From and for an electronics newbie


 
K

KellyMc

TVWBB Fan
OK, I've got all my parts in hand for a stand-alone 4.1 setup and am taking a hold-on-a-second moment, given that this is my first electronics project of any significance.

I get the impression from the forum that there are probably plenty of others in the same boat, so I thought I'd start this thread and try hard to not self-filter my embarrassingly simple questions ...


I understand the basics of soldering and have successfully built a couple of beginner project kits and built/fixed stereo wires on occasion, watched plenty of online videos, etc.

-- How am I most likely to irrecoverably mess this thing up?

-- I'm rocking a 25 watt ECG soldering iron and just picked up a fresh tip for it at Fry's but was eying the fine-point tips available for other brands which seem like they would make it much easier to keep from dribbling gobs of solder around every connection. Is it worth considering? What are the indispensable accessories -- desoldering braid/pump? flux pen?

-- I have not ordered a case yet. Looking at Bryan's assembly note about test fitting the LEDs -- should I really really order the case before I start, or is it reasonable to measure the lead heights to install everything for later placement in a case. Similarly, I'm planning to get it running and tested stand-alone and add the rPi later. Bad ideas?

I'm sure to have more questions, but I'll stop for now. Any tips anyone has to offer are most appreciated.

Kelly
 
You're going to want a fine tip for your iron, thin solder also. I'm decent at soldering and using a normal size chisel point tip wasn't the best option for smallish work like this but I was impatient so went with what I had/could find.

Bad solder joints are the most likely problem but are recoverable most of the time.

I left my LED leads full length for now until I decide if I'm staying with the 4.0 or building a 4.1.

I only used desoldering braid on one component and that was really just so I could reposition it a little better.
 
The best advise is to double check everything(orientation is a biggy) before you solder it down, much easier to remove without solder then remove with solder.

Get some solder flux at radio shack. It will help you get good solder joints. Add the flux to the pad on the board, heat the component and the boards pad for a second or so and then add the solder to the pad and component(not the iron), so that the solder will wick towards the heat. After remove the solder and then remove the iron.

You can leave the leads long on the LEDS and when you get the case you can reheat the solder joints and push down the LEDS to the correct height, More then likely they will be the same height as the LCD, But I don't use a case on mine so im not to sure about that.
 
If you can touch the pad & lead at the same time with the tip, you're golden. I use .032" solder, but only because I found a 5lb spool. Bigger will work, smaller would be a PITA, but it would work too. Populate the components, then go back & check to make sure you've got them in the right orientation. Then check again. A piece of carpet or foam works well to hold loose components in when you flip the board, but make sure it doesn't melt easily.

I've built 1.5 HM4.0s (I was short 2 parts on the 2nd, so I waited until I needed to order more parts from Mouser, but haven't wen't back & finished it yet....). That was the extent of my electronics soldering experience. Since then, I've designed, had OSHpark fab & then populated 2 more projects, with some 0603 SMD components. They all even work. I bought better iron than what you're describing, but not much better skill. I'm impatient, my hands shake more than I'd like & I try to fit in soldering during work and/or wife complaining. Basically, if I can do it, anyone can. It's really forgiving.
 
Great help and encouragement so far -- thanks!

I did get some .032" solder. The stuff I've used previously looks about as big around as a pencil by comparison. I've also never used flux, so hopefully that will help.

Bryan's assembly instructions seem very clear and I'm amazed by the silk screening on the board, which clarifies so much of the component placement -- I was expecting just a lot of difficult schematic deciphering.
 
You don't really need additional flux with through-hole & rosin core solder. (rosin=flux). it can help on SMD pads to keep the solder in place when reflowing.
Save the pics & zoom in if needed.

Pad / lead / tip. Touch tip where pad & lead meet. wait ~1sec. touch solder to where pad & lead meet. If solder melts, just wait till it flows & covers the pad, then a bit more. remove solder. wait ~1sec, remove tip.
If the solder doesn't melt when you touch the pad/lead, touch the tip/lead & make a bridge to help xfer heat. then touch the pad/lead (should melt before you even touch the pad).
The ~1sec will depend entirely on your iron & temp settings. Hotter & strong, maybe a bit less, colder/weaker, a bit more. I've been doing through hole at 320*C, but you could go down to ~260 & still get it done. I'm impatient.
Repeat about 150 times. Enjoy the fumes.
 
The Flux is helpful for someone who has yet perfected the a good solder technique. It helps get a good flow of solder over the whole pad for a good bond. I don't use it all the time, I do like using it on the some components like the Lcd screen, more then others.
 
Thanks for all the tips. I'm going to get started soon -- tonight or tomorrow if not right now. I've just spent about half an hour walking through the assembly instructions and putting parts in order. A couple of immediate questions ...

-- Soldering the fan driver Q3 to the big pad for heat sinking purposes is listed as optional. No big deal to skip it? That looks challenging.

