hybridfree/eevblog-posts huggingface dataset:
AD623ANZ in-amp output problem - Page 1
Forum section: electronics / beginners

author: MarkusAnd
author_rank: Contributor
timestamp: March 19, 2021, 06:47:47 pm
content: Hi!I'm trying to get the AD623 in-amp to work for a future project but I have some problems with the output.I'm using a single voltage supply of 5V and a 0.5V PWM input from an Arduino. The gain resistor I'm using is two 220k resistors in parallel so 110kOhm. Therefore my output gain should be about 2 and my output 1V. I'm measuring 3.65V on my output, and it doesn't matter if I change the value of my resistors or even remove them completely, the output is still the same.What am I doing wrong?

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: March 19, 2021, 07:10:31 pm
content: A 0.5V PWM signal isn't the same as a 0.5V DC signal. It's a signal that alternates between 5V and 0V (the two possible outputs from the digital pin) such that it is 5V only 10% of the time.As far as the amp is concerned, you are hammering it with occasional 5V pulses which, since it is being operated at 5V, you are overdriving it. You should low-pass filter the PWM output.If you look at the datasheet, the permitted maximum input voltage is 1.5V less than the supply - about 3.5V.EDIT: usually you would use an RC network for the filter but it is possible to use just a resistor in combination with the output pin's capacitance (usually about 5pF or so). So, a quick and dirty test would be to put a resistor in series between the pin and the amp and see if that helps.

author: MarkusAnd
author_rank: Contributor
timestamp: March 19, 2021, 07:17:14 pm
content: I switched the input to the Arduinos 3.3V pin and removed one of the resistors. The theoretical gain is now 1.5 so the output should be just under 5V. The output is showing 4.1V and as before the output doesnt change even though i change the resistor values.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: March 19, 2021, 07:21:24 pm
content: If you are operating the amp at 5V, the maximum input voltage is 3.5. So by applying 1.5 gain to 3.3V, you are beyond the operational range of the amp.See page 5 of the datasheet:https://www.analog.com/media/en/technical-documentation/data-sheets/ad623.pdfIf you want to get 5V out of the amp, you need to supply at least 6.5V to +Vs.

author: MarkusAnd
author_rank: Contributor
timestamp: March 19, 2021, 07:23:29 pm
content: So the max output is (supply voltage - 1.5V)?

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: March 19, 2021, 07:33:24 pm
content: The same page of the datasheet indicates the maximum output. You can see that it depends on the resistance of the load. If your load resistance is low enough, then 4.1V is entirely feasible as the upper limit.What are you trying to do with the amp?

author: MarkusAnd
author_rank: Contributor
timestamp: March 19, 2021, 07:40:23 pm
content: The amp will be used to amplify a voltage drop over a shunt. Now I'm just trying to see if i get this to work with simpler inputs. My input is still 3.3V but I changed the Vs to +7V. My gain resistor is 220k so the gain should be about 1.5. My output is 6.5V
AD628A differential amplifier offset issue - Page 1
Forum section: electronics / beginners

author: mitrynicolae
author_rank: Contributor
timestamp: April 30, 2019, 08:46:58 am
content: Hello everyone,I have an issue with an AD628A differential amplifier. The IC is powered from a 5V power supply. VRef is connected to ground and the secondary amplifier stage is not used. I also have an adjustable power supply on which I can change the voltage from 0 to 30V. The positive of the power supply goes to + and the negative of the power supply goes to -. The measurements are performed on the Cflit pin, with no external capacitor connected. Now for every voltage between 8.5V and 20V for example, the output of the differential amplifier is spot on (from 0.849 mv to 1.998mV) (0.001 mV difference which is in specs). The issue is that between 8.5 and 7 volts the values are no longer proportional and bellow 7 volts the IC no longer read the correct value. Instead for whatever voltage value between 0 and 7 volts the output is always 0.695V. Can somebody explain why is this happening?Thanks!

author: mitrynicolae
author_rank: Contributor
timestamp: April 30, 2019, 08:56:30 am
content: P.S. I would expect that if the adjustable power supply is not connected the IC should output 0V, because on the positive input we have 0V (from Vref) and since the negative input is not connected the resistors can be omitted and the amplifier is pretty much an buffer. Apparently something is wrong because with the external power supply disconnected the output is 0.695V

author: pwlps
author_rank: Frequent Contributor
timestamp: April 30, 2019, 08:59:54 am
content: The ouput will always be clamped to some value above the negative supply voltage, it can't go to zero if the power supply is 0-5V.In the datasheet the output voltage swing is given as −14.2 to +14.1 for a +/-15V supply, that is about 0.8V above the negative rail. It is not given for the internal first stage amp but from your measurements it looks like it is similar.
AD7798 ADC DATA READ PROBLEM - Page 1
Forum section: electronics / beginners

author: the_mighty@420
author_rank: Newbie
timestamp: December 18, 2018, 07:45:26 am
content: I'm facing problem when reading data register,The SPI communication works perfect, all the registers can be write/read.The data register show -1 (which in datasheet indicates that there is a problem in Vref, checked with setting REF_DET bit and reading STATUS register which shows 0x60).I'm using adc in BIPOLAR MODE, the steps performed to initialize adc are,1. send 0x000A to mode reg.( this sets adc in continuous mode with 16.7 Hz update rate).2. send 0x0030 to conf. reg.( this sets adc in bipolar, Gain 1, reference detect ON, BUFFER ON, Channel to 1 ie AIN1+ and AIN1-.3. send 0x60 to IO reg. to check p1 and p2 are working.Please advice why is this happening am i giving wrong Vref, but the datasheet show Vref can be in between 0.1-AVdd and for this i can read upto +-AVdd-100mV (BUFF ON).Please see attached image for reference.I'm trying this CKT from a week now, monitoring Vdd mode works gives some integer value and STATUS reg. shows 4 in this case.

