WOW, have things changed , man o man. i am in the market for a new phone, and just a quick google search brought up emulators for iphone and android phones of the different calculators - have you used/compared any of the emulated versions vs a 'real' unit? a buddy of mine is a ME/aerospace machinist and once he picked up a iphone he was amazed at how many apps you could get for it related to his field - all the charts/calculations he use to have to keep track of do 'old skool' are all in his phone now and take no time to access.

thanks for the info,
bob

Droid48 is an HP 48 Emulation app, 100% compatible, even the memory slots are duplicated and programs can be stored. No IR transfer, but the keyboard is the same, and all functions work the same. I use it a lot.

Now, back to the regularly scheduled discussion on regulators...

 

@tom66:
thanks for the suggestion. one issue i am trying to cover is in case the the power for some reason goes lower than 12V. it shouldn't be an issue but just in case. w/ the ldo reg it can put out 8V w/ just 9-10V in.

@all:
for the reg circuit, what size traces should used?. the tl750M08 datasheet claims it can put out 750mA max, but again, i see my uses @ 300mA max but would like a bit of headroom, so possibly make them so they can take full advantage of the regs capabilities.

again, this is just for the first one/s, other will get a more efficient power reg design, i am just running out of time.

 

these worth making? a friend that normally lays out boards isn't available, so i had a go at it....be gentle....

are these correct? i left it up to eagle after i brought in the schematic. are 15mil traces large enough? if not, what should i go to? at this point time is getting close, so i just need them to work, so if it will work that is excellent and please lmk any problems for future knowledge, if i have errored, please lmk so i can get them fixed and to the board house. board size is ~ 1.125 x 1.5" give or take. all traces are on the bottom layer - would it be better to use 2 layers - cost would be the same...

thanks,
bob

 

It's a good first attempt and likely to work just fine.

One thing I'd suggest is reading up on including a ground plane. Basically a large area of copper connected to the ground, which simplifies wiring.

 

i will look into the ground plane and how to put it on, in the mean time i switched the 2 100μF caps as i brought them in mixed up. is this better?

 

any other feedback from anybody?

 

Can you upload the board file as an attachment?

 

here it is from my home server - please be nice as it has been submitted as the board panel was filling up. if it doesn't work, well, i will chalk it up as a lot of learning experience any feedback would be appreciated for learning though.

8VRegulatedPWR

 

I put your board through Eagle3d and rendered it in Pov-Ray.

I like to do that, to check component placement. Here I noticed that C3 and C4 is maybe a little bit too close to the regulator...

But then again, I could be wrong...

Looking at it like this, everything seems to be in order...

 

excellent, very, very nice . appreciate it very much. they very well may be too close, i can bend them or the regulator legs before it is mounted a bit if necessary and use this as a learning experience for the next ones. the one thing about this project is that once it is placed, it shouldn't be moved, and after i get a bit better w/ the board layout, i will probably make a more efficient regulator that SgtWookie had talked about and replace this one, but for the time being this will be much better than a proto board .

again, thanks for taking the time to do that, i really appreciate it. is there a tutorial for that process that you may have readily available? it would be nice for the sizing of parts like you have done and also just to see the item in 3d. i have attempted to take eagle items into solidworks and it doesn't work so well other than basically hole locations on the pcb itself, the components are really messed up and i haven't found a way to get it to work w/ eagle.

thanks,
bob

edit: you got me curious so i went and checked a printout w/ the actual components and the regulator's pins are in the middle to middle front of it, so they are going to be pretty close. i am thinking i should put the ceramic caps in first and then solder the the regulator elevated a bit so its heat doesn't mess w/ the ceramic caps. don't know if this would be an issue or not, but it is about the best i can do at this point. is there a 'rule of thumb' of how close to put through hole parts?

i was thinking, after i have more time and if i go back and make a unit like SgtWookie suggested, i would just do smd, 1206 or 0805 for convenience because 0603 i start to need the microscope for placement

again, thanks for everything.

 

Before I found Eagle3D and Pov-Ray, I used to print out the board layout, and use a needle to make the component holes, and eventually place the components physically, to check placement.

Like this:

You will find lots of tutorials here:

http://www.google.no/#hl=no&biw=128...+pov+ray+tutorial&spell=1&fp=4df74765b24aeeaf

 

that sure is one way to do it . thanks again, will check out that link

 

just a question about a ground plane - for a circuit like these 2, is there any benefit other than simplify the traces? or is it just good practice to start using and get in the habit of creating one regardless of the circuit?

should the same be done w/ a power plane?

 

Ground planes greatly reduce the amount of etchant consumed, as comparatively little copper has to be removed. Also, ground planes have VERY low inductance compared to traces. An infinite plane has virtually no inductance, where as a narrow trace has comparatively high inductance.

A power plane is great for the same reason, but this generally involves making 2 or more layers. A 4-layer board might have traces routed on the top and bottom, with complete power and ground planes located in the middle layers.

 

thanks SgtWookie. sounds like for my uses ground plane is good as tom stated for th components and then use both ground and power planes when i move to a full smd board? the more i learn about this stuff from this view the more i am impressed you can buy a computer m/b for $60 or so...

again, thanks for all the info and assistance. got my 2 boards send off, although i had a time constraint so i didn't add the ground plane to the boards i sent off, but did make them that way after the fact and can see a benefit and the routing is much easier, could have probably made the boards 25% smaller, but again, this has been a great educational experience, now lets just hope that when i get them assembled i don't let the magic smoke out. i did run the eagle drc/erc so hopefully it caught any errors i have made. time will tell.

after the programming is done, on w/ the eagle3d stuff for future boards - just out of curiosity, does that whole setup run in win7 64bit (i know....)

bob

 

...
after the programming is done, on w/ the eagle3d stuff for future boards - just out of curiosity, does that whole setup run in win7 64bit (i know....)
...

I'm using Ubuntu and Win XP, so I do not know.

 

thanks SgtWookie. sounds like for my uses ground plane is good as tom stated for th components and then use both ground and power planes when i move to a full smd board? the more i learn about this stuff from this view the more i am impressed you can buy a computer m/b for $60 or so...

The "Expensive Parts" of motherboards are the connectors, such as PCI Card Edge, and the onboard peripheral ports (USB/keyboard/etc), power connectors, etc, followed by Heat Sinks on chipsets, and then capacitors and inductors on the CPU power supply area.

Everything gets cheaper when working in lots of 100,000, silicon is nearly free, relative to the hardware. Cost for a Retail $60 Motherboard is under $30 before packaging/branding/etc.

Similar economies of scale apply to power inverters and other very common electronic gadgets. In many cases, $10 or more of parts/components can be scavenged from a $3 device. The cheap DMMs are a good example of this.

This is one reason PIC microcontrollers are great, as you can save a dime getting the minimum you need for RAM and peripherals, those choices turn into profits, compared to "all in one" controllers that are essentially the same with more or less I/O.

 

finally got caught up w/ some other stuff and had a question in regards to this:

the datasheet - http://www.fairchildsemi.com/ds/4N/4N33M.pdf

claims forward current up to 80ma and forward voltage of 1.2-1.5V. i am considering that my main input will be 13V max, so the R2 resistor for 1.3V/5ma to the incoming side will be of 2.7KΩ, why does the schematic say 10KΩ is necessary? is my math incorrect or am i missing something? are the leds in these to be used like a normal led? even if 15V was coming in, i am still well under anything near max if i am reading the datasheet correctly

edit: also, i don't have to have a common ground between the sides according to the datasheet....again if i am reading it correctly...just wondering why that schematic was created that way? what should i expect for a V drop across the diode? 1V? if i am using only +DC, is there any possibly way for it to go under 0V since the original power is coming from a wallwart, but i just didn't think they could go less than 0V.

thanks,
bob

 

Optoisolators are used for isolation, so the ground doesn't need to be common on both sides, there only needs to be a path for current to flow on both sides (+12V and Signal Gnd on left, +5V and Digital Ground on Right).

They are both 'ground', referenced to their source, but they do not need to be tied together, actually, shouldn't be connected.

 

how much current do i need to draw to heat up the regulator? it is rated for 750mA.