hybridfree/eevblog-posts huggingface dataset:
Measuring light reflection in very tight space. - Page 1
Forum section: electronics / projects

author: eTobey
author_rank: Super Contributor
timestamp: May 14, 2023, 05:44:10 pm
content: Hi,i have to measure the reflection of a disc, but i dont know, how i can properly align the LED to the phototransistor. The LED does not distribute the light at 180° degrees with an even intensitiy (see the picture). Anyone has an idea how to get some good illumination?CheersToby

author: Twoflower
author_rank: Frequent Contributor
timestamp: May 14, 2023, 06:24:26 pm
content: You can just by a ready made device like this:ELI TR9904 Reflexlichtschr 3,0mm PCB-MtNot sure how strong the sensitivity falls off if you reduce the distance below the focal point (the device above has a working distance of 3mm).Edit: Just noticed Reichelt mentioned the package weight in scientific notation

author: eTobey
author_rank: Super Contributor
timestamp: May 14, 2023, 06:48:29 pm
content: This is waaay to huge, but i also found some smaller ones of this kind. But now i wonder, where the center point of detection is. Is it in the middle of the two elements, or just under the phototransistor?With my seperate elements, i was thinking about how i could put the LED in a slight angle, to fully iluminated the surface under the phototransistor.

author: eTobey
author_rank: Super Contributor
timestamp: May 14, 2023, 06:57:34 pm
content: I found another funny thing:I wonder if this part is good, when the datasheet is already kinda funny.

author: Twoflower
author_rank: Frequent Contributor
timestamp: May 14, 2023, 07:03:17 pm
content: Your picture showed the 1...3mm form the top of the photo-transistor no limitation of the sensor dimensions ;-) But yes there are also SMD types (e.g. GP2S700HCP). The GP2S700HCP datasheet has also a diagram showing the relative sensitivity over distance. The 1mm is probably to close.I would assume that both emitter and receiver are looking inward that the sweet-spot is aligned to the center of the device.

author: eTobey
author_rank: Super Contributor
timestamp: May 14, 2023, 07:39:05 pm
content: I have read a few times those elements "facing the same directions" or "both are in the same plane". So it would look like in my drawing. I just ordered one, and i will investigate.
measuring low current with a dmm - Page 1
Forum section: electronics / projects

author: dannyf
author_rank: Super Contributor
timestamp: January 31, 2016, 01:24:45 am
content: I just finished a page detailing my attempt at measuring low current (down to nA or pA range, depending on the meters used) using digital multimeters - good-old DT830 in this case:https://dannyelectronics.wordpress.com/2016/01/28/the-nano-ammeter-you-already-have/In the end, I used it to measure the leakage current (as measured in parallel resistance) of an electrolytic capacitor, as shown in the chart below.The set-up can be used for measuring low current in other applications, like dark current from a LED.Hope it helps.

author: uncle_bob
author_rank: Unknown
timestamp: January 31, 2016, 01:53:03 am
content: HiA couple of things to watch out for:Some DVM's are better than others when run this way. The "not so good" ones have noisy input resistors. The best demo I ever saw of this was at a large DVM plant outside Seattle. No it's not just a knock on cheap no-name DVM's ....Some DVM's go to crazy high input impedances on the most sensitive scale. They essentially don't have an input resistor, the advertised impedance in that case is just the leakage on their input stage and pc board. If you have one of these, it will be *very* noisy using the meter's internal R as a load. Simple answer in this case - strap on an external resistor.Bob

author: MK
author_rank: Regular Contributor
timestamp: January 31, 2016, 09:56:51 am
content: the humble racal dana 5004 has a bias compensted input and a 10G resistor on the input connected to gnd, and using the 20 V range should have less than a volt on the display. not bad for a bipolar input.

