Van's Air Force
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Diode Question
- Thread starter Brambo
- Start date
JonJay
Well Known Member
Rick_A
Well Known Member
Need a Schottky diode
Try one of these:
http://www.periheliondesign.com/powerschottkydiodes.htm
I've got the same diode you have sitting in my "stuff I bought but won't use box". You could buy the basic diode for less and fabricate your own mount but I got mine from Eric.
Try one of these:
http://www.periheliondesign.com/powerschottkydiodes.htm
I've got the same diode you have sitting in my "stuff I bought but won't use box". You could buy the basic diode for less and fabricate your own mount but I got mine from Eric.
When I get to the power system on my RV-7, I plan to use a part in this family:
http://ixdev.ixys.com/DataSheet/L227.pdf
This will reduce the voltage drop and it also has higher current and power dissipation capability. I don't think it would need a separate heatsink: just bolt it to the firewall or some other metal part.
http://ixdev.ixys.com/DataSheet/L227.pdf
This will reduce the voltage drop and it also has higher current and power dissipation capability. I don't think it would need a separate heatsink: just bolt it to the firewall or some other metal part.
AeroLEDs_Support
Well Known Member
The forward voltage drop across a diode is a function of the type of diode, and the amount of current flowing through it. Standard silicon diodes range around 0.7V, but the actual voltage will depend on the current.
The best diode for low drop and power loss is a Schottky diode. Typically the higher the current rating of a Schottky diode, the lower its drop will be. Most Schottky diodes will drop between 0.1 and 0.5V depending on their current rating and the actual current flow.
A lower forward voltage means that the diode will burn less power and run cooler.
You need to also consider what the max reverse voltage is that you need to hold off when selecting a diode.
Dean Wilkinson
AeroLEDs LLC
www.aeroleds.com
DGlaeser
Well Known Member
Ebus Diode
For the E-bus diode, a Schottky is arguably overkill. While the alternator is working, the E-bus sees 13+ volts even with a regular diode - and a Schottky will give you about a half a volt more. In battery only mode, the E-bus is powered directly from the battery (no diode) and sees less than 13V. So the 'loss' of a volt for the E-bus for normal operations is no big deal.
I went with the Schottky because I got one for about the same price as the regular square one - and it looks cooler
Spending a lot of money for that half a volt is not warranted IMHO.
That one is pricey! I went with a 50HQ035 which I got for about $9 (but I just checked and Digikey no longer has them in stock).
For the E-bus diode, a Schottky is arguably overkill. While the alternator is working, the E-bus sees 13+ volts even with a regular diode - and a Schottky will give you about a half a volt more. In battery only mode, the E-bus is powered directly from the battery (no diode) and sees less than 13V. So the 'loss' of a volt for the E-bus for normal operations is no big deal.
I went with the Schottky because I got one for about the same price as the regular square one - and it looks cooler
Spending a lot of money for that half a volt is not warranted IMHO.That one is pricey! I went with a 50HQ035 which I got for about $9 (but I just checked and Digikey no longer has them in stock).
For the E-bus diode, a Schottky is arguably overkill. While the alternator is working, the E-bus sees 13+ volts even with a regular diode - and a Schottky will give you about a half a volt more. In battery only mode, the E-bus is powered directly from the battery (no diode) and sees less than 13V. So the 'loss' of a volt for the E-bus for normal operations is no big deal.
I went with the Schottky because I got one for about the same price as the regular square one - and it looks cooler
Ixys has many parts in that family. I couldn't find an online price for the 120A version but see that the DSS2X81-0045B is about $20. I think that makes it a win over the 50HQ035 since you only need one and mounting is much simpler. The Ixys DSS 2x series is isolated from the case so you basically only need to bolt it down. I've seen plenty of failed chassis insulators for parts like the 50HQ035. There's not much worry with an isolated part like the DSS.
gmcjetpilot
Well Known Member
Penny wise
. Voltage drop is about 1.1 volts for the power P-N diodes (0.70 volt is drop for signal diode). The Schottky is about 0.20 volt, so the difference is almost a full volt, worst case.
