newby needs a diode 101 please - Page 1
Forum section: electronics / beginners

author: bnrr
author_rank: Newbie
timestamp: July 28, 2014, 09:06:55 am
content: Hello, I am a newby with no background in the electronics world. I just began an interest in the field as a hobbyists,and bought myself a simple built kit as a start. Just by looking at all the components it gave me alot curiosity???What is a diode?what is a Q1, Q2 and so forth. I already know what the diode is, and already beginning to understandthe symbols of the schematic s. My biggest set back is identifying the diode, which pin is the anode and which is the cathode? What are these color bands? I check online, but they do not explain or have details of what I am looking for.The EEV community is my last resort. Can anyone in the EEV community help me or provide me classroom instructions. I be very grateful and appreciated for any help or responds.Thank you and God Blessed

author: sybergoosejr
author_rank: Newbie
timestamp: July 28, 2014, 09:14:27 am
content: most diodes only have 1 line around them and they mark the negative - side.multiple color bands are more likely resistors and the colors relate to the resistance.here is a page on diode polarityhttps://learn.sparkfun.com/tutorials/polarity/diode-and-led-polarity

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: July 28, 2014, 09:15:18 am
content: There is a lot of information out there, doesn't take much effort to google and find something useful, just saying.eg.http://www.allaboutcircuits.com/vol_3/chpt_3/1.htmlQ1 = transistor #1 on a schematic, Q2 = transistor #2 and so on

author: Kremmen
author_rank: Super Contributor
timestamp: July 28, 2014, 09:43:39 am
content: Quote from: bnrr on July 28, 2014, 09:06:55 amPerhaps it became obvious already, but just to make sure: in schematic drawings the components are identified by what are called "reference designators". Q1 and Q2 are such designators. For each type or class of components, there is a letter or sometimes letter combination denoting that particular type. Thus R is for resistors, C for capacitors, D for diodes, Q for transistors, U for various integrated circuits etc etc. The number following the lettercode is the sequential order so that you can identify the particular component in say a parts list for the circuit. Simple as that.You should be aware that there are slightly varying practices of assigning the letters. The main standards AFAIK are ANSI/IEEE and IEC that deviate slightly in some details. But generally they do agree. The point is that you cannot blindly assume there is only 1 presentation in the entire world...

author: bnrr
author_rank: Newbie
timestamp: July 31, 2014, 03:55:09 am
content: Thank you everyone for your kind response to my post. The links that were provided by both Mr Holcomde andMr Kremmen was the tutorials that I had been using to help my understanding in identifying the diodes polarity.The diodes would have markings such as the "-" and "+". The diodes that I have has none of these markings.There are only the color bands, in which I understood that the colors gray or black should be near the negativeside? Is that correct? The diode that I have trouble with is just the color bands and the black band is the thirdcolor and the last color is white. It's these color in which I found to be confusing, because in tutorials it is only listingas the glass type and no explanation if the same thing applys to the ceramic (tan colored) types.is it same the same method for ID? Please correct me if I am wrong

author: IanB
author_rank: Super Contributor
timestamp: July 31, 2014, 05:34:06 am
content: Diodes should not have more than one band on them. The body of the diode should be a single color and then there should be one circular band at one end. If it doesn't look like this then perhaps it isn't a diode?For example, look at the pictures in this link:https://learn.sparkfun.com/tutorials/polarity/diode-and-led-polarityThe top diode is black with a grey band, the second diode is glass with a black band. I have not seen any diodes that look different from those pictured.

author: Unknown
author_rank: Unknown
timestamp: July 31, 2014, 07:27:36 am
content: Quote from: IanB on July 31, 2014, 05:34:06 amIt's not common these days, but some diodes are/were colour coded. You still see it occasionally, particularly in zeners &/or MELF. Google "diode colour code" (there were a few different ones).Quote from: bnrr on July 31, 2014, 03:55:09 am(emphasis mine)Bnrr, I think we're going to need to see pictures. I don't recall ever seeing tan-coloured ones; I suspect they're probaby resistors, not diodes.

author: Anks
author_rank: Frequent Contributor
timestamp: July 31, 2014, 12:01:53 pm
content: could be a fuse able resistor or 0 ohm link.