author: dannyf
author_rank: Super Contributor
timestamp: January 31, 2016, 01:01:05 pm
content: This approach can be used to measure small capacitance as well, when excited by an ac source (like 50/60hz mains). Unfortunately, most el-cheapo dmm doesn't specify the input impedance of its ac volt ranges.
measuring OP-AMP gain-bandwidth - Page 1
Forum section: electronics / projects

author: mike zias
author_rank: Newbie
timestamp: October 01, 2024, 01:34:04 am
content: I have a reasonably good lab set-up. I am measuring the gain-bandwidth of some op-amps. I have a 741, 358, and ancient 709. On my 741 I get a 23 db/decade slope. In theory this should be 20 db/decade. I am confining most of time to 20 and 40 db gain. How close to 20 db/decade is a real 741 op-amp?

author: TimFox
author_rank: Super Contributor
timestamp: October 01, 2024, 01:46:47 am
content: Over what range of frequency did you measure that slope?(e.g., 400 to 40,000 Hz for two decades)The slope will be less at very low frequencies and higher at very high frequencies.

author: mike zias
author_rank: Newbie
timestamp: October 02, 2024, 12:48:41 am
content: my 40 db gain was at 8.53 khz and my 20 db gain was at 75 khz. Input voltage at 0.01 vrms. However, I notice my signal generator output (HP 3311A) has a distortion on one side of the sine wave. I have been using RMS voltage measurements so I thought the distortion would not be a big factor. I have a HP 3581A wave analyzer, but it only goes to 50Khz. I may try that and see what slope I get.

author: mawyatt
author_rank: Super Contributor
timestamp: October 02, 2024, 03:12:34 am
content: Might try using 6.02dBV/Oct instead of 20dBV/Dec. Has advantage of finer granularity for spotting where slope changes.Best

author: magic
author_rank: Super Contributor
timestamp: October 02, 2024, 05:38:22 am
content: 3dB is a lot, you should be able to easily see it on a scope.I got sensible results consistent with datasheet specs using the circuit below, which operates the chip at -1 closed loop gain and artificially reduces open loop gain by 80dB. Apply frequency of interest to in, measure out and err amplitudes (or phase if you care) and your open loop gain is V(out)/V(err)·R3/R4. Try not to put too much capacitive load on err, or maybe reduce R1,R2 resistance if the time constant is getting uncomfortably long (but note that the feedback network loads the output, as usual).

author: Terry Bites
author_rank: Super Contributor
timestamp: October 07, 2024, 04:53:52 pm
content: https://www.analog.com/en/resources/analog-dialogue/articles/simple-op-amp-measurements.html741s only exist because people keep buying them by accident. The 70s are long gone.

author: Randy222
author_rank: Frequent Contributor
timestamp: October 07, 2024, 09:23:03 pm
content: I guess you need to define what the test spec is. Is -3db where you call it a start or end ?

author: Kleinstein
author_rank: Super Contributor
timestamp: October 08, 2024, 07:15:47 am
content: The -3 dB point wout be for the unity gain in the follower circuit.For the gain bw product one is interested in the range with -20 dB/decade slope a little below the unitiy gain BW. In most cases a frequency roughly a factor 10 to 100 below the GBW is used. So measure the gain there and than calculate frequency times measured open loop gain. Data-sheets sometimes give the frequency they actually use (e.g. 1 MHz for fast op-amps).
Measuring output impedance of high speed differential driver (LVDS) - Page 1
Forum section: electronics / projects

author: cirthix
author_rank: Contributor
timestamp: April 07, 2016, 09:13:42 am
content: Hi,I have an ASIC which drives a 100-ohm differential pair, to be routed and terminated properly. The datasheet for this chip is pretty poor. I am supposed to use a series resistor on each output pin close to the driver, but I do not know the optimal value. 33ohm works well, 75ohm works but not that well. 10ohm similarly works but not that well.I know that the purpose of the series resistors is to terminate reflections and provide a uniform 100-ohm transmission line. The value of the series resistor should be (100-driver_impedance)/2, right? (of course 75 breaks this and does not work well)I'd like to determine the optimal value, but my scope is not fast enough to directly look at the waveforms (chip rise/fall times are ~130/170 picoseconds).I suppose I could just keep using the 33ohm value because it works and makes sense, but I'd like it to be properly done.Thanks

author: CM800
author_rank: Frequent Contributor
timestamp: April 07, 2016, 09:42:13 am
content: I'm not to familiar with high speed design, but could you just put the output into resistors, measure the current and use V=IR to get the output impedence, or at least the resistance, from there do the calculation?