An extra $20 going to kill you? Aeroelectric recommend the cheap rectifier p-n diode block, which Radio Shack use to carry in store. Having 0.20 volt drop (Schottky) verse 1.1 volt drop (p-n junction rectifier diode) is worth extra nickles to me. Again its arguable. (The Radio Shack bridge in my junk drawer says 1.7 volt fwd volt drop! That's fine if you are running at 100 volts or 200 volts, 1.7 volts is not much.)
On a good day say your alternator supplies 14.3 volts at the main buss, so you will only have 13.2 volt for your essential buss? Now the scenario is your alternator dies, you're down to battery power (12-12.6 volts). Do you want another 1 volt drop? Some radios will not run on 11 volts. Aeroelectric says add a second switch & more wire for an aux circuit to power the essential buss directly from the battery, by-passing the main contactor/relay and diode. That will get the voltage back up but it's more complication.
How about not having a diode or switch bypass for the essential buss at all! If you want to "shed load", manually turn items off or pull CB's (yes I have pull-able CB's). Aeroelectric loves fuses of course, and if you use CB's the terrorist will win, I'm told. (its a joke)
If you want an isolated and have alternative power to the essential buss, you could use two switches, one to isolate and one by-pass direct battery power, no diode. You just need to remember the sequince of switch thowing, MAKE before you BREAK the connection.
The claim to fame of the "25A, 50V Full-Wave Bridge Rectifiers" was you could walk down to Radio Shack and buy one for $4. I was told they don't carry them in store any more, avaiable only on-line now.
I can see where $4 does sound better than $30. I totally understand. I have the cheapskate gene as well. Either diode is OK and will work, but check out the link for Perihelion Design. Here is their propaganda sheet of why its better. I know aeroelectric poopoo's the idea; probably because he didn't think of it first. Why waste energy? Periheliondesign has a good price; wholesale they cost $25-$29 anyway. They really are better than any diode you can get for what we are using it for.
I would argue.
. Voltage drop is about 1.1 volts for the power P-N diodes (0.70 volt is drop for signal diode). The Schottky is about 0.20 volt, so the difference is almost a full volt, worst case.An extra $20 going to kill you?
Aeroelectric recommend the cheap rectifier p-n diode block, which Radio Shack use to carry in store. Having 0.20 volt drop (Schottky) verse 1.1 volt drop (p-n junction rectifier diode) is worth extra nickles to me. Again its arguable. (The Radio Shack bridge in my junk drawer says 1.7 volt fwd volt drop! That's fine if you are running at 100 volts or 200 volts, 1.7 volts is not much.)On a good day say your alternator supplies 14.3 volts at the main buss, so you will only have 13.2 volt for your essential buss? Now the scenario is your alternator dies, you're down to battery power (12-12.6 volts). Do you want another 1 volt drop? Some radios will not run on 11 volts. Aeroelectric says add a second switch & more wire for an aux circuit to power the essential buss directly from the battery, by-passing the main contactor/relay and diode. That will get the voltage back up but it's more complication.
How about not having a diode or switch bypass for the essential buss at all! If you want to "shed load", manually turn items off or pull CB's (yes I have pull-able CB's). Aeroelectric loves fuses of course, and if you use CB's the terrorist will win, I'm told.
(its a joke) If you want an isolated and have alternative power to the essential buss, you could use two switches, one to isolate and one by-pass direct battery power, no diode. You just need to remember the sequince of switch thowing, MAKE before you BREAK the connection.
The claim to fame of the "25A, 50V Full-Wave Bridge Rectifiers" was you could walk down to Radio Shack and buy one for $4. I was told they don't carry them in store any more, avaiable only on-line now.
I can see where $4 does sound better than $30. I totally understand. I have the cheapskate gene as well. Either diode is OK and will work, but check out the link for Perihelion Design. Here is their propaganda sheet of why its better. I know aeroelectric poopoo's the idea; probably because he didn't think of it first. Why waste energy? Periheliondesign has a good price; wholesale they cost $25-$29 anyway. They really are better than any diode you can get for what we are using it for.
