hybridfree/eevblog-posts huggingface dataset:
AD574 Precision Voltmeter Schematic - Page 1
Forum section: electronics / projects

author: Chris56000
author_rank: Frequent Contributor
timestamp: May 10, 2017, 03:22:23 pm
content: Hi!I get, in my job, quite a number of industrial panels for repair, in which the AD574JN pops up, and as remaining supplies of this device are into three figures,I have been looking for a circuit I can make to test it!I have came across a number of links for a "High Precision AD574 Voltmeter Schematic that all appear to be this:-http://8085projects.info/ad574-based-high-precision-digital-voltmeter-circuit.htmlbut I can't seem to find any source or hex to go with it!Does the Microcontroller used here need to be programmed, and has anyone come across the original article that had the code please?I found this attachment, but it's password protected and the site "developer downloads"http://developerdownload.info/958211/I got it from gives no indication of what the password is or how to register for it!Any ideas?Chris Williams

author: Kleinstein
author_rank: Super Contributor
timestamp: May 10, 2017, 05:09:56 pm
content: The voltmeter circuit will likely only use a few of the input channels and also likely not the full functionality. So one would need a different software to do a more thorough test anyway. For a test it also takes something like a test signal - e.g. a slow ramp or a reasonable quality triangle and maybe a few fixed values.
AM6012 vintage DAC help - modifying vintage DSP gear - Page 1
Forum section: electronics / projects

author: ChristofferB
author_rank: Frequent Contributor
timestamp: April 24, 2018, 08:45:52 pm
content: So i've gotten a mid-80's studio reverb unit that i've been messing around with, z-80 based, and has a 12 bit DAC - AM6012.I got the idea that it'd be interesting to be able to force individual bits to 0, so that the resolution of the DAC could be lowered by forcing the LSB's to 0, or introduce glitches, but I don't understand the description in the datasheet -it seems that the 4 MSB's are different from the rest, needs a separate register and register clocking strobe.Would me forcing some of these bits to 0 inhibit operation alltogether?This is what I plan to put on a small pcb that plugs into the ADC socket, which in turn has a new socket, see attached. Of course, i'll have similar channels for all bits.The reason i'm not just putting a switch in line with the pins and a pull-down is that i want to have the switches on a separate 19" panel, and i dont think the DAC would enjoy 30-cm leads.Thanks in advance!
AD620 for shunt current measurement - Page 1
Forum section: electronics / projects

author: antepf
author_rank: Newbie
timestamp: April 04, 2017, 04:03:25 pm
content: Hello! I would like to measure the current using shunt resistor, as shown in the schematic. I want to amplify the voltage drop over the shunt resistor. I tested the circuit but I observed that the gain is not constant.Where do you think is the problem?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 04, 2017, 04:20:47 pm
content: With INAs one usually needs to connect the ref input. The other point is that there is a limited common mode range. So it is a good idea to have a defined DC level for the input side, by something like having one side of the shunt connected to GND of the INA side - they can't be fully isolated.

author: ocw
author_rank: Regular Contributor
timestamp: April 04, 2017, 05:25:33 pm
content: If you want gain you need a gain setting resistor between the two Rs IC pins. The schematic shown appears to be a simplified schematic. The shown battery, power supply and load need to be isolated from (or properly connected to) the AD620's supply. You can see more details at:http://www.analog.com/media/en/technical-documentation/data-sheets/AD620.pdfSomething like a INA240A# or a INA19X might be better for a current shunt monitor.
AD650 replacement ? - Page 1
Forum section: electronics / projects

author: tchiwam
author_rank: Regular Contributor
timestamp: January 16, 2024, 06:52:02 pm
content: Anyone here have good replacement for the AD650 that is not going obsolete ?Linearity:<0.07% @ 1MHz<0.002% @ 10kHzVoltage output can be anything, we can design around it...Input level from 0dBm to +15dBmLooking for something integrated, but hey I might just build one myself if it continues...

author: moffy
author_rank: Super Contributor
timestamp: January 16, 2024, 08:45:13 pm
content: Try TI the VFC320:https://www.ti.com/lit/ds/symlink/vfc320.pdf?ts=1705437675963&ref_url=https%253A%252F%252Fwww.ti.com%252Famplifier-circuit%252Fspecial-function%252Ffrequency-converters%252Fproducts.htmlor the VFC110:https://www.ti.com/lit/ds/symlink/vfc110.pdf?ts=1705437757328&ref_url=https%253A%252F%252Fwww.ti.com%252Famplifier-circuit%252Fspecial-function%252Ffrequency-converters%252Fproducts.html
AD7731 reference input problem - Page 1
Forum section: electronics / projects

author: spencer2004
author_rank: Contributor
timestamp: June 24, 2014, 01:45:58 pm
content: Hi.I am currently making my own multimeter which uses a Linear Technology AD7731 ADC, it requires a +1.25V and -1.25V reference for it to work with bipolar input signals. I have made a circuit that outputs +-1.25V from a 2.5V reference which you can see below:The circuit uses an OPA4227 quad opamp, I forget which reference IC I used.The circuit works perfectly until it is connected to the AD7731; the positive reference seems to be unaffected but the negative reference drops to around 1.05V. I have measured the current going in to (or rather out of) the negative reference input and it drawing 41mA when it's supposed to draw no more than 10uA.There are definitely no shorts from the negative reference to anything and there is a very high resistance from the negative ref pin to ground. I have tried another AD7731 but it has the exact same problem.Does anyone know what is going on? because I really don't

