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1  Community / Bar Sport / Re: Who hasn't accidentally touched a mains voltage once or twice? on: Today at 03:54:05 am
The other thousand people are not posting because they're dead smiley

The reason I asked is because this has happened to me several times and frankly, I am underwhelmed.  Now, I was never drenched in salt water and standing in a puddle when this happened, but still.  I do wonder about the people in 240V countries.  I have to imagine that the voltage is substantially more dangerous there.
2  Community / Bar Sport / Re: When did 'bugs' become 'glitches' on: September 15, 2014, 03:12:30 am
About ten minutes into "Robocop".

Fun glitch.  Sometimes extreme violence is entertaining if the person getting violated is an extreme asswipe.  smiley-red
3  Community / Bar Sport / Re: Lead free solder on: September 15, 2014, 03:10:19 am
Iv heard that lead free solder is an environmental disaster as the extra tin mining generates more pollution than is saved.

Anyone got a link to documented fact please.

Yes i have tried google.

I don't think the calculus being employed was ever what was more polluting or not.  It's what is more toxic to humans or not.  Still, I like leaded solder.  Damn the torpedoes!
4  Community / Bar Sport / Who hasn't accidentally touched a mains voltage once or twice? on: September 15, 2014, 03:07:40 am
Maybe I am accident-prone, but I think I have touched a US mains voltage (120VAC RMS) at least half a dozen times in my life.  It's not fun, but I am not hardly dead either.  I have always sort of assume everyone else has.  Wires get frayed.  Little kids are overly enthusiastic about putting keys into small holes (that was the worst one).  Shit happens.  Any of you somehow completely avoided doing this?
5  Community / Bar Sport / Re: Your latest purchase on: September 15, 2014, 01:11:17 am
One thing that pisses me off is that the "programmer" on the USB sticks cannot be used to program bare chips.  The bare chips have to be flashed with a bootloader first which requires a "real" programmer.  .

Now, now...http://www.cypress.com/?id=4&rID=98796

Disclaimer... Have not tried it!

Ray

Thanks.  I will give this a shot tomorrow to program a dev board that I made via these pins and I will get back to you all on if it worked or not.
6  Community / Bar Sport / Re: Your latest purchase on: September 14, 2014, 03:03:34 am
PSoC 4200:  I bought a 10 of the chips at $1 from Cypress and also bought 3 of their $4 CY8CKIT-049 development USB sticks.  One thing that pisses me off is that the "programmer" on the USB sticks cannot be used to program bare chips.  The bare chips have to be flashed with a bootloader first which requires a "real" programmer.  The cheapest programmer is the MiniProg3 which is $90 and it doesn't look like there are cheap clones on eBay (as there are for so many architectures).  That really irritates me.  I thought I was going to be able to get away with using the  CY8CKIT-049 as a programmer (not as a debugger or emulator though) and I didn't understand the whole bootloader B.S.  Honestly, I thought bootloaders more of an Arduino thing than a normal professional strategy and frankly I have used real programmers/debuggers for everything else other than Arduino.  It's just that I have always been able to get super cheap programmers before.  I don't want to pay $90 just to evaluate a chip.  Not happy.  Did get it to change the blinkenlights speed, though (i.e. the IDE works for me fine with the  CY8CKIT-049).  Still, I would rather work off the board I built out of these now useless bare ICs.
7  Using Arduino / Project Guidance / Re: General Load Cell Setup And Questions on: September 13, 2014, 10:31:59 pm
PS, turn the load cell around, the down arrow should be at the load end.

Thanks again.  Once I did that it starts with an offset voltage which I can zero and there is no pre-tensioning needed, it is sensitive to even small weights.  It isn't the most sensitive.  At these voltages and the 10 bit ADC I seem to get about 1 bit change on the ADC for every 4 grams.  Still, if it turns out to be linear that is good enough.  I can try it out with a better ADC and see what happens too.

