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 181 Using Arduino / General Electronics / Confused by how opamp is supposed to work on: May 04, 2011, 06:31:44 am I am having some trouble understanding and getting this opamp to work. My first opamp... Maybe I'm missing a fundamental principle of opamps...?SituationVery simple: I have a small signal (mV or maybe tens of mV). I would like to amplify it so that it's larger and so I can read it through an ADC later.MethodI'm using an Analog Devices OP177 opamp.Datasheet-recommended application circuit for"Differential amplifier":It's very simple according to the data sheet: (http://www.analog.com/static/imported-files/data_sheets/OP177.pdf)[Application circuit above is from datasheet]My circuitFor testing, I'm simulating a small input signal by using a potentiometer connected to a DC supply of +10 V. The pot is set to output a voltage of about +10mV (with respect to GND)...So +10 mV goes to IN+ pin of opamp, and GND goes to IN- pin of opamp.I supply the opamp with 10V for supply V+ pin, and GND for supply V- pin, even though the app circuit recommends -10 V for supply V-...Could that have been an issue?Thus, my final circuit:ProblemI expect a gain of 100 (b/c I used 1 MOhm and 10KOhm resistors).So V_output should be 10 mV * 100 = 1 V.But instead at the output, I'm getting 9.5 Volts (!?!)i.e., nearly the supply voltage with which I'm powering the opamp.Note: When I changed the supply voltage, same problem; e.g. if supply voltage is 15 V, I'm getting opamp output of 14.5 V.Why is the opamp not giving me the expected correct output, even though there's nothing complicated here?
 182 Using Arduino / Networking, Protocols, and Devices / Re: Is it possible to get a serial monitor in a command prompt? on: April 21, 2011, 03:54:07 am i think most, if not all, new windows versions come with Hyperterminal in the menu. quick and easy and solves your problem, IMO.
 183 Using Arduino / Networking, Protocols, and Devices / Re: >Working, with library!< Interfacing ADS1213 22-bit ADC on: April 21, 2011, 03:52:08 am Murdock, I'm curious what kind of noise levels (i.e. precision), or lack thereof, you are getting so far?Maybe you can post up a summary of numerical results you're getting, as well as a schematic/summary of your overall circuit layout.
 184 Using Arduino / Networking, Protocols, and Devices / Re: >Working, with library!< Interfacing ADS1213 22-bit ADC on: April 19, 2011, 10:53:51 pm @Murdock,This library is a nice contribution; and glad you got your initial problem solved.I look forward to checking out one of these chips when, one of these days, I get finished with my other projects!@Lefty:Now, after trying bunches of clean voltage sources (regulation, precision reference, etc.) I can't help but think that this basic fact (i.e., my current breadboard layout versus refined PCB) might be the culprit in my own 24-bit endeavors resulting in consistent stability of only about 19 bit-precision.I'm always a little hesitant about soldering a veroboard circuit (just the complaint of "oh man, things aren't rearrangeable so I've to be sure about my planned layout and if there's major mistakes, I've to desolder a bunch of things and re-solder") but this time, it seems absolutely necessary that I try veroboarding this and shortening wires, etc. to check for any improvement.
 185 Using Arduino / General Electronics / Re: Breakout Board for Xbee on: April 18, 2011, 04:49:10 pm If/when you initially configure your XBee using the computer,you might also want to get a USB adapter for the Xbee.one of the choices is sparkfun's "usb explorer", but IMO that one's expensive; I've seen significantly cheaper ones.
 186 Using Arduino / General Electronics / Why is the Arduino powered by a 9V, e.g. battery? on: April 18, 2011, 04:43:23 pm The Atmega328 chip can use 5V, thus it makes sense to use the USB-charging-method, because USB protocol provides 5V power.So why is it that the Arduino when powered externally, say, by a battery needs a 9V power supply?Given that one can additionally use a transformer/regulator/etc. combination to in turn change the voltage the device finally gets, HOW does one go about actually choosing what voltage to power your project with?For example, what voltage battery would you choose in the following two contrasting cases?Atmega-chip+one-LED (simple) ---versus--- Atmega-chip+Xbee+LCD+buzzer (more power-demanding)
 187 Using Arduino / Displays / Re: name: something that converts LCD ribbon to breadboard size on: April 18, 2011, 01:21:44 pm Thank you Andy. It was an erroneous measurement indeed. It was a 0.5 mm pitch, I verified; so I'm in the process of ordering the Seeedstudio item as well as stock up on a couple of those ebay ones too.Liked the tutorial on your page; appreciate this reference. And your page on the easing-function idea was gold to discover. Look forward to reading future articles.One question on the soldering idea in Step2; I'm surprised how fairly convenient this procedure is... Wonder if this method would work for SMD chips/parts in general as well...How is it that the solder only gets attracted to the pads (and as you said repelled by the board in between) without causing any bridges, generally speaking? I can see how that's clear if the pads were far enough from each other but since the pads are so thinly spaced, why doesn't this just result in connected blobs (as opposited to isolated pads)?
 188 Using Arduino / Displays / Re: name: something that converts LCD ribbon to breadboard size on: April 17, 2011, 05:47:42 am Quote from: brucethehoon on April 16, 2011, 02:04:49 pmok. since I just HAD to make sure I knew my search terms were good, I found this:http://www.seeedstudio.com/depot/lcd-ext-breakout-of-05mm-fpc-p-200.htmlif the pitch is correct, that is just about the best deal you're going to find....  Like...  VERY good deal for how flexible it is.this is so perfect, and not that expensive either. thank you much!I'm not sure about the exact pitch spec of my LCD's cableout, so I measured using a caliper, and it was around 0.25mm.How is the design of one of these FPC connectors - do you think the 0.5mm pitch input of the Seeedstudio breakout can accommodate a 0.25mm cable securely despite the extra space?
 189 Using Arduino / Displays / name: something that converts LCD ribbon to breadboard size on: April 16, 2011, 02:22:08 am Hey all, I got an LCD off ebay that has a 50-pin ribbon (?) cable coming out its back that looks sorta like this (not the same but this is just something similar I found on Google images):So, since there's no breakout/shield included, I want to find some way of connecting/magnfiying these 50 pinouts to breadboard size so that I can hook the LCD up to the Arduino Mega.I'm wondering how you would go about this... I suppose I need some cable/board that converts from this very-thin-spacing LCD ribbon to a breadboard/IDE/DIP sized connector/cable/pinout.Does such a thing exist and, if so, what name should I search for?