author: jahonen
author_rank: Super Contributor
timestamp: June 24, 2014, 02:22:08 pm
content: Perhaps you mean Analog Devices AD7731, which would make more sense. Anyway, the problem is that you can't connect negative voltages to AD7731, or more precisely, voltages outside range bounded by GND and AVDD.QuoteIf you want to measure negative voltages, you must level-shift the signals such way that they remain between AGND and AVCC. Note that negative voltages can only be measured as differential voltages, but common-mode voltage must be between aforementioned range.Regards,Janne

author: Paul Price
author_rank: Super Contributor
timestamp: June 24, 2014, 03:24:07 pm
content: To output a negative voltage your op-amp Vss negative power pin must be more negative than the output by .5 to 3V (depending on the op-amps your are using.) No -VSS = no negative voltage output.You can measure/amplify any input negative voltage using a single positive voltage supply by simply using an op-amp inverter configuration if your op-amp input range allows operation down to 0-volts.

author: spencer2004
author_rank: Contributor
timestamp: June 24, 2014, 06:19:46 pm
content: Oh wow I feel pretty stupid right about now, I have no idea why I thought I needed a negative voltage reference :/At least I know how I can get it working now, thanks Janne!
AD8034 input ruins voltage divider - Page 1
Forum section: electronics / projects

author: john23
author_rank: Frequent Contributor
timestamp: September 07, 2024, 07:45:55 am
content: Hello,I am trying to use AD8034 as a comparator,P12 is constant DC. as shown in the photos below.I put simple voltage divider to be in the minus of AD8034.However when i connect the voltage divider to the minus of the AD8034 i get 1.6 instead of (12/30)*10=4VWhy the opamp ruins my voltage divider?Thanks.

author: Someone
author_rank: Super Contributor
timestamp: September 07, 2024, 07:55:57 am
content: ABSOLUTE MAXIMUM RATINGSDifferential Input Voltage 1.4 VQuote from: john23 on September 07, 2024, 07:45:55 amDon't!
AD8099 Power Supply Confusion - Page 1
Forum section: electronics / projects

author: MuriTheMyth
author_rank: Contributor
timestamp: May 22, 2024, 07:08:26 am
content: Hello folks, I hope you are well!I'm kinda confused by the statement of AD8099 datasheet. I'm planning to use ±5V supply, does the current values stated refers to current for each rail or combined?Also, should I design the -5V rail against the "short circuit current" or "quiescent current"? AD8099 is the only one drawing -5V and the output is fed into two TLV3601 comparators.Thanks for your time! I've included a clip of referenced datasheet in attachment.Sincerely,Muri

author: mikerj
author_rank: Super Contributor
timestamp: May 22, 2024, 07:34:40 am
content: Quote from: MuriTheMyth on May 22, 2024, 07:08:26 amThe quiescent current of an op-amp flows (conventionaly) from the +Vs to the -Vs pin. Remember that an op-amp has no "knowledge" that it is connected to a split rail supply, it just sees a potential difference from +Vs to -Vs, so from a quiescent current point of view +-5v rails are the same as a 10v single rail.Quote from: MuriTheMyth on May 22, 2024, 07:08:26 amNeither. Short circuit current is an abnormal operating condition i.e. something has already gone wrong at that point. If your -ve rail can't provide enough current to drive the rated short circuit current then it's not going to make anything worse, in fact it will reduce power dissipation in the op-amp. Under normal operation you can expect some current to be going in or out of the op-amp output pin, depending on its load, and if the op-amp is amplifying an high frequency AC signal it's internal power consumption will also increase. You design your supply rails to deliver the total current that the op-amp requires under normal working conditions plus some margin (100% or more wouldn't be unreasonable for very low current rails).

author: aliarifat794
author_rank: Regular Contributor
timestamp: May 22, 2024, 11:01:46 am
content: Design your -5V rail to handle the quiescent current primarily but also consider short circuit conditions for robustness.Your -5V supply should have a margin above the quiescent current requirement and include protections for short-circuit conditions.

author: MuriTheMyth
author_rank: Contributor
timestamp: May 22, 2024, 08:22:01 pm
content: I'm wondering if this combination will work for the negative rail of AD8099. I already have a +6V rail to power drivers and LDOs on the board.Thanks a lot guys for your advice!
AD8232 AFE Fault Condition Protection - Page 1
Forum section: electronics / projects

author: MildInductor
author_rank: Regular Contributor
timestamp: May 20, 2024, 12:38:20 pm
content: Hello, I am looking at the example circuit layouts for the AD8232 AFE. I see that current-limiting resistors are used in series to the electrodes to protect the patient from a fault condition where over 10uA runs through the electrodes. As a thought exercise I am trying to think of a relatively 'foolproof' topology for ensuring that the chance of a 10uA current running through the electrodes is almost 0%. Assume that the AD8283 is powered solely from a 9v battery. Also assume that the current-limit series resistors fail (completely short) and that the AD8283 has some sort of internal failure where the 9v battery rails are shorted to some combination of the electrodes. Although I realise that something would have had to have drastically gone wrong for both failure conditions to occur, I am wondering what another line of protection could be? Perhaps a resistor in series with the 9v battery to limit the current flow to the whole circuit. But then wouldn't limiting the whole circuit to 10uA of current flow be shortsighted, especially if you were to add other ICs in the mix. What other options are there? Some sort of current limiting circuit?

