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Diode

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n38139

Well Known Member
I want to install an aux battery in my electrical system just for my
EFIS. I have the battery issue worked out but I want to put a diode in the system to isolate the battery. A friend of mine did the same thing I am going to do but I cannot find the p/n diode he used. Any of you electrical gurus know what I need?

thx
 
I dont remember the part #, but I went with a Schotkky diode for the lower voltage drop it offered.

They are rated as to voltage, and reverse current. You need to find one that will handle the load you intend to subject it to, plus a bit extra for a safety factor---I used 50%.

Be sure to work in a heat sink into your plans, if your application is going to need it---look at the specs for each diode.

You can find many kinds of mounting for these diodes, may help fit into your particular needs.

Bob Nuchols has a simple setup shown in his Aerolectric Connection book, uses a different diode---but a lot out there flying.

Good luck.
 
Mike S said:
They are rated as to voltage, and reverse current.
Click to expand...

I'm guessing you meant to say "rated as to current, and reverse voltage". At least, those are the important things to look at, along with forward voltage drop at working current. (Reverse current is going to be negligibly small.)

That Schottky diode Perihelion has http://www.periheliondesign.com/powerschottkydiodes.htm is overkill to isolate an EFIS battery, but will certainly work, and probably won't even need a heat sink in that application.

--Paul
 
Garage Guy said:
I'm guessing you meant to say "rated as to current, and reverse voltage". At least, those are the important things to look at, along with forward voltage drop at working current. (Reverse current is going to be negligibly small.)


--Paul
Click to expand...

Yep, my bad.

Not enough coffee at that early post.
 
cheaper and better schottky

Search for DSS2X121-0045B-ND at Digikey.

Two diodes per package, much higher current ratings, better mounting arrangement, and cheaper than the perihelion shottky. If I remember correctly when I researched this one, it also had a lower forward voltage drop.
 
Last edited:
I used the perihelion Shottky for my E-bus but I used some other sort of diode (don't remember exactly what) for my GRT Aux battery.

I use the Aux bat to initialize the GRT before start up while my Avionics bus is off. On the last few flights, the GRT "grays out" and re-initialized when I start the Engine. I'm thinking that I've blown the diode in the aux bat charging circuit. (The charging circuit connects to the Main Bus, not the Avionics Bus.)

Bottom line. I'll be getting another Shottky from Perihelion.
 
Jkkinz said:
B&C Specialty Products also carries them[/url]
Click to expand...

Those 'essential bus diodes' at B&C are regular old P-N junction silicon bridge rectifiers, where you end up using only one diode out of 4 in the bridge. Which will work too, but the much lower forward voltage drop of a Schottky is a real plus in this application IMO.

--Paul
 
To isolate my aux bat I used a Schottky Diode from Digi-Key. Their part number is 90SQ030-ND. It is rated for 9A. I am not expecting nearly that much current. No heat sink required. Looks like the forward voltage drop in the current/temp range I am using it will be <.3v.
 
Actual Diode Part Number

Can someone please let us know which diode part number is supplied with the Vans master relay. (Not the Vans pn.) I am interested in purchasing some replacement diodes from Mouser. Some of the diodes in this thread are personal recommendations or favorites that cost from $2 to $30 each and are either shottky or silicon. I am only interested in the replacement part number or the specs for these diodes. Also, these are listed as anti-spike diodes, can anyone explain to me how they clamp spikes. I really am not interested in speculation, just how they really work.

Thanks
 
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