ID Component - Page 1
Forum section: electronics / beginners

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 22, 2017, 11:38:39 pm
content: Anyone know what D1 is? Searched for S1 R diode and still unsure. Thanks for any help.

author: shobo
author_rank: Regular Contributor
timestamp: April 22, 2017, 11:45:38 pm
content: the diode is a zenner,the package idk.

author: tautech
author_rank: Super Contributor
timestamp: April 22, 2017, 11:50:05 pm
content: The symbol in your image tells me it's a Schottky diode. Google both the Zener and Schottky diode symbols and see.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 22, 2017, 11:56:00 pm
content: Sorry, I added the Zener to make the device work. Verified that D1 is faulty. Now would like to replace D1 ("S1 R").

author: tautech
author_rank: Super Contributor
timestamp: April 23, 2017, 12:08:39 am
content: Quote from: OpenCircuit on April 22, 2017, 11:56:00 pmOK so the SMD diode. First ensure you know the package and be sure of it by measurement.Let's say it's SOT-23/4, include that in a Google search like: SMD marking S1 SOT-23/4 diodeBut could it be SI ?

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 23, 2017, 01:00:46 am
content: I'm no engineer but the way I read it - a Schottky diode here provides reverse voltage protection, losing only about 0.2 volts drop in normal series operation, without sacrificing itself or blowing a fuse if reverse voltage is applied. I have seen other devices (like car stereo head units) which simply put a reverse-biased diode across the DC input, but if the polarity is reversed, the diode shorts, a fuse or foil run burns out; unit needs repair.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 23, 2017, 03:29:02 am
content: Body Dimensions:Length: 4.5mmWidth: 2.45mmHeight: 2.5mm apprx.Input voltage is 10vDC which inputs into a 7805 voltage regulator just after the switch.I have searched both S1 and SI. Will keep digging....

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 23, 2017, 03:50:10 am
content: Did some digging... Does SOT-89 seem correct given the dimensions? I am not certain about height due to location on PCB.I believe:1. SOT 892. Schottky Diode3. can tolerate 10V input min.4. in 3 is not used/no conact.5. 2A is sufficient.Should be able to find a suitable replacement with these specs.

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 23, 2017, 02:41:01 pm
content: Quote from: mzacharias on April 23, 2017, 01:00:46 amI would add that a zener diode in this polarity only acts as a regular diode. The value of the zener is pretty irrelevant, but a Schottky would still be preferable.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 23, 2017, 03:19:49 pm
content: Quote from: mzacharias on April 23, 2017, 02:41:01 pmPlease explain....Positive ID the component? "S1 R"

author: mfratus2001
author_rank: Contributor
timestamp: April 23, 2017, 03:51:46 pm
content: With SMD components, the code on the package might only mean something to the manufacturer.I would replace it by use. You need to determine how much voltage it has to withstand, how much current it could be expected to pass, and what pins are actually used.It is a Schottky diode, according to the schematic. You have shown a partial schematic, so what is the rest?I saw a reference to a video game with this diode, but I can find no cross for it. Reportedly it fed a 3-terminal 5V regulator.Schottky diodes are low-voltage, and often low-current. You could replace it with a standard or fast-recovery diode, if that is all you can find.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 23, 2017, 05:28:26 pm
content: Quote from: mfratus2001 on April 23, 2017, 03:51:46 pmThanks. Was wondering why I could not make a determination after a search. I did find an 80 page .pdf on the matter, but it was a lot of general (uncertain) references.You found the device in question that is supplying a 7805 (5v regulator-removed and tested). Was trying to keep it simple by only showing the introduction of the circuitry as things get complex really fast with electronics and I am no EE. The component in question ("S1 R") has a 50% voltage drop even after other potential parasitic components, so I added the zener and the device worked fine. I wanted to add a Zener to allow current to back flow in the event of over voltage.Based on the schematic, "S1 R"/D1 is pin 1 and pin 2 use only. C67 is not populated so that pin is not used and pin 3 terminates immediately at the PCB. I think you are correct again: Device requires a 10V 800mah power supply, so I think a SOT 89-2a-30V should satisfy a replacement. Sadly, I have other components that indicate similar internal structure, but I cannot ID them either based on the markings.Saving that question for ON Semi....I await their response. Guessing the problem is package size and labeling for later identification.Not sure why the manufacturer used this diode given the circuitry. Based on the schematic it is in and out. Need to see if the initial PCB release included C67 cap as an explanation. It is a revision 2 board. First attempt at cutting cost?

author: mfratus2001
author_rank: Contributor
timestamp: April 23, 2017, 05:59:26 pm
content: SB10-05P-TD-E is a 50V, 1A fast-recovery diode in a SOT-89-3 case. It would work if the source voltage was coming from the left-hand trace.This is a standard design that is probably only for polarity protection. With C67 it could be a single-wave rectifier, but lacking that capacitor it would not make a good power supply.Any good diode would work, but not a zener. It would not protect the circuit fully.You will find the top tab and the bottom middle pins are connected and are the cathode. Pin 1 is the anode.

author: OpenCircuit
author_rank: Regular Contributor
timestamp: April 23, 2017, 08:47:40 pm
content: Found SR240 from dead Roomba board. Schottky 2A. Should be OK.Here is the offender from D1:

author: mzacharias
author_rank: Frequent Contributor
timestamp: April 24, 2017, 01:09:57 am
content: Quote from: OpenCircuit on April 23, 2017, 03:19:49 pmApprox. 0.2 volt drop (loss) as opposed to approx. 0.6 volt drop across a standard diode or forward-biased zener.