author: Miyuki
author_rank: Frequent Contributor
timestamp: April 07, 2016, 10:03:48 am
content: 1st rule: Don't touch it when it works. It will always be worse.

author: Gyro
author_rank: Super Contributor
timestamp: April 07, 2016, 11:36:51 am
content: The only thing I can think of is measuring the output voltage swing with different value load resistors close to the chip - that ought to give you a practical indication of internal resistance.
Measuring PDNs on a spectrum analyzer+TG - Page 1
Forum section: electronics / projects

author: jmw
author_rank: Frequent Contributor
timestamp: March 29, 2023, 02:52:13 pm
content: I've long been curious about old saws like "always add .1 µF capacitors next to ICs" so I've been on-and-off been going down the rabbit hole of actually measuring what capacitors do on a PCB. I made a test board, ran some experiments, and put together the results here:https://jmw.name/projects/exploring-pdns/It's about a 5–10 min read. Comments, suggestions, pedantic corrections, etc. are welcome. The page covers some of the theory and setup, and has experiment results for:decoupling capacitor placementbulk capacitor placementDC bias effectdecade capacitor combinationspower plane capacitancemeasuring milliohm resistances
Measuring peak value for a (1-5) ns pulse and discharge in 0.5us or faster - Page 1
Forum section: electronics / projects

author: JonyMicheal
author_rank: Newbie
timestamp: April 01, 2017, 10:16:05 am
content: I need to measure the peak value (the pulse height) of a single incoming signal with a very short pulse width (1-5)ns.Is there any peak hold detector circuit/IC that can accomplish this task? Any article? thesis?OBS: it is also important to discharge the circuit within 0.5us.Thanks in advance!

author: danadak
author_rank: Super Contributor
timestamp: April 01, 2017, 11:25:40 am
content: A possibility (basic approach) -http://www.edn.com/design/analog/4347624/High-speed-peak-detector-uses-ECL-comparatorhttp://www.edaboard.com/thread177024.htmlhttp://pdfserv.maximintegrated.com/en/ds/MAX9691-MAX9693.pdfFast comparatorRegards, Dana.

author: David Hess
author_rank: Super Contributor
timestamp: April 01, 2017, 12:53:09 pm
content: Quote from: danadak on April 01, 2017, 11:25:40 amThis circuit requires a repeating signal and the single shot performance is not specified or measured.Peak detection at nanosecond speeds is a hard problem. If you can generate a trigger signal which shows exactly where the peak is, then a sampling bridge can grab it.I would test using an RF emitter follower driving a small holding capacitor just to see how fast it can be.
Measuring power in LTSpice - Page 1
Forum section: electronics / projects

author: fcb
author_rank: Super Contributor
timestamp: October 10, 2014, 04:45:50 pm
content: Any idea how to measure power (as in milliwatts) dissipated by a part in LTSpice, I'm simulating a small (discrete) AC amplifier?

author: Rufus
author_rank: Super Contributor
timestamp: October 10, 2014, 04:49:59 pm
content: Quote from: fcb on October 10, 2014, 04:45:50 pmHolding Alt turns the cursor into a thermometer while over a part. Left click to add a power trace.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 10, 2014, 04:50:42 pm
content: Sure, just press alt as you hover over the part, the cursor should turn into a thermostat.

author: liquibyte
author_rank: Frequent Contributor
timestamp: October 10, 2014, 05:11:54 pm
content: Ctrl-alt if you're using LTSpice in wine on linux. Just wanted to put that out there for anyone that might be doing so. Alt-left click in most distros grab the window for moving unless you specifically reassign the meta key.