author: whoopigoldberg
author_rank: Newbie
timestamp: June 04, 2024, 05:17:39 pm
content: Quote from: MildInductor on May 20, 2024, 12:38:20 pmIndeed, providing a backup line of protection to ensure that even if both the current-limiting resistors and the internal failure of the AD8232 AFE fail, the patient is still protected from excessive current flow through the electrodes is a wise decision.Your initial notion of connecting a resistor in series with the 9V battery to limit the current flow to the entire circuit is sound. However, as you pointed out, restricting the entire circuit to 10uA of current flow may be overly restrictive. Instead, you may take a more flexible approach.
AD8302 front-end - Page 1
Forum section: electronics / projects

author: ealex
author_rank: Frequent Contributor
timestamp: March 09, 2017, 04:30:59 pm
content: helloi'm planning to make a simple / low quality VNA based on the AD8302 chip from analog:http://www.analog.com/media/en/technical-documentation/data-sheets/AD8302.pdfthe entire thing will run up to 50MHz, that's the limit of the DDS i've already built.reading the documentation i understand that, for the best range, both inputs should be at -30dBm if both signals are equal, as the allowed input range is [0 .. -60dBm]that will allow measuring 30dBm gain or 30dBm loss in one go.i'm thinking of making the input stage like this:the idea is to extend the range of measurement via SW1 and SW2:- SW1 and SW2 opened -> 60dBm of attenuation, it can measure gains of mostly 60dBm- SW1 and SW2 closed -> 0 dBm attenuation, it can measure DUT attenuation down to 60dBm- SW1 closed and SW2 opened -> 30dBm attenuation, it follows the datasheet recommendationthe main problem is that i don't know how to choose the relays for SW1 and SW2 - grab the cheapest RF / small signal relay ? or look after some specific parameters ?also, is the entire thing work trying to do ? or i should just use coaxial attenuators inserted in front of the entire thing ?
CMOS opamp overshooting? - Page 1
Forum section: electronics / projects

author: federunco
author_rank: Newbie
timestamp: May 21, 2021, 04:02:07 pm
content: HelloFor my final high school lab report I'm making a project that involves opamps, as this project needs to be powered by a battery, I've chosen a single supply-ready opamp, the AD8609. I've coupled the stages with a coupling capacitor, but I've quickly realized that this generates some sort of overshoot on the output, by removing it the overshoot disappears and the circuit behaves normally.Here's the circuit I've used:Here's the output signal with the coupling cap:Here's the output without the capacitor:I'm trying to explain why the coupling capacitor causes overshooting but I can't derive any transfer function of the inverting amplifier, can someone here suggest me how to do it?

author: David Hess
author_rank: Super Contributor
timestamp: May 21, 2021, 05:41:39 pm
content: If you have a single supply operational amplifier, and the non-inverting input is grounded to make an inverting amplifier, and you have AC input coupling, how is the output sitting at 1.65 volts?I see a 2 megohm feedback resistor. Could your AC coupling capacitor be leaking by only 825 nanoamps? That would create the 1.65 volts of output. A low leakage capacitor is required here; usually a plastic film capacitor but ceramic could work also.AC input coupling normally requires the non-inverting input to be somewhere between the supply voltages, because otherwise the amplifier will be saturating on one polarity and maybe with no signal if the offset voltage is in the wrong direction.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: May 21, 2021, 06:32:38 pm
content: You should at least post the whole schematic.What is above the opamp and R13. There are some wires going off-screen.From your schematic it is also not even clear if your source and the opamp share a common ground reference. Because I refuse to make assumptions about such things, there is not much more to be said.
Ad8630 quad opamp drop in substitute - Page 1
Forum section: electronics / projects

author: de_light
author_rank: Regular Contributor
timestamp: September 27, 2021, 04:44:44 am
content: Anyone know of any drop in substitutes for an AD8630ARZ quad opamp? Trying to build the skulcom DC electronic load and my chosen vendor that I've picked the entire BOM from is missing this as the only component.Datasheethttps://www.analog.com/media/en/technical-documentation/data-sheets/AD8628_8629_8630.pdf

author: David Hess
author_rank: Super Contributor
timestamp: September 27, 2021, 01:05:13 pm
content: Could you use two duals instead or are you using the Skullcom circuit board?

author: Kleinstein
author_rank: Super Contributor
timestamp: September 27, 2021, 01:10:44 pm
content: There are not that many quad Az OPs. The MCP6V79 may be about similar, if the case fits. Chances are the bias can be a bit high, but it is different between units anyway. Other wise use the vendors search function.Ideally I would go for single OPs or maybe duals.

author: chuckb
author_rank: Frequent Contributor
timestamp: September 27, 2021, 01:32:07 pm
content: The OPA4187 is a nice quad chopper. I have not compared all the specs.

author: RoGeorge
author_rank: Super Contributor
timestamp: September 27, 2021, 02:08:08 pm
content: TLV4333was cheap last time I looked.No idea if that fits the specs you need.
AD9106 dds chip power supply connections (internal LDO purpose????) - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: June 25, 2014, 09:06:15 pm
content: I have been really confused about this one for a while.http://www.analog.com/static/imported-files/data_sheets/AD9106.pdf'This chip has three built in regulators. DLDO1, DLDO2, CLDO.It says:The power supply rails for the AD9106 are AVDD for analog circuits,CLKVDD/CLDO for clock input receiver and DVDD/DLDO1/DLDO2 for digital I/O and for the on-chip digital data path. AVDD, DVDD, and CLKVDD can range from 1.8 V to 3.3 V nominal. DLD O1, DLDO2 , and CLDO run at 1.8 V. If DVDD = 1.8 V, then DLDO1 and DLDO2 should both be connected to DVDD, with the on - chip LDOs disabled. All three supplies are provided externally in thiscase.This also applies to CLKVDD and CLDO if CLKVDD = 1.8V.I don't understand the purpose of all those on chip regulators.Does it mean that the chip needs 1.8V for circuits associated with CLDO/DLDO1/DLDO2 and they are provided so that you can only use 3.3V supplies (for DVDD and CLKVDD?)But it says"Clock Power Supply Output (Internal Regulator in Use), Clock Power Supply Input (Internal Regulator Bypassed)"It is an output? Why?What is the purpose of these pins??I want to use a minimum of external parts to make this chip run. What do I do? Decouple the LDO pins? I just don't understand why they are outputs.
AD9739A for Software Radio/Function Generator - Page 1
Forum section: electronics / projects

