View Full Version : What is this do-dad?

11-20-2004, 10:23 PM
What is this do-dad and how does it get used?

And I don't mean the penny. I already know it can't be used for anything. http://bbs.homeshopmachinist.net//biggrin.gif

Several of them came with some 24V Finder relays that I bought on ebay.

11-20-2004, 10:38 PM
It's a 6amp, 200volt rectifier diode. They may have been supplied for use in applications where you want to snub the inductive kickback when the coil is released. Generally, this needs to be done if the relay is being driven electronically (rather than other switch or relay contacts). The diode would go across the coil with the banded end (cathode) toward the positive driven side of the relay.

11-21-2004, 12:24 AM
You can't get better answers anywhere on the net.

Steve Stube
11-21-2004, 01:35 AM
Maybe we could shorten the "time til answered" to a tad less than 15 minutes:-)

That's a long time to wait.

11-21-2004, 11:34 AM
<font face="Verdana, Arial" size="2">Originally posted by suprdvn:

And I don't mean the penny. I already know it can't be used for anything. http://bbs.homeshopmachinist.net//biggrin.gif


Penny?I thought those were backups for screw in fuses http://bbs.homeshopmachinist.net//biggrin.gif

11-21-2004, 02:38 PM
I'll just add to what Den said. When the magnetic field of the relay collapses a AC
Wave is generated and that diode placed as
Den stated allows half of the sine wave to go directly to ground so the spike is greatly reduced.

11-21-2004, 03:02 PM
those are great answers...and correct in every way but just in case you were looking for a simpler definition: a diode acts as an "electrical check valve" of sorts...allowing current flow in only one direction and blocking it in the other

11-21-2004, 07:04 PM
Thanks for that abreviated answer "chkz". I'm an electronic idiot and I understood what you said. So that's what a diode does. By the way, the penny only works up to 15 amps. You have to change to a nickle after that. http://bbs.homeshopmachinist.net//biggrin.gif

Al Flipo
11-21-2004, 07:12 PM
Could they be used to make a rectifier?

11-21-2004, 07:37 PM

12-16-2004, 11:31 AM
Thank you all for the great answers. I have determined that I am supposed to use it in my setup.


Which end is the banded end? The thin silver band or the black band with the numbers?

12-16-2004, 11:57 AM
The silver band indicates the cathode. The cathode is the negative side of the diode. If positive voltage is connected to the other end (no band) and a complete circuit formed then current will flow. If positive voltage is connected to the end with the band then no current will flow. If AC is connected to the diode and a circuit completed with a load following the band side of the diode then positive voltage will be measured at the band end of the diode across the load.

J Tiers
12-16-2004, 12:41 PM
Yep, a rectifier diode. Used and specified many of those.

Relating it to a schematic diagram, the schematic symbol is an arrow touching a short line.

The silver banded end of the part corresponds to the end with the line on the schematic.

Current is "conventionally" said to flow in the direction of the arrow, which is from "plus" to "minus".

It is useful in any application where you want current to flow in one direction only, within its voltage and current limits. A rectifier at a relatively low frequency, ablocking diode, a "flyback" diode (as noted above for relays) etc, etc.

12-16-2004, 01:53 PM
So if I understand this correctly the silver band (cathode) gets hooked up to the 115v side of the coil on a relay. The coil relay is being turned on by a solid state relay on the output board, thus the need for the diode.

So here's another question:

I will also be using some 24vdc output solid state relays on the output board to turn on other 24vdc relays. Will the same diode work for that? or is it not even necessary?

12-16-2004, 02:13 PM
The diode goes NOWHERE near the 115v http://bbs.homeshopmachinist.net//eek.gif

It would be placed across the 24 volt coil with the silver band receiving the +24 volts.

Solid state relays don't need them because they don't have a coil or the kickback from it. In the solid state relay, you're powering an LED whose light turns on photo-sensitive switching transistors (with a few more parts in between http://bbs.homeshopmachinist.net//smile.gif )

added - darn, must be a little slow today http://bbs.homeshopmachinist.net//wink.gif


[This message has been edited by nheng (edited 12-16-2004).]

12-16-2004, 03:20 PM

Sorry if I wrote that in a confusing way. I know that the solid state relay does not need it.
I got a little confused myself. It makes sense that this particular relay is for the mechanical relays activated by 24v. That's where I got it from in the first place.
So if I would have thought that thru before I typed I would not have had to ask my last question.

I get it now. Thanks everyone.