Just fried things big time - need advice

Man, am I disappointed and frustrated. I made a REALLY stupid mistake in one of the connections when building a Dr. Lava kit, and definitely fried something, or a couple things. The resistor has got to be gone, but I'm afraid the diode also burned up. Can anyone help with a diagnosis?

I have a detailed post waiting, about my incredibly brain dead mistake in case it's needed. But first, here's the end result. For the first few seconds of operation, a nice, bright red light came out, but then went extremely dim. So dim that it could only be seen by very closely shining it on my hand. The resistor was scorching hot, and got slightly brown/burnt looking in the middle. By scorching hot, I mean it instantly burned the living hell out of my finger. The capacitor was only slightly hot.

Here's the question. If the resistor got that burnt, could that be damaged, causing the dim light? Or do you only get the dim light after killing the diode?

I'm really keeping my fingers crossed the diode might be ok. I only got two of them, and am afraid I killed one by, I'll say it again, making the DUMBEST connection mistake possible! Should've gotten at least one more. I put so much work into this thing the last couple nights, that to have it end in disaster is saddening. I hope the next one survives my lack of EE skills. If so, it'll be one hell of a nice "plastic box" laser, which is why it's taking so damn much work to make.

Thanks for reading.

A follow up post will be made late tonight, with a description of what NOT to do, aka. "How Bimmerboy fried his laser".

Using the burnt diode for testing this morning, I though I corrected my mistake, but no dice... still all screwed up. The laser goes constant on in the momentary switch position, and the off position! The only way to turn it off is to flip the switch to what I thought was constant on. And the pushbutton momentarily turns the thing off instead of on! Man, I'm confused.

Now that I'm pretty sure the diode end of the circuit is properly wired, the problem must be how I have the two switches wired into things... which means I must've made at least TWO mistakes last night! Also, I forgot to mention in the first post that the batteries (two alky AA's for testing) are quickly getting very hot as well.

I have a LOT to learn about EE. I tried to get all fancy shmancy without knowing what the heck I'm doing. In the meantime, the second kit of being built to the exact Dr. Lava design. That, I can handle... sheesh.

BTW, anyone need their house re-wired?... lol.

It sounds like you have a short going back to the batteries...if they are getting warm - they could be hooked up incorrectly - I smoked 4 AA NiMh's that way, by doing a "lack-of-coffee" move, where I shorted them out, and they ALMOST caught fire...YUCK ! Despite the cost of the batts - the mistake really ticked me off, cause I am usually better than that !

Go over your wiring again - the diode MAY still be okay....were you using felusmage's wiring to set it all up ? check your positive and negative connections...even though I have been doing electronics forever (it seems) I STILL get anode/cathode confused somehow - so I always look them up to make sure ! I hope it's okay - one thing to do, is build the whole thing out first - test it with an LED - THEN use the laser diode...safe is slower, but causes less agravation !

SenKat said:

It sounds like you have a short going back to the batteries...if they are getting warm - they could be hooked up incorrectly

Click to expand...

I was thinking that was short-like behavior, but can't figure out what I did wrong. Just cannot see where a short may be. I'll take a couple pics of my super genius design upon getting back home tonight. Much easier than a verbal only decription, and the flaw will likely be quite obvious to those who know circuits.

SenKat said:

were you using felusmage's wiring to set it all up ?

Click to expand...

Sort of. The idea and inspiration definitely came from Stephanie, but decided it was a good idea to combine that design with the Dr.'s, plus my own bit of magic... heh. I also liked the idea of making a little circuit board, and the Radio Shack box, a la Mr. Wesley, except I wanted to have the board on the opposite end of the box. A couple pics will bring the mangled idiocy to light.

I know I'm being hard on myself, but I should've thought twice, and done once on something like this. With any type of project I've done before, be it electrical, mechanical, woodworking, or whatever, I kind of wing it and figure things out as I go. Over the years, I've never had a failed project, and never had to do re-do anything. Apparently, I've been lucky as my seat of the pants approach bit me in the rump this time.

More to come!... lol.

Here's a WA guess. The leads coming from the diode are real close together. Easy to short out if you have a BIG iron and solder. That would cook the resistor as you stated and heat the cap and cells in the process. I don't think the diode could carry that much current without acting like a fuse. The heat on the back may have damaged the diode -- just maybe.

As for the rest of your wiring -- Red is +, Black is - . You may be fighting two problems.

Mike

I'd love it if it was that simple, but alas...

Nah, for all the lack of good equipment and experience, I do clean work, even with pretty small items. I also tend to make myself sound dumber than I am many times, with the self-put downs and negativity. That's the frustration talking. Although there's no EE diploma hanging on the wall here, I can credit myself with knowing that red is positive, and black is negative... or is it? :thinking:

Just kidding.

Now, time for me to stop talking about myself, and get down to business. There a laser that needs a' buildin'. Pics will be up in a few minutes, and hopefully some advice will help get things right for the second try.

Bimmer --

All kidding aside, I really don't know how that diode junction could smoke the resistor. I still think there's a dead short somewhere near the base of the LD.

I think that it would take over 500 ma to let the smoke out of that resistor. What's the voltage across the diode junction ? There is always the possability of a shorted capacitor. Crap like that happens in a million parts. Is the cap polarity connection correct ??
This stuff seems simple but often easily overlooked by the best of us.

Mike

Bimmer --

I've re-read all the posts. Get rid of all the switches and get back to a basic LD, R/C and 2 cells. It's gotta work. The old KISS method is your fall back position. A whisker of stray solder can short the base of the LD and cause your problem. Eliminate the easy stuff first. Been there - done that myself.

Mike

Ok, we've got pics of the diode cooking device (patent pending), and a few questions. First one being, what's wrong with this circuit?

Second, why were the switches acting in a backwards fashion? What was meant to be off, was constant on, and vice versa. Momentary shuts off when the button is pressed, not on. As they say en español, QUE?! The words "*** backwards" also come to mind.

Third, what do I do to fix it, while retaining the intended functionality? I hadn't even tried to wire up for constant on yet... lol.

Here's the diode. Didn't open the case for a pic, but I can guarantee no legs or leads are shorted, and they're individually wrapped in electrical tape. Negative goes to the leg that is obviously connected to the case. When negative is pointing away from you, forming the top point of a triangle, the positive lead is connected to the left leg.

That's a little heat sink I channeled to give the module support, and a bit of heat removal. When finished, AA will be used to glue them together.



Here's where the magic happens. Magic smoke is more like it.

The diode positive, one cap leg, and one resistor are connected at the same point like a three way hub. The other resistor leg goes to the pushbutton, then the toggle, to the pos. end of one battery. The diode negative goes to the other cap leg, which goes to the switches, then to the negative of the other batt.



This pic better shows that nothing is accidentally touching. The parts are tight, and don't move around.



The cap and resistor. Still not sure which cap legs are pos. and neg., but I think I got it right.



Switch and button... button and switch. Just keeping with the *** backwards theme. As can probably be seen in the other pics, I believe the mistakes are in the switch hookups, but don't know why.



So, what now?

SenKat said:

It sounds like you have a short going back to the batteries...if they are getting warm - they could be hooked up incorrectly - I smoked 4 AA NiMh's that way, by doing a "lack-of-coffee" move, where I shorted them out, and they ALMOST caught fire...YUCK ! Despite the cost of the batts - the mistake really ticked me off, cause I am usually better than that !

Click to expand...

Me too. In my setup with the third and last diode last night, I managed to reverse-bias it oo: .... luckily, the diode withstood reverse-bias of 3.4V (and protected that electrolytic capacitor in the process) before I realized that the current readout was zero and the leads flipped. Rewired it properly, and all was well.

Regarding Bimerboy's problem, I concur with Hemlock Mike: get back to barebones. I would strongly recommend getting a regulated DC power supply with current limiting if you are going to be doing electronics hacking with any regularity. After fifteen years or so, I'm just now getting back into it myself, and picked one up.

well, from those pics I can tell that you have it wired so the switch and button short the batteries when on. That's why it turns off!

to fix it, cut the black wire going to the button from the perfboard and cut the black wire going to the switch from the battery and connect the black wires from the perfboard and battery together.

Then, cut the red wire running to the button from the perfboard and conect it to the other half of the black wire that you just cut running from the button.

take a look at picture #3.

There are two wires, one red and one black, coming out of the general vicinity of the batteries (as oppsed to the red-black pair higher up, which I assume is heading to the laser).

