Where to go from here

[Mery128]

So I recently started watching Dave's videos, and have always had a bit of an interest in electronics but never really had the money to fund any "fiddling" or "tinkering" or getting any kind of decent equipment but have found that now I do. So I took Dave's advice and have gotten myself an oscilloscope and I have a cheapy "won hung-lo" meter which I plan on replacing with a pair of Extech EX330s soon(TM). But Im kinda running into a problem of "Where do I go from here" I have some projects in mind but I don't really have the experience designing circuits yet and was wondering if anyone had a suggestion of what to do to get familiar building and designing power supplies (a keen interest of mine actually). So, I have looked at some of the talking electronics projects but Im just really 100% sure where to go with things at the moment and had a bit of a "So I got my oscilloscope, now what?" moment last night and thought Id make my first post here on the forums and see about getting some input on it.

Also as an aside I would like to say: Dave I love the videos I've seen on youtube, Im glad I found them and want to say thank you for making them, they inspired me to rekindle my interest in electronics.

[Dongulus]

Obtain some busted electronics and try to fix them. Repairing electronics is a great way to learn a lot quickly.

[zapta]

What kind of projects do you think will be more interesting for you, audio (e.g. amplifiers), digital (counters, logic, blinking stuff), radio (transmitters or receivers), general analog (e.g. build your own power supply), etc.

Once you figure out, you can find schemas for simple circuits that you can build and debug. This will force you to learn enough to complete the projects.

[Mery128]

I have some interest in digital, I snagged an arduino board and have fiddled with that some. Id say for the time being Im interested mainly in building test gear and power supplies and such. The idea of snagging some busted electronics and fixing them up sounds like it would be a good fun time. Would you guys say that throwing together pretty much any circuits I can find schematics for on a breadboard and then tinkering with them from there is a pretty worthwhile endeavor?

[Flump]

these two should get you started, the transistor one especially.

edit
i just tried to attach two free pdf books but it failed
so google these and download them.

1-100TransistorCircuits.pdf
50-555Circuits.pdf

[Lee697]

I find more satisfaction in making circuits that have a purpose too... After I kept killing SLA batteries leaving lights on in my observatory, I made a timer switch, that turns off after a period. About to make another to cut power to the soldering iron after a few hours too....
Lee

[nsayer]

One place I turn for inspiration is the shared projects feed at oshpark.com. They're not always documented very well, but there are some interesting ideas there.

[Lee697]

.... had a bit of a "So I got my oscilloscope, now what?" moment last night and thought Id make my first post here on the forums and see about getting some input on it.

My advice would be, if you haven't already - watch Daves video on how to not blow up your oscilloscope....(#279)....

[GreyWoolfe]

Check out W2AEW's videos.  I built the curve tracer circuit that he did and it is a handy little project.

[malch]

A useful project is a MegaSquirt kit to control your car's ignition and fuel. 

[Mery128]

@Lee697 That actually is the very first video I watched. I was a little stunned to be honest, I had never thought about the fact that things you plug in all tie into the same ground line like that.

@Flump I've actually read those and fiddled with the circuits some they're really interesting.

I have been really wanting to build a power supply, I've been looking at some schematics that I've found on google. I somewhat would like to know if there's any good literature on power supply design, or maybe some suggested reading for that. I'm still somewhat shaky on the concept of why some components are selected for circuits. I have a feeling reading all of the art of electronics may make this more clear but something that's more concise would be awesome too.

One more thing I'm somewhat curious about: Circuit Simulation.
Is circuit simulation a valuable tool or is it more of a trap for new players? Half the time I've thrown diagrams into a simulator it seems like they don't function as described or it seems like most of the components are actually pointless in the simulation. (I am willing to accept this may also be me not understanding quite how everything is supposed to work together)

Also thank you all for your input on this it's very much appreciated.

Edit: Corrected spelling and added Circuit simulation paragraph.

[RazSlack]

I have been really wanting to build a power supply, I've been looking at some schematics that I've found on google. I somewhat would like to know if there's any good literature on power supply design, or maybe some suggested reading for that. I'm still somewhat shaky on the concept of why some components are selected for circuits. I have a feeling reading all of the art of electronics may make this more clear but something that's more concise would be awesome too.

