12v to 7.5v

Here is my great sketch :D

PSOneLCDrough.jpg


I want to completely eliminate the two boards, and solder the leads from my circuit board directly to the LCD itslef, which will make it much cleaner, and definately more safe thatn what I have now. I am trying to find the schematics of the PSOne lcd with no avail, but I shall keep searching.
 
mikeblas said:
I'm not sure why you've chosen a four-pin plug for the power input. I'd use a 3-pin regulator, and assign the pins so that you're guaranteed to not short or damage anything if something is plugged-in backwards.
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The four pin connectoor is a female molex connector so i can actually plug then power from the PSU directly in. I would leave out plugs 3 and 4 so that there was no chance in harming anything. Other than the diode, everything else checks out? I am just going to make 2 holes to solder wires from the board to the LCD. If it all checks out, onto the board layout!


mikeblas said:
What's all that crap, by the way? I see it in many people's posts, and it's annoying to have to delete it every time I respond by quoting.
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That is my folding badge, it basically tells how many points we have, and how many work units we have done. Check it all out in the Distributed Computing Forum
 
mikeblas said:
Then you're achieving no regulation, which seems pretty bad. The Zv will take 4.3 volts off the input, and the input isn't regulated -- it'll vary between 0 and 14.8 volts or so.
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His computer's 12 volt rail is regulated... subtract 4.3 from that and you get 7.7, assuming that there's enough current draw to bias the zener. And in the zener region, the diode's drop shouldn't vary much.

So it should be a constant 7.7 volts.
 
fenton06 said:
Other than the diode, everything else checks out?
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As far as I see, yeah.

fenton06 said:
That is my folding badge, it basically tells how many points we have, and how many work units we have done.
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You must be very proud -- buy why does it need to be in practically every post?

gee said:
His computer's 12 volt rail is regulated... subtract 4.3 from that and you get 7.7, assuming that there's enough current draw to bias the zener. And in the zener region, the diode's drop shouldn't vary much.
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Oh! Did I misremember the thread? I thought this was going into a car.
 
lol...you gusy argued about a car voltage for some reason...but yeah, its in my computer, here is me showing it off. :D Now, onto the board layout!

mikeblas said:
You must be very proud -- buy why does it need to be in practically every post?
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It doesn't have to be, but it can...it's just a way we can promote what we do. See, no stats.
 
mikeblas said:
You must be very proud -- buy why does it need to be in practically every post?
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Consider it a special, Kyle-sanctioned meta-signature
mikeblas said:
Oh! Did I misremember the thread? I thought this was going into a car.
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There's another thread, very similar to this one, about running stuff from 12V. I've gotten them mixed up, too. :)

 
OK, so I avhe the board layout done....TADA!!!!

BoardLayout.jpg


Now this brings about 3 questions:

1) What is a female RCA connector called in Eagle? I want to essentially put 2 boards on one.

2) Does this work?

3) How do I print out what I need to lay on my blank PCB?

 
mohonri said:
Consider it a special, Kyle-sanctioned meta-signature
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I wish we had special software to deal with it. I find it annoying as a day at the DMV.

fenton06 said:
OK, so I avhe the board layout done....TADA!!!!
1) Does this work?
2) How do I print out what I need to lay on my blank PCB?
Click to expand...

1) Looks OK, as far as I can tell. It's hard to see all the traces because of the silkscreen being there. I think you could do a better job with the layout. And remembe that you can't fold the regulator down, since you'll need to mount a heatsink to it. The datasheet will tell you which case can handle what current before a heatsink is necessary, and I think for that TO-220 package, you need one starting at 1A.

2) Contact the company that's going to make the PCB for you. You might not want a silkscreen once you hear the price -- most companies charge for it. Otherwise, I think it's just a layer in the Gerber output file you'll send to them.
 
OK, no folding down of the regulator :D

I am etching my own PCB, so I need to print the layout without the components...I will have to do some playing probably....

What could I do different about the layout? I don't know much about electronics, so any help witht the layout would be nice.
 
fenton06 said:
The stuff on the right is for the RCA plug....
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What's the RCA plug for? It's just connected to those two pads, and nothing else.

fenton06 said:
What could I do different about the layout?
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Just make it neater. You might check with your PCB manufacturer to see how wide or thick your traces need to be for the weight of copper they're going to use in order to carry the curren't you plan to push.
 
mikeblas said:
You might check with your PCB manufacturer to see how wide or thick your traces need to be for the weight of copper they're going to use in order to carry the curren't you plan to push.
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...and then double it, if you're etching your own PCB. I usually etch into at least one or two traces. If I didn't give myself a safety factor, I'd have to solder wire shunts on everywhere.
 
mikeblas said:
What's the RCA plug for? It's just connected to those two pads, and nothing else.
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It's a completely different part, I just want it on the same board as the regulator. I want to make the LCD kind of modular. With this board, I just unplug the RCA cable and the power and I can take it out.

