Can anyone recommend a ADC?

Hi Guys,

Can anyone recommend a Through Hole ADC that has built-in error checking? I'm reading a signal that increments by 1 or 2 points and the Arduino analog pin by itself changes by 1 or 2 values. So, it's hard to see what is a real signal change and what is just the signal floating.

I'm thinking of something with built-in error checking and a higher bit resolution.

Thanks,

Cameron.

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Higher resolution in DIP package is certainly available.
http://www.digikey.com/product-search/en?pv69=80&FV=fff40027%2Cfff80183&k=adc&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

Pick the number of bits & the interface you want to use.

Error checking, not really an option. Your code will have to decide that based on the data received.

ADC don't really have any kind of 'error' detection, that is up to your coding logic. As far as external ADC I have good luck using one of the adafruit modules. They also offer a arduino library support code.

Thanks, guys,

I now understand that error checking isn't an option. :slight_smile:

The problem I'm facing is that my signal (straingauge to INA125 to AnalogPin 0) is only producing changes in 1 scale increments, but the drift is causing me not to know if it's the weight (1 gram) or the drift.

So I am thinking that I might need one of these two options or (both):

  1. An external ADC chip with a higher bit resolution. (could this make matters worse)?
  2. I have heard of DELTA-SIGMA as an option to provide more accurate results. But the chips cost like $20.00 compared to $4.00.

I'm thinking that the Arduino analog pins are not too accurate because of what spycatcher2k said:

due to the non isolated ground for the analog ports

What would you guys recommend?

If it was my project I would ditch the INA125 and read the strain guage directly with the following 16 bit ADC. As it has programmable gain it will perform the function that the INA125 was performing. Again adafruit has library code to make it pretty easy to get going on an arduino based project. It is a delta sigma converter.

Hi retrolefty,

Yeah, that sounds very tempting, but the person i'm building it for doesn't want any breakout boards. He wants it to be made on his own breadboard so he wants to buy the ADC directly from somewhere like Digikey.

Sucks, I know.

cameronasmith:
Hi retrolefty,

Yeah, that sounds very tempting, but the person i'm building it for doesn't want any breakout boards. He wants it to be made on his own breadboard so he wants to buy the ADC directly from somewhere like Digikey.

Sucks, I know.

Well the underlining ADC chip is a TI ADS1115 available from many chip suppliers. But as it's a SMA package part not really breadboard friendly. The adafruit module supplies pins so that the module could be plugged into a breadboard. But let partner decide. Most modern parts are no longer available in DIP packages, so he is really limiting his possible solutions. This ADC is perfect for direct reading of resistance bridge devices like strain gauges without the complexity or noise sources that having to add external amplifier.

That's a good point retrolefty,

But, just to confirm even a through hole dedicated ADC should in theory be much better than the in-built Arduino analog pins?

Does everyone agree with this?

cameronasmith:
That's a good point retrolefty,

But, just to confirm even a through hole dedicated ADC should in theory be much better than the in-built Arduino analog pins?

Does everyone agree with this?

Well the AVR analog input pins are 10 bits of resolution and single ended and the datasheet specs for the ADC sections says something about total accuracy being +/- 2 LSBs, so useful but not instrumentation quality ADC. Reading low level signals like resistance bridges is not a good match for the AVR cuilt in ADC. So AVR adc is useful but limited.

Lefty

Okay, i'm really stuck on this problem.

What would you guys recommend to get a good reading from a 1 gram straingage? I'm using an INA125 and the Analog Pin on the Arduino. I'm open to suggestions on what people would use?

spycatcher2k, do you think the product ADS1115 16-Bit ADC - 4 Channel with Programmable Gain Amplifier : ID 1085 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits would do the job?

Thanks,

Cameron.

that is the exact same size board as listed earlier, even the same black carpet background in the photo.

when I started surface mount, I would drill a hole between pads and insert a plastic pin. that would align one side.
then solder a single pad on the opposite corner. if everything was aligned, I would solder one side, remove the pin, then solder the other side.

you could buy a chip carrier, make a tiny board and make your own insertable device. it might meet your needs.

another option is design the boards and have them made for you.

get that, work out the details and use it in your final design if all works well. the beauty of these pre-built parts is that they offer you fast prototyping.

14-bit thru hole ADCs
http://www.digikey.com/product-search/en?pv1173=2&pv69=80&FV=fff40027%2Cfff80183%2C264000a&k=adc&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

and 16-bit
http://www.digikey.com/product-search/en?pv153=5&pv69=80&FV=fff40027%2Cfff80183&k=adc&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

Thanks crossroads,

What do you think about this one? http://www.digikey.com/product-detail/en/NAU7802KGI/NAU7802KGI-ND/2769783

The price is super cheap compared to the rest, which kind of worries me :S

10 & 80 samples per second.
24 bit - you're going to need a good PCB or will likely see a lot of jitter type noise at the very low voltage levels.
I2C type interface, shouldn't be too hard to code for.

check the data sheet for, and use a guard ring.

That makes sense, Crossroads.

So, im going to stick with the 16 bit processors. :slight_smile: Hopefully, that will give me the resolution I need, and work well on a breadboard.

Thanks a lot for your help, Crossroads. I wish I knew electronics like you do. I think you wrote this book right? http://www.amazon.com/Arduino-Teens-For-Course-Technology/dp/1285420896/ref=sr_1_1?ie=UTF8&qid=1397097395&sr=8-1&keywords=arduino+for+teens

It looks super interesting even though i’m not a teenager :S, the part about reading datasheets is VERY interesting. I think i’m going to purchase it.

Yes, my wife & I wrote that book. It's really for anyone transitioning from PC coding only into embedded hardware. I think you'll get a bunch from it.

Thanks Crossroads. I'm going to order it when I get back from California next week. :slight_smile: It looks really interesting

Thank you again for all your help. I'll let you know how the 16 bit ADC works-out when I get it.

ok.