Soldering question....somewhat a newbie

ToddSTS · « **on:** 15 Dec 2004, 04:23 pm »

So I'm fairly new to DIY and soldering. I have done a Swenson and Vinnie mod on my Toshiba. Now I'm working on some Sonic Impact mods. My question is:

Do you use a grounding wristband when soldering electronic components?

The reason I ask is I have been using one and I get a slight pain/burning sensation at the wrist strap whenever I am touching anything electrically connected to the soldering iron tip.

(Like desoldering braid, the component to be soldered, etc. ) Is this normal? To make sure I wasn't going nuts I changed wrists on the wrist strap and did indeed feel the pain/sensation in the other wrist. I'm not talking excrutiating pain, just kind of annoying. Is my soldering iron going bad? Its a radio shack 40W model. Its new but I left it on for about 24 hours yesterday (whoops!

managed not to burn down the house). I noticed this with my old RS 25 watt iron before I ditched it too. I'm thinking I may have messed it up. But it still gets hot. Is it normal to get some stray voltage out of the iron? I haven't caused cardiac arrest or loss of bodily function control yet, but I figured I'd ask for some input before I eventually kill myself.

Thanks for any help.

Todd

ctviggen · « **Reply #1 on:** 15 Dec 2004, 05:08 pm »

To what are you grounding the wrist strap? It should be connected to the ground for the device on which you're working. Are you sure that you're not feeling heat? Also, do you turn the power off for the device? I've never felt pain when using a wrist strap. So, is your theory that you have some type of short from the solding iron, through the ground of the device and to you? Interesting!

ToddSTS · « **Reply #2 on:** 15 Dec 2004, 06:09 pm »

Actually the wrist strap is grounded into the 3rd prong of the same outlet as the iron is plugged into. The iron is a rather cheap Radio Shack model 40W, and doesn't have a power switch or a separate ground (third prong). If its plugged in, its on. I'm not feeling the heat, I don't think, because my wrist is too far away from the tip, I can feel the desoldering braid heat up, for instance, and it is a separate sensation entirely from the pain/burning sensation I get in my wrist near the strap.

It is my theory that I'm getting some sort of low level electrical connection between my grounding strap and the iron through my left hand. My left hand holds the solder/braid, my right hand holds the iron. Ordinarily the grounding strip is on my left wrist. I switched it once just to make sure I wasn't going nuts or feeling some sort of carpal-tunnel thing in my left wrist. I got the same pain/sensation in my right wrist when I did the switch.

Thanks for replying. It is interesting as long as I don't die.

Todd

JoshK · « **Reply #3 on:** 15 Dec 2004, 06:53 pm »

Maybe your outlet is reversing polarity and you are getting a surge of current from the live side instead of tying it to ground.

ctviggen · « **Reply #4 on:** 15 Dec 2004, 09:41 pm »

I don't think your grounding system works. When I used to do this, the ground strap was solely to maintain you and the electronics at the same potential. If you connect the ground strap to the third prong of the outlet, the electronics are still (potentially) at a different potential. Not only that, but the ground is physically connected to the neutral at the fuse box (all the grounds -- theoretically, if you have a new house -- connect to one bar and all the neutrals connect to another bar, but both bars connect to earth ground). You're setting up another path over which current can flow.

ToddSTS · « **Reply #5 on:** 15 Dec 2004, 10:29 pm »

Hmmm.....I'm using the Radio Shack anit-static mat and grounding system for working on electronics. I believe it is supposed to put me and the electronics (sitting on the mat) at the same potential. The wrist wrap attaches to the mat via a metal button, the button also has a lead that is supposed to be plugged in to the third prong of an outlet (according to the instructions), so everything, the mat, and me, and the electronics (sitting on the mat) should be grounded to the same place.

JoshK, I thought the same thing. So I switched the plug around in the outlet but it didn't fix the pain/sensation. Also, I think I used a tester on the outlet before.....but I will check that again tonight.

I have some latex rubber gloves I can wear to isolate my left hand from the part I am holding. If I get the same thing happening tonight I will try that. But I would think this shouldn't happen in the first place.

Thanks for the input. If I never post again........ maybe I'll be nominated for the Darwin Awards

........hopefully there's DIY electronics in the afterlife!

Edit: ctviggen: So could I disconnect the grounding wire from the mat to wall, leaving my wrist connected just to the anti-static mat and still be safe from ESD into the electronics? Thanks.

Todd

bigdog · « **Reply #6 on:** 16 Dec 2004, 02:27 pm »

The wrist strap is supposed to have a current limiting resistor in it to prevent electrocution is case you touch something live. Typically, the resistor is about 1 megohm (which is transparent to the tiny currents present in ESD). Sometimes the wrist cord itself is made of a high resistance material instead of having a discreet resistor.

Also, the tip of the iron is supposed to be grounded through the third prong of the iron's power cord.

So I suspect your iron is defective (dangerously so), and possibly your wrist strap is bad as well.