author: olsenn
author_rank: Frequent Contributor
timestamp: December 01, 2011, 08:17:30 pm
content: Anybody want to have a look at the datasheet for the DA Converter AD9739A and let me know just how kick-ass it is?

author: Simon
author_rank: Unknown
timestamp: December 01, 2011, 08:28:45 pm
content: well you might like to state what your looking for in it to kick ass, most IC's are a compromise to better one characteristic, which one do you want ?

author: olsenn
author_rank: Frequent Contributor
timestamp: December 02, 2011, 12:34:44 am
content: I don't have any immediate uses for the chip; I just came accross it today and thought that it's declared specs for bandwidth and sample rate are really good. Potentially, something like this could produce just about any waveform of any frequency to reasonably high resolution.Do you know of any equivelent chips from TI? I like dealing with them more for some reason... although I doubt something like this would have a free sample, haha

author: Bored@Work
author_rank: Super Contributor
timestamp: December 02, 2011, 06:10:16 am
content: Quote from: olsenn on December 02, 2011, 12:34:44 amPotentially? The thing is worth nothing if you (i.e. the designer) can't handle it. This includes, but is not limited to, finding workarounds for all the quirks it certainly has and who happen not to be documented in the datasheet, on top of those documented in the datasheet. It is worth nothing if you don't manage to build a proper analog front-end for it. UIt doesn't matter what a single IC can, as long as you can't operate it in the right way and in the right circuit.QuoteIt is just 70 USD a pop, so if you like it, get that 160 BGA and have fun. 70 USD is nothing compared to the rest you have to spend to make that thing fly.

author: joelby
author_rank: Frequent Contributor
timestamp: December 03, 2011, 08:51:28 am
content: Looks like Digilent are about to release a FMC card with it for $349:http://digilentinc.com/Products/Detail.cfm?NavPath=2,648,976&Prod=AD9739A-FMCIt should be reasonably straightforward to interface with any FPGA with SERDES, such as a $15 Xilinx Spartan-6.
AD9834 outpuc AC coupling - Page 1
Forum section: electronics / projects

author: dreamcatch16
author_rank: Contributor
timestamp: May 11, 2014, 05:45:23 pm
content: Hi,I have a very basic question about AC coupling the output of the AD9834,Please what is the best practice? do I put the passive high pass filter just after the output of the DDS or I have to amplify first than apply a passive high pass filter?The second is? do I have to use small or high cap for the high pass filter? "and adjusting the resistance accordingly"Thank you in advance for your help.
AD9850 DDS module - Page 1
Forum section: electronics / projects

author: akis
author_rank: Frequent Contributor
timestamp: November 30, 2014, 09:00:43 pm
content: I have got a bunch of these modules on ebay from different suppliers. I have noticed that a few do not work properly, from the ones I have tested. What happens is sometimes they produce a nice sine wave output at the desired frequency, and sometimes they do not. Flicking the Vcc line sometimes fixes the problem (if you can call that a fix). To explain further, when I flick the Vcc line, the AD9850 module does not power down completely as it is being kept half-powered by the 4 wires connecting it to the Arduino board. But it seems doing this "nudges" something and then the AD9850 starts, even though the Arduino was doing nothing at the time, which further means that the frequency was already transmitted properly but the AD9850 was refusing to produce it, until I flicked the Vcc line.If anyone has any ideas please let me know.Many thanks.

author: c4757p
author_rank: Super Contributor
timestamp: November 30, 2014, 09:14:20 pm
content: Are you twiddling the reset line on startup?

author: akis
author_rank: Frequent Contributor
timestamp: November 30, 2014, 09:48:58 pm
content: Only when I program it as part of the programming code. But when I flick the Vcc line, the programming has already been done.Anyway out of 6 modules, 4 work OK, and 2 are funny like that. For my luck, picking randomly out of the box I soldered the one that is funny... I have replaced it now with one that works.My small worry is that maybe I am doing something wrong and the ones that work only do so out of fluke.

author: dannyf
author_rank: Super Contributor
timestamp: November 30, 2014, 09:51:11 pm
content: I have used maybe 10 of such modules. No problem whatsoever.QuoteMaybe. or even likely.

author: Rigby
author_rank: Super Contributor
timestamp: December 01, 2014, 12:33:49 am
content: Seems more likely to me that he's doing things right, or right enough, but that there are some counterfeit or maybe "overused" parts that found their way to him.Check the data sheet and make sure you're within tolerances everywhere. If you are, then you have bad parts. Bad meaning counterfeit, used and broken, or parts rejected in QA.