How thick should I make the traces? I'm not sure on the current thats going to be used, its just hooked to my PSU, so how thick would i need to make them?
 
fenton06 said:
I'm not sure on the current thats going to be used,
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We've provided this information several times in the thread.
 
My memory seems to be failing me at the young age of 17! So this is going to have roughly 1 amp running through it, so would .032, .04, or .05 traces be good? I am thinking the .04 or .05 would be better because I am etching my own PCB...

Edit - wow...I did some more research, and found that I need .05, so if i am going to double that, I need .1 traces...is this too big? Or is this acceptable.
 
fenton06 said:
My memory seems to be failing me at the young age of 17! So this is going to have roughly 1 amp running through it, so would .032, .04, or .05 traces be good? I am thinking the .04 or .05 would be better because I am etching my own PCB...

Edit - wow...I did some more research, and found that I need .05, so if i am going to double that, I need .1 traces...is this acceptable?
Click to expand...

50mil traces is what i use for power and ground signals.. but i guess 100 would be good too.. i mena the bigger you go the better... do you have issues with space?
 
I am etching my own circuit board...and the .1 traces are really big...could i do the .05 traces and be ok? I could do a little bit larger than that, but I think the .1 is overkill.
 
fenton06 said:
I am etching my own circuit board...and the .1 traces are really big...could i do the .05 traces and be ok?
Click to expand...


you're gonna have to as someone else, if i gave you an answer i'd be lying..
 
.05 should be just fine. You'll find traces on "real" PCBs that are smaller than that and carrying more current. Take a look at the traces in a PSU--there's commonly well over 10A going through some of those traces, and they're not much bigger than .05.

 
ok...here is the 3rd rendition...

BoardLayout3.jpg


Now how do I get it so I can print the layout to put on the blank PCB? I am using Eagle btw...

 
f U z ! o N said:
silicon diodes drop .7v for whoever asked that, germanium diodes drop .3v
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in general.. but i think the drop of diodes can be altered by the amount of doping they have as well.. so a Silicon diode isn't always .7V.. that's just the common drop..

that is.. IIRC
 
RancidWAnnaRIot said:
in general.. but i think the drop of diodes can be altered by the amount of doping they have as well.. so a Silicon diode isn't always .7V.. that's just the common drop..
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If it has much more doping than normal, it'll be called a Zener diode.
 
mikeblas said:
If it has much more doping than normal, it'll be called a Zener diode.
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Zener diodes operate in a different region altogether (reverse drop) - They're regular silicon diodes but they're manufactured in such a way that they have an awful reverse voltage rating.

If you want a very low forward drop with any amount of current, use a schottky diode. Germaniums don't scale to high currents.
 
gee said:
Zener diodes operate in a different region altogether (reverse drop) - [...] use a schottky diode. Germaniums don't scale to high currents.
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Oops! That's right.
 
mikeblas said:
If it has much more doping than normal, it'll be called a Zener diode.
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ahhh yes yes yes... you are correct

I've heard that Zener diodes are falling out of fashion..?? :confused:
 
masher said:
Plaid miniskirts...
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Lies... if you could choose between seeing a hot chick wearing a plaid miniskirt, or a zener diode, you'd probably not choose the miniskirt. :D
 
mikeblas said:
In favor of what, exactly?
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sorry.. the Zener diode as a voltage regulator is falling out of fashion... in favor of actual regulators made with transistors,resistors and what not..

i'm guessing it's cause diode drop voltages can vary much more with temp than regulators made with transistors and crap... i don't know... just a guess..

anyway.. that was what one of my professors said
 
masher said:
Plaid miniskirts...
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That was actualy one of my first guesses. The stock market keeps going up, and it's said that hemlines follow the market. I hope we have a great year!
 
RancidWAnnaRIot said:
sorry.. the Zener diode as a voltage regulator is falling out of fashion... in favor of actual regulators made with transistors,resistors and what not..

i'm guessing it's cause diode drop voltages can vary much more with temp than regulators made with transistors and crap... i don't know... just a guess..

anyway.. that was what one of my professors said
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depends.

zeners aren't as temperature or current stable as a TL431 or similar device, and shunt regulators in general (which is pretty much all you can build with a zener diode) are inefficient. But they're dirt cheap, occupy less PCB space, and some applications where voltage stability isn't an absolute requirement and efficiency isn't an issue, zeners get designed in. I've done it.

And zeners are great for circuit protection.
 
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