author: fcb
author_rank: Super Contributor
timestamp: October 10, 2014, 05:17:13 pm
content: Thanks Rufus & Alex Eisenhut - pressing Alt certainly shows power dissipation in the part hovered over, however it doesn't appear to be correct - it shows the 'steady state' power, not the real power (e.g. an AC coupled 16R load resistor shows 3.29e-13 femto-watts, when it has 4Vpkpk sine-wave applied.)

author: Rufus
author_rank: Super Contributor
timestamp: October 10, 2014, 06:01:39 pm
content: Quote from: fcb on October 10, 2014, 05:17:13 pmHovering over circuit nodes/elements shows the dc operating point values on the status bar. Clicking adds a trace for that value (assuming you have run a transient analysis).Once you have a trace displayed Ctrl-clicking the trace label will show you the average and integral of that trace over the displayed range.

author: fcb
author_rank: Super Contributor
timestamp: October 10, 2014, 06:17:27 pm
content: Brilliant Rufus, that worked really well.
Measuring pulsed current - Page 1
Forum section: electronics / projects

author: PbFoot
author_rank: Contributor
timestamp: September 27, 2012, 12:02:49 am
content: Hi,I am working on a device which pulses an array of high-output LEDs. I am using a TIP120 to drive 4 parallel groups of 4 series LEDs. I each LED is rated for 3V at 1A maximum pulse. I am using a duty cycle of 1%, so each pulse is in the microseconds range.My question is this: I have set up my bench power supply for 12V and 4A limit. When I run my LED array, the ammeter on the power supply only reads about 25mA. I know this can't be right, and I suspect this is because of the very short pulses. Am I right?Part 2: How can I verify that my LEDs are using the correct current? Do I need a current probe for my scope?-PbFoot

author: Short Circuit
author_rank: Frequent Contributor
timestamp: September 27, 2012, 12:31:23 am
content: Add a small sense resistor in series with the leds, and you can measure the voltage drop with your scope. Ohms law does the rest.Choose a very low value so the circuit is not affacted too much, perhaps 100mOhms for 1Amp peak so you get 100mV reading.

author: robrenz
author_rank: Super Contributor
timestamp: September 27, 2012, 12:36:24 am
content: Preferably non inductive

author: David_AVD
author_rank: Super Contributor
timestamp: September 27, 2012, 12:57:40 am
content: The current meter will be reading the average, so that 25mA is in the right range for 1% of 3 Amps.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 27, 2012, 03:55:10 am
content: A uCurrent for a scope would be a very useful tool for a lot of stuff. An upper bandwidth of 50kHz or so should be fairly easy, maybe up to 1MHz or so with careful design. For isolation, TI makes an isolated Delta Sigma modulator.
Measuring PWM frequency of LED flashlight outputs - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: April 23, 2018, 10:40:18 pm
content: I am trying to using a photoresistor powered by a 9V battery and using a flashlight pointed at the photoresistor to try to measure the PWM frequency at different output power levels but the problem is I don't understand why when I use an incandescent bulb powered by mains (220V) I get a sine wave with a frequency of 100 Hz instead of the 50 Hz main line frequency.Without understanding why this is the case I cannot measure PWM frequencies with confidence.What am I missing here?

author: hamster_nz
author_rank: Super Contributor
timestamp: April 23, 2018, 10:49:59 pm
content: Power (heating and glowing) is V^2/R...It drops to zero when the voltage crosses zero, and reaches a maximum twice - at the positive and negative crests.

author: StillTrying
author_rank: Super Contributor
timestamp: April 24, 2018, 12:55:04 am
content: There's close ups of the 100Hz light from a bulb in the first post here.https://www.eevblog.com/forum/chat/20w-halogen-bulb-viewed-by-a-photodiode/

author: SG-1
author_rank: Regular Contributor
timestamp: April 24, 2018, 02:43:48 am
content: With AC the frequency of the energy is 2 times the frequency of the voltage or current.

author: Circlotron
author_rank: Super Contributor
timestamp: May 03, 2018, 10:20:28 am
content: A photoresistor (LDR?) may not respond fast enough. A phototransistor certainly will.