-- Any tips for soldering the big hole/pin components like the power jack? I assume the idea is that if I get the pad and pins heated up right, the solder will grab the right places and fill in the hole rather than running out the bottom like I would imagine a liquid behaving.

And one total electronics newbie question -- the transistors in Bryan's instructions are of two different colors. Mine are all blue. That doesn't mean anything as long as I check that the color bands are right, I would assume?
 
Done! (all except LCD and LEDs, actually. I'm thinking about going ahead and getting the case before I continue.)

It was not too bad. I'm glad I did some practice boards ahead of time and very glad I got a new iron. I picked up the 40w Weller pen iron with the LEDs, which comes with a fine tip. It made a huge difference compared to my previous iron.

I certainly haven't tested it yet, so I may have botched some joints, but I feel pretty good about it and can't point to any that look obviously bad.

Thank again for the advice, all. On to the next phase.
 
I use a magnifying glass, or jewelers loupe and look at all the connections front and back before doing the smoke test (powering on ). Once you let the smoke out, it won't work.

dave
 
On third thought, I'm going to get it working before I worry about enclosing it. But ...

Does the LCD need to be set off a bit for proper case fitting, or should I let it sit all the way down on the pins? And can anyone give me a proper height for the LEDs from board to LED tip? I know I would likely need to melt and adjust, but I might as well try to get it right as a starting point. I might get lucky.
 
The LEDs are easy to adjust, just leave them long. The LCD is more difficult - I'd leave it high as well if you are going to adjust later. Or put a cable on it.
 
KellyMc said:
On third thought, I'm going to get it working before I worry about enclosing it. But ...

Does the LCD need to be set off a bit for proper case fitting, or should I let it sit all the way down on the pins? And can anyone give me a proper height for the LEDs from board to LED tip? I know I would likely need to melt and adjust, but I might as well try to get it right as a starting point. I might get lucky.
Click to expand...

The LCD will need to sit all the way down on the pins if using the 3D printed case.
 
OK. I put the LCD all the way down and made the tops of the LEDs the same height as the LCD screen.

In other news, I finally found the best use for that stereoscopic dissecting microscope in my closet. I found about 6 suspect joints, most of them big blobs where the solder hadn't moved through the hole, and touched them up.

And I committed my biggest newbie mistake -- let the barrel of my iron sit on the button for a second while I was attaching the LCD. I had to trim the molten plastic a bit to get the cap to fit back on, but I think it will be OK.

The rPi should be here today.
 
KellyMc said:
OK. I put the LCD all the way down and made the tops of the LEDs the same height as the LCD screen.

In other news, I finally found the best use for that stereoscopic dissecting microscope in my closet. I found about 6 suspect joints, most of them big blobs where the solder hadn't moved through the hole, and touched them up.

And I committed my biggest newbie mistake -- let the barrel of my iron sit on the button for a second while I was attaching the LCD. I had to trim the molten plastic a bit to get the cap to fit back on, but I think it will be OK.

The rPi should be here today.
Click to expand...



I cant count all the times I have hit the button with the iron lol
 
Better than your hand...
I just blew up an electrolytic capacitor as I was removing some SMT FETs that I want to re-use... Talk about magic smoke! I still haven't found the casing. the one next to it got blown off it's pads.
 
KellyMc said:
I really should have been more conscious of the learning curve for soldering under a microscope. I could see that happening very easily.
Click to expand...

Heh, for my first try at SMD, I used a USB microscope. My desk is so horribly cluttered that I had my soldering project to the left of my laptop, but the microscope program was on the 2nd screen to the right. My hands were so damn uncoordinated it wasn't funny. Looking at the board to get close enough to get in the microscope view, then looking to the right & not moving was futile.

Now I just use a $20 2x magnifying lamp. It has a tiny 5x window that I can use to confirm solder. Other than orienting LEDs, I could probably do it by eye. All I've done so far is 0603 resistors & LEDs, but I think I'll use more SMD in future projects. It's cheaper & not that much harder (and I've bought a hot-air rework station, so I could reflow them if needed).
 
Yeah, but I'd have to buy a toaster oven....I now have 2 decent irons & a hot air setup. I needed to pull some micro relays, the iron wouldn't do it, so I bought an Ayoue 968A. That kinda blew through my project budget.... (that and 2x $100 orders from mouser, $80 crimper, etc, but don't tell the wife, she only saw the new hair dryer in the basement :) ) All this to sit in a chair & drink beer while my fireworks are going off, rather than running away with a torch & beer after lighting them.

If only I was travelling to our electronics plant more often - In ~2009, I had a laptop that the video chip de-soldered itself. I had a trip already planned, so I had them run the motherboard through the reflow oven. Worked for about 6 weeks, until it de-soldered itself again.
 
You must log in or register to reply here.

 

Back
Top