VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Avionics / Interiors / Fiberglass > Electrical Systems
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 05-17-2018, 08:03 AM
jeffsvan jeffsvan is offline
 
Join Date: Jul 2010
Location: detroit, michigan
Posts: 154
Default Diode for starter, master and aux ground power solenoids/relay

Could someone recommend a Diode (part#) to put across the posts on the relay/solenoids that I can easily purchase. Want to reduce spark jumping back at the switches.

Can I use the same diode part# for all three (trying to keep it simple)
Reply With Quote
  #2  
Old 05-17-2018, 08:13 AM
Fred.Stucklen's Avatar
Fred.Stucklen Fred.Stucklen is offline
 
Join Date: Oct 2006
Location: Brooksville, FL
Posts: 320
Default Diode

A 1N4001 (or higher voltage 1N4004) will work in all three locations....

Quote:
Originally Posted by jeffsvan View Post
Could someone recommend a Diode (part#) to put across the posts on the relay/solenoids that I can easily purchase. Want to reduce spark jumping back at the switches.

Can I use the same diode part# for all three (trying to keep it simple)
__________________
Fred Stucklen
wstucklen1@cox.net
RV-7A N924RV Flying (1520 Hrs & counting)
RV-6A N926RV 875 Hrs (Sold)
RV-6A N925RV 2008 Hrs (Sold)
Reply With Quote
  #3  
Old 05-17-2018, 08:43 AM
az_gila's Avatar
az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 9,632
Smile

Common parts and easy to obtain...

https://www.ebay.com/itm/10x-10pcs-I...g/252410601393
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
Reply With Quote
  #4  
Old 05-17-2018, 09:19 AM
lrgabriel lrgabriel is offline
 
Join Date: Jun 2012
Location: Reno, NV
Posts: 61
Default

Those diodes are significantly underrated for flyback application. I would look for something in the 3A If and 1000V Vr range, like the RGP30M-E3.
Reply With Quote
  #5  
Old 05-17-2018, 09:57 AM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,075
Default

Quote:
Originally Posted by lrgabriel View Post
Those diodes are significantly underrated for flyback application. I would look for something in the 3A If and 1000V Vr range, like the RGP30M-E3.
Meh...

Even the 1N4001 (1A 50V) is adequate, if you look at *peak* ratings. But the 3A versions are physically more robust (fatter body and heavier leads). And the higher voltage ratings don't cost that much more. When I ran an electronics repair company, we just purchased the higher rated devices to minimize our inventory.

Another number for the 3 amp 1000 volt devices is 1N5408.
https://www.ebay.com/sch/i.html?_fro...n5408&_sacat=0

The same device can be used on all the relay coils you're likely to use in an airplane.
Reply With Quote
  #6  
Old 05-17-2018, 10:22 AM
jeffsvan jeffsvan is offline
 
Join Date: Jul 2010
Location: detroit, michigan
Posts: 154
Default

I found some 1N5406 in my parts inventory.
Would that work?
I'm not super keen on electronics specs.
Reply With Quote
  #7  
Old 05-17-2018, 10:24 AM
lrgabriel lrgabriel is offline
 
Join Date: Jun 2012
Location: Reno, NV
Posts: 61
Default

Quote:
Originally Posted by rv7charlie View Post
Even the 1N4001 (1A 50V) is adequate
I've seen 430V spikes from my intermittent duty starter solenoids. In fact, one such spike blew out my 400V rated flyback diode, shorted it to ground, and disabled my landing gear.

...I might be a little bit passionate about this!
Reply With Quote
  #8  
Old 05-17-2018, 11:34 AM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,694
Default

The 1N5406 diode should work fine. When the controlling switch is opened, the polarity of the coil induced voltage is such that the diode will be forward biased and conduct any induced current. The induced voltage will be limited to the forward voltage drop of the diode which is about 1 volt. The 1N5406 diode is rated at 3 amps average and 200 amps peak for 8 milliseconds. Be sure to connect the banded end of the diode to the positive side of the coil and the other end of the diode to the negative side of the coil. Like Charlie said, any diode will work. The important thing is for the diode to be mechanically strong enough not to break from vibration.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #9  
Old 05-17-2018, 11:44 AM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,075
Default

Quote:
Originally Posted by lrgabriel View Post
I've seen 430V spikes from my intermittent duty starter solenoids. In fact, one such spike blew out my 400V rated flyback diode, shorted it to ground, and disabled my landing gear.

...I might be a little bit passionate about this!
For total clarity, are we talking about diodes in the same location? I was addressing a suppressor across *the coil* of the contactor, to suppress arcing across the controlling switch. If the diode was across the *contacts* of the contactor, to suppress flyback from the starter windings, the equation would change quite a bit.
Reply With Quote
  #10  
Old 05-17-2018, 12:03 PM
lrgabriel lrgabriel is offline
 
Join Date: Jun 2012
Location: Reno, NV
Posts: 61
Default

The diode that failed was across the contactor's coil (protecting the controlling switch).

I had assumed that as long as the flyback diode's Vr rating was sufficient for bus/coil voltage, and it had a reasonably high If, it would work for flyback purposes. Based on the failure though, I think the Vr has to exceed whatever inductive spike you'd see...even if it's in the forward direction of the diode.

Edit: I'm going to get the scope out and play around with this today. I thought I had a handle on what was happening, but the more I think about it the more questions I have...

Last edited by lrgabriel : 05-17-2018 at 12:08 PM. Reason: Deeper thoughts
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 06:38 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.