author: the_mighty@420
author_rank: Newbie
timestamp: December 19, 2018, 07:54:54 am
content: Problem solved.While designing PCB misplaced the PIN 9 with PIN 10, so the Vref(+) was at ground potential.Now all OK.
AD8210's input sourcing current when input not connected to power rail - Page 1
Forum section: electronics / beginners

author: Flanbix
author_rank: Contributor
timestamp: April 24, 2014, 02:40:10 pm
content: Hi,I got a AD8210 that I wanted to use as a current monitor. The "line" where the current flow is either 24V 12V or floating.My problem is that when the line is floating (no power rail attached at the dashed line), my LED still switch on.It seems that the voltage is somehow coming from the inputs of the AD8210 with a current of around 3mA.But my idea would be that the LED should be off when is line is suppose to be floating. It is the case if I got a load with a resistance low enough to pull this voltage lower than the forward voltage of my LED.I wonder if it is a normal operation of the component and if it is okay to use it like that (Load sinking some current from the AD8210) when no power rail is attached...Thanks.Flanbix
AD9833 Amplitude change - Page 1
Forum section: electronics / beginners

author: TheDice_again
author_rank: Newbie
timestamp: March 22, 2022, 07:15:53 pm
content: Hello I would like to be able to change the amplitude of the AD9833 output signal. The board is controlled by an Arduino micro. I've read a lot that it shouldn't work with a normal poti? Are there still other options?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 22, 2022, 10:01:11 pm
content: For not too high a frequency one can still use a more normal pot with not too high a resistance (e.g. 1 K) . The problem is that parasitic capacitance will also effect the amplitude for the higher frequency part.There are variable gain amplifier chips and programmable gain amplifiers. Some multiplying DACs can be used as variable gain attenuator for the lower frequency range.Many other DDS chips have the option to change the DAC reference voltage for a fine adjust of the amplitude.Coarse amplitude steps can be build with relays and CMOS switches.

author: TheDice_again
author_rank: Newbie
timestamp: March 23, 2022, 07:47:22 am
content: which boards are these? are they as easy to program as the AD9833?Ijust need to change the amplitude of a 50Hz signal.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 23, 2022, 07:59:22 am
content: For a lower output frequencey (e.g. up to 100 kHz) a normal potentiometers is OK and also digital potentiometers work (keep in mind the signal has to stay inside the supply range).The variable gain amplifiers come as integrated circuits and are not common to use with hooby systems like the Arduino - so no such boards. Many of the variable gain amplifers are controlled with a votlage or current.Variable attenuators / amplifiers for the RF range come as rather expensive modules, so not suitable here.

author: MarkF
author_rank: Super Contributor
timestamp: March 23, 2022, 01:29:27 pm
content: The AD9834 DDS is an example that has an external reference voltage to control the output amplitude. (See attached app note CD0156.)The programming for the AD9833 and AD9834 is the same.I built a DDS Function Gen based on the AD9834 and used a MCP4802 to control the amplitude and DC offset.$Re: Looking for <$50 function generator.The external voltage reference is 0V - 1.2V.Edit: I don't know if those AD9834 boards bring out the ext. ref. voltage for the user to set.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 23, 2022, 03:43:41 pm
content: https://www.eevblog.com/forum/projects/ceramic-potentiometer-maximum-frequency/A pot will do unless the flatness of your response is super critical.
AD9851 with Hantek 4202C - Page 1
Forum section: electronics / beginners

author: Deboscope
author_rank: Contributor
timestamp: November 17, 2019, 10:01:16 am
content: Hi, I have ordered a AD9851 chip, what would be some interesting measurements to perform using this chip?Excuse my newbiness..

author: German_EE
author_rank: Super Contributor
timestamp: November 17, 2019, 10:44:58 am
content: The AD9851 is a DDS chip that accepts a clock of up to 180 MHz and generates a sine wave output anywhere between millihertz and half the clock frequency. Without some supporting circuitry around this chip including a CPU to drive it you will not be doing much.Please read the data sheet for the AD9851 againOnce you have the control circuit built then you can generate a range of frequencies and perhaps see the response of RF filters using your oscilloscope.
ADA2200 Working - Page 1
Forum section: electronics / beginners

author: john1998
author_rank: Newbie
timestamp: June 13, 2018, 08:50:05 am
content: I am trying to understand how ADA2200 works using the datasheet. I am getting confused because the components specified in it works for digital electronics but it is also said that no ADC is being used and something called Analog Sampling Technology is utilized. It will be very helpful if anyone could help me understand how the entire thing functions and how everything falls into place.

author: JS
author_rank: Frequent Contributor
timestamp: June 13, 2018, 08:59:03 am
content: Theory of operation isn't enough?I haven't read the whole thing, but it should work as old days analog demodulators did, but controlled by a digital port to change the parameters, signal path is fully analog. Discrete sample time is probably archived by a sample and hold system with a chain to hold a few samples but never digitalized, meaning the instant voltage is stored in a cap or someting but never converted to discrete numbers. Then, with many samples stored, mixing them makes a filter that you can control with digital signals, changing the path of the signals to different routes.Something like that?JS
Adapt JBC Nano Handpiece - Page 1
Forum section: electronics / beginners

author: Mike_P
author_rank: Newbie
timestamp: October 25, 2017, 01:49:16 am
content: Is it possible to adapt a JBC nano handpiece to run on one of their standard stations?Thanks,

author: stylius
author_rank: Contributor
timestamp: February 28, 2018, 08:34:39 pm
content: Hello. Do you got some info about it? I am interesting too.
Adapter for Radio Audio Adapter?! - Page 1
Forum section: electronics / beginners