author: grifftech
author_rank: Frequent Contributor
timestamp: May 03, 2018, 03:04:40 pm
content: red line is voltage curve
Measuring real power consumption - Page 1
Forum section: electronics / projects

author: hlavac
author_rank: Frequent Contributor
timestamp: June 15, 2012, 11:47:53 am
content: How do I go about measuring real current consumption of a circuit?If I just sample the current shunt, I will miss some spikes... I'd probably need ridiculously high sample rates...I was thinking, could I somehow run the current sensed thru an integrator and sample that at regular intervals?Like, measure the real amount charge that has passed thru the circuit, sample that at regular intervals and get the real average current by dividing the charge by the time span instead of averaging the samples of immediate current?Maybe two integrators so I can do double buffering and not miss part of the waveform.Like, have two caps each charged with a current that is proportional to the current consumed by the measured device and tracks it very fast.I could then sample one of the caps then discharge it, and next time sample then discharge the other cap... and so onSimilarly I'd have to integrate the voltage over the same period to be able to calculate power...Could this work?

author: jimmc
author_rank: Frequent Contributor
timestamp: June 15, 2012, 01:09:39 pm
content: If you are talking about a fixed voltage DC power source, you can average the current before sampling and then perform the integration digitally.If you want the integrated power (=energy) then, since the voltage is fixed, multiplying the voltage by the integrated current will give the total energy in Joules (Watt seconds)A simple RC lowpass filter should suffice for the averaging.However if the voltage varies with time (as well as the current) then you would need to take the product of instantaneous voltage and current before averaging (and then integrating).This would require an analogue multiplier before the lowpass filter.Jim

author: digsys
author_rank: Unknown
timestamp: June 15, 2012, 01:22:00 pm
content: What are you considering "fast" sampling?? 1Ksps, 100Ksps? Maybe you look at True RMS converterchips, have them do the dirty work and read them at a "reasonable" read rate. Some of thesehave other maths functions as well. IF you want fast and accurate, you won't do better and easier.
Measuring series battery voltage - Page 1
Forum section: electronics / projects

author: Prithul0218
author_rank: Contributor
timestamp: September 28, 2018, 02:39:29 pm
content: I want to measure the voltage of 2 LiPo battery connected in series using the ADC from Texas Instrument - ADS1115 configured in differential.Datasheet:http://www.ti.com/lit/ds/symlink/ads1115.pdfI think there is 2 way to do this:1) See picture A. Connecting the battery pack directly to the ADS1115. But I am worried that the 8.4V on pin AIN3 will kill the ADC.2) See picture B. Connecting the first battery directly and connecting the the other one with a resistor voltage divider. But I only have some 5% 10K resistors, I don't really wanna use them as I will lose accuracy. I don't even have an accurate multimeter to calibrate with a pot.So, I would prefer using the first method for best accuracy. But I don't know if it will work. Or if the 8.4V potential on pin AIN3 will kill the ADC. Will it?Which method should I use?Thanks.

author: MosherIV
author_rank: Super Contributor
timestamp: September 28, 2018, 07:16:38 pm
content: HiYes, circuit A will definitely kill the ADC.There are special battery monitoring devices from many manufacturers where you can just hook up the cells strait to the device.

author: Zero999
author_rank: Super Contributor
timestamp: September 28, 2018, 08:38:44 pm
content: Yes, as mentioned above, circuit A will kill the ADC.It should be possible to calibrate the second circuit, in software. Measure the voltages of both batteries directly, using the ADC. Now connect each battery to the potential divider. Note how much the reading of each battery, differs from the theoretical 50% of the battery voltage, take the average and use that scaling factor in your code.