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Jeff R
Well Known Member
I looked at that Perihelion diode. They claim a .18 volt drop at 10 A, but that is at a temperature of 150 degrees C. If you run a high current and/or don't heat sink it well, the diode's insides's may very well get that hot and you will then see this low voltage drop, but your diode will not enjoy a long life. For high reliability, you should never exceed the situation where your semiconductor's internal junction temperature exceeds 110C. Just for reference, that Schottky diode will propably have a drop of about .32 volts at 10 A at 25 C. That, of course, is much better than a silicon diode, and I hardly mean to imply that the Perihelion diode is not good, since it is a good one.
Whether or not you should use a Schottky or not should come down to power losses, as the voltage drop differences are probably not all that significant. But, if you are pulling 10 A, the Schottky will burn up around 3 W, while the silicon will be up around 9, give or take. That is hardly insignificant, and my choice would be to use a Schottky.
Heck, as a power supply designer, I might be tempted to use synchronous rectification, where I could use a MOSFET and get that loss down to a quarter of a watt....
Whether or not you should use a Schottky or not should come down to power losses, as the voltage drop differences are probably not all that significant. But, if you are pulling 10 A, the Schottky will burn up around 3 W, while the silicon will be up around 9, give or take. That is hardly insignificant, and my choice would be to use a Schottky.
Heck, as a power supply designer, I might be tempted to use synchronous rectification, where I could use a MOSFET and get that loss down to a quarter of a watt....
it's not the volt, it's the watts!
IMHO, the problem with 1 volt drop is not that you loose 1 volt, but that the diode will have to dissipate that volt times the amps going through.
Example:
1 volt drop X 20 amps = 20 watts.
20 watts generate an appreciable amount of heat.
0.4 volt drop X 20 amps = 5 watts.
That's why a low-drop diode is preferable.
Off course it all depends on how much load you are going to put in your e-buss.
IMHO, the problem with 1 volt drop is not that you loose 1 volt, but that the diode will have to dissipate that volt times the amps going through.
Example:
1 volt drop X 20 amps = 20 watts.
20 watts generate an appreciable amount of heat.
0.4 volt drop X 20 amps = 5 watts.
That's why a low-drop diode is preferable.
Off course it all depends on how much load you are going to put in your e-buss.
While the alternator is working, the E-bus sees 13+ volts even with a regular diode - and a Schottky will give you about a half a volt more. In battery only mode, the E-bus is powered directly from the battery (no diode) and sees less than 13V. So the 'loss' of a volt for the E-bus for normal operations is no big deal.
I went with the Schottky because I got one for about the same price as the regular square one - and it looks cooler
The way I read this (and is exactly the way I intend to wire mine) is that you have dual batteries - a primary for full electrical system operation, and a secondary e-buss battery for "sub-optimal" operations, using the diode between them to keep the secondary battery at full charge. In this case, yes you do want either a schottky or a constant-duty solenoid to connect them, in order to keep the voltage drop low. Any equipment on the e-buss pulling power through the schottky (or regular diode for that matter) will not give a hoot about the voltage drop during normal operations - but your battery will. The whole point of having the e-battery on the e-buss side of the diode is to provide e-power in the event of primary alt/batt failure, right? So why would you intentionally design the system so the e-battery never sees full system voltage to maintain a peak charge? If your e-battery has less than full charge, it's not going to deliver it's needed load for nearly as long as you may plan for, or need it to.
During normal operations, any equipment pulling power on the e-buss will pull energy from the battery until the battery voltage equals the post-diode voltage, which is 0.7 (or .1, or .3, whatever type diode you have) volts below the optimum charging voltage, and you'll never EVER be able to fully charge that e-battery. In order to keep the highest possible charging voltage on your e-battery, you need to lowest possible voltage drop across that diode.
Use a schottky and keep the charging voltage up on your e-battery.
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Mike S
Senior Curmudgeon
I have pretty much the above setup, except that my aux batt is charged from my aux alternator.