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 31, 2020, 05:27:11 pm
content: HiI have a bunch different Radios who use all a different Plug type.And there is that Hytera who use even a total different design:https://ae01.alicdn.com/kf/HTB1kpyVhPoIL1JjSZFyq6zFBpXay.jpg?size=88122&height=1000&width=1000&hash=058400c1b9eb4f9060c5fd1066bba7d6So I got the idea why not make my own Adapter for aka order some PCB and solder the connector together.Challenging enough. To figure out what the Pin Layout of each Radio is can I use a Multimeter on the Headphones and see which pin is get up on a continuity mode?Thanks

author: zakk
author_rank: Newbie
timestamp: January 01, 2021, 09:27:36 am
content: Hello mate. I'm assuming your radios are for two way/Ham use, due to the brand you've mentioned.You can buzz them out with a multimeter on cont mode, it just can be a PITA. You'll want some small clips for your multimeter leads, to be able to press the PTT etc to confirm the wiring (I'm not sure about you, but I sadly only have two hands)You're other option which has worked for me in the past, is to google the radio's pinout. You quite often find them published on Russian sites oddly.If you are trying to use one mic and speaker for multiple radios, you might hit an impedance issue. Different manufacturers use different impedance values and some incorporate different PTT arrangements.I apologise if I've misinterpreted your question, but I'm happy to offer what advice I can.
Adapter for RF generator to coaxial - Page 1
Forum section: electronics / beginners

author: stafil
author_rank: Regular Contributor
timestamp: June 03, 2020, 09:59:08 pm
content: Any idea what adapter do I need to connect this to my scope:https://www.ebay.com/itm/35MHz-4000MHz-RF-Signal-Generator-Signal-Source-ADF4351-VFO-HXY-D6-V1-02-50-ohms/362852575960

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: June 03, 2020, 10:02:27 pm
content: One of these.SMA to BNC jumper.

author: graze
author_rank: Newbie
timestamp: June 04, 2020, 11:52:22 am
content: Yeh its a SMA connection heres a better picture fyihttps://www.rclife.co.uk/Frsky/Frsky-Accessories/Frsky-90-Degree-Antenna-Adapter

author: Mechatrommer
author_rank: Super Contributor
timestamp: June 04, 2020, 12:01:45 pm
content: Quote from: graze on June 04, 2020, 11:52:22 amthats not any better

author: KMoffett
author_rank: Regular Contributor
timestamp: June 04, 2020, 05:37:21 pm
content: If it's just function generator to scope, ground_loop showed the correct adapter.

author: WattsThat
author_rank: Frequent Contributor
timestamp: June 04, 2020, 05:45:27 pm
content: Don’t ignore the generators 50 ohm output impedance. A typical scope is 1 Meg so the output amplitude will likely be wrong when loaded at that 1 meg rather than the correct 50 ohm load.

author: tkamiya
author_rank: Super Contributor
timestamp: June 07, 2020, 03:10:42 am
content: That is an SMA connector on the board. Keep in mind, SMA connectors are NOT designed for frequent connect/disconnect cycle, and not mechanically very strong.What I would recommend is to buy a short cable SMA male to BNC female. Make sure there are no stress on SMA side.

author: stafil
author_rank: Regular Contributor
timestamp: June 07, 2020, 04:11:48 am
content: Quote from: WattsThat on June 04, 2020, 05:45:27 pmThanks, I got a BNC-T adapter and 50ohm BNC terminator. I should be ok, right?

author: stafil
author_rank: Regular Contributor
timestamp: June 07, 2020, 04:13:39 am
content: Quote from: tkamiya on June 07, 2020, 03:10:42 amIt's just a cheap $20 RF generator I got from eBay, thanks I'll keep it mind. Wouldn't want to break it before I even try it once.
Adapter question VSSOP and SSOP to DIP - Page 1
Forum section: electronics / beginners

author: Chris Wilson
author_rank: Super Contributor
timestamp: February 05, 2018, 02:29:21 pm
content: If I buy VSSOP to DIP adapter PCB's will I also be able to mount SSOP devices to them, or do SSOP and VSSOP have different pin spacings? Thanks.

author: Peabody
author_rank: Super Contributor
timestamp: February 05, 2018, 03:05:49 pm
content: I'm not familiar enough with those packages to say, but if you do find they don't match, you may be able to find an adapter that has one pattern on one side of the board, and the other on the other side. So in effect two single-sided boards, with both sides connected to the DIP pins. I found those for SOP and TSSOP, and got the 20-pin version, which of course works for that size and anything smaller. Just gives you a bit more flexibility.
Adaptive liquid crystal glasses for epilepsy sufferers. - Page 1
Forum section: electronics / beginners

author: BJ
author_rank: Newbie
timestamp: October 08, 2016, 02:50:02 am
content: I had a random thought when reading how a certain type of internet lowlife has been sending seizure inducing videos to known sufferers.I'm sure you're familiar with the original Hitchhiker's Guide to the Galaxy series, and the novelty device in it called the Joo Janta Peril Sensitive Sunglasses, which work on the principle of the Ravenous Bugblatter Beast of Traal, which isQuoteIn the presence of danger, the sunglasses of course immediately become opaque, rendering the wearer oblivious to all possible harm.I'm thinking a liquid crystal lens, actuated by a small microcontroller could sense rapidly strobing light of the sort epilepsy sufferers are sensitive to and block it completely, or potentially flatten the light curve to something tolerable, perhaps even smooth it out altogether.This started out a little tongue in cheek, but I'm thinking liquid crystal technology (you're looking at it right now I'm sure) has advanced to the point that driving glasses capable of completely nullifying street light and shadow strobing effects should be easily and cheaply feasible. One could even face down a Nullarbor trucker's "wall of light" with impunity.^^^^^^^^And just in case no one has thought of it before. Prior art Patent Trolls. MAKER Community, have at it.
ADC (AD9214) how to use and how dose it work. - Page 1
Forum section: electronics / beginners

