Author Topic: Did I burn my voltage regulator?  (Read 3287 times)

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Offline ribsTopic starter

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Did I burn my voltage regulator?
« on: June 17, 2007, 08:50:40 PM »
Hi - I just "finished" soldering my $50 robot, for the most part.  Earlier I accidentally put in the voltage regulator in backwards, and decided to desolder it, pull it out, and put it in again.  Unlike the other few other places where I was using desoldering braid to great effect, it took a lot of frustrating fiddling to get the solder off the 3 pins (I assume because of the heat sink built into the chip).  When I went to pull it out, the heat sink was very hot.  Not hotter than boiling - I touched a damp sponge to it and it didn't hiss - but quite hot.

I hear those ICs are very easy to mess up if you heat it up too much with the iron.  What are the chances I fried something in there?

The reason I am concerned is while doing my connectivity test I noticed that I have non-infinite resistance across any two of the voltage regulator pins (e.g. ground to input, input to output, ground to output).  The multimeter moves around when I measure resistance, but it kind of homes in around 240ohm if I measure resistance across Ground and Input.  Then it occurred to me that I have no idea what resistance it should read anyways, so I have no way of telling if it's busted or not.

I have not yet attached any servos or anything - I've essentially finished step 3B and am doing the connectivity test of step 3C.


Thanks,

Ken

Offline ed1380

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Re: Did I burn my voltage regulator?
« Reply #1 on: June 17, 2007, 09:26:53 PM »
mine has gotten so hot so many times and it still works

I have a 150watt gun and I didn't fry it, burned my fingers and it still works
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Offline frank26080115

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Re: Did I burn my voltage regulator?
« Reply #2 on: June 17, 2007, 09:30:58 PM »
I measured a 7805
all non infinite
Try measuring the output voltage instead
the one and only time my regulator got hot, the output dropped from 5 volts to 1.4 volts, but that was a LDO regulator

Offline Admin

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Re: Did I burn my voltage regulator?
« Reply #3 on: June 18, 2007, 06:52:16 AM »
Put it in to a breadboard, wire it up, and measure the output voltage with a multimeter.

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the one and only time my regulator got hot, the output dropped from 5 volts to 1.4 volts, but that was a LDO regulator

Some regulators have whats called a 'thermal shutdown' which basically stops the flow of electricity when it overheats.

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I was using desoldering braid to great effect, it took a lot of frustrating fiddling to get the solder off the 3 pins (I assume because of the heat sink built into the chip).

The last time I used a desoldering braid was back when I was a noob . . . but I remember it being totally useless . . . get a solder sucker (~$10), they are amazing!

Offline ed1380

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Re: Did I burn my voltage regulator?
« Reply #4 on: June 18, 2007, 07:00:41 AM »
Quote
I was using desoldering braid to great effect, it took a lot of frustrating fiddling to get the solder off the 3 pins (I assume because of the heat sink built into the chip).
150watt gun FTW
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Offline JonHylands

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Re: Did I burn my voltage regulator?
« Reply #5 on: June 18, 2007, 07:50:21 AM »
The last time I used a desoldering braid was back when I was a noob . . . but I remember it being totally useless . . . get a solder sucker (~$10), they are amazing!


Desoldering braids are actually much better than solder-suckers for certain types of desoldering. You have to have liquid flux to use it effectively.

- Jon

Offline ribsTopic starter

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Re: Did I burn my voltage regulator?
« Reply #6 on: June 18, 2007, 09:00:36 AM »
Thanks all.  That puts my mind at ease.

I was thinking of wiring it up separately and measuring the output, but 1) that would mean desoldering it again and 2) I haven't actually received my battery packs in the mail yet, so barring duct tape and wires and a bunch of batteries I didn't have an easy way to get 6v into it ;)  I don't have one of those power supplies, and will probably not get one until I decide that robotics is going to be more than a one-time hobby for me!

If I duct tape 6 25watt irons together is that the same as a 150w gun? ;)

The desolder braid actually worked great for everything else (and I messed up quite a bit, it being the first time I've ever held a soldering iron), but it was tough to get the heat transfer from the iron through the braid and then to the solder when it was on the voltage regulator with the heat sink.  It probably would have helped if I had cut a small piece of the braid off instead of using it while it was still attached to the spool - it seems like the braid conducts heat quite well (was getting uncomfortably hot where I was holding it) so in addition to the voltage regulator heat sink I suppose the entire desolder braid spool was a giant heat sink as well.  Well, all good lessons to learn, anyways.

Offline ed1380

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Re: Did I burn my voltage regulator?
« Reply #7 on: June 18, 2007, 11:27:30 AM »
Quote
If I duct tape 6 25watt irons together is that the same as a 150w gun?
as long as the tape hold you're good to go. 8)
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Offline Admin

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Re: Did I burn my voltage regulator?
« Reply #8 on: June 18, 2007, 02:05:36 PM »
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so barring duct tape and wires and a bunch of batteries I didn't have an easy way to get 6v into it
Get some cheap alligator clip wires from radio shack.

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I haven't actually received my battery packs in the mail yet
As long as you arent running servos off of it, you can just attach a 9V battery to the regulator to get your 5V output.

 


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