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1  Community / Exhibition / Gallery / Re: Dummy load on: May 26, 2014, 12:06:24 pm
Well, I finally finished building my version of this. Scaled it up some. Isn't working. I've stared at it for a while, and can't find any solder bridges, bad connections, or mis-wiring -- doesn't mean there are none. Given that it's off-topic, does anyone have any experience with:
as being good/bad?

Or, if folks are up for it, I can post the circuit, and description of the symptoms.
2  Community / Exhibition / Gallery / Re: Dummy load on: February 12, 2014, 10:10:35 pm
I was inspired by Dave Jones blog about making a simple dummy load for testing stuff (power supplies, batteries, etc.) ...

Holy thread resurrection, Batman!

Thanks for the circuit, Nick. I'm going to build it -- except I'm going for higher wattage. How much? Well, that'll depend on the what the landlord has on hand to donate -- maybe a couple big mosfets in parallel. He sure enjoys giving me stuff for my projects. smiley At most, I shouldn't have to buy anything but big heatsinks.
3  Community / Bar Sport / Re: Weird or Innovative Repairs, Catastrophic Failures on: January 26, 2014, 10:38:37 am
Other people would trade the vehicle in because the ash tray was full.

These days, cars don't have those. My car is model year 2003, and it doesn't have one. Maybe the new version is something like trading in car because the USB port is broken.

For lots of bad repairs, check There, I Fixed It. Not much in the way of electronics, but some funny stuff.
4  Community / Bar Sport / Re: A very good Multimeter?? on: January 25, 2014, 11:16:51 am
THe GPIB cable can hang a man. It's too much to handle. USB is soft and easy.
Exactly my point!  smiley-twist
5  Community / Bar Sport / Re: A very good Multimeter?? on: January 24, 2014, 07:55:11 pm
IEEE bus? GPIB?

Yes.

Initially known as the HPIB - Hewlett-Packard Interface Bus, standardized as the IEEE-488.
6  Community / Bar Sport / Re: A very good Multimeter?? on: January 20, 2014, 07:40:22 pm
I don't know why you need it except for constructing a death ray. But here you go:

http://www.keithley.com/products/dcac/dmm/broadpurpose/?mn=2100120

The Keithley 2100 series is cheaper than the 182 for sure and reaches 10nA accuracy and 0.1uV accuracy. To get nV you need nano-voltmeters with the $3,000 price tag.

USB? Kids these days have it too easy. You should have to use the IEEE bus and like it!

This might be a good solution: http://www.kickstarter.com/projects/eevblog/current-gold-precision-multimeter-current-adapter
Maybe you can order one of these current adapters on eevblog.com.

Shiny!
7  Community / Bar Sport / Re: Your latest purchase on: January 19, 2014, 07:58:25 pm

Thanks cr0sh. I actually tried to order from them, but wound up not proceeding, based on the 3 strikes rule:
 - required creating an account
 - no info on shipping method (I use different addresses for USPS vs. UPS/Fedex)
 - Paypal

Too picky? Well, I keep a minimum amount in my Paypal account, and never intended to use it for anything other than incoming. And my CC doesn't work via Paypal -- I guess my carrier just disallows them. I pretty much feel that a real business ought to be able to take cards directly. So, in the short term, I made a wierd face and bent the stem back to straight, but it still catches. Didn't break anything, that I can tell. Might be a function I'll never use anyway. I just like to have things "right".  smiley-roll

Sphere Research looks better to me. But they don't have one. smiley-sad But I feel more comfortable shooting them an e-mail asking if they can let me know when they find another.
8  Community / Bar Sport / Re: A very good Multimeter?? on: January 19, 2014, 07:38:55 pm
What's an "acceptable" price tag?

Let's toss out an example. An instrument I got to fondle briefly, many years ago. Given that amperage is measured by running the current through a resistor, and measuring the voltage, we can consider a voltmeter. This instrument is a voltmeter, not a multimeter.

The Keithley 182 can be had for about $2800+ used according to this small sample, and I don't know whether that includes calibration. On the 3mV range, it will resolve 1nV with a 1/60th second integration time.

Is that an acceptable price? Well, if you really need to make those sorts of measurements, then it probably needs to be. Are there other instruments which will do this? Sure. I just tossed that one out as an example. An HP 3457 DMM is about $650 with a NIST traceable calibration, but it won't do nanovolt.
9  Community / Bar Sport / Re: Your latest purchase on: January 19, 2014, 10:05:46 am
Hi, Congratulations on the Tech License, nice CRO, good popular brand.
Excellent price, there will be lots of know-how around if any problems with the unit.

Tom..... smiley

Thanks. Well, if anyone has a 311-1192-00 10K pot w/switch in their back pocket, I'd be interested in that. and the 2 knobs that go on it. It works, at least as far as I can tell just turning it, but the center stem is bent, so there's a catch, where turning the switch stem moves the pot, and vice versa.
10  Community / Bar Sport / Re: Your latest purchase on: January 18, 2014, 05:11:09 pm
Thanks!