author: Austin
author_rank: Newbie
timestamp: June 18, 2024, 02:11:00 pm
content: Hi!I'm learning how to use the AD9214 ADC IC.This IC is not recommended for new design but i have few laying around so i decided to use it.The IC works on single rail power and datasheet says it can read 2Vpp analog signal.My question is , is it possible to tie the negative input(Ain~) to ground and send in +/-1Vpp signal in to the positive(Ain) input and measure correctly?And could anyone teach me how this figure22 circuit work?

author: xvr
author_rank: Frequent Contributor
timestamp: June 18, 2024, 04:52:51 pm
content: QuoteNo. No any inputs can goes below ground.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 18, 2024, 05:02:44 pm
content: Fig. 22 is there mainly to illustrate how input protection and input impedances work. Actual device may or may not actually works as illustrated.Good practices are to never intentionally forward bias any of the diodes. Keep Vin between supply voltages. Don't go below Vss, don't go above Vdd. If you need bipolar input then either shift Vss down, or shift your signal up.

author: Austin
author_rank: Newbie
timestamp: June 18, 2024, 10:25:22 pm
content: Thank you for your reply !Another question came up in my mind by reading your reply.If I offset both Ain and Ain~ to half the Vdd, will it work fine?

author: Kim Christensen
author_rank: Super Contributor
timestamp: June 19, 2024, 04:34:32 am
content: You want to bias the inputs at 1/3 of AVdd as described onpage 15 of the datasheet.
ADC, 4 PCB layers - Page 1
Forum section: electronics / beginners

author: Tantalum
author_rank: Regular Contributor
timestamp: July 01, 2022, 06:28:18 am
content: HelloJust one dumb questionTake a 4 layer PCB, with GND on layer 2 and PWR on layer 3. This PWR layer is divided in 3.3V and 24V blocs.Now, if I add an ADC IC which is powered by 3.3V, on layer 1, can I place it over a zone where layer 3 is 24V or is this is a bad practice?I make the assumption that layer 2 has a perfect uniform ground over the whole PCB, in other words, the return path is fine.Thanks

author: Faranight
author_rank: Unknown
timestamp: July 01, 2022, 07:30:16 am
content: If there is a uniform ground plane underneath then it shouldn't be a problem. Just make sure you decouple the ADC power/reference pins properly.But generally, in multilayer PCB's it's a good idea (from EMI perspective) to alternate between ground and non-ground planes i.e. you want every second layer to be a ground layer. I suggest you go to youtube and watch some of the Rick Hartley's videos on PCB and EMI design. Then again, this is normally a problem with high speed circuits. DC should be fine.

author: Tantalum
author_rank: Regular Contributor
timestamp: July 01, 2022, 08:14:31 am
content: Thanks for your answerYes, the ground plane is fine:I will need to move the ADC to the right over the 24V layer.The power monitor IC, is already on that layer.I haven't done any separation between analog and digital ground, I don't actually need highly precise measurements.

author: Faranight
author_rank: Unknown
timestamp: July 04, 2022, 08:19:08 am
content: Hmm, your clearance between traces/vias and the copper pour seems rather large. Any specific reason for that? You could probably reduce it a bit.I'm assuming this is a 4 layer board (edit: duh, its in the title), and that those resistors/caps are 0805. Just remember to keep the MLCC caps close to the pins they're supposed to decouple (power and ground).Ideally you want a connection from an IC power pin over a decoupling cap over to the IC GND pin on the same layer of the board. Put a grounding via or two close to the ground pin.I can't see what those parts are because the solder mask is apparently underneath the elements. Your software should probably complain about that.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 04, 2022, 09:24:32 am
content: Quote from: Tantalum on July 01, 2022, 06:28:18 amI stopped reading right there.I do not answer dumb questions.Bye.
ADC Datasheets - Page 1
Forum section: electronics / beginners

author: backd00r
author_rank: Contributor
timestamp: April 18, 2017, 12:27:52 am
content: sampling rate

author: Ian.M
author_rank: Super Contributor
timestamp: April 18, 2017, 12:58:31 am
content: No. It depends on the ADC's architecture. Seehttps://www.maximintegrated.com/en/app-notes/index.mvp/id/1023
ADC driver using differential op amp with negative voltage input. - Page 1
Forum section: electronics / beginners

author: DanioIO
author_rank: Contributor
timestamp: March 03, 2015, 06:00:58 pm
content: Hi,I have an ADC driver based on AD8138 it is supply with 3.3V and GND. My circuit is based on Texas instrument document sloa098 shown on a picture bellow. My main question is can I measure negative input voltage with this circuit without blowing my op amp? The input voltage will be in range of +-3V.

