Diode question

is there any diff. between using a regular diode (tan with the colored bands) and using one that is grey with markings? (the gray ones feel like rough ceramic). I'm thinking one dissipates heat quicker.

Thanks.

Vas

vasdef said:

is there any diff. between using a regular diode (tan with the colored bands) and using one that is grey with markings? (the gray ones feel like rough ceramic). I'm thinking one dissipates heat quicker.

Thanks.

Vas

Click to expand...

Diodes come in a dozen different types and do different jobs; silicon diodes, germanium diodes, tunnel diodes, zener diodes, varactors, switching diodes, power diodes, microwave diodes and on and on. What i'm saying is you haven't given us enough information to know if you even have the right kind of diode let alone to know about wattages, voltages.

Were the diodes you bought packaged with information? If you bought them from a place like Radio Shack it will tell you what kind of diode it is, what it's used for and what it's elctrical specifications are.

If you have some of that info we might be able to help.

double a is right on target, there are all sorts of diodes,

i'm guessing here, ( so this is basically a shot in the dark ) your talking about a regular leaded diode, like the 1N4000 series, 1 type is cylindrical, the other is round....round type is molded with a ceramic material, the cylindrical is a plastic material ( can you see a fine seam down the sides ( from the mold ) )

if these are your standard diodes for rectifing at 1/2 or 1 Amp, 0.7 volt forward voltage drop, i found the round did a better job as the cylindrial would begin to crack ( fail ) at the seam due to heating effects....most of the heat is transferred thru the leads so the package is the weakest link....( here considering that the die package is the same in both as well as the package size is the same )...leakage current is generally worse in the plastic over the ceramic ( mosture absorpsion during and after manufacturing )


just my 2 cents from many years ago when i was working for a semi company making diodes, SCRs, xsistors, etc...

I've built a bunch of LED lights in the past year or so, I've never had a problem until I tried these gray diodes. What I don't know is anything about the diff. types of diodes. The tan ones I mentioned are (to me) the run of the mill ones you get at Radio Scrap. So when I needed 10 ohm, 1 watt diodes this time, I sent for them from Mouser. I don't remember what type they are. I built a light using 18,000 mcd LED's from superbrightled.com and one by one, each bulb fried. I've used these LED's for other projects, but never had a problem. I guess I need to do some diode homework.

Thanks for the replies,

Vas

what is a 10 ohm diode ?

diodes are not rated in ohms

vasdef said:

I've built a bunch of LED lights in the past year or so, I've never had a problem until I tried these gray diodes. What I don't know is anything about the diff. types of diodes. The tan ones I mentioned are (to me) the run of the mill ones you get at Radio Scrap. So when I needed 10 ohm, 1 watt diodes this time, I sent for them from Mouser. I don't remember what type they are. I built a light using 18,000 mcd LED's from superbrightled.com and one by one, each bulb fried. I've used these LED's for other projects, but never had a problem. I guess I need to do some diode homework.

Thanks for the replies,

Vas

Click to expand...

Now things are begining to make sense, Tan with bands is probably a "resistor" not a diode. Resistors are rated in OHMS and the color bands tell you how many ohms resistance. The other thing you need to know is how many watts of power they can take before they overhead, split, burnup. Larger power resistors can be rectangular ceramic bars.

In a simple LED light a "resistor" will limit the current flowing to the LED to prevent damaging it.

I strongly suggest you take your parts back to a Radio Shack store and ask them what you've got. [Although that may not always work as one day many years ago I took some leaky (defective) diodes band to RS, the sales clerk looked them over real good and said to me with a straight face and said "I don't understand is there some fluid leaking from the diode?" I spent the next 5 minutes explaining how a diode functions and what is meant by a leaky diode.]

Ooops, sorry, I meant resistors. Looking further into the gray ones I mentioned before, they were metal oxide. So, in the future, what are the type of resistors to use that dissipate heat the best?

Vas

go with metal oxide, most common, you should go with the largest size that can fit ok, always a good idea when you have the room cause of drift and thermal runaway if they get too hot - well, you know the story unfortunately...tolerance is a factor, 1% is pretty standard, [1 to 10 ohms+], you can get tighter tol but seldom are those stocked, even at the specility radio electronic hobby shops....( in the leaded for the most part) for very tight tol your getting into "precision resistors" and their rather expensive....heck your solder joint or wire type / lenght can also cause resistance change when your down in the 1000 milliohms.....


rob