author: Leestons
author_rank: Contributor
timestamp: July 31, 2014, 04:19:22 pm
content: As mentioned above I'm pretty sure you're looking at a resistor, not a diode.Resistor :Diode:

author: ciccio
author_rank: Frequent Contributor
timestamp: July 31, 2014, 07:33:52 pm
content: Quote: As mentioned above I'm pretty sure you're looking at a resistor, not a diode.No, the OP can be right: I met color-coded diodes, but this was years ago, and they went in the trash bin as soon as possible (paint strips were almost unreadable).They were 1N914 or 1N4148 signal diodes, but they were color-coded.And "tan color" resembles me the color of some small signal glass diodes...A photo could help.Best regards

author: Richard Crowley
author_rank: Super Contributor
timestamp: July 31, 2014, 07:41:43 pm
content: I agree, I have seen glass-case diodes with color bands (like resistors). However, I agree with ciccio that they are emminently disposable.They look too much like resistors, and they are hard to read. Proper-looking diodes are so dirt-cheap, there is no reason to fool around with these oddball parts.OTOH, these days we have things like the $20 LCR-transistor-diode tester which makes identification and characterization as cheap and easy as possible.HOWEVER if the parts in question are a tan body with four color bands, there is a 99.999999% chance it is a RESISTOR and NOT a DIODE!!!

author: G7PSK
author_rank: Super Contributor
timestamp: August 01, 2014, 03:31:12 pm
content: I have some Zener diodes from the 80's that are tan coloured with a yellow band.

author: bnrr
author_rank: Newbie
timestamp: August 03, 2014, 07:55:35 am
content: Hi everyone, I am sorry it took me a while to post a reply. I had found the cause of my confusion in identifying the components of my built kit with help from lesston who provided pictures of diodes and resistors.seeing the pics of the resistor in which I have been mistakenly identifying as a diode has always been a resistor.With the picture of the resistor, and the part list that came with the kit identifying each of the components, I discoverthe list had a typo, instead of describing the resistor as a resistor it describe the resistor as a diode, also on the lista description of the diode as diode. As newbie I accepted the description of each on the list as two types, and my confusion started when trying to figure out the polarity of the two components. I don't want to make a long story ofmy blunders, but like to thank everyone in the EEVB community's for their tremendous support and teaching in diodes 101.Thank YouGod Bless each and everyone

author: Leestons
author_rank: Contributor
timestamp: August 03, 2014, 08:02:22 am
content: Knew it!Glad you got it worked out bnrr

author: zapta
author_rank: Super Contributor
timestamp: August 03, 2014, 03:14:14 pm
content: If you have a multi meter, try to measure the resistance of the parts in directions, resistors will have the same resistance in both directions. Diodes have lower resistance in one direction.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 03, 2014, 04:11:47 pm
content: Now that I have one of those $20 LCR/transistor/diode/SCR testers, I find it really convenient to just routinely test each part to confirm that it is really what I think it is. Also parts seem to be getting smaller while my eyesight doesn't show any signs of getting better (or even maintaining status-quo). So both for identification of what the part IS, plus verification of the VALUE, that little $20 gadget is marvelous.

author: WarSim
author_rank: Frequent Contributor
timestamp: August 03, 2014, 05:28:24 pm
content: Quote from: Richard Crowley on July 31, 2014, 07:41:43 pmJust to clarify a little more. If it is a colour coded diode it is not identified by a yellow band. The band can be any colour depending in its class. The Cathode band is identified because it is over twice the width of the others.This is to help you differentiate between banded capacitors which use a 50%. Wider band and inductors with 50% narrower band.But these are rare, when laser etching became better the industry preferred the crazy small printing instead of bands/dots for inductors capacitors and inductors but not for resistors.

author: Richard Crowley
author_rank: Super Contributor
timestamp: August 03, 2014, 05:41:38 pm
content: Quote from: WarSim on August 03, 2014, 05:28:24 pmIndeed, the last band in the photo is yellow because yellow = 4 and this is a 1N914diode. Note that the colors are gray, black, yellow (914). It is not clear what the first band is (maybe brown = "1N"?)The photo (which I "borrowed" from the interweb) should say something like "WIDE band indicates cathode".

author: WarSim
author_rank: Frequent Contributor
timestamp: August 03, 2014, 05:43:31 pm
content: Quote from: Richard Crowley on August 03, 2014, 05:41:38 pmHow does it feel to the masters of the lost arts, and purveyors of the obsolete?.