Flux is usually applied to the joint to be formed just before heat is applied. The only reason nigel recommends liquid flux is because the flux will wick via capilary action inbetween the leads all by itself where paste flux will just kind of glob in bad places unless you're careful with it. Mind you there is always a flux residue afterwards that needs to be dealt with, sometimes acidic and VERY bad if left in place.

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How should I apply to the joint? By using cotton tips??

Thanks

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bananasiong

 

With the little brush that comes in the top of the bottle - rather like a nail varnish bottle (if you do your nails?).

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

You only need enough to 'wet' the surface, whatever method you chose to apply it is your own buisness. Cotton would be a HORRIBLE idea. I've tried to clean leads with cotton swabs before, and they always catch the threads and tear it to shreds right on the board leaving cotton mess behind. If it doesn't come with a brush like Nigel says use a generic nylon paintbrush from a hobby store.

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Don't use plumber's flux that has acid in it.

I haven't used liquid or paste electronic flux for about 40 years. Instead I have been using solder with electronic flux as its core.

I never had to clean a pcb, I just solder and it works. My soldering iron is temperature-controlled so it never gets too hot and never burns the flux like cheap soldering irons.

Maybe you are using the horrible new solder without lead in it. I haven't tried it but others say it sticks poorly.

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Uncle $crooge

 

You don't do Surface Mount then?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

I replaced surface-mount 14 pin ICs without using extra flux.
I had some defective MP3 players that were "unrepairable" by a store.
I removed a few good parts from one and swapped the bad parts in another and got one working perfectly.
The parts were all tiny surface-mount things but I removed and replaced them without using extra flux.

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Uncle $crooge

 

You can be sure of one thing auidoguru... =) The joints would be stronger with flux.

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14 pin ones are hardly anything difficult

My usual ones to change are 80 pin, and fairly small spaced - liquid flux is pretty well essential - although an alternative method is to use solder paste.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

You use a SMT inductor, look at the datasheet, it recommends several SMT inductors.

Again, read the datasheet, it is tuned by programming; this is done by transferring the configureation data into the RAM from a microcontroller.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

While waiting for the smt parts, I tired to modify the 'crappy' rf module. I'm using a CMOS NAND gate for the transmitter, when I pull up one input of the NAND gate with a 10 khm:, it doesn't oscillate as expected. So I turn the transmitter on and off using a transistor by PIC. It works at the bit rate of 10 ms. I'm still learning the method of coding and decoding, this is what I can do so far.
I wonder why I can't modulate from the logic gate..

Thanks

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bananasiong

 

Do the Cmos gated oscillator like this:

Attached Thumbnails

 

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Uncle $crooge

 

Any NPN transistor will do right? I'll use 2N3904 for this. If I do it this way, can the bit rate be faster? But I don't know whether the poor receiver can receive as fast as the transmitter do or not.

Thanks

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bananasiong

 

I think the LM567 in the receiver is slow. Its max switching speed is f0/20. f0 is about 7kHz so the switching speed is 350Hz.

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Uncle $crooge

 

So the fastest switching time is 2.85 ms per bit right?

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bananasiong