Author Topic: Wire size thats good for flying wire probing?  (Read 335 times)

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Online FaringdonTopic starter

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Wire size thats good for flying wire probing?
« on: June 28, 2024, 06:10:33 pm »
Hi,
When wanting to probe across say a 0603 capacitor in a live circuit...we often solder
a twisted pair 7/0.2mm wire to it. -And connect the scope probe to that.

This works, but really is too big and heavy to solder to an 0603, it could risk terminal damage to the 0603.

Kynar wire would be better, but is impossible to strip....and everywhere you go has blunt kynar strippers.

Also, any wire strippers you see in any company are always blunt, since juniors etc try and strip wire in the strip hole
that's too small for the wire.

So a pair of sharp sidecutters and circumnavigating the wire's plastic end is the only option to strip
off the end of plastic coated wire.

So, do you know what commonly available wire is between kynar and 7/0.2mm for the said purpose?
It needs to be multistrand.
'Perfection' is the enemy of 'perfectly satisfactory'
 

Offline rvalente

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Re: Wire size thats good for flying wire probing?
« Reply #1 on: June 28, 2024, 06:20:45 pm »
I use solderable enamel wire, I keep two irons at the bench, one with a flat tip at 400°C, a little rosin core solder and I can strip the enamel from the wire, a second iron with a finer tip, to solder to the board. My go to wire is the 30 AWG for signals and 28 AWG for power
 
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Offline Gyro

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Re: Wire size thats good for flying wire probing?
« Reply #2 on: June 28, 2024, 06:24:34 pm »
Oh God, it's the flux story all over again. Just buy some Kynar strippers! ...except of course you won't :palm:


P.S. How about responding to some of your other threads that people have spent time on rather than stating yet another stupid one!
Best Regards, Chris
 
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Online FaringdonTopic starter

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Re: Wire size thats good for flying wire probing?
« Reply #3 on: June 29, 2024, 09:18:27 am »
Quote
I use solderable enamel wire, I keep two irons at the bench, one with a flat tip at 400°C, a little rosin core solder and I can strip the enamel from the wire, a second iron with a finer tip, to solder to the board. My go to wire is the 30 AWG for signals and 28 AWG for power
Thanks, that sounds good, and i always like to twist the probe flying wires.....but i find enammelled wire is not easy to twist....not as easy as 7/0.2mm. Its just that 7/0.2mm is just that bit too bulky.
'Perfection' is the enemy of 'perfectly satisfactory'
 

Online Psi

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Re: Wire size thats good for flying wire probing?
« Reply #4 on: June 29, 2024, 09:35:57 am »
I use a roadrunner pencil/wire to attach some thin wires to the component legs.
(Road runner wire is enameled but the coating instantly burns off when you touch it with the soldering iron, no scraping required.)
Then i run those wires around 1-2 inchs where they attach to bigger wires and then I hot-glue those bigger wires to the PCB.  It give the assembly some strength so if you yank on the wires it doesn't transfer to the component and rip traces off.

Downside is the hot glue melts if you hot air the board, but you can use a different glue if you want.
« Last Edit: June 29, 2024, 09:37:58 am by Psi »
Greek letter 'Psi' (not Pounds per Square Inch)
 
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Offline tooki

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Re: Wire size thats good for flying wire probing?
« Reply #5 on: June 29, 2024, 10:14:56 am »
FYI for the benefit of others: 7/0.2mm is 0.22mm2 or 24AWG.

I “love” how OP’s question is essentially “what’s between Kynar and 24AWG”, as if an insulation material were on the same axis as wire size…

OP: what is it you want? Thin or thick insulation? Something flexible? Something rigid? Why not use softer stranded wire (i.e. something with finer stranding and softer insulation)? You can get ~24AWG wire with 128 strands, which is far, far limper than 7/0.2mm. Silicone or soft PVC. PVC is super easy to strip, so you can use a full automatic stripper. (Some, but not all, silicone works in those.)

If you want something stiffer with thin insulation, try mPPE insulated wire, like UL style 11027 (many vendors) or Alpha Wire Ecowire or Ecowire Plus.

Or if possible, how about not soldering wires at all, and instead using better probe holders that can just hold the probe tip in place?
 
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Offline Gyro

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Re: Wire size thats good for flying wire probing?
« Reply #6 on: June 29, 2024, 10:48:41 am »
Be careful of using stranded wire for tacking onto SMD. Firstly the risk of stray strands, attached or loose, is high - not sure (fear) what you mean by "live circuits". Secondly, solder wicking is likely to turn the wire stiff (potentially much stiffer than single core Kynar) just where you don't want it to be.
Best Regards, Chris
 
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