HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
<<  <  Page 2/2
78RPM
User Rank
Platinum
Re: Fascinating. Can improve accuracy
78RPM   4/18/2014 9:13:24 PM
NO RATINGS
Good idea, armorris. We could use devices using far less current and much lower voltage.  Your comments inspire me to suggest that we could use an FPGA which could draw a couple of nanoamps in sleep mode while providing all the op amps we need and all the peripheral eeprom or SD card data storage we might require when active.  We could store a graph of data over a long time period using very little power.

armorris
User Rank
Platinum
Re: Fascinating. Can improve accuracy
armorris   4/18/2014 4:54:15 PM
The author did a nice machining job on the mechanical parts, and the documentation was good, but as 78RPM pointed out, the circuit relies too heavily on the positive and the negative voltages being exactly the same. As 78RPM mentioned, a "rail splitter" circuit  would solve that problem. Then, you could just run the circuit on one 9 volt battery. A rail splitter would consist of a second opamp and two identical-value resistors. The output of that additional opamp would be a virtual ground. Even if the two resistors (say 10K) are not identical, their ratio would not change and the error could be reliably nulled out.

You could make those resistors 100K and use an MCP607 ultra-low current dual opamp, which draws less than 25uA per opamp, and make a 9 volt battery last a really long time.

78RPM
User Rank
Platinum
Fascinating. Can improve accuracy
78RPM   4/18/2014 3:18:24 PM
NO RATINGS
This is a fascinating project that could be a good science fair experiment measuring the effect on cloud temperature between summer and winter of carbon emissions using long-term readings. One could hook the output to an Arduino or Raspberry Pi and keep a log of readings on an SD card. One could also calibrate an analog panel meter using a custom decal (e.g., DecalPRO) with direct voltage or intensity units.

One problem with using two batteries for positive and negative supplies is that they get imbalanced over time. A better solution would be to use a rail splitter buffer opamp to create a virtual ground exactly half way between positive and negative points.  TI offers a variety of these. The outputs of this, +,-, and VGND provides the supply voltages to your circuit.

<<  <  Page 2/2


Partner Zone
Latest Analysis
With Radio Shack on the ropes, let's take a memory trip through the highlights of Radio Shack products.
We Have FPGAs with On-chip MCUs, but How About MCUs with On-chip FPGAs?
Polish design firm NAS-DRA has proposed parasitic robotic drones that capture carbon dioxide from the air during the day and release it at night to plants growing on their wings.
Computer security firm Norton has partnered with clothing company Betaband on a pair of jeans that will keep your RFID-tagged credit cards and documents safe from wireless theft.
With erupting concern over police brutality, law enforcement agencies are turning to body-worn cameras to collect evidence and protect police and suspects. But how do they work? And are they even really effective?
More:Blogs|News
Design News Webinar Series
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
12/10/2014 8:00 a.m. California / 11:00 a.m. New York
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Dec 15 - 19, An Introduction to Web Application Security
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  67


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service