author: JoeAtl30319
author_rank: Contributor
timestamp: March 04, 2015, 12:55:55 am
content: It looks like you're trying to measure a 6v P2P signal even though your supply is only operating on essentially 3v P2P. The first problem you'll have relates to the fact that if you measure something like -3 volts referenced to ground, you'll hit the negative supply rail on the op amp (I'm ignoring component values, as they're not listed, to make this assumption). I don't know if the particular op amp you're using will blow up, but at best the the output of the op amp will simply be ground and you'll loose data. To avoid this, you'll need to "compress" the input signal, maybe by using an attenuator so the input signal is only 3v P2P to the op amp. After attenuating the signal, you'll need to "bring up" the signal, using the resistive network connected to the power rail after C1, so the lowest negative excursion never goes below ground. Something like 1.5 volts after C1 may work with the attenuated signal.Alternatively, and possibly easier, would be to give the op am a negative supply rail of -3 volts. You'll need to adjust the ADC references so it gives you the correct output, but it may be your best bet unless you're absolutely committed to using a 3volt supply.

author: Dave
author_rank: Super Contributor
timestamp: March 04, 2015, 01:19:45 am
content: Why do I have the feeling that he wants to measure a DC signal with this circuit?This circuit is intended for AC signals, you have a termination resistor and an AC coupling capacitor on the front.

author: JoeAtl30319
author_rank: Contributor
timestamp: March 04, 2015, 01:32:22 am
content: Dave is correct, this circuit will only work for AC signals. If you measure -3volts DC, you will not get any output to the ADC as a DC signal will not pass through C1.
ADC for strain gauge measurement - Page 1
Forum section: electronics / beginners

author: A2
author_rank: Contributor
timestamp: August 11, 2014, 01:12:48 pm
content: I have strain gauge of 1K, 50000 microstarin , & Gf = 2, so for 1 microstarin change in resistance is 2milliohm.I am using external reference created by IDAC current on reference pins1. Currently i am using ADS1248, by directly passing 50uA through strain gauge without any bridge, with PGA = 32So ideally at 1000ohm i.e 0 strain, voltage is 50000 microvolt& 1 microstain voltage is 50000.1 microvolt. So change of 100nV.Will ADS1248 will be able to sense such small changes?2. If not, is there any ADC which can do this job better3. Is is correct method to directly send current across strain gauge & measure change in resistance rather than brigde

author: tszaboo
author_rank: Super Contributor
timestamp: August 11, 2014, 01:41:53 pm
content: If you look at table 5 from the datasheet, you will see that at 5 SPS you have about 500nV peak to peak noise on your ADC, so your measurement will be deeply buried in the noise. Since your susceptibility is so low, I would use the the bridge + Instrumental amplifier + general purpose ADC method.

author: David Hess
author_rank: Super Contributor
timestamp: August 11, 2014, 02:51:29 pm
content: You really need a half or full bridge even if only one element is active so that you can raise the excitation current or voltage while canceling out the offset. Otherwise you are measuring 100 nanovolt changes on top of 50 millivolts. Just balancing the 1000 ohm strain gauge with a trimmed 1000 ohm precision resistor and bipolar reference would be a great improvement.There is not much improvement to be had with the ADS1248.
ADC for Thermopile based IR image sensor - Page 1
Forum section: electronics / beginners

author: sangar
author_rank: Regular Contributor
timestamp: February 16, 2019, 08:00:07 am
content: Hello All,I am looking for an ADC which converts analog output from my ML8540 (48 x 48 pixels) IR image sensor that supports 6fps. How should be my ADC ?. I am struggling to get clear information from ML5840 such as the rate of temperature change (I assume "resolution" for this) and step voltage ( I assume "IR sensitivity VIR" for this ) for it. The product spec I have says the "resoultion" is 0.5C @ 4fps and "IR sensitivity VIR" is 400uv. Does it means a 0.5C change in temperature will give a rise of 400uV in analog output.Also, it says the "Measurement range" is -30 to 300C.I think, a voltage (0 to 5V) will be fed at Neagative bias pin is equal to -30C.So, for 300C, it will be 132mV.As for sampling rate required from the ADC, 1 frame consist of 2256 pixels, 6fps=13536 pixels.So,the ADC I will select should have an ODR greater than >13.536 Ksps.Is my understanding correct?.Please correct me if I am wrong. For your reference, I attached the link for the product spec I am referring...http://symmetron.ru/suppliers/lighting/files/lighting/components/ir-sensors/infrared-array-sensor/ML8540.pdf]http://symmetron.ru/suppliers/lighting/files/lighting/components/ir-sensors/infrared-array-sensor/ML8540.pdfThanks,Sangar
ADC INL error - Page 1
Forum section: electronics / beginners

author: JoeyG
author_rank: Regular Contributor
timestamp: October 29, 2023, 12:14:12 pm
content: I'm trying to work out the INL error percentage from a ADC data sheet as a percentage.If the datasheet saysVdd_ref =- 3v0 (FSL full scale reference)ADC INL is -+2LSBAssume zero offset errornumber bit is either 8What is the percentage error acceptable at V_adc = 1VHere is my calculationsfor 8 bit ~ 256 levelsADC LSB is = Vdd_ref/256 = 0.012V = 12mVFor the 1v ADC reading it can be:Reading low 1v-2LSB = 1v -2x12mV = 0.976 IE -2.4%Reading high 1v-2LSB = 1v _ 2x12mW = 1.024 IE +2.4%IE the Error can be _+2.4%

author: radiolistener
author_rank: Super Contributor
timestamp: October 29, 2023, 01:05:13 pm
content: 2 LSB * 3 V / 256 = ±0.0234375 = ±2.34375 %

author: Andreas
author_rank: Super Contributor
timestamp: October 29, 2023, 09:53:28 pm
content: No,Inl is defined as best straigth line. (you are assuming the end point method).So deviation from actual value may double.See figure 4 here:https://www.allaboutcircuits.com/technical-articles/adc-integral-nonlinearity-inl-best-fit-line-inl-definition-absolute-accuracy-relative-accuracy-and-total-unadjusted-error/with best regardsAndreas
ADC input level offset circuit - Page 1
Forum section: electronics / beginners

