Question about recifiers

[macula56]

a while back i stumbled upon a post that listed all of the rectifiers and their voltage drops, including solid state. i have been searching for it for a while now and can not find it. does anybody have this info? thanks as always, JMac.

[jojokeo]

Is this it?

[HotBluePlates]

Be aware that the chart is best used as a guide, especially to show the relative difference between rectifiers.

There are a number of reasons why that chart won't be accurate under all circumstances. I was pondering a post last night on that topic; got some preliminary reading to do before posting it.

[macula56]

that's post i was looking for didn't include a cool list like that. thanks jojokeo.

[FYL]

Most datasheets were written when slide rules were high-end tools and manual calculations ruled. Just get the equivalent plate resistance and use modern tools such as a pocket calculator or a spreadsheet...

Per the datasheets, the specified or calculated equivalent plate resistances of common rectos are:

5Y3GT      50 V @ 125 mA => 400R
5R4WGB    35 V @ 100 mA => 350R
5U4G        58 V @ 225 mA => 270R
5U4GB      44 V @ 225 mA => 200R
5V4GA      25 V @ 175 mA => 150R
6CA4        20 V @ 150 mA => 110R
5AR4        16 V @ 200 mA => 82R

What is the voltage drop across a 5AR4 with 250 mA per plate? Per Ohm's law U = R * I = 82 * .25 = 20.5 V. Etc.

[mresistor]

When did we start using U to designate Volts/voltage? Isn't that Soviet nomencalture? Serious question.....

[jojokeo]

I found a link from the past called "design guide for rectifier use" that you may be also thinking of. The pdf file was too large to post but the link should work. http://www.hammondmfg.com/pdf/5c007.pdf

[HotBluePlates]

When did we start using U to designate Volts/voltage? Isn't that Soviet nomencalture? Serious question.....

It's non-english nomenclature. You'll see the same in German, French, Italian, etc.

[RicharD]

FYL's post is great information.  I added it to the cheat sheet.

[FYL]

When did we start using U to designate Volts/voltage? Isn't that Soviet nomencalture? Serious question.....

U is the norm, V the unit. Just like P and W for power or I and A for current.

[FYL]

It's non-english nomenclature. You'll see the same in German, French, Italian, etc.

It's the worldwide standard. A lot of people in the US don't use it, the same people use uF instead of µF and prefer 3 1/2" to 3.5".

[Willabe]

FYL,

I thought people (on a computer) used the lower case " u " because standard keyboards dont have that key, but you got it on the screen. How did you do that?   

   Thanks,    Brad

[sluckey]

It's ASCII alt codes. For ex., ALT + 230 is µ, or ALT + 234 is Ω, or ALT 14 is ♫. Here's the table. Most of these work in your word processor or on Hoffman's forum but don't work everywhere. I keep this file on my desktop for easy reference. Hold down the ALT key while typing the number on your numeric keypad. When you release the ALT key, the symbol will appear. Wont work on a laptop without a numeric keypad.

[jojokeo]

figures the very first alt1 is the happy face ☺☺☺

[Willabe]

Wow, very cool!

     Thanks,   Brad

[FYL]

I thought people (on a computer) used the lower case " u " because standard keyboards dont have that key, but you got it on the screen. How did you do that?   

There's more than standard keyboards and drivers... I've got direct access to µ ± × ¹ ² ‰ ½ ¾ ® ™ and other special chars I use daily thanks to a custom driver.

 

[HotBluePlates]

Most datasheets were written when slide rules were high-end tools and manual calculations ruled. Just get the equivalent plate resistance and use modern tools such as a pocket calculator or a spreadsheet...

Per the datasheets, the specified or calculated equivalent plate resistances of common rectos are:

5Y3GT      50 V @ 125 mA => 400R
5R4WGB    35 V @ 100 mA => 350R
5U4G        58 V @ 225 mA => 270R
5U4GB      44 V @ 225 mA => 200R
5V4GA      25 V @ 175 mA => 150R
6CA4        20 V @ 150 mA => 110R
5AR4        16 V @ 200 mA => 82R

What is the voltage drop across a 5AR4 with 250 mA per plate? Per Ohm's law U = R * I = 82 * .25 = 20.5 V. Etc.

This is excellent information, and is correct. But the catch is that just knowing the effective plate resistance and voltage drop will not tell you for sure what the voltage will be at the first filter cap (which is what I assume J-Mac is really wanting to figure out). To figure that out, you have to go look up the charts O.H. Schade prepared in 1943 and go through a fairly significant calculation process.

Ultimately, that was going to be the point of the thread I wanted to start, to help answer the question of "how much voltage?" and "how big a filter cap?" which is always asked.

[FYL]

Just calculate pulsed DC value, then factor in the recto, this will give a pretty good voltage approximation - we're dealing with quite simple CRC or CLC filtering structures working on 50/100 or 60/120 Hz only.

Calculate max allowable DC ripple at C1, say 10% of useful B+.
Peak to peak voltage ripple Ur is 1 / (2 * Pi * F * C) for full wave and 1 / (Pi * F * C) for half wave.
You may use the empiric formula C1 = (I * 6 E-3) / Ur for less than 1 A current draw.

Is C1 OK for the recto and PT used? If yes you're nearly done.