20-60 Volt, If = 1A - 5A say. Then set filters and choose by $ or Vf or whatever search.digikey.com/scripts/DkSearch/… \$\endgroup\$ – Russell McMahon Mar 16 '12 at 9:33
  • \$\begingroup\$ just a quick question. would a 1N4001 do the trick? \$\endgroup\$ – Thomas Andreè Wang May 31 '16 at 12:29
  • \$\begingroup\$ @ThomasAndreèLian Short answer: No. Longer: A IN4001 is designed to operate only at low frequencies. Losses and voltage drop can be expected to be poor at the frequency of operation of most supplies of this sort. Without looking at the specs my recollection is that they may be OK at say 1 kHz and not good above 10 kHz and probably marginal or worse even then. \$\endgroup\$ – Russell McMahon Jun 1 '16 at 13:26

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