how to connect a diode

Diodes

351w fastback said:

i just got my tauras electric fan and i am going to hook-up a diode between the two wires that connect to the fan. i am following the instructions found on the ford muscle website http://www.fordmuscle.com/archives/2003/02/electricfan/index.shtml

i just got the diode and i have never hooked one of these up before so how do u do it?
thanks

Click to expand...

Ok, I see the diagram.
I presume you don't know one end of a diode from the other.



One end of the diode has (usually) the cathode end marked with a stripe. The cathode is represented by the straight line in the above diag.



When you solder the diode in place be careful NOT to overheat it!

Roy.

PS, Lots of common diodes could handle this job. If you can't find the one they call out, re-post and I can give you some substitutes.

meanroy said:

When you solder the diode in place be careful NOT to overheat it!

Click to expand...

Yes, they become more of a wire than a diode if you overheat them and it makes you scratch your head for a long time as to why your circuit isnt working correctly

One more tip

This goes back to my high school electronics class. To help prevent over heating the diode while you are soldering it in, put a small alligator clip, or even a surgical clamp between the diode and where you are soldering. THis acts as a heat sink so the heat from the solder doesn't make it back to the diode.

Hope this helps.

351w fastback said:

i just got done soldering it on. i dont think i overheated it but if i did, how can i tell? the diode used in the diagram was discontinued at radio shack so i used a 1n5404 instead. thanks for the help

Click to expand...

It's probably just fine. It's a Silicon diode and they are fairly forgiving.

I checked the specs on the one you substituted, It's fine.
The original is the 1000 volt model, the one you substituted is only good for 400V. LOL!

You can tell whether it is good by checking the resistance with either a cheap voltmeter, or a real expensive one. It needs to be a cheap because the cheap ones supply a significant amount of current to measure the resistance. The real expensive ones ($150.) have a special position for measuring diodes.
If the diode is good it will read "open" (nearly infinite ohms, at least megohms) in one direction, and very low in the other.
But you would have to disconnect one end of the diode before measuring it. (otherwise you would just be measuring the motor winding resistance)
Unless there is something obviously wrong, it's not necessary.

The effect on your circuit if the diode is shorted will be that the motor circuit will draw current but won't run, or possibly, will blow a fuse. If the diode is "open", the danger is that the relay may stick closed or simply wear out quickly. (relay points arc when opening and closing because there is no place for the back EMF to go when the relay contact are open..) In either case you will know somethings wrong.

Roy.