Curious what others think of installing a blocking diode to prevent AC Noise

[Mopar1973Man]

Still looking at the wrong way. It not suppose to be any AC voltage at all. It suppose to be PURE DC or a flat line on the O-scope. Zener is only going to clamp one side of the sine wave. A very random AC noise wave might not clamp properly.

 

[eddielee]

I agree that i was looking at the Zener the wrong way. It can be difficult to find information about some of these diodes.

After a lot of consideration and a few discussions with an electrical friend of mine, I have come up with a Schottky rectifier.

Say the left leg is connected to the power supply for the components at the fuse block and the right leg is connected to the ground, with the middle leg supplying the component with power. Stick the appropriate fuse inline with the rectifier and you have a rectified current.

This rectifier is rated 40A bypass with .61V to .77V drop @ 20A with 1.25mA to 15mA reverse leakage current. 15/1000= .015A maximum leakage which is half the alternators allowed leakage.

So from the power to the fuse #3 20A in the PDC where the ECM, PCM and IP get their power supply to the Schottky rectifier to a fuse back to supply the components with rectified power. The third leg will be grounded, preferably to the alternator minimizing resistance.

 

 

 

This will rectify AC current, however, the main purpose is to maintain any possible AC voltage to be within specs of .03V or less to the sensitive electronics.

 

https://www.westfloridacomponents.com/T621APL03/40CPQ100+40+A+100V+Schottky+Rectifier+Diode+International+Rectifier.html

Edited January 8, 2016 by eddielee

[Mopar1973Man]

Problem how will it handle the high current draw or charge rates of 140 Amps? How about grid heater cycling in and out? Assuming that diode would require a heck of a heat sink? Mounting location under the hood wouldn't work in the summer time.

[eddielee]

The diode will not have to handle the 140A charge current as it is only supplying the ECM, PCM, IP and lift pump with power.

Pull the FMX fuse at #3 in PDC tie into the power there, run out of fuse box to the diode attached to the truck as a heat sink, through a 20A fuse and back to the #3 fuse to supply power.

Edited January 8, 2016 by eddielee

[CSM]

interesting!  

[dripley]

Just now, CSM said:

interesting!  

you beat to that one. I like the out of the box thinking. But my electronically disinclined brain cant add anything to the topic.

[eddielee]

I ordered 4 of these nice little rectifiers so I can play and test the results of this little project.. I am getting a little excited about it too.

[banzaitoyota]

My Mechman alternator is performing flawlessly 

[balsip]

I went through electrical engineering in 1969 and we were taught that they were functionally the same as a regular diode but with much lower voltage drop and much faster switching time, ideally suited for switching mode power supplies that rectify in the KHz range rather than 60hz. So I do not see how they would block ripple? They are better specs these days but functionally the same as far as I know, and 1969 shows how old I am. I agree that the alternator full wave bridge will probably be the culprit for ripple and should be replaced instead of trying to mask the root cause.

[Mopar1973Man]

14 minutes ago, balsip said:

I agree that the alternator full wave bridge will probably be the culprit for ripple and should be replaced instead of trying to mask the root cause.

Bingo... Here we are back around full circle just the way I see it too. Why not fix the actual issue than band-aiding over the top with add-ons. Still ask the same question. Why is it that these truck went for years without a issue and now all of a sudden requires add-on band-aids, modification, etc.? I would start back at resolving the issue at hand first.

But I would start looking at better quality diode packs on the alternator.

http://www.fostertruck.com/diode-pack-rectifier-bridge-for-dodge-denso-alternator.html

[eddielee]

as I said before the reason I want to install, Schotky rectifiers now, is so that if the alternator degrades and/or goes out the rectifiers will prevent damage to the electronics, especially after installing a new component.

Edited February 3, 2016 by eddielee

[Royal Squire]

Couldn't you just mount an ac voltmeter on your dash

[Mopar1973Man]

53 minutes ago, Royal Squire said:

Couldn't you just mount an ac voltmeter on your dash

Easier yet just do the AC voltage test every oil change...