author: dadler
author_rank: Unknown
timestamp: January 17, 2016, 10:50:34 pm
content: Hi-I am working on a project, where I wish to sample the supply voltage to a subcircuit.The voltage range is 14-16V. I want to scale and offset this to be sampled by a 0-5V ADC input (I may end up using a 4.096V external reference for the ADC, but the ask is the same regardless). The bandwidth can be extremely low, as I am only interested in slow changes to the supply voltage.I have come up with the following two circuits:1) Scale/offset with non-inverting op amp:2) Use TL431 as regulated offset voltage (could also scale to full range with another op amp):The tempco of the TL431 is pretty terrible, but the gain required by the first circuit makes me uneasy from an accuracy/noise perspective.Which of these is better? Is there a better way of doing this?Thanks

author: dadler
author_rank: Unknown
timestamp: January 18, 2016, 12:53:40 am
content: Thanks for the insight. What you have proposed isn't far off from what I have configured in my layout right now (May replace BAT54 with BAV99 due to leakage)Although it seems you've added a couple of caps for additional filtering/transients?According to the datasheet, the TL431 isn't stable with a capacitive load--but I could not get the circuit above to oscillate, even with a wide range of load capacitance. I also breadboarded a version with capacitance across the TL431 as you have done in your circuit, and it was stable as well.
ADC – LDR Light Controller – Arduino for Beginners - Page 1
Forum section: electronics / beginners

author: Radhuvir_G
author_rank: Newbie
timestamp: November 22, 2014, 07:40:43 am
content: since in the below link the LDR was used for light detection….Can solar panel used as LDR??it is possible or not...........http://www.ingenstech.com/9-adc-ldr-light-controller-arduino-beginners/

author: Simon
author_rank: Unknown
timestamp: November 22, 2014, 07:42:14 am
content: why don't you try it ?

author: Seekonk
author_rank: Super Contributor
timestamp: November 22, 2014, 09:37:09 am
content: Yes it can. I have used little calculator types and monitored the voltage. In a simple dusk to dawn application they can be fed into the A/d pin as long as the open circuit voltage is below 5V. In applications where you want to measure actual light level, a resistor load must be placed on them. This is because a solar panel is actually a current source.
ADC mode of operation: CPOL and CPHA - Page 1
Forum section: electronics / beginners

author: raff5184
author_rank: Regular Contributor
timestamp: May 07, 2019, 05:21:29 pm
content: HiI'm trying to understand the mode of operation of the ADS 7883 ADC converter.http://www.ti.com/lit/ds/symlink/ads7883.pdfBut from the diagram on page 9, I can't actually tell because the SDO data are not exactly in correspondence of the falling or rising edge of the SCLK.I think the CPOL is 1 (look at the beginning of the SCLK signal, it's high) but what about the CPHA?Thank you

author: imisaac
author_rank: Regular Contributor
timestamp: May 10, 2019, 07:18:58 pm
content: Looking at the timing diagram of the datasheet, the data bit is sampled at the falling edge. So, I guess the CPHAS=1.That is, I think that the SPI mode 3 (CPOL=1, CPHAS=1) may work for this ADC.

author: raff5184
author_rank: Regular Contributor
timestamp: May 10, 2019, 07:51:11 pm
content: that's what I eventually realized.Another question, can I use a CLK at 4 MHz or 8MHz, or do I necessarily need to use a 32MHz clock (at 3.3V)?

author: Bassman59
author_rank: Super Contributor
timestamp: May 10, 2019, 08:58:56 pm
content: Quote from: raff5184 on May 10, 2019, 07:51:11 pmThe SPI clock also determines the sample rate, so if your application can work with a reduced sample rate, then it should be fine.
ADC on an STM32 and high voltage inputs - Page 1
Forum section: electronics / beginners

author: roogadget
author_rank: Contributor
timestamp: September 26, 2018, 04:32:17 am
content: Hi,I am designing a sensor device.The sensor takes in a input voltage between 0 - 12 V. I need to do some magic in the middle to get it into the ADC pin (say >1V low, 2.5 High).What is the typical way to do this?

author: ataradov
author_rank: Super Contributor
timestamp: September 26, 2018, 04:48:37 am
content: Not clear why you don't want to have the lower level to be 0 on the MCU side as well. This way a simple resistor divider may work.If the signal is fast changing and you want to reduce noise, then opamp to buffer the divided signal before the MCU. This will ensure consistent impedance matching.
adc  opamp  frontend  - Page 1
Forum section: electronics / beginners

author: 5282
author_rank: Regular Contributor
timestamp: March 10, 2017, 07:29:00 pm
content: hi,1-why ADC op-amp use -5v 0v +5v supply power why not use single supply??2-the -5v 0v +5v connected to low voltage 3v ADC that's mean more op-amp gain can damage the high cost ADC ?

author: rstofer
author_rank: Super Contributor
timestamp: March 10, 2017, 08:25:49 pm
content: You can buy single supply op amps, they are all over the place. You can, in fact, use any dual supply op amp in a single supply configuration.One thing you need to watch out for with single supply op amp circuits is how you bias the signals to get the op amp up into the middle of its range (if your input is actually AC).With the lower supply voltages, you will need to make certain you buy rail-to-rail input/output op amps.Google for "Op Amps For Everyone" and read chapter 4.