author: Rasz
author_rank: Super Contributor
timestamp: December 01, 2014, 12:45:47 am
content: start by measuring voltagewhen it works, when it doesnt, and when you do your secret flick
ad9910/ 9954 modules - Page 1
Forum section: electronics / projects

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2025, 12:20:39 pm
content: i recently bought the above two modules on aliexpress.haven't been able to test them yet as i have no supporting documentation.the seller is YourCee. i have asked them to send whatever they have, but still...does anyone have schematics?

author: iMo
author_rank: Super Contributor
timestamp: January 16, 2025, 12:53:07 pm
content: Looks like the datasheet schematics implementation, nothing special there on the pcb except the DDS chip itself (you have to download its datasheet first and read)..Follow the signal's labels at the headers. You would need a microcontroller to setup the DDS (perhaps you may find the ready drivers for popular ones), and you will get signals out of the SMAs.Only thing you would need for the setup of the DDS is the frequency of the crystal oscillator there on the pcb (you will find the freq written on its case).

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2025, 01:18:02 pm
content: thanks, iMolooks like it, but I'd like to know the output filter component values.The on-board oscillator is a 40MHz cmos output thing overdriving the ref input with a 3.3v square wave. this one will go in the bin. I have the original 9910 AD demo board for which i have a direct drive 1GHz reference source and a small controller handling basic cw tone generation

author: iMo
author_rank: Super Contributor
timestamp: January 16, 2025, 01:57:08 pm
content: Yup, the external 1GHz source is good for better spectral purity. I would expect 400MHz low pass on both channels, for initial testing purposes. What real part values have been populated there is a different story, of course..You will get it when you start to sweep with the output frequency..

author: phenol
author_rank: Regular Contributor
timestamp: January 16, 2025, 05:39:27 pm
content: i figured it out and while it works, the ref clock sensitivity is some 10db worse than AD's demo board. not sure if they populated it with subpar chips but upon closer inspection it becomes obvious that the board is poorly laid out with decoupling caps placed far from the power/gnd pins. the chip designers have thoughtfully located gnd pins next to every Dvdd/Avdd/clk_vdd pin but the board designer failed to make proper use of them

author: phenol
author_rank: Regular Contributor
timestamp: January 17, 2025, 01:23:58 am
content: i soldered 0402 decoupling caps very close to all avdd pins but it didn't improve anything. input sensitivity is nowhere near the claimed 50mv p-p figure in the datasheet. either those chips are scrap or the ref clk inputs are shot thanks to blasting them with 3.3v swing from the onboard 40mhz oscillator. the max swing there shall not exceed 1000mv p-p as per the datasheet.the board has provision for a pi attenuator from the oscillator to the ref input but it's jumpered with a 0r resistor instead and a 20p cap to gnd... i cant help but wonder why
ADA MP-1 high voltage power supply - Page 1
Forum section: electronics / projects

author: Gothenlor
author_rank: Newbie
timestamp: December 04, 2024, 03:55:40 pm
content: Hi,I don't understand a part of the high voltage power supply of the ADA MP-1 schematic (see attached)It seems that the ground reference is controlled by U2, but why and how ? It looks like a log amp topology, which if I understand correctly, acts like an envelope follower. But I don't understand what it does exactly.Why not just connect the negative rectifier bridge side to ground directly ?The ground reference will be separated by few kohms (R10) and -15V rail of the rest of the circuit ground reference. Or am I missing something ?Note that the two first triodes are referenced to -15V, not ground. Does it justifies the U2 circuit ?Can you explain the purpose of this circuitry, and it's advantages compared to a classic bridge rectifier configuration ?Thanks
Adafruit NeoPixel nonsense (Why won't it work?) - Page 1
Forum section: electronics / projects

author: Youkai
author_rank: Regular Contributor
timestamp: May 07, 2019, 11:48:36 pm
content: I'm having some trouble getting my NeoPixel's working. At this point I'm just trying to do a simple test to get the thing to cycle through R, G, B, W for a second each to confirm it's working.This topic is related to my other thread:https://www.eevblog.com/forum/projects/borderlands-style-jewelry-box-research-thread/I have wired up the attached circuit which is a small section of the whole circuit I'l be designing. I am using an Arduino Uno. I plugged the power (Yellow) into the 5v pin, Ground (Black) into the GND pin, and data (Green) into pin 6. Then I used the below code to run the strip. I'm getting nothing. No light at all.Originally I had it doing a "for" loop to set all of the pixels to the same color but I read in the uberguide that the arduino 5v pin might not be able to supply enough current for that so I brought it down to just the third pixel.I also tried a NeoPixel strip with only wires (i.e. none of the other circuitry) and that didn't work either. I'm hoping that the issue is with my program and not that pixels are so fragile that I accidentally bricked two of them.Code:#include <Adafruit_NeoPixel.h>#define neoPixelPin 6#define neoPixelCount 8Adafruit_NeoPixel lidPixel(neoPixelCount, neoPixelCount, NEO_RGBW + NEO_KHZ800);void setup() {lidPixel.begin();lidPixel.show();Serial.begin(9600);Serial.println("Starting");}void loop() {lidPixel.setPixelColor(2, lidPixel.Color(255, 0, 0, 0));lidPixel.show();Serial.println("Red");delay(1000);lidPixel.setPixelColor(2, lidPixel.Color(0, 255, 0, 0));lidPixel.show();Serial.println("Green");delay(1000);lidPixel.setPixelColor(2, lidPixel.Color(0, 0, 255, 0));lidPixel.show();Serial.println("Blue");delay(1000);lidPixel.setPixelColor(2, lidPixel.Color(0, 0, 0, 255));lidPixel.show();Serial.println("White");delay(1000);}

author: MarkF
author_rank: Super Contributor
timestamp: May 08, 2019, 12:11:12 am
content: I didn't look through all of your code.But, I found one setup error:Code:Adafruit_NeoPixel lidPixel(neoPixelCount, neoPixelCount, NEO_RGBW + NEO_KHZ800);should beCode:Adafruit_NeoPixel lidPixel(neoPixelCount, neoPixelPin, NEO_RGBW + NEO_KHZ800);

author: Youkai
author_rank: Regular Contributor
timestamp: May 08, 2019, 12:17:24 am
content: WOW. I'm a dummy! Yeah that did it. You are a genius! Haha thanks.