If I read that right, your momentary switch and your DPDT switch (the blue one, stands for double-pole, double-throw) are both shorting out the batteries when actuated. When they are both open, only then do you get voltage to the diode.

edited to add: Regarding the capacitor, the light-colored band is the negative terminal, it should be connected to the cathode. If that's wrong, rewire it first thing!

Hemlock Mike said:

I think that it would take over 500 ma to let the smoke out of that resistor. What's the voltage across the diode junction ? There is always the possability of a shorted capacitor. Crap like that happens in a million parts. Is the cap polarity connection correct ??
This stuff seems simple but often easily overlooked by the best of us.

Click to expand...

Well, Mike... I have a confession to make. The diode's maiden, and final voyage was stupidly done with E2 lithiums instead of alky's. They're good for at least 500mA, right? I only tried testing with alkalines after the bad stuff happened. I'll go wet noodle lash myself now.

The setup in the pics are actually using the second set of components. Scrapped the first set in case of damage. So, the cap is quite likely just fine, but I'm almost ashamed to admit, I'm still not 100% sure what the cap's polarity is. I think I got it correct, but...

Tremendous thanks for the help, guys. I'm a little tired to figure out what the Dr.'s corrections means at the moment, but will study over morning coffee.

Burning up the first diode or not, I must say this has been one hell of a cool GB. Lot's of fun, and a good learning experience. Rock to the Doc! :rock:

I'll be back with a laser that lasts longer than three seconds.

I just thought I'd point out that I also tried the 'home brew' laser approach with a DVD-RW laser, and it started out so bright than an EE friend laughed that the unfocused beam would make one hell of a flashlight. Now, though, it's so dim, I dont know if it would even damage your eves if you looke dinto it (not aobut to try that, just in case, but...) and all I did was hook up red-red and black-black to 2 plain, old, ordinary energizer AA batteries!

It doesn't take much to damage a diode, I learned that the hard way, that's why I'm gonna be sticking to prebuilt ones for a while... Best of luck to you, though!

That's the nice thing with these, we have the spec sheets for them and know the safe range. The resistor/cap supply on these itself is minimalistic, so just plain hooking two batteries straight to a laser diode is just asking for it to break. Better luck next time!

I have two DVD reds running straight on two Alkie cells with no resistor BUT I did a lot of measurements before I connected them that way. I may be sorry if I use different cells.

When pushing the limits - do the math...

Mike

Houston, we have lift off.

Sir Doc, your fix worked, and the icing on the cake is that I understand it now! I even feel a bit smarter as well... lol. The help is highly appreciated!

A few more harrowing experiences during last night's completion added to the drama. There were a bunch of drunk people in the house, which was highly distracting. While carrying on a conversation, I wound up soldering the positive lead to the feedback leg, electrical taping individual legs, then wrapping all three. AS5'ed the threads, put on the back casing, and never noticed the problem until testing later after dinner. Got that sinking feeling because it obviously didn't work, but I was SURE everything was correct! :laughing:

So, after finding the issue and starting the re-do, I'm getting tired now, and grazed both diode legs with the iron. Saw a bright red flash across the table. The batteries were in the case. Finished everything up, crossed the fingers, and the damn thing didn't work. Whoops, there goes another rubber tree plant.

Un-did the re-do, and hooked up my trusty 'ol burnt out testing diode. Ohhh no, it worked. By now, I'm getting more tired, discouraged, and a little pissed off, but decided to give it one last go for the night. Re-did the un-did re-do, and it STILL did not work. About to give up, I got out the multimeter and started checking the switch and button. Everything seemed ok. Put the batteries back in yet again, hit the switch and voila! Red motherfreakin' light! YES! I have no idea why it didn't work, and then did with no changes, and at this point, do not care. No, I didn't put the batteries in backwards or have a loose connection... hehe.

Breaking seal on a fresh pair of green BLPS glasses tonight, and I'mma' goin' balloon huntin'. Thanks to everyone for responding to my former plight!

A quick note about mounting the diode into the holder. The back end of the case is the perfect tool for the job. Turn it around backwards, let the diode legs go through the hole, and you have a nice, flat surface to press with in a vice. Used the vice on the second diode, and it went in smooth as glass. The first one got the rubber mallet treatment.

I'll be back to report on the burning of the latex!

Bimmer --

With all this help -- you better be bustin' balloons !!
Congrats on the bright red output. How much LD current are you getting ??

Mike