author: Prithul0218
author_rank: Contributor
timestamp: September 29, 2018, 05:21:31 am
content: Quote from: Hero999 on September 28, 2018, 08:38:44 pmThat's a clever way to calibrate the divider.Thank you so much.
Measuring SMPS standby/quiescent current - Page 1
Forum section: electronics / projects

author: Phaedrus
author_rank: Frequent Contributor
timestamp: May 06, 2014, 05:02:16 pm
content: I'm trying to measure the standby and quiescent current of an off-line SMPS. It has a +5V standby rail which must meet certain efficiency parameters at 0mA, 100mA, 1.5A, and 3A loads. The 1.5A and 3A tests are no trouble at all for me to measure, but the 0mA and 100mA are proving difficult...I have the following equipment:Fluke 87 VFluke 115Tektronix TDS 3014CExtech 380820 Power AnalyzerBrand 20-1850 Power MeterBK Precision 8540 150W DC LoadThe Brand meter can't resolve below 100mA AC current, and it's only 2-3% accurate at that range, so it's no use. The Extech power analyzer bottoms out at 50mA; on the 0A and 100mA standby tests it reads zero load.I cut open a power cord and used the 87 V to measure current through the L wire. This is pretty accurate: above 50mA it tracks with the Extech almost exactly, with the Extech consistently reading 2mA higher (probably the effect of the Fluke's burden voltage). However, I have a problem. The Fluke's A range only reads down to about 50mA; below that it reads 48-49mA even if the actual reading should be much lower. When I switch it to the mA range, the meter reads about 0.1mA for about fifteen seconds as the rail feeds off its capacitance, then the rail drops out. The PSU won't draw enough current to run through the mA/uA port of the Fluke.I'm kind of at a loss here. How can I accurately measure AC current that low, when the PSU won't run through the mA/uA port on the Fluke? I'm considering one of Dave's uCurrents...

author: Vgkid
author_rank: Super Contributor
timestamp: May 06, 2014, 05:10:46 pm
content: CMPhaedrus how about considering an external current shunt.

author: georges80
author_rank: Frequent Contributor
timestamp: May 06, 2014, 07:01:25 pm
content: For measuring switcher performance, I use a Tek A6302/AM503B combo. DC to 50MHz capability and lets you see the actual waveform and not just some RMS value. It can easily measure down to 10mA or lower.cheers,george.

author: dannyf
author_rank: Super Contributor
timestamp: May 08, 2014, 01:33:22 pm
content: QuoteGoogle Agilent seamless autoranging.While you are at it, google its inventor's story too,

author: Someone
author_rank: Super Contributor
timestamp: May 09, 2014, 12:07:32 am
content: Quote from: georges80 on May 06, 2014, 07:01:25 pmYes, a proper clamp on current probe (ideally plus differential probe) is the best way to measure power consumption, with complex loads a multimeter could provide a very poor estimate. The maths function will reveal the interesting real power vs apparent power, and both the majors have good guides to measuring mains power.There are AC coupled current probes from Tektronix which can be bought cheaply, and don't require the large probe power supply.
Measuring the Voltage of a Spark - Page 1
Forum section: electronics / projects

author: Mad Phil
author_rank: Newbie
timestamp: October 20, 2013, 12:30:56 pm
content: Hi All, I've recently been working on a project testing the controller boards that are found in combi boilers domestic gas boilers. Most of the testing processes have been worked out but i'm still having problems testing a spark voltage as i have absolutely no idea how go go about this, so if anyone has any ideas that would be most appreciated.Thank you for all your suggestions and it has given me food for thought.Basically I'm trying to determine if the spark unit is good or on its way out, so really it would be a ball park reading not an exact voltage reading which would then go into a microcontroler.

author: Marco
author_rank: Super Contributor
timestamp: October 20, 2013, 12:57:47 pm
content: AFAIK oven/boiler ignition transformers can do 10+ kV and the spark is going to be a high frequency signal, to know it's peak voltage I think you'll be wanting a MHz bandwidth divider/probe or better. So a 20+ kV MHz+ scope probe and a scope, or a fast peak detector (designed with input impedance similar to a scope) with a meter if you're only interested in the peak voltage (a multimeter built in peak detector does not qualify as fast).