There's two kinds of power supplies: Feedback linear series pass transistor, and switch-mode. When designing a power supply, first you have to think what it has to accomplish. Does it have to go down to 0 volts? How many channels do you want? How much space can it take up?

I'd recommend starting with a linear power supply, unless you want a PSU that can output at least 300 watts, and they're easier to understand.

[tautech]

I have been really wanting to build a power supply, I've been looking at some schematics that I've found on google. I somewhat would like to know if there's any good literature on power supply design, or maybe some suggested reading for that. I'm still somewhat shaky on the concept of why some components are selected for circuits. I have a feeling reading all of the art of electronics may make this more clear but something that's more concise would be awesome too.

Just build a simple PSU for starters. Hunt around for a pair or old 12V downlight transformers.(get proper transformers not SMPS)
Wire their outputs in series, rectify, smooth and simple adjustable linear regulator and hey presto close to 30V @ 4 amps. Use a thermal and SC protected regulator.
Stick it all in a nice case(not too small) and add panel meters, 10 turn pot, extra outlets etc later as you need/ can afford them.
Don't worry about adjustable current current yet, you may find you don't need it.
For the first power up of a circuit you have built, just add a small Auto bulb in series as over-current limiter/indicator. That will keep the magic smoke in.

The Art of Electronics is an excellent reference/ideas book, but it is likely to do your head in until you are more experienced. Apply the KISS principle.

From that you have posted it seems Power Electronics is your interest.
Great fun controlling 100's to 1000's Watts with logic and power devices!

Become confident with just glue logic and Fets etc then proceed to micros as your knowledge grows.
Have fun and welcome to the forum.

[radioFlash]

As far as power supplies, you can look up datasheets / example circuits using voltage regulators such as LM317 and LM723.

Here's an interesting document on Power supplies:

DC Power Supply Handbook
HP  / Agilent Note 90B
http://cp.literature.agilent.com/litweb/pdf/5952-4020.pdf

[Lee697]

@Lee697 That actually is the very first video I watched. I was a little stunned to be honest, I had never thought about the fact that things you plug in all tie into the same ground line like that.

I saw it after I tried to blow mine up! I was measuring the voltage across a resistor (not at ground) with one PSU no prob, then switched PSUs little did I know the second one was mains-earth referenced.... couldn't work out why every time I touched the ground clip to this resistor the PSU fan would power up and it would be delivering 2A... I'm glad I found out without destroying something....

[Mery128]

This might be better for a new thread but, what I'm kinda not groking here is say in this circuit:
http://www.rason.org/Projects/powsupply/powsupply.htm

Why would one use the 3055 transistors? it looks like they're hooking back straight into the output of that rectifier so ultimately they're just pulling the electricity straight through them, if thats the case 1) Wouldnt they just blow up? (I suppose they're beefy little buggers) 2) When you're designing a circuit what are you going to look for in a transistor data sheet to decide "This is the transistor I want".

I suppose Im looking to learn how to fish with these things rather than just be handed a fish.

@radioFlash I havent gotten to read that document yet, hopefully it will maybe make this more clear. Thank you

@tautech Yep I think I am a power junky lol. I also somewhat feel that it would be a really good idea to understand what seems to be a fundamental part of any project before moving on to the other parts of projects. (IE: What do all electronics need. Power. \^.^/ )

@RazSlack Im probably interested in something that can do around 100W~200W  but I think for now Im going to get the parts to build the LM723 supply I linked and am going to fiddle with adjusting it some. To be honest I dont even know the benefit of being able to drop to zero volts on a power supply so Im sure I have alot to learn!

[tautech]

This might be better for a new thread but, what I'm kinda not groking here is say in this circuit:
http://www.rason.org/Projects/powsupply/powsupply.htm

Why would one use the 3055 transistors? it looks like they're hooking back straight into the output of that rectifier so ultimately they're just pulling the electricity straight through them, if thats the case 1) Wouldnt they just blow up? (I suppose they're beefy little buggers)

The 3 x 3055's are configured as 2 series pass and 1 driver.
Really forget that build there are much better.

Base your build on a 317 or 338 and let the IC do the work.
Get the datasheets and have a study.