author: 5282
author_rank: Regular Contributor
timestamp: March 10, 2017, 08:50:01 pm
content: Quote from: rstofer on March 10, 2017, 08:25:49 pm1-thank you i will use it with ADC so the single supply will be same as dual supply ?2-the ADC is 3v and op-amp may damage ADC if i make wrong gain with an input ??

author: danadak
author_rank: Super Contributor
timestamp: March 10, 2017, 09:39:04 pm
content: In CMOS if you exceed ~ 1 diode drop beyond either supply rail, you can triggera parasitic SCR internal to CMOS structure, that in turn shorts internally thesupply rails and usually blows open the bond wires for Vcc/Vdd and Vss.https://en.wikipedia.org/wiki/Latch-upIf the SCR not triggered you can still damage the parasitic diode internal to CMOSwith excess current, depends on the source that is driving the pin, eg. its currentcapability.You can add external schottky diodes at pin, and a series R to pin from source voltage beingmeasured to protect against over voltage, and excessive loading of OpAmp output.Or a voltage divider to scale the input. Note if you add series R that may effect A/Dconversion settling time for its input sampler, so be aware of speed you run it at.Some methods of offsetting inputs.https://www.dropbox.com/s/k1yn4m7heaixvmg/ADinput%20negative%20inputs.zip?dl=0Regards, Dana.

author: 5282
author_rank: Regular Contributor
timestamp: March 10, 2017, 10:12:08 pm
content: Quote from: danadak on March 10, 2017, 09:39:04 pmthank you
adc  opamp interface - Page 1
Forum section: electronics / beginners

author: 5282
author_rank: Regular Contributor
timestamp: February 04, 2017, 02:11:24 pm
content: i'm poor man and i not have money to buy new oscilloscope so i will make onepleas help memy adc is 5v reference 5v/255=about20mvin some case the signal not swing from 0 to 5v may be from 4v to 5vand as example i want opamp amplifying the signal swing from 4v to 5v to swing from 0v to 5vthis picture will explain what i meanfirst as example the sine wave swing from 4v to 5v that's mean 1vppand i want opamp convert the signal from 1vpp to 5vppwhat must i learn to do this

author: Brutte
author_rank: Frequent Contributor
timestamp: February 04, 2017, 03:22:19 pm
content: You need a so called "analog front-end".This is basically something that can:a) shift a signal (offset)b) attenuate/amplify the amplitudec) match impedances of source and sinkd) filter out unnecessary components.As for examples:a) sine that is 3V centred can be offset by -1V to be 2V centred.b) 1 V square wave can be amplified twice to become a 2V square wave.c) if the source of the signal is a tiny potentiometer and you need to control a 100W DC motor with that then even though voltages ranges may match, direct connection won't work without something that can accept a signal of kohm input resistance and can output a mohm signal for powering DC motor. BTW, ADCs usually need <1kohm signals and many sensors do not offer less than 10k output resistance so even though the span is smaller - same rules apply.d) a 0V:5V 1kHz sine fed to the ~1sps ADC returns junk. You need to get rid of everything that sticks well below 0.5Hz to be able to get a reasonable 2.5V on the output.Now a simplest analog front end can be made with passives but unfortunately it is very limiting w.r.t the gain (only attenuation possible) and matching impedances.I suggest you should get a rail2rail output opamp (like MCP6004) and studydifferential amplifier. You can make any offset, any gain and any reasonable input and output impedance with that configuration, it is only a matter of picking right resistor values.

author: 5282
author_rank: Regular Contributor
timestamp: February 04, 2017, 08:20:02 pm
content: thank youi want simple circuit to study it.

author: danadak
author_rank: Super Contributor
timestamp: February 04, 2017, 11:22:28 pm
content: Here is a sound card oscilloscope, freebee. You need to protectsound card inputs, so google "sound card input protection", a numberof hits. Its is also a function generator, you might need to use OpAmpscaling on sound card output so you can offset it for use in digitalcircuit work.https://www.zeitnitz.eu/scope_enhttp://www.zelscope.com/Regards, Dana.

author: Rerouter
author_rank: Super Contributor
timestamp: February 04, 2017, 11:29:51 pm
content: What your describing is 2 parts, 1 an AC coupling measurment (generally done with a capacitor), and an amplifier.

author: rstofer
author_rank: Super Contributor
timestamp: August 05, 2017, 04:23:42 am
content: Chapter 4 of Op Amps For Everyonehttps://focus.ti.com/lit/an/slod006b/slod006b.pdf
ADC over range input.. ADC is broken already ? - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: July 12, 2017, 05:09:21 pm
content: Hello !i have question. please, let me know..i have stm32f051 discovery board.before, for digital LPF, i used 5V square signal via function generator.problem is this. stm32 Vref is 3V. 5V is already 2V over voltage.and function generator output impedence is 50 ohm.it's already 40mA input to ADC comporator...i'm now not in university hostel.. so i can't test now..i want know your opinion about my board ADC status...please answer about my question, plase, let me know.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: July 12, 2017, 05:28:02 pm
content: 5V with a 50R source impedance into a 3.3V part isn't too bad. It could have killed it, but I don't think it would happen instantly, how long did you keep it connected?However, are you sure the output is 5V? Most 50R sources will actually put out twice they voltage they claim, under the assumption that you'll be connecting them to a 50R load and the divider will drop the voltage in half to the claimed value. It's entirely possible the function generator was actually putting out 10V, unless you've measured it to confirm. 10V with a 50R source impedance into a 3.3V part will almost certainly blow the pin IMO.