author: MarkF
author_rank: Super Contributor
timestamp: May 08, 2019, 12:22:57 am
content: No genius. Just 35+ years of writing code.

author: Youkai
author_rank: Regular Contributor
timestamp: May 08, 2019, 02:10:58 am
content: I've got almost 20 years of writing code in me. Sometimes it takes a genius to catch the "obvious" variable error. In that case I named them similarly enough my brain just read it the "correct" way when I scanned the code.
Adapter board to test UTP on a 75R VNA - Page 1
Forum section: electronics / projects

author: fozzyvis
author_rank: Regular Contributor
timestamp: November 01, 2024, 12:32:44 pm
content: For a client of mine (AV industry), I regularly need to test or reterminate "long" rolls of UTP/STP.Besides using a simple connection tester, I thought I could use my HP 8711A (converted to an HP 8712 with full vector capabilities) VNA for TDR measurements.This would give me the following advantages:Looking at the reflected signal, I'd also be able to see if there are any issues with the cable along the length (impedance bumps due to cable damage that don't show up on DC).I'd be able to have a reasonably close idea of the length of the cable.I'm not sure if my reasoning is correct though:I'd need an impedance translation to match the roughly 150STP to the 75of the VNA. I'd need to search for ideas how to do this. Given I'm moving from an single-ended source to a differential pair, I´d presume some kind of balun configuration will be needed.Finding the velocity factor of the cable should be reasonably simple given a decent piece of cable with a known length.I'll also need to come up with an idea of how to be able to use the same adapter on the four pairs (one by one, obviously).Should this be doable (for someone with little experience)? Am I missing something obvious?I know some Cisco switches (such as the 2960x that can be had for cheap) have TDR functionality which was useable, but only up to a specific FW version that basically made the functionality useless. Still, I'd like to think about making something myself.
Adapter Boards - Page 1
Forum section: electronics / projects

author: docmur
author_rank: Regular Contributor
timestamp: January 28, 2017, 06:20:51 pm
content: Hey GuysDoes anyone have any recommendations where I can get adapter boards for 4-PLCC -> DIP (for LED's) and SOT23-5 -> DIP? I found boards for ~$3 a board but I was wondering if anyone knows anywhere cheaper? Digikey doesn't have any 4-PLCC -> DIP boards at least as of right now.ThanksDocmur

author: Vtile
author_rank: Super Contributor
timestamp: January 28, 2017, 06:31:43 pm
content: It always amaces me that these adapter stamps are so super expensive, must be a good business.

author: Ian.M
author_rank: Super Contributor
timestamp: January 28, 2017, 07:11:09 pm
content: If you want pre-assembled with headers, you'll pay a premium. If you are happy with bare board, there are considerable savings to be made.I *think* PLCC-4 would fit on Tripad board (0.1" pitch stripboard with the strips cross-slit every three holes) If sohttp://www.ebay.co.uk/itm/Veroboard-Copper-Tripad-Board-100-x-160mm-/401035221181would be enough for 130 parts (allowing 3 strips across for ease of cutting straight down the line of holes in the middle of a strip, then cut every 6 holes along the cross slit). Offer one up to a piece of nomal stripboard and see - Tripad cross-slits are the same with as the slits between strips. If you are UK based, its stocked by Maplin Electronics. I cant find any international suppliers.Sparkfun do SOT23-6 breakout boards for $0.95:https://www.sparkfun.com/products/717and Adafruit do a set of 13 breakout boards, 5 of which are SOT23-6 for $4.95:https://www.adafruit.com/product/1230. Both can also be found at various resellers . . .

author: james_s
author_rank: Super Contributor
timestamp: January 28, 2017, 07:38:05 pm
content: You can get various breakout boards on ebay, sometimes I just make my own when I want to prototype something. It's also possible to prototype on perfboard even with very small SMT parts. Check out some of the projects onhttp://elm-chan.org/for examples.

author: bson
author_rank: Unknown
timestamp: January 28, 2017, 09:52:50 pm
content: I use SOT23 adapters I got a 50 pack of from an eBay seller (China or Hong Kong, forget). They're 10 pin with 0.95mm spacing on one side and 0.5mm on the other. Something like an SOT23-3 obviously only uses 3 pads, but that doesn't terribly matter as long as I can get it into a breadboard.

