CREE XR_E Question (s)

[Bikecop]

I am attempting my first mod, a 3 cree LED bike light similar to Nightriders.

I am finding it @#$% difficult to solder the wires to the cree stars; its too much like microsurgery! I am getting solder bridges to the ring. In addition, I have managed to knock off one of the cree's domes. So, I have some questions:

1) Can I reattach the dome? Should I use epoxy or some other material?

2) How are you guys soldering on the wires? what gauge wire do you use, what kind of iron and tip, how much heat?

I know these are "newbie" questions, and I appreciate your help!

 

[Mirage_Man]

I am attempting my first mod, a 3 cree LED bike light similar to Nightriders.

I am finding it @#$% difficult to solder the wires to the cree stars; its too much like microsurgery! I am getting solder bridges to the ring. In addition, I have managed to knock off one of the cree's domes. So, I have some questions:

1) Can I reattach the dome? Should I use epoxy or some other material?

2) How are you guys soldering on the wires? what gauge wire do you use, what kind of iron and tip, how much heat?

I know these are "newbie" questions, and I appreciate your help!

Don't know about #1 but #2 I use a Weller analog soldering station with the stock tip @ about 600 deg. I use 22g wire.

Disclaimer (I have tought myself how to solder by asking questions and reading blurbs on line. If anyone knows anything can be improved upon please let us know).

Make sure to clean the solder pads and bare wire with alcohol first. Then wet the tip of your soldering iron with a little solder and apply a small amount of solder to the solder pad. Let cool. Tin the wires you are soldering, let cool. Then place the tinned wire onto the presoldered pad and apply the iron to the wire and push with a little pressure. When they melt position the wire and remove the iron. Make sure you don't move the wire while the solder is cooling or you may get a cold joint. Try not to let the iron sit too long on the LED. It really just takes some practice.

Remember that more does not me an better. Less actually is better to a certain extent. Do a google search and you will find pages like this. Here is a diagram of what a correct solder joint looks like...

Good luck and try practicing on something that didn't cost you anything.

 

[nightrider]

I am attempting my first mod, a 3 cree LED bike light similar to Nightriders.

I am finding it @#$% difficult to solder the wires to the cree stars; its too much like microsurgery! I am getting solder bridges to the ring. In addition, I have managed to knock off one of the cree's domes. So, I have some questions:

1) Can I reattach the dome? Should I use epoxy or some other material?

2) How are you guys soldering on the wires? what gauge wire do you use, what kind of iron and tip, how much heat?

I know these are "newbie" questions, and I appreciate your help!

If you think soldering to the star is microsurgery, then soldering to the emitter is nanosurgery. Really, it's not that hard with some practice.

You need a small (25 watt will do) soldering gun with a nice, clean, pointy tip. Get the smallest diameter solder you can find. I like the 0.032 diameter rosin-core solder (Radio Shack). As Mirage_Man said, if you don't have much experience, practice on something else until you get the hang of it.

I use 24 ga wire, and the soldering gun should only need to be in contact with the star for a few seconds to complete a connection.

Sorry about the dome. I've never had that happen, so I don't know what to tell you... maybe someone else can chime in with Cree dome re-attachment... if that's possible.

You are soldering to the gold tabs on the star, right? Not to the emitter itself? I got a little worried when you said "solder bridges to the ring." Example shown in this photo:

 

[daq]

Hi Bikecop,

Nightrider is quite the inspiration, isn't he? He pushed me over the edge to do my first homemade light too.

I feel your pain. It sounds like you're soldering the emitters like I did.

1) I never lost the dome, I don't know what to suggest.

2) I ended up using 24 AWG stranded wire when soldering to the emitter (not the star).

Mirage_man's advice is good. I know the theory of soldering, but am woefully lacking in the "how". A co-worker helped me re-do mine (to go from 22 AWG to 24 AWG wire). The thing I noticed is that he pre-tinned the wire leads and the pad, then he put a little extra solder on the tip before applying heat. This way you're only holding the iron and the wire and not trying to hold the solder too.

I can tell you from experience that solder wick is helpful for removing the shorts. First, put the iron right on the short and "pull away" as much solder as possible. This might do the trick completely. If not, use the solder wick to get the rest.

Keep up the good work. Try to enjoy the process as much as the product. Be sure to show us some pictures.

 

[Doug S]

.

I am attempting my first mod, a 3 cree LED bike light similar to Nightriders.