author: dr.diesel
author_rank: Super Contributor
timestamp: October 20, 2013, 12:57:54 pm
content: How accurate of a measurement do you require? You can get a rough idea by measuring the spark gap distance. There are several key variables that influence this, ambient pressure, humidity, etc, but will get you in the "ball park".http://www.kronjaeger.com/hv/hv/msr/spk/

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: October 20, 2013, 01:41:48 pm
content: Automotive KV meter .

author: Neilm
author_rank: Super Contributor
timestamp: October 20, 2013, 01:45:44 pm
content: Breakdowns (sparks) are very hard to measure accurately. They are very short term events - what you see is probably due to persistence of vision rather than the sparks presence. Not only do you need fast responding equipment, you also have to remember that the breakdown is a broadband artifact. It is what was used in early Morse transmitters. So any results you do measure could be affected by the EMI this generates and ruin the result.So look at getting something that is properly designed to do this, rather than trying to make something.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 20, 2013, 02:37:54 pm
content: Just add a second spark gap in series with the first and see how much margin is left.
Measuring three phase power - Page 1
Forum section: electronics / projects

author: GabYoung92
author_rank: Regular Contributor
timestamp: December 20, 2012, 11:19:31 am
content: I'm looking at somehow creating a circuit to measure three phase power, however I'm not sure of the approach I should be taking.The plan is to interface the measurement of current + voltage to a micro through isolation to calculate power, phase, frequency etc... to be outputted to a computer to be logged.I understand how using a shunt will convert the current to a voltage. It's just, how should it be arranged?

author: notsob
author_rank: Frequent Contributor
timestamp: December 20, 2012, 11:28:29 am
content: This App Note and chip may be of usehttp://www.analog.com/static/imported-files/application_notes/2698536550528608457AN641_0.pdfhttp://www.analog.com/en/analog-to-digital-converters/energy-measurement/ade7752a/products/product.htmlCheers

author: GabYoung92
author_rank: Regular Contributor
timestamp: December 20, 2012, 11:34:43 am
content: Thanks, that is definitely an option.Just curious, would it be possible, and not too silly to use say an atmega8 to measure the waveforms and do the calculations?

author: notsob
author_rank: Frequent Contributor
timestamp: December 20, 2012, 11:40:23 am
content: Have a look at Silicon Chip issue 190-191 July Aug 2004, they have an energy meter (single phase) using a sister AD chip and a PIC micro

author: penfold
author_rank: Frequent Contributor
timestamp: December 22, 2012, 11:49:17 pm
content: Just as a side though I had whilst reading this, when it comes to isolating the voltage measurement, has anyone tried putting a micro with adc on the primary side and isolating a digital comms signal coming from that? Its not something I've tried, I just always find isolating digital signals a lot more preferable to analogue ones
Measuring variable frequency current - Page 1
Forum section: electronics / projects

author: BorisRap
author_rank: Contributor
timestamp: February 22, 2024, 11:26:01 am
content: Hi guys,I'm doing a project in which I have to measure the current through a laser diode and read it with a micro controller.Here is the catch: The diode is controlled by an IC that varies the current and also performs some modulation. The current can vary from 1A to 3A and the modulation can be from DC to 2Mhz.I don't need to know the instantaneous current in the diode, getting some rough approximation is ok, it's just for safety reasons, to turn off the diode if too much current is being drawn.Due to the control IC topology the current must be high side measured.What simple solutions would yo recommend? I know that maintaining the gain in a 2Mhz bandwidth span is no easy job.Thanks for your help!

author: MarkT
author_rank: Frequent Contributor
timestamp: February 22, 2024, 08:21:40 pm
content: Simple, low-pass filter the current signal with an RC circuit. Then the bandwidth can be low, 10Hz or whatever is sensible for warning of overheating.With a high-side shunt you would low-pass filter the signal from both sides of the shunt independently so that common-mode and differential signals are both band-limited.

author: Benta
author_rank: Super Contributor
timestamp: February 22, 2024, 09:45:08 pm
content: I thought most lased diodes have a built-in photodiode for this function.What laser diode is it?