The one problem I have is that the bridge is putting out 0.343mV with no load.  This is amplified to 2.24V (G=6531, gain resistor is 10 ohm) by the INA125P.  This is no problem to zero in software, but it eats almost half the resolution of the ADC.  Is this normal or am I screwing up now in another way?  I can turn the gain down, of course, but then I lose sensitivity.  Is this a normal trade off?   How do you null out a offset voltage like that?
8  Using Arduino / Project Guidance / Re: General Load Cell Setup And Questions on: September 12, 2014, 03:23:17 am
Wonderful!  That is exactly the sort of advice I was looking for.  I was worried that I had it backwards but I thought the strain gauges being nearer to the loading point (surface in my case) was preferable because the load should bend the metal there more and therefore and strain the gauges more.  Probably a bad move, though.  I will be turn that around tomorrow night and and work on mounting some kind of pan with a default mass and set point and see if this clears up the linearity issue.   Also, I will check the voltages again after turning it around before deciding on how heavy of a pan I will need to get it into the linear region.  Thanks again.
9  Using Arduino / Project Guidance / Re: General Load Cell Setup And Questions on: September 12, 2014, 02:45:45 am
You also need to 100% sure that the load cells have been attached symmetrically and in accordance with the guidance that came with them, surface prep is very important, as is use the correct adhesive.

You mean strain gauges, right?  The load cell is the whole assembled apparatus with the selection of adhesive and surface prep already taken care of.  It came as one piece and I didn't have to do any of that.  Now, I got it from a cut rate Chinese eBay supplier, but these particular cells seem to be popular and a lot of sellers are selling them.  A similar listing:  

http://www.ebay.com/itm/Electronic-Scale-Weighing-Sensor-Load-Cell-20Kg-Portable-/191192554761

Does it look like I mounted it right?  I have to assume all the adhesive and strain gauge placement is correct.

Thanks for the ADC link, but I know my problem is well before I get to the final conversion.  If the voltage is not linearly proportional to the weight I am screwed no matter what ADC I use.
10  Using Arduino / Project Guidance / General Load Cell Setup And Questions on: September 11, 2014, 10:53:05 pm
I have a load cell of the variety typically used for scales and I am trying to make a scale using an instrumentation amplifier (INA125P) and an Arduino.  The instrument amp and the Arduino are well-behaved.  I am not getting linearity out of the load cell and I suspect this is because I have physically set it up wrong so I am looking for some advice.  

Here is the setup with 1478 grams of mass on it:



The base is an single egg pan that the Teflon wore out on, so I re-purposed it.  It is very rigid.  The load cell is tightly screwed into the base with two washers as a shim between the load cell and the base.

The voltages that I am getting out of the load cell, after the amplifier, for the following masses, are:

Test Mass (g)    Amplified Voltage (mV)     Expected ADC Value     Actual ADC Value
0 64.4(64.4/4995)*1024 = 1311
469 65.7(65.7/4995)*1024 = 1311
1000 87.3(87.3/4995)*1024 = 1816
1479 370(370/4995)*1024 = 7672

So it doesn't look like it is getting linear until I have 1,000 grams on it.  If it even is at that point.

My 5V reference is reading 4.9946V.  This is the excitation voltage.  The amplifier is set up according to the following schematic:  http://airtripper.com/wp-content/uploads/2013/10/arduino-ina125-amplifier-schematic.jpg except that the voltage is 8V, the gain resistor is 10 Ohm, and VREFCOM is tied to ground (I think this is an error in his schematic, the op amp seems to expect that to be tied to ground so that the voltage reference output pins work correctly).  Also the Arduino AnalogRead values are not exactly as expected, though they are pretty close so I don't think that is a problem.  I don't expect any of this matters, I think I just physically have this load cell set up wrong which is why it is not providing sane voltages.

What am I doing wrong?
11  Using Arduino / LEDs and Multiplexing / Re: TLC5958 on: September 09, 2014, 11:01:21 pm
when I tried in the past to get TI chips that were not at Digikey those samples requests never came through.  I would like a few of these.