[Richard Crowley]

This might be better for a new thread but, what I'm kinda not groking here is say in this circuit:
http://www.rason.org/Projects/powsupply/powsupply.htm

Why would one use the 3055 transistors? it looks like they're hooking back straight into the output of that rectifier so ultimately they're just pulling the electricity straight through them, if thats the case 1) Wouldnt they just blow up? (I suppose they're beefy little buggers) 2) When you're designing a circuit what are you going to look for in a transistor data sheet to decide "This is the transistor I want".

The LM723 is the voltage regulator driver chip. It was a predecessor for the chips that tautech is touting. Perhaps he is too young to remember the roots of the integrated circuit family.

The CONTROL output from the 723 (pin 10) drives Q1, and then Q1 drives the main PASS ELEMENTS Q2 and Q3.  The main path of current is from the output of the bridge rectifier (D1-D4), filtered by C1-C4, controlled through Q2 and Q3, through R6 and R7 in parallel, and out to the load.  The 723 chip senses the voltage across  R6/R7 which indicates the current.

The three major parameters we look for when selecting a transistor are
1) Voltage rating
2) Current rating
3) Current gain

The reason that circuit uses Q2 and Q3 in parallel is because a 2N3055 doesn't have enough current rating by itself, but two of them working together (in parallel) will meet the requirement.

[tautech]

This might be better for a new thread but, what I'm kinda not groking here is say in this circuit:
http://www.rason.org/Projects/powsupply/powsupply.htm

Why would one use the 3055 transistors? it looks like they're hooking back straight into the output of that rectifier so ultimately they're just pulling the electricity straight through them, if thats the case 1) Wouldnt they just blow up? (I suppose they're beefy little buggers) 2) When you're designing a circuit what are you going to look for in a transistor data sheet to decide "This is the transistor I want".

The LM723 is the voltage regulator driver chip. It was a predecessor for the chips that tautech is touting. Perhaps he is too young to remember the roots of the integrated circuit family.

Not at all Richard. I cut my teeth on octal base valves.
I respect your detailed circuit analysis, however the OP and the thread name suggests limited knowledge and experience so IMO it is best to apply the KISS principle.

With a 317/338 it is possible to build a "rats nest" PSU to get him started, try that with a 723.

[Mery128]

While KISS is a good idea. Im not afraid to go look up complicated concepts as need be. I personally learn better in my opinion from the "this is why we do this" than "just do it this way" approach.  All of the input is greatly appreciated, I think Im going to pick up a few of the components discussed here and see what I can throw together.

[Richard Crowley]

Not at all Richard. I cut my teeth on octal base valves.
I respect your detailed circuit analysis, however the OP and the thread name suggests limited knowledge and experience so IMO it is best to apply the KISS principle.

With a 317/338 it is possible to build a "rats nest" PSU to get him started, try that with a 723.

No offense meant, tautech. 
I agree that 723 is pretty long in the tooth and there are more modern (easier/faster/better/cheaper) solutions to that problem.
That is, indeed, a decades-old ham-radio solution.

@Mery128, you would probably be better off with a more modern circuit design with modern components.

For example, here is a more modern version of that circuit...
http://www.circuitdiagram.org/12v-10a-power-supply.html

[Mery128]

Can that be re-designed pretty simply with swapping the LM7812 for a variable voltage regulator? Perhaps having to change out the transistors to match the new parameters of the new regulator?  Or maybe that's more of my mystery to solve looking through datasheets. Also for what its worth, I wasn't really married to that design I linked, it just seemed like a good starting point to try and figure out "why are these parts picked?"

[Richard Crowley]

Yes, there are variable-voltage versions of that same circuit. Use the image search feature of Google and look for variable-voltage power supply circuit or schematic diagram.  You will find enough to keep you busy for the rest of the day.

[Mery128]

One more question on that, is circuit simulation a worthwhile endeavor on these kinds of circuits or is it ultimately a waste of time and I'd be better served buying real components and blowing them up on my breadboard?

[tautech]

Fuse the AC supply and let a modern regulator give you the additional protection needed.
ie. thermal and SC.

Once built you can use your scope to measure ripple and fine tune the main smoothing cap value at full load. Use Auto bulbs for loads.
That way you won't need to shell out for larger than necessary E-caps at crazy prices.
Think also of paralleling 2 or more caps to get the results desired.
Sure you can do the calcs but at this stage its about getting up and running. 

Many use simulation and it is a worthwhile tool for complex stuff.
Use the tools you have to gain understanding.
Use datasheet typical applications as a gospel of stuff that works.