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BrnAgainRoc

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So I just finished soldering up a second Egg Timer Quantum. I've attached some ematches but continuity isn't being found.. I'm not sure if it's possibly the ignitors I'm using (chinese) or if I messed up again on the soldering. Is there any other way to test the continuity to make sure it's indeed working correctly?
 

rharshberger

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So I just finished soldering up a second Egg Timer Quantum. I've attached some ematches but continuity isn't being found.. I'm not sure if it's possibly the ignitors I'm using (chinese) or if I messed up again on the soldering. Is there any other way to test the continuity to make sure it's indeed working correctly?
Did you Ohm the the igniters to make sure they weren't bad? That would be the first check to eliminate a potential problem.
 

cerving

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Most of the time it's the solder joints on the optoisolators. It's VERY easy to miss one of the solder joints... you have to wick the solder up those stubby leads to make sure they actually hit the pads. Sometimes it's better to just get out the solder wick and remove solder, then touch them up.
 

rharshberger

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Good call. I guess I could check that first.
That's just a low hanging fruit type test, it gets more complicated after that and the best thing you can do is take a number of high quality pictures (I use my Samsung Note 5, which has an excellent camera) of the board from above, each side and below, making sure everything is in focus and well lit then contact Eggtimer support and explain the issue and send the pictures, its amazing what Cris can do with a few good closeup photos. If you have a good magnifier be sure to check carefully for bridged solder joints, or that the Optoisolator's (I think that might be the part) pins are all completely soldered with no bridges between pins.

Edit: Cris and I must have posted fairly close together.
 
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OverTheTop

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Inspect all solder joints under magnification. x10 is the specified minimum for inspecting surface mount work. Make it a habit even if you think your eyes are good enough. It is worth the effort.

Don't panic. Shouldn't take too much to fix :)
 

Charles_McG

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As Cris mentioned, it turned out to be the optoisolators on my Quantum. The rest worked fine - just no continuity on one channel.
 

mccordmw

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Most of the time it's the solder joints on the optoisolators. It's VERY easy to miss one of the solder joints... you have to wick the solder up those stubby leads to make sure they actually hit the pads. Sometimes it's better to just get out the solder wick and remove solder, then touch them up.
+1 to this.


Every time I had an issue when putting together the 3 Eggtimers I've built, it was due to the stubby legs in those two optoisolators.


I get the best results using a generous amount of no-cleanup flux to help wick the solder up the legs and pads. Even if the solder joints look good to you, if there's no continuity or no firing, retouch up the solder on those optoisolators. They are very likely the cause.
 

djs

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Is there any other way to test the continuity to make sure it's indeed working correctly?
For testing my quarks, I use an LED and 100 ohm resistor in series. Then I don't have to waste ematches or ignitors, and also is much safer.
 

rharshberger

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For testing my quarks, I use an LED and 100 ohm resistor in series. Then I don't have to waste ematches or ignitors, and also is much safer.
Christmas tree light bulbs are what I use (incandescent type).
 

NateLowrie

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For testing my quarks, I use an LED and 100 ohm resistor in series. Then I don't have to waste ematches or ignitors, and also is much safer.
I do this to. It works very well for flight testing. I will hook up the LED/resistor and then stick the whole thing in my vac chamber. I'll turn on the vac for 3 seconds to let the pressure drop and then close the valve. The apogee LED lights at this point. Then, I crack the valve to start to let pressure back in and look for the main deployment light.

Regards,

Nate
 

OverTheTop

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I get the best results using a generous amount of no-cleanup flux to help wick the solder up the legs and pads. Even if the solder joints look good to you, if there's no continuity or no firing, retouch up the solder on those optoisolators.
OK. Careful with these suggestions. There are two sentences and two potential problems. Let me explain (I am an electronic engineer. Trust me :))

1) When using a no-clean flux ALWAYS WASH THE BOARD AFTERWARDS. Use flux remover or metho and a toothbrush. Why? No-clean flux is designed to leave no ionic residues on the PCA once it has been activated. If you put lots of flux on the board (you do because it is no clean, right?) the only part of it that gets activated is where the soldering iron gets the temperature above a certain value for a certain time. The unactivated flux is hygroscopic and when it absorbs water it creates conductive paths between the tracks. Then dendrites of metal grow along these paths and periodically short between traces. As you can imagine it isn't great for reliability. It is also still corrosive. PCAs in production typically go through an oven the entire assembly is heated and all the flux activated. If you use a flux-cored solder that has no-clean flux IN IT there is no need to clean.