author: PCB.Wiz
author_rank: Super Contributor
timestamp: February 22, 2024, 10:24:58 pm
content: Quote from: BorisRap on February 22, 2024, 11:26:01 amIs this eye safety, or diode safety ?This is really a eFuse or circuit breaker type problem, so the MCU can be used to set the trip point (if that needs to be variable), but not be involved in the turn-off.TI's load Switches section for example, has many devices and some include current set and cut-off.Or, you can just use a simple current limiting element, in series with the diode.
Measuring voltage /current in a non symmetric pulse train  - Page 1
Forum section: electronics / projects

author: MadScientist
author_rank: Frequent Contributor
timestamp: July 27, 2021, 12:09:53 pm
content: Techniques to measure voltage of a 10khz non symmetric pulse trainI’m just reviewing how best to implement a voltage and current ( via resistor sense) meter that is subjected to non symmetrical pulse trains.Ideally I’d like to measure peak , average and RMS valuesI was thinking of digitising it and attempting to derive the numbers mathematicallyAnyone have alternative suggestions. Accuracy needs to be about 0.5% so not horrendous.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 27, 2021, 12:24:16 pm
content: I think that is the way to go, all the calculations are very simple code.

author: MadScientist
author_rank: Frequent Contributor
timestamp: July 27, 2021, 12:28:23 pm
content: Yes my approach was to use the “ mid-ordinate” method. Ie spaced samples.

author: TimFox
author_rank: Super Contributor
timestamp: July 27, 2021, 09:35:33 pm
content: Peak, peak-to-peak, average absolute value, and average values are easily done with analog hardware, but you are probably better off calculating RMS digitally for messy waveforms.
Measuring voltage using ACPL-C87B, question about grounding - Page 1
Forum section: electronics / projects

author: mike buba
author_rank: Contributor
timestamp: August 12, 2024, 10:00:44 pm
content: Hi All,I am thinking of using theACPL-C87Bfor measuring inverter voltage (both DC and AC). In the technical manual, there is a typical application circuit (shown below).Pin 4 is connected to the GND and the bottom side of the voltage divider.However, if I am measuring line-to-line voltage (Vab, Vbc, and Vca), then in each of these cases, my 5V DC GND will be connected to the line voltage potential. Similarly, for DC measurements, with a grounded mid-point, the negative DC rail will be at -1/2 DC voltage.Basically, my voltage divider schematics will look like this, with both L1 and L2 at the high(er) voltage, e.g., 230 Vac RMS and 680 Vdc, but the ACPL-C87B says connect analogue PCB GND to L2.Is it possible to use the ACPL-C87B to measure AC voltages? And how should my connection between L1 and L2 and the input pins to the voltage sensor look?Kind regards, MB

author: ArdWar
author_rank: Frequent Contributor
timestamp: August 13, 2024, 04:21:03 am
content: The two sides of the IC are galvanically isolated. You can pick any voltage (within isolation rating) as "GND1" and it'll be fine. One common challenge with isolated sensor like this here is how to supply VDD1 that is relative to GND1 while also galvanically isolated to VDD2/GND2.Note that if you use multiple IC for multiple Phase-Phase measurement then each of their GND1 and VDD1 must also be isolated from each other.
Measuring water temp with K type thermocouple? - Page 1
Forum section: electronics / projects

author: SNGLinks
author_rank: Regular Contributor
timestamp: March 04, 2015, 03:54:55 pm
content: I wish to measure how my hot water temperature changes with time. I have a Uni-T UT71B that comes with a K type thermocouple.Can I put the thermocouple directly in the water or will the water's conductivity upset the result?

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 04, 2015, 04:14:27 pm
content: Thermocouples are extraordinarily LOW impedance. They are two pieces of wire welded together.It seems unlikely that leakage from that near-zero impedance circuit over to ground would have any significant effect on the measurement.Fresh water is generally high-impedance (high-resistance) at DC. Water with impