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Magpie
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[*] posted on 5-11-2017 at 10:44
difficult soldering job


I'm assembling a breadboard circuit to test a component for my stepper motor overhead mixers. To do this I have to place a 1nF capacitor in the circuit. I can barely see this thing let alone solder it into the circuit. It is flat and is about 1mm x 2mm.

Can anyone tell me how to do this?




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Twospoons
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[*] posted on 5-11-2017 at 11:34


I trust you have a fine tip soldering iron? And fine solder? And by 'breadboard' I assume you mean one of those plug in strip boards?
So you want leads for your capacitor. I suggest you take a length of solid tinned copper wire and bend it into a hairpin. Put the capacitor between the legs of the hairpin. Solder very carefully - tweezers and a magnifier are almost essential kit. now cut the loop of the hair pin and you should be good to go.

Me, I'd normally make a PCB for this sort of thing - breadboard and SMT are not good companions.

Could you not find a 1nF leaded capacitor?




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aga
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[*] posted on 5-11-2017 at 11:49


Sounds like you have an 0805 packaged surface-mount component.

They are so small they will fly away if you sneeze.

It is possible to solder wires to them, but not worth the effort/frustration - they are designed to be placed and soldered by machines, not humans.

You can buy ceramic disc capacitors of the 'normal' type which are much easier to handle/solder as they are about 10mm in diameter and have 1 inch wire legs, perfect for a breadboard.

Edit:-

http://uk.farnell.com/multicomp/mcbu5102k5/cap-mlcc-y5p-1nf-...

i guess you got one that looks like this (under a microscope !) :-

http://uk.farnell.com/vishay/vj0805y102kxbbc31x/capacitor-ml...

[Edited on 5-11-2017 by aga]




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Magpie
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[*] posted on 5-11-2017 at 13:31


Thanks for the nice direction Twospoons. I decided to order one that has leads.



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[*] posted on 5-11-2017 at 14:30


0805 and 0603 aren't that bad. For breadboard its kind of handy to save space, like resistors for LEDs

1) Melt a small amount of solder on one of the pads
2) Use tweezers to pick up the component, melt the solder and stick it on. The joint will be ugly due to lack of flux but thats OK
3) Solder the other side, let it solidify then re-solder the first side

You need a good quality soldering station plus some nice lead solder




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[*] posted on 5-11-2017 at 17:20


If you are doing a bit of breadboarding, a nice thing to have is a mixed bag of capacitors, and one of resistors too. $10 will usually get you about 100 caps, or 300 resistors. Usually at least 5 of each value over a range. By the time you factor in shipping it works out quite well vs only buying what you need.



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[*] posted on 5-11-2017 at 21:17


I have done surface mount LED's and capacitors by the method twospoons suggests. But of course I had to devise it my self after the shortcomings of my first two attempts and burnt finger tips. Lesson 1, soldering one side and then the other does not work. Too small of a work piece. Soldering the second side removes the first. Lesson 2, pre cutting the wire like chopsticks taped together was hard to do because of solder surface tension, pull off easy. Leads deform easy while applying the holding force to chopstick configuration, at least with thin wire.

Bend enameled wire in u, burn it or preferentially twist a diamond file inside the u shape, place the piece and solder, snip off extra. With LED's one leg can be longer of course, but tape or twist leads so they don't break off from strain in storage.

I found some already made on eBay, they were enamel dipped ceramic capacitors with stubby leads, super cheap too. They looked to be smc cube like shape under enamel. Great for breadboard.

The mixed bags are a solid idea, one each of ceramic/electrolytic caps and some resistors is practically a must unless you enjoy burning fingertips while removing parts from dead or sacrificial electronics. But hey, never too good to get me hands dirty, just a big hassle. Still happen on numerous occasions

Electronics are fun and confusing like chem :)

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I was specifically soldering the smallest LED's I could get to small enameled wire... For an art project/gift. Made at least 10x of each color(r-o-y-g-b-v) and a couple UV guys as well.

Pinched a few SMC caps and did the same b/c radio shack is a ripoff for small components and Chinese suppliers take ~3 weeks. On the fly improv, at its best.

There is no problem doing so to a pcb. They are minor nuisance there.

[Edited on 7-11-2017 by violet sin]




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[*] posted on 6-11-2017 at 09:14


I do a lot of electronics, which means I also do tons of soldering. To do surface mount components while not easy is doable. You will need either solder paste or fine .03 Rosen core solder, a good hands free magnifier, tweezers, flux pen, and a fine tipped soldering iron. Start by tinning your soldering iron, then tin your solder pad on your work piece, dab on some flux on the tinned solder pad. Take the tweezers and grab hold of the component and place on the tinned and fluxed solder pad. Hold down the component with the tweezers in the middle, using the tips of the tweezers. Apply heat to the component leads, you will feel a slight downward shift of the component when the solder melts. Repeat on opposite component lead. Keep downward pressure on middle of component to keep it from shifting if you other lead also results. Let solder solidify, remove tweezers. This is harder to explain than to do. If you have holes in your circuit board for through hole component than that is the way to go.
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[*] posted on 6-11-2017 at 13:33


I am not an expert in electronics but 1nF seems like an extremely small amount of capacitance.