2) Reworking joints that are already acceptable increases the thickness of the intermetallic bond and makes them more brittle. If a joint is acceptable, don't attempt to make it look pretty as you will just be compromising reliability. If it is sub-standard then of course you need to fix it.

I can see why people want to do both of these things but when you dig beneath the surface into the materials, properties and processes you can adversely affect performance of the assembly.

Sorry for the bad news :). A lot of things relating to soldering are counter-intuitive.
 
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BrnAgainRoc

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So I have continuity in both channels, the drogue side test fires, the main doesn't. thoughts?
 

cerving

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OK. Careful with these suggestions. There are two sentences and two potential problems. Let me explain (I am an electronic engineer. Trust me :))

1) When using a no-clean flux ALWAYS WASH THE BOARD AFTERWARDS. Use flux remover or metho and a toothbrush. Why? No-clean flux is designed to leave no ionic residues on the PCA once it has been activated. If you put lots of flux on the board (you do because it is no clean, right?) the only part of it that gets activated is where the soldering iron gets the temperature above a certain value for a certain time. The unactivated flux is hygroscopic and when it absorbs water it creates conductive paths between the tracks. Then dendrites of metal grow along these paths and periodically short between traces. As you can imagine it isn't great for reliability. It is also still corrosive. PCAs in production typically go through an oven the entire assembly is heated and all the flux activated. If you use a flux-cored solder that has no-clean flux IN IT there is no need to clean.

2) Reworking joints that are already acceptable increases the thickness of the intermetallic bond and makes them more brittle. If a joint is acceptable, don't attempt to make it look pretty as you will just be compromising reliability. If it is sub-standard then of course you need to fix it.

I can see why people want to do both of these things but when you dig beneath the surface into the materials, properties and processes you can adversely affect performance of the assembly.

Sorry for the bad news :). A lot of things relating to soldering are counter-intuitive.
Yes, as I've mentioned several times I recommend NOT using additional flux, and NOT washing the board. That's why it's "no-clean" flux. If you want to make it look a little prettier, get an old toothbrush and gently brush away any excess flux, AWAY from the center of the board. If you have little micro solder balls, that will get rid of them too; if you brush TOWARDS the components, you may get a solder ball underneath a part and possibly bridge a via, that would be bad.

If you feel that it's necessary to rework a solder joint, I recommend hitting it with some solder wick first to reduce the amount of solder. When you resolder the joint, you won't be creating a big blob of solder. If the solder joint isn't nice and shiny, that's a good indication that you've got too much solder, and/or your soldering iron temperature is too low.

The newer "black" optoisolators that are now shipping have a bit longer leads, and are lower profile too. They'e easier to solder. They're also single-sourced, which is something I try to avoid for commodity parts like those, but in this case the benefits outweigh the possible disadvantages (mainly, out of stock issues from the distributors).
 
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BrnAgainRoc

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So I've spent two nights diagnosing my continuity issues and ematch firing issue. I think I've resolved both issues now!!ImageUploadedByRocketry Forum1478751306.913650.jpgImageUploadedByRocketry Forum1478751317.625802.jpg
 

BrnAgainRoc

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Good! What was the problem?
I picked up some high quality solder wick to clean up the resistors and legs on the optoisolators. Removed all the excess. Tinned the pads slightly to give a solid foundation. Temperature was everything. Thanks for your help!! Can't wait to use it in my lvl 1-3 rockets!
 

OverTheTop

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Glad it worked out for you. The skill is getting a good joint without having excess solder. You don't want to be a member of the Solder Conservation Society either :) . Practice is good. Comparing with joints on existing commercially made boards is a good thing to aim for (except for Chinese toys).
 

BrnAgainRoc

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It's rather difficult to get anything else on the board soldered incorrectly by following directions. It's really the small legs on the optoisolators that you can't really see too well that require that 3-4 second heat up, apply solder, then keeping the heat on for an additional 2-3 seconds to make sure the transfer of heat makes it to the pads. Once I noticed the initial leg doing it, I literally set myself on a mission to clean and redo ALL of them.
 

OverTheTop

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When soldering remember that
Solder follows three things:
Flux
Heat
Other solder
(that's why tinning the surfaces helps in some situations.

Think about those three things when soldering, considering where the solder needs to be on the final joint.

Soldering is like welding. You really need two parts, usually different size and shape, to get to the same temperature at the same time. That is a point of finesse which also makes the joints less brittle (to a small degree usually anyway). You accomplish it by how you place the iron tip (among other variables, of course :)).

It's rather difficult to get anything else on the board soldered incorrectly by following directions.
Egg instructions are great!
 
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