author: ammjy
author_rank: Regular Contributor
timestamp: July 12, 2017, 05:35:07 pm
content: Thanks you so much, your answer Mr. suicidaleggroll !yes. im sure and remember signal was 5V. and i did connect in 10 minuite..(oh.. actually after read your answer. i'm not sure signal was 5V... actually i don't know well my function generator how work in his inside... my one is cheap from aliexpress..)and i didn't saw any blow from pin. after lab works, i erased successfully flash stm32.again, thanks a lot !
ADC over-voltage protection - Page 1
Forum section: electronics / beginners

author: rexxar
author_rank: Frequent Contributor
timestamp: April 19, 2014, 11:26:48 pm
content: As the title says, I need to protect some ADC inputs from over-voltage. This is something that I'm giving children (8-9 years old) to play with, and there is a non-zero chance that 9V is going to get put up the ADC input.Basically, the uC is reading voltage drop across a type of conductive play-dough (nominally several Kohm), and PWM driving either a speaker or RGB led. The kids also have a 9v battery they use to light up LEDs, and so far, about half of them have put the uC input in the same piece of dough with the 9V battery.So, what is the easiest way to do this? A zener diode, maybe? Ideally, I'd like it to either short to ground, or have the ADC input go open circuit, to make the thing 'not work', but that's not terribly important. (For reference, the uC is an ATmega88)

author: Marco
author_rank: Super Contributor
timestamp: April 19, 2014, 11:36:56 pm
content: 1 kOhm series resistance and a couple red LEDs to ground?

author: Simon
author_rank: Unknown
timestamp: April 20, 2014, 07:13:06 am
content: don't forget reverse voltage and remember that 1K is about as much source impedance as the inputs can take

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 20, 2014, 07:24:28 am
content: http://www.analog.com/en/interface-isolation/protection-products/adg465/products/product.htmlanalog sells a number of adc input protection products that you might find more convenient then doing it yourself.
ADC pin protection - Page 1
Forum section: electronics / beginners

author: stafil
author_rank: Regular Contributor
timestamp: April 27, 2020, 01:01:23 am
content: Very simple and stupid question.If I want to use my MCU's ADC pin to sense Voltage, how do I protect it? Shall put a rail-to-rail OpAmp in front of it and use it as a buffer? Or is some other, cheaper or better way?Edit: I guess a Zener diode should do the trick?

author: Manul
author_rank: Super Contributor
timestamp: April 27, 2020, 01:31:36 am
content: Simple solution would be to use current limiting resistor and clamping diodes (schottky diodes recommended) to gnd and vcc. There are many SMD dual diodes like a BAT54S ready made for such purpose. If you use really high current limiting resistor you may omit the diodes and ESD protection diodes of MCU will do the job (simplest, not very professional).In very high accuracy or high bandwith applications you may be interested in analyzing the influence of such protection circuits (it will have some).

author: Siwastaja
author_rank: Super Contributor
timestamp: April 27, 2020, 06:49:54 am
content: Manul's circuit isn't complete as is (or will be very inaccurate, and fail as soon as you start multiplexing other ADC inputs).You need lower impedance to drive the ADC.For low-bandwidth, low sampling rate applications, the cheapest and most obvious way is to add a capacitor from ADC input pin to ground, say at least 100nF. Then you need to limit the sampling rate, so don't configure the ADC to do automatic conversion at high sample rate. Instead, run conversion at, say, 10, maybe 100 samples/second, which is just fine for battery voltages, thermistors etc.If you need high sample rates, use an opamp buffer to drive the ADC.Also remember that the clamping diode to Vcc has a very real risk of increasing the Vcc bus voltage, thus destroying everything. Calculate carefully! For example, if the input has a risk of being at 10V, and Vcc=5V, current of (10V-5V)/1kOhm = 5mA will flow. If the Vcc is loaded at less than 5mA, the voltage will rise.
AFE range switching design review request - Page 1
Forum section: electronics / beginners

author: Bootalito
author_rank: Unknown
timestamp: February 06, 2018, 09:30:51 pm
content: I'm designing a 200W 30A 150V Electronic DC load. Below is my voltage input AFE design.It has two ranges a 0-150V and a 0-15V range simply switching in a different "taps" on a divider network.Can I get people to critique please.

author: max_torque
author_rank: Super Contributor
timestamp: February 06, 2018, 10:21:17 pm
content: hmm, not sure about that way to be honest!Your fets need to be driven with a high side driver because they float on the input to the ADC, and you have no series R between your input protection (BAT54 (leaky!) and Zeners) and the ADC input, so all that will happen is the internal diodes in the ADC will do the clampingI'd have a fixed 50:1 input divider with precision resistors, buffered by an op amp, with two gain settings 1:1 and 10:1, feed that into the ADC input, through a suitable AAF (depending on your sample rate and bandwidth requirements)

author: max_torque
author_rank: Super Contributor
timestamp: February 06, 2018, 10:25:44 pm
content: I'd also add that anything you might connect to a 150v input is (highly) likely to contain more than 150v and hence you should design (creepage/clearance/component ratings) you input to safety survive far more than that (300v wouldn't be un-typical)

author: Bootalito
author_rank: Unknown
timestamp: February 06, 2018, 11:26:39 pm
content: Quote from: max_torque on February 06, 2018, 10:21:17 pmDuh..of course. There Vgs would be...nothing...anything...wouldn't work. By high side are you talking about a pchannel mosfet? How would I drive that to not exceed Vgs?As far as the op amp buffer what do you think of a diff op amp configuration in unity gain:Quote from: max_torque on February 06, 2018, 10:25:44 pmI've been moving things around on my PCB a bit just to see where things fit and have been consultingwww.CREEPAGE.com. I'm maintaining 3.5mm to 4.5mm creepage between parts that will regularly see this much deltaV. I've cut around the center pin of the mosfets I'm using as well: