Sorry to hear that, but if it's any consolation, there are few things as well understood and treatable. He's lucky to live in a time with so much hope for ever-better treatments and even a cure in the wings. My step-grandmother lived to a ripe old age with diabetes in the days when that was so very unlikely. A challenge, yes, but one that can be met. Good luck.

Hey Jason,

Sorry to here that your child is not well, but as wayneh say's, medicine has come on leaps and bounds. I hope all will be well with you and your family.

Best wishes, Steve.

Thanks and I know he will be ok but it's just hard for me ....
I finishing up the circuit ( I hope ) and will posting it up later ..

 

It is the role of one generation to absorb the agonies of the next. Someday they will carry the baton for themselves. These things are always harder on the parent. Children adapt. That's what they do, while their parents watch in breathless awe.

 

Here is what I have and does it matter what value the caps are and is there a max value I can use or is there a way I cna figure out the best value to use????
What 's you thoughts and would you change anything and why??

 

What's D2 doing (the middle one near the regulator)? And what is that 10µF capacitor for, seeing that there is the 75µF capacitor nearby.

The LM317 datasheet specifies the recommended capacitors to use. Who am I to argue?

I think a common approach for the caps is to use both a small, eg. 0.1µF ceramic capacitor and a larger (50-1000µF) electrolytic in parallel. This approach filters both high and low frequency noise. For the latter, bigger is generally better but a big cap can act as a large load - a short - when power is first applied. So there's no reason to use more than the circuit needs.

The "need" is defined by the load current and acceptable percentage of ripple in the DC voltage. For an unregulated DC supply, a big load and a small ripple calls for a LARGE capacitor. For your supply using a regulator, I'm frankly not sure how big a capacitor to use. When in doubt, follow the data sheet.

 

What's D2 doing (the middle one near the regulator)? And what is that 10µF capacitor for, seeing that there is the 75µF capacitor nearby.

The LM317 datasheet specifies the recommended capacitors to use. Who am I to argue?

I think a common approach for the caps is to use both a small, eg. 0.1µF ceramic capacitor and a larger (50-1000µF) electrolytic in parallel. This approach filters both high and low frequency noise. For the latter, bigger is generally better but a big cap can act as a large load - a short - when power is first applied. So there's no reason to use more than the circuit needs.

The "need" is defined by the load current and acceptable percentage of ripple in the DC voltage. For an unregulated DC supply, a big load and a small ripple calls for a LARGE capacitor. For your supply using a regulator, I'm frankly not sure how big a capacitor to use. When in doubt, follow the data sheet.

Here the schematic I was working off of and does it matter if the fuse is on the input or the output of both ...
http://i1160.photobucket.com/albums/q485/jdansti/5df3af84.jpg


But also was looking at
http://www.sentex.ca/~mec1995/circ/VarReg1/VarReg1.html

Or mod this to work for me

 

Why don't you just build a simple power supply without all the bells and whistles and as you go along and learn more things then you can add more stabilization and filtration to it .
I've been using a very simple one for half a year and it was no problem , never failed even after shorting it and whatnot .
Just the lm317 and the two adjusting resistors (for the voltage adjustment)
1 electrolytic at a few hundred microfarads and a 100nf in parallel on the output and that diode across the lm317 .
I think that's more than enough for now

edit: Don't forget to heatsink the lm317!
If you will be pulling 100-200ma then a small crappy heatsink will suffice .
More -> Then you will need a slightly bigger slightly less crappy heatsink

 

Or mod this to work for me...

Why mod it? Either of those will work fine. As Shagas has pointed out, unless you have very particular needs and/or sensitive equipment, the simplest circuits will be just fine. Just read and follow the data sheet.

Oh, and you can put fuses anywhere and everywhere. The point is to spend a small amount of money on a fuse that protects something relatively more valuable. The most expensive thing in a power supply like these is - by far - the transformer. So it makes sense to use a fuse to protect the transformer.

And, since you may not take the time to put fuses on some of your experimental circuits, it can make sense to put a fuse on the power supply output. It may or may not protect the supply, but might save your latest experiment from an unintended short or mis-wiring. You might even want a, say 100mA fuse to your breadboard if you know the circuit you are building shouldn't need any more than that. If it draws more, you know you've made a mistake and the fuse might save a component or two. Many components are cheaper than fuses, though.

 

Hey Jason,

I think I agree with Shagas & Wayneh, just build something simple to begin with, since you'll be using a wall wart. You can easily build little sub circuits to add to it after. You'll even be able to re-use the components if you leave a bit of lead length (boardside rather than solderside!).... Breadboard one out and try it, go on you know you want to.

 

Hey Jason,

I think I agree with Shagas & Wayneh, just build something simple to begin with, since you'll be using a wall wart. You can easily build little sub circuits to add to it after. You'll even be able to re-use the components if you leave a bit of lead length (boardside rather than solderside!).... Breadboard one out and try it, go on you know you want to.

Hey Steve

Thanks for the encouragement ... My plan is to order the parts and play with it and hook it up to my 20mhz scope ..

 

Why mod it? Either of those will work fine. As Shagas has pointed out, unless you have very particular needs and/or sensitive equipment, the simplest circuits will be just fine. Just read and follow the data sheet.

Oh, and you can put fuses anywhere and everywhere. The point is to spend a small amount of money on a fuse that protects something relatively more valuable. The most expensive thing in a power supply like these is - by far - the transformer. So it makes sense to use a fuse to protect the transformer.

And, since you may not take the time to put fuses on some of your experimental circuits, it can make sense to put a fuse on the power supply output. It may or may not protect the supply, but might save your latest experiment from an unintended short or mis-wiring. You might even want a, say 100mA fuse to your breadboard if you know the circuit you are building shouldn't need any more than that. If it draws more, you know you've made a mistake and the fuse might save a component or two. Many components are cheaper than fuses, though.

Why don't you just build a simple power supply without all the bells and whistles and as you go along and learn more things then you can add more stabilization and filtration to it .
I've been using a very simple one for half a year and it was no problem , never failed even after shorting it and whatnot .
Just the lm317 and the two adjusting resistors (for the voltage adjustment)
1 electrolytic at a few hundred microfarads and a 100nf in parallel on the output and that diode across the lm317 .
I think that's more than enough for now

edit: Don't forget to heatsink the lm317!
If you will be pulling 100-200ma then a small crappy heatsink will suffice .
More -> Then you will need a slightly bigger slightly less crappy heatsink

Thanks for the info guy and I will be starting small and then building from there ... But I will post up pics and my findings with each circuit and show what I have learned ...

 

Don't forget to heatsink the lm317!
If you will be pulling 100-200ma then a small crappy heatsink will suffice .
More -> Then you will need a slightly bigger slightly less crappy heatsink

+1
I've built these with the LM317 as the weakest link - due to excessive heat - and I think that is the most common noob mistake. But on the one supply that I placed a nice big heat sink, it immediately revealed that my transformer was the weakest link. At 600mA or so, the transformer gets a lot hotter than the LM317.