author: jc101
author_rank: Frequent Contributor
timestamp: January 30, 2017, 12:34:48 pm
content: I have recently used some SO8 adapter boards for PLCC-4 LEDs, they worked very well.
Adapting a Dynamic Microphone to the RØDE Filmmaker Wireless Microphone Kit - Page 1
Forum section: electronics / projects

author: graybeard
author_rank: Frequent Contributor
timestamp: June 08, 2020, 12:43:53 pm
content: In this video I make measurements of the (RØDE) Rode Filmmaker wireless microphone system. The measurements completely define the input circuitry and system gain. Then I design a simple preamplifier to adapt a dynamic microphone to the filmmaker. I go over the design process for the preamplifier and explain how it works. I use the IV curves of the JFET and graphically solve for the quiescent point of the preamplifier. In the end I do a comparison between the electret condenser microphone that comes with the filmmaker kit and an adapted Sony F-27 cardioid dynamic microphone.You can find a copy of the charts here with additional measurements that are not included in the video
Adaptive biomech motor controller - abcore - Page 1
Forum section: electronics / projects

author: rickey1990
author_rank: Regular Contributor
timestamp: April 08, 2016, 11:01:39 am
content: These boards are designed to be cheap, so groups and schools can afford them to teach basic electronics skills, plus you get a robot at the end of it., 100 kits - 100 boards, all the components, 100 motors, 100 battery boxs, Come to around £220. the boards can be used in various ways, you can link them for a master slave config. you can make individual robots that join together, producing different states. another example is using two independent Abcores. this gives the robot two states: turning and forward. Under normal conditions, forward is the least energy state. So the robot will continue forward until a flagellum strikes an obstacle and loads up the motor. It will then reverse the flagellum and go into the turn state. This puts a higher load on the motor and thus, after a few seconds, the Abcore will reverse and resume moving forward.VIDEOShttps://drive.google.com/open?id=0B0FrqQK-7VK8dm1BTFFaaG9nN0khttps://drive.google.com/open?id=0B0FrqQK-7VK8b0NGMThab29FU0U
ADAR7251 AFE for Photodiode Data Acquisition - Too good to be true? - Page 1
Forum section: electronics / projects

author: mattico
author_rank: Newbie
timestamp: June 28, 2020, 06:02:51 pm
content: I ran across thisADAR7251 AFEand it seems too good to be true so I had to run it by you guys.It's a 16-bit 1.8MSPS Quad channel Sigma-Delta ADC with LNA, PGA, Equalizer, and on-chip Reference. It costs less than my single channel ADS1602. The built-in amplifiers mean you don't have to worry about ADC drivers and can possibly remove a gain stage from your design. Sig-Delt with decimation filter means you don't need a high order active antialiasing filter. It's got 2 aux ADCs for monitoring temperature or whatever. It's got parallel out or single/dual serial out with a SPI control interface. Of course all that integration is the whole point of an AFE but this is the first one I found which seems generically useful rather than being limited to a single application.The only issues I could think of are:1. 0.5 db Channel-Channel gain mismatch is meh but it should be easy to cal out unless it changes a lot with time or temperature2. Application notes focus on radar and aren't much help for general applications3. 65dB PSRR is lower than some alternatives4. Dual-SPI data + SPI control is annoyingA bit about the application. Trying to accurately measure the width and average value of ~40us light pulses at about 10nA photodiode current. So looking for about 500kHz bandwidth, high transimpedance gain and low noise. The attached schematic shows the basic idea. Hopefully the optics can work with the smaller area photodiode (~2.5pF) but if not might have to live with more like 60pF of diode capacitance, hence the tuning cap. The RC network is from the datasheet to create a bandpass, the ground signal is AC coupled as suggested by Analog Devices for single-ended signals.Please nitpick away. I've not much experience in precision analog stuff so I'm hoping the AFE let's me get away with this extremely simple design.

author: moffy
author_rank: Super Contributor
timestamp: June 29, 2020, 12:43:31 am
content: Looks like an interesting chip but not particularly low noise based on the FFT graphs. If I was trying to determine the average power of the pulse I would be tempted to integrate over the pulse period then divide the final output by that period. It is the definition of average. Increases accuracy and reduces your overall data rate.

author: awallin
author_rank: Frequent Contributor
timestamp: June 29, 2020, 05:30:28 am
content: - negative bias usually helps to reduce the photodiode capacitance (but gives worse dark current)- 1.8MSPS seems like a low sample-rate for a ~us pulse?- check if your signal only swings one way, and if the ADC has bipolar input - are you using the full 16-bit range of the ADC?

author: d-smes
author_rank: Regular Contributor
timestamp: June 29, 2020, 09:00:26 am
content: That 470 / 220 pF capacitor network on the inputs to the ADC will attenuate your pulse somewhat (acts as voltage divider). Be sure and factor that into your gain calculation.
ADC 20Msps Schematic Review - Page 1
Forum section: electronics / projects

author: yammy_96
author_rank: Newbie
timestamp: October 13, 2025, 05:50:04 pm
content: ADC: AD9629-20https://www.analog.com/media/en/technical-documentation/data-sheets/ad9629.pdfXO : CO32D6http://www.hci.com.hk/uploadfiles/Show/20220609095346687.pdf- ADC sampling at 20Msps using 40MHz XO. I will use internal divide by two within the AD9629 to generate the 20MHz sampling signal- 40Mhz XO is LVDS outputCan I enable the XO by connecting Pin1 to XOVCC?Did I hook up the Clock correctly to the ADC?Is the 100 Ohm termination correct?Do I need an LVDS Driver to go along with the XO?Would you recommend using a different XO?This design takes a 3MHz IF signal which is oversampled at 20Msps.Sample rate does not need to change and is why I do not choose PLL.Can
ADC ADS1274 need help with differential vref/inputs - Page 1
Forum section: electronics / projects