Maybe they've become more circumspect about who gets samples or what for.
So, you might need a letterhead or a good story for the samples.
[Unlimited top-side then, shall it be?]

Um, no.  Otherwise, good point.  These parts are simply not in stock at Digikey, which they use to ship samples from, at least in the USA.  Taking 15 seconds to visit the part pages can be used to confirm this.

http://www.ti.com/product/tlc5955/samplebuy
http://www.ti.com/product/tlc5958/samplebuy

Free sample, means Free sample.  However, Not In Stock means Not In Stock,.

12  Community / Bar Sport / Re: Your latest purchase on: September 09, 2014, 03:20:05 am
I'm having an interesting discussion off in another forum

http://www.eevblog.com/forum/microcontrollers/one-dollar-one-minute-arm-development/

My latest is to order a couple of INA125Ps from DigiKey to attempt a project similar to this one:

http://www.instructables.com/id/Arduino-Load-Cell-Scale/
13  Using Arduino / LEDs and Multiplexing / Re: TLC5958 on: September 09, 2014, 03:13:52 am
I pointed out the TLC5955 months ago in this message:

http://forum.arduino.cc/index.php?topic=229971.0

The TLC5958 is a member of the same family (maybe it's the same die), just a couple more bits dedicated to analog dimming and they charge you almost another two bucks per chip.  I wonder if that is worth it.  I am thinking probably not.

Still none of them at Digikey which means I can't get samples yet.  At least when I tried in the past to get TI chips that were not at Digikey those samples requests never came through.  I would like a few of these.
14  Using Arduino / LEDs and Multiplexing / Re: Reading access-is keyboard from Arduino on: September 09, 2014, 03:06:46 am
1. What connector (and from where) can I purchase so that I can connect the rainbow cable from the keyboard to a breadboard and from their to an arduino.

2. What arduino should I purchase

3. Would it be easier to purchase a USB shield and reverse engineer the io for the keyboard? If I go down this path will the usb shield provide enough power to power this keyboard?

Rainbow connector?  I see an 30 pin FFC connector.  Why so many pins?  It looks like the keyboard is laid out 10x10.  I can't tell if it is 1mm or 0.5mm but at some point you will need something like this:

http://www.ebay.com/itm/5pcs-FFC-FPC-connector-32pin-pitch-1-0mm-Bottom-contact-/181139979355
http://www.ebay.com/itm/5pcs-FFC-FPC-Connector-32Pin-pitch-0-5mm-Bottom-Contact-Pick-Drawing-Socket-/191229135712

Not exactly easy to breadboard with., not impossible either.

Do you have a continuity tester?  First thing I would do is experiment with the contacts on the end of the FFC connector gently to see if I could determine the organization of the keyboard.  I would stick a key down and probe one pin and drag the probe across the others.  Assuming no continuity, I would move to the next pin and do the same.  At some point you should have continuity between two pins, one is the column and one is the row, then you figure it out from there.  This assuming there is no more direct way to figure it out.

Assuming you need 20 lines to address the keyboard you are either looking at the Mega or a multiplexing solution like a pair of 74HC138 or serial-in-parallel-out shift registers to write to one side of the key matrix and then a pair of parallel-in-serial out shift registers to read the other side of the key matrix.
15  Using Arduino / General Electronics / Re: ATTiny85 SOIC Eagle footprint on: September 09, 2014, 02:29:09 am
ATTiny85 SOIC is "S8S1, 8-lead, 0.150" Wide Body, Plastic Gull Wing Small Outline (JEDEC SOIC)" with 1.27mm or .05 inches between pins.  Any package with that outline could be used, you would just have to make connections correctly ignoring whatever the pin names are on the other device.  I just don't know Eagle that well.  In DipTrace it is very easy to copy an existing footprint for a different device with the same packaging and just rename the pins.
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