Since capacitor is so small why not embed it in something large that would have regular leads? I guess this is what has been done with the new capacitor I have on order.

I also thought that since the capacitance is so small could I substitute a piece of wire that is not too conductive?




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[*] posted on 6-11-2017 at 14:00


The 1nf cap most likely is being used to
help reduce noise, you can try just using a jumper and see what will happen. It's not going to hurt anything.
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[*] posted on 6-11-2017 at 15:26


Would it be possible to see the circuit diagram ?

It's almost impossible to judge whether the capacitor is required or not without the whole picture.

While 1nF sounds like a really small value, it can make all the difference.

In electronics 100 Farad thru to 1 pico Farad can be required, depending on what it is supposed to be doing.

If it is for decoupling then a piece of high-resistance wire (aka a Resistor !) will not work at all, neither will a jumper.




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[*] posted on 6-11-2017 at 18:45


Quote: Originally posted by aga  
Would it be possible to see the circuit diagram ?


Yes, here is the circuit:



555-Timer-IC-Testing-Circuit.jpg - 38kB

The IC being tested is a 555 timer.

[Edited on 7-11-2017 by Magpie]




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[*] posted on 7-11-2017 at 01:39


Yeah, the 1nf isn't really needed. You can just leave that pin open.



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[*] posted on 7-11-2017 at 07:58


Yes pin 5 (control voltage) can be left open or float. Normally I ground any unused pins, but use a 10nf cap and not a 1nf.
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[*] posted on 7-11-2017 at 14:09


Quote: Originally posted by Magpie  
I am not an expert in electronics but 1nF seems like an extremely small amount of capacitance.


That depends very much on what you are doing.
In power electronics it would be small. In amplifiers and small signal applications it would be typical. In RF it would be large. In silicon chip designs it would be enormous (I have seen the circuit of an image sensor where the integration capacitors were 30fF - as in 10-15 farads!)

In the 555 circuit the 1nF is filtering for an internal threshold voltage - it works fine without it, but there will be a little bit more jitter on the output waveform, depending on how good the power supply is.

[Edited on 7-11-2017 by Twospoons]

[Edited on 7-11-2017 by Twospoons]




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[*] posted on 7-11-2017 at 14:42


Can't remember ever having connected pin 5 on a 555 type IC to anything, ever.

Internal to the chip, it is a point in a voltage divider chain, comprising 3 resistors from 0v to Vcc, on the 'high' side.

A capacitor there will reduce noise a bit, but this is just a very simple timer/oscillator chip, so if you really really needed pinpoint accuracy it would not be the right chip.

Edit:

To be fair, the 555 has been around forever due to it's reliability and robustness, so don't ditch it in favour of a PIC or AVR.



[Edited on 7-11-2017 by aga]




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[*] posted on 7-11-2017 at 17:00


Thanks, everyone. I had no idea we had so many knowledgeable in electronics.

I activated the circuit with a 9v battery and the LEDs did not come on. Therefore I conclude that the 555 is defective. This IC came in a packet of 10. All 10 are apparently defective.




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[*] posted on 7-11-2017 at 19:04


That's disappointing...I know I've fried a 555 before, it's disappointing to loose such a useful IC - let alone have 10 defective ones!



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[*] posted on 7-11-2017 at 19:09


I would expect either both or one LED to be on in the case on a defective chip. Unless its shorting out the supply. Did anything get hot? I'm surprised you have 10 chips DOA, unless they're fakes. Source?




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[*] posted on 7-11-2017 at 22:17


If all ten ICs are defective, that's usually a sign that the first time I tested them, I royally fucked up the testing circuit and burnt them all out when doing the testing.

You could just drop $6 on an arduino, and spend your time programming various stirring cycles. That's what I've been doing with mine.




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[*] posted on 7-11-2017 at 22:42


I agree, it's not very likely that all 10 chips are dead unless they are fake or you killed them. The leads should light up unless the chip is shorting the battery.

Start by redoing the circuit from scratch. Also, it's not a bad idea to add a current limiting resistor in series with the battery. This reduces the risk of frying components.




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[*] posted on 8-11-2017 at 04:37


In agreement with logic and common sense the 555 IC is not bad. I had two failed LEDs in the circuit. When I replaced these the LEDs pulsed as expected, even without the 1nF capacitor. Thanks for all your help.



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[*] posted on 9-11-2017 at 05:18


I don't know much about this but look in fluorocarbons FC40 in particular. Supposedly if you put this stuff in a beaker and boil it the fumes are very heavy and stay inside the beaker and are very hot. It is used for soldering difficult parts on circuit boards. All you do is dip the circuit board in the fumes with the piece you want to solder and the flux and solder itself and the heat from the fumes solders it in place.
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[*] posted on 9-11-2017 at 12:57


You're talking about vapor phase reflow soldering - not really something for the home lab. Hot air works just as well in a lab situation, and hot-air rework stations can be had for about a hundred bucks. I bought one out of china that included an IR pre-heater and soldering pencil too. Or you could buy a cheap toaster oven for IR reflow - that works pretty well too.

[Edited on 9-11-2017 by Twospoons]




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