author: TrickyNekro
author_rank: Frequent Contributor
timestamp: May 24, 2014, 11:23:32 am
content: Hallo guys and girls,I need your help with understanding how the above ADC (ADS1274) works as far as the inputs are concerned. I am aware that this is a fully differentialADC, and probably I will use some channels as differential and some as single ended but that´s not a concern I know what to do.My question is about the range of the ADC. The datasheet is somewhat confusing to me about that. Say that I have a differential Vref voltage of 2.5Vmeaning I have 2.5V at Vref_Positive and 0V at Vref_Negative. Which is my usable range at the inputs?For example, I tie VIN_Negative at 2.5V (for the channels I want to use as single ended). That means that when VIN_Positve is at 5V it will give methe most positive reading and when the VIN_Positive is at 0V it will give me the most negative? Or will it give me the most negative reading whenVIN_Positive is also 2.5V, same as VIN_Negative?When you tie one of the inputs at the middle of the range the datasheet refers to true bipolar operation so...I think the first one is the answer but the datasheet is a little bit unclear about that, though to tell the true I have not read the applications note yetregarding the software design. We are a little bit tight on time for a project we are doing and too much information sometimes can be confusingPlus I do not have the comfort of doubt, I have to be sure of what I am doingAlso, is there something I have to be extra careful about, when using this ADC? Anyone who has worked before with those ADCs and what to sharesome tips, I will be more than grateful to listen!Thanks in advance for your time and advices,With kind regards,Lefteris
ADC and Teensy connection - Page 1
Forum section: electronics / projects

author: 0822lyy
author_rank: Newbie
timestamp: January 24, 2025, 06:00:12 am
content: I am working with ADC named ADS8568 and I ran into a problem.I am using an Arduino Teensy 4.1 as interface between a PC and an ADS8568. ADC is in hardware and parallel mode. I am trying to get digital output of converted analog input of A0 channel. (Therefore, only channel A0 was connected and used, differing from the circuit diagram. Otherwise, such as references remain the same.)The power connection was referenced from the ADC's datasheet (Typical Application, p.42), but I don't sure it is right.I don't sure where is the problem lies whether in the software or the hardware. So the full circuit layout and datasheets are attached.Also this is the Arduino code. I used direct register access, and the Teensy pin's GPIO(register) mapping is verified.I use sine wave with an amplitude of 2.0V and applied it to the analog signal(A0).The serial output is just 0 and I think the ADC is not working because BUSY signal is not working though CONVSTA signal is rising. I checked the input signals are go well in the ADC chip.Thx for your help

author: moffy
author_rank: Super Contributor
timestamp: January 24, 2025, 06:31:13 am
content: The level of ringing on the scope traces is horrendous, it's either a scope grounding issue or more likely due to the use of a breadboard and jumper leads. Can you make a prototype PCB to connect the Teensy to the ADC? The supplies and ground need solid connections.

author: 0822lyy
author_rank: Newbie
timestamp: January 24, 2025, 01:16:17 pm
content: Quote from: moffy on January 24, 2025, 06:31:13 amThank you for the advice. The PCB is currently under delivering.The CONVSTA occurs once every 5ms, and the oscilloscope image was observed in milliseconds. Therefore, it might have appeared that a significant amount of noise was present.Could the noise potentially cause the ADC to stop functioning entirely?
ADC circuit  - Page 1
Forum section: electronics / projects

author: comeau
author_rank: Contributor
timestamp: May 28, 2017, 02:29:32 am
content: Hello all,I've been rattling around with idea I have and I think it might be good. It also might be terrible. I have no idea.Basically, it is an ADC that should ideally work as fast as a flash ADC, but use only 3 comparators per stage vice the 2^n of a flash ADC. The savings are clear (if it works). At just 3 bits of resolution, you are saving 2 comparators. At full 8-bit resolution, you are saving 232 comparators.Obviously, it is too good to be true.The system takes an input signal, compares it to a reference voltage and outputs a binary signal. The clever bit is that it then switches a mosfet to reduce the input signal by the reference voltage and then uses that as an input to the next stage. The input signal continues to get chopped in this way until it reaches the last stage.I built this circuit in LTSpice and it seems to work at least up to 1kHz. I think I can get it to work up to higher frequencies and in real life. Before I waste more time however, I would like a second opinion. The LTSpice circuit is attached as well as a picture.I request the following free services:1) Has this already been done? If true=>project end2) Is there a basic reason this circuit won't work in real life? If true=>project end3) Is there an obviously better way to do this?-Comeau

author: Helix70
author_rank: Unknown
timestamp: May 28, 2017, 06:23:40 am
content: What problem are you solving?

author: ebclr
author_rank: Super Contributor
timestamp: May 28, 2017, 06:41:38 am
content: You can do with only 1 comparatorhttp://www.ti.com/lit/an/slyt423a/slyt423a.pdf

author: comeau
author_rank: Contributor
timestamp: May 28, 2017, 10:55:58 am
content: To answer both your questions at once. A delta-sigma ADC has a set sampling rate. This reduces the ability to convert at a much higher frequency. The alternative for lightning fast response is to have 2^n comparators in a flash ADC. This is expensive and impractical and it looked like an improvement could be made.Quote from: ebclr on May 28, 2017, 06:41:38 amThere is more than 1 comparator in a delta-sigma ADC.Quote from: Helix70 on May 28, 2017, 06:23:40 amI'm imagining an ADC that is all the fast (solely limited by circuit design and processor speed) and is also incredibly accurate. This ADC, if it works, would have the potential for unheard of accuracy at relatively cheap prices. (optimistic)Anyways. From the general lack of compelling counters, it seems like this might be worth actually building up after all.