My radios, EFIS, GPS, and other "E" stuff is powered directly from the aux battery, which is connected to the main batt through a 35a Schottky diode, in a DO-4 case, in a heat sink.
In normal operation, the aux system powers the "E" stuff directly, in a failure of the main batt/alt system, the aux system never even sees it, due to the diode.
If the aux system fails then the main system powers the "E" stuff through the diode.
Warning lights, and EFIS instrumentation allows me to keep tabs on the two systems, otherwise the "E" stuff just goes along on whichever of the two systems it needs to, all automaticly.
At least this is the design, I have yet to get the plane in the air, so I have no empirical info.
For your setup, you don't even need schottky, since your aux alt will always keep a top float charge on your e-battery - but without it you'll partially drain the e-battery if your aux alt goes TU. I know you didn't ask (and it doesn't matter) - but I approve your design!
Mike S
Senior Curmudgeon
For your setup, you don't even need schottky, since your aux alt will always keep a top float charge on your e-battery - but without it you'll partially drain the e-battery if your aux alt goes TU. I know you didn't ask (and it doesn't matter) - but I approve your design!
Greg, thanks for the words of approval.
The way I came to this setup was due to having bought a project someone else started, and it came with dual batt/alt.
Being as I am too cheap to replace existing stuff unless there is a real need, I decided how to best use what I already had. After a lot of reading here, and Aerolectric Bob's stuff, I came up with the above.
In the event of a failure, my system will probably allow me to continue any flight on aux system alone,----Nuckols way of doing things---by my intent is to have the choice of where I land to fix things. This may mean I finish the original flight, or it may mean I only fly on for a half hour--------but I get to make the decision, not the airplane.
Perihelion Power Schottky question
I have a couple of Perihelion power schottkys. They are the 60 A versions.
Part number is the 122NQ030 IR 6037.
I don't have the info from the Perihelion & it is no longer on their website.
Just need some simple help on wiring this thing up so I don't ruin the part.
I understand what the device is supposed to but still unsure. It has 2 8-32 screws at each end of the device & also a very large screw right on top of the diode - could be a 1/4-20 or 5/16-18. The head of the bolt is painted red.
Is this a set up so that it could act like a switch i.e. small input current which gates the circuit?
Thanks very much
Brian RV-8
I have a couple of Perihelion power schottkys. They are the 60 A versions.
Part number is the 122NQ030 IR 6037.
I don't have the info from the Perihelion & it is no longer on their website.
Just need some simple help on wiring this thing up so I don't ruin the part.
I understand what the device is supposed to but still unsure. It has 2 8-32 screws at each end of the device & also a very large screw right on top of the diode - could be a 1/4-20 or 5/16-18. The head of the bolt is painted red.
Is this a set up so that it could act like a switch i.e. small input current which gates the circuit?
Thanks very much
Brian RV-8
rapid_ascent
Well Known Member
Refer to the datasheet. Its just a diode so effectively only 2 terminals.
http://www.smc-diodes.com/propdf/122NQ030(R)-1%20N1017%20REV.B.pdf
http://www.smc-diodes.com/propdf/122NQ030(R)-1%20N1017%20REV.B.pdf
Canadian_JOY
Well Known Member
The package sold by Perihelion is actually a pair of diodes. Each one has a screw at the input and a screw at the output. Eric ships them with a shorting stub in place so you can parallel them to effectively double the current capacity to 60A.
His wiring diagrams on this page give a good idea of the possible wiring combinations.
http://www.periheliondesign.com/powerschottkydiodes.htm
Also the pdf manual he provides describes the diodes as being the following parts.
IXYS DSSX61-0045A
I have one of these Power Deuce packages installed for E-Bus isolation. Works a charm!
His wiring diagrams on this page give a good idea of the possible wiring combinations.
http://www.periheliondesign.com/powerschottkydiodes.htm
Also the pdf manual he provides describes the diodes as being the following parts.
IXYS DSSX61-0045A
I have one of these Power Deuce packages installed for E-Bus isolation. Works a charm!
