MiniPOV2, LED lights blown out

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MiniPOV2, LED lights blown out

Post by Guest »

I got my MiniPOV2 kit over christmas and just recently decided to begin soldering it together. I got everything soldered in perfectly up to the resistors, but while soldering the first LED to the PCB the LED turned black inside and blew out.
1. Is there any technique I can use to prevent this from happening again?
2. Where can I buy the exact type LED that is included in the kit? It only lists them on the building instructions site as "Red Oval LEDs," and for some reason I doubt radio shack would have them.

Thanks a bunch.

kragen
 
Posts: 21
Joined: Sat Mar 12, 2005 4:55 am

Post by kragen »

I'm starting to want replacement LEDs myself --- I haven't yet broken any of them but I'm sure I will.

I'm no soldering expert, but I think the following things help avoid the kind of soldering problem you describe:
- soldering from the back side of the board
- waiting until the iron is hot enough before soldering (solder should melt easily onto the tip)
- but not using an iron that's [i]too[/i] hot, because then you don't have enough time to maneuver the solder into place, and you might lift pads.
- and using a sufficiently powerful soldering iron so it doesn't cool down when you touch it to the pad; mine is only 15W though and it worked OK.

The optimal iron temperature depends on your solder.

Probably ladyada or other posters have 100x as much soldering experience as I do.

st2000
 

Post by st2000 »

Not knowing where on the scale of soldering experience you are on - it's hard to give advice.

I can't believe any soldering job will turn the inside of an LED black. If you use a 15 W iron, you should be able to flow solder around an LED in about 3 to 6 seconds. Try not to hold the soldering iron on any part (other than the battery clips) much longer than that.

I had problems aligning the LEDs. So, I soldered one side on all of them. Then went back and re-flowed the solder while seating them flat on the circuit board with my finger. Then it was easy to solder the other side of the LEDs.

LEDs are diodes and only pass current in one direction. So, unlike incandescent light bulbs, they need to be inserted correctly or they will not light up at all. One lead is longer (I think the anode) then the other and there is a flat side on the base of the LED's plastic (I think the cathode side). Align the flat side of the LED to the painted on picture on the circuit board.

What tripped me up was the images of the POV on the web site where the two batteries are aligned. I think the current design need the two batteries offset and close to the processor (i.e. leave the battery connectors furthest from the processor empty). This last battery position is for people who want more power or something - it's not needed for the intended design.

st2000
 

Post by st2000 »

Sorry, forget the battery stuff and LED seating gibberish. I thought you were putting together the big POV. However, the LEDs still need to be aligned correctly.

LED_Lighting_Company
 
Posts: 15
Joined: Sat Feb 25, 2006 7:55 pm

Soldering tips

Post by LED_Lighting_Company »

Hi guys,

My first post to the forum, just ordered SPOKEPOV, cant wait to checki it out.

Just a few tips, sorry if I am teaching you to suck eggs.

Check the spec of the solder, it should recommend heating temperature.
To help solder flow, use a solder which contains flux agent of use a seperate flux pen or paste, this will help solder to flow.

Ensure that the solder tip is clean, any solder/flux residue will contaminate the solder iron tip and reduce temperature. Always wipe the iron tip on a damp sponge before soldering.

Apply a very small amount of solder to the iron tip then touch the pad on the board and component and apply the solder so it flows nicely covering the pad and component leg. You should have an even amount similar to dome. Excess leg can be cut down to the top of the dome.
Do not apply too much pressure to the pad as it will lift. Pads can be fixed, but if your soldering is not up to scratch, then repairing tracks and pads will be well out of reach.

I also place and solder the components starting with the lowest in height first, resistors, diodes, ceramic caps, chips holders, electrolytic caps, leds etc.
Try using a piece of foam, larger than the board. Place components of the same type, put the foam on top of the board, then flip it over, careful not to loose any parts, this will make it abit easier.

Try to place components and then bend the legs slightly to preventing it from falling out, if the legs cannot be bent try and hold the device in place and just tack it. For example, if you are installing an IC bace, tag opposite coners. They can be reflowed to get the correct position with more solder added after the other legs have been soldered.

Hope this has been of help.

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