I am finding it @#$% difficult to solder the wires to the cree stars; its too much like microsurgery! I am getting solder bridges to the ring. In addition, I have managed to knock off one of the cree's domes. So, I have some questions:

1) Can I reattach the dome? Should I use epoxy or some other material?

2) How are you guys soldering on the wires? what gauge wire do you use, what kind of iron and tip, how much heat?

I know these are "newbie" questions, and I appreciate your help!

My wire of choice for this is a 30 gauge solid [not stranded] Kynar insulated wire. This wire is most often seen used in ''wire wrap'' applications, an old prototyping technology. The Kynar is a very thin insulation, typically about .005'' on 30 gauge. I apply SMT type solder paste with a syringe to the Cree solder pad, then position the wire and apply heat via a small soldering tip. Optical aid [magnification] is very useful.

 

[CM]

If the dome comes off, it will never be the same even if you re-attach which I think is not possible anyway.

If you can't solder even to the stars, might I suggest practicing your soldering skills? The easiest way to get the feel for soldering is to take two wires twisted together and practice soldering there. The joint should be shiny and smooth. Apply heat to the joint, not to the solder. Use some flux (very light amount) to prevent oxidation of the surfaces as it heats up. You can practice on other types of joints but they should all look smooth and shiny. Once you get consistency in your technique, then you're there.

 

[Bikecop]

Thank you all for your replies. I am embarrassed to admit that I have been trying to solder the wires onto the emitter pads! I didn't realize until I saw the photo in Nightrider's post showing his wires soldered to the pads on the star. I will very humbly unsolder the wires from the emitter and solder them onto the pads while burning with shame!

I'm sure glad that I ordered some more stars from Download; looks like I may need 'em!

Thanks again,

Larry

 

[Lumbee1]

I am glad I came across this thread. I will be receiving some emitters soon and was very concerned about soldering them. I have soldered before but nothing even close to this level. I work at a very large computer company so I might just bring everything in and let one of the engineers do it. They have microscopes, high-end soldering irons, and years of experience.

 

[mpf]

Cree open circuit after soldering

Just tried soldering my first Cree emitter on the top pads after snipping the corners to isolate the bottom pads.
Got some solder on the ring. Used solder wick to remove it.
When I had finished the Led was open circuit.
I am sure it was not before as I tested it but no circuit after I was finished.

Anyone else have this problem?
matthew

 

[Doug S]

Re: Cree open circuit after soldering

Well if you killed it, I'd love to have it. I have been soliciting some dead ones. See this thread:
http://www.candlepowerforums.com/vb/showpost.php?p=1778318&postcount=17
Actually I might be able to help you out too. If you want to, you can send some good ones with your dead one, tell me what length wires you want attached. I'll attach them for you and send them back. I have the necessary equipment. PM me if interested.

Just tried soldering my first Cree emitter on the top pads after snipping the corners to isolate the bottom pads.
Got some solder on the ring. Used solder wick to remove it.
When I had finished the Led was open circuit.
I am sure it was not before as I tested it but no circuit after I was finished.

Anyone else have this problem?
matthew

 

[Anglepoise]

Best tip on soldering I can pass on is get a small bottle of flux.
There is just not enough flux in the small diameter solder we use. Having extra flux makes a huge difference and turns a difficult job to an easy one.

 

[nightrider]

Thank you all for your replies. I am embarrassed to admit that I have been trying to solder the wires onto the emitter pads! I didn't realize until I saw the photo in Nightrider's post showing his wires soldered to the pads on the star. I will very humbly unsolder the wires from the emitter and solder them onto the pads while burning with shame!

I'm sure glad that I ordered some more stars from Download; looks like I may need 'em!

Thanks again,

Larry

Oh well, live and learn. That's really the purpose of the star... to make the soldering process much easier and lessen the chance of damaging the emitter. I think you'll find soldering to the star much easier!

BTW. I noticed that some folks, in other posts, were confused about which pads on the star were positive and which were negative... and there are a couple different versions of the star MCPCB out. When in doubt, just use a meter to check for continuity to the respective terminals on the emitter. In the photo I posted above, the two star solder pads nearest the negative end of the emitter are negative and opposite is true for the positive. Some stars will have 3 negative and 3 positive solder points on each star.

Good luck.
Remember... learning is half the fun. We've all made plenty of dumb mistakes... sometimes that's how we learn.