Yes, ham fests live. We have 3 more this year that I can think of off the top of my head, here in Colorado.

Landlord came down and gave me a quick intro to scope usage. Seems this one is working fine, other than dirt in the pots and switches. W00T! He also gave me a 10x probe passed along from a friend of his who was at the show when I bought the scope.

The part that really tickles me, now that I'm looking into this? It's apparently worth a lot more than I paidsmiley-evil Okay,mine hasn't been refurbed. Do I care? No.
11  Community / Bar Sport / Re: Your latest purchase on: January 18, 2014, 02:36:37 pm
Hello all!

Okay, my Arduino activity has been zero for a while. Other stuff taking up too much room in my head. Just got my ham technician's license, and bought a Yaesu FT-60R. But what I dropped in to share with you is this, purchased for $45 at the NCARC ham fest today. I have yet to plug it in. Didn't come with probes. I think you can see in the pic that the "B (DLY'D) Trigger Slope" pot stem is bent and the collar is broken. It does turn, so maybe the pot is still OK. Seems to not quite have a full range of motion. Seller said the the pots all need cleaning. So, I have a project.  smiley-grin
12  Community / Bar Sport / Re: Quis posses scribes vel dices Latinam on: September 01, 2013, 06:08:27 pm
I did 3 years of Latin during high school, but i'm sad to say it's practically all gone now ! I speak Greek though (as I'm of Greek descent), does that count ?

I did 4. And 2 of German. I remember so little of that now, {mumble} years later.

Gallia omnia in tres partes divisa est. Incolunt habebem primam ...

Arma virumque cano, Troiae qui primus ab oris ...

We read Caesar, Cicero, Pliny, Ovid, Virgil, and few other things. I learned more about English in Latin class than I learned in any English class.
13  Using Arduino / Microcontrollers / Re: does the Arduino Duemilanove w/ ATMEGA328 have and RTC onboard? on: September 01, 2013, 04:56:00 pm
If your Arduino is near a window another choice is to use a GPS module to get the time. It's very accurate and never needs setting.

At the risk of bringing to mind a Chicago Transit Authority song, I'll just mention that GPS time is, currently, about 16 seconds out of sync with UTC. Randall doesn't mention whether it's ahead or behind. Might not matter, depending on the application. See also http://gpsinformation.net/main/gpstime.htm
14  Using Arduino / General Electronics / Re: Sizing transformer for linear DC supply on: June 19, 2013, 07:44:35 pm
Thanks all for the continued advice. In re. switching mode power supplies, sure I'd like to learn about them. For various reasons, at the outset this didn't seem like the time/place for such. Well, no matter, I've learned a few things, and that has value to me, by itself.

The Pila IBC charger is embossed with the legend "6V / 2-3A". This wasn't something I looked at initially. The supplied wall-wart switching supply is labeled 6V 2A. I simply assumed that Pila would supply a wall wart adequate to the task, and it never occurred to me to measure it. I have noticed that it does continue to charge when the voltage sags to 5.5V. What circuitry is in there besides the actual charge controller I don't know, so I'm not going to mess with supplying higher voltage. (Yes, I looked at that thread on Candlepower Forums, and it looks there's not much else, but I'll stay conservative here.) Every Li-Ion charger I've seen will accept a range of cells, so trying to infer current requirements from the spec for one model of 18650 isn't informative. The Pila states that it charges at 600mA. I have cheap-o Ultrafire charger which states that it charges at 750mA. But the cells get warmer in the Pila -- explained, maybe by the presence of heatsinks right below the battery bay. Well, that's pretty much a tangent.

I'm going to go with more heat sinking, and see what happens. Grabbing some smaller caps too, just for grins.
15  Using Arduino / General Electronics / Re: Sizing transformer for linear DC supply on: June 17, 2013, 08:59:53 pm
... you won't buy anything by 'tuning' the regulator with the input filter value.. When it dries out prematurely due to high ripple currents it won't have far to go to fail, leave it where it is and either put your money in an efficient power supply or into getting rid or your waste energy as heat in an efficient heat waster.. Sinkr.

... your 1.5 A (Read the Specs carefully the LM350T is a 1.5A part it's the K version that is rated @ 3A) linear regulator and it would require a minimal heatsinking

The TI datasheet I have makes no distinction between the T and the K. Here's what seems relevant.
Quote
These specifications are applicable for power dissipations up to 30W for the TO-3 (NDS) package and 25W for the TO-220 (NDE) package. Power dissipation is ensured at these values up to 15V input-output differential. Above 15V differential, power dissipation will be limited by internal protection circuitry.
Well, maybe it isn't the right datasheet, but I hope I can trust Digikey to provide such. Going straight to TI.COM, I find the same datasheet, and it specifies 3A.

Now I do realize that there's an unspoken 'given sufficient heat sinking'.

What size heatsink do you have on the regulator? With a 2A load it will only dissipate 5W, and the TO220 version should be able to handle that easily, with a modest heatsink.

Looking again at the Digikey page, I think too small, but not by much. I will see what I can do about that. Yet another case of being in a hurry ending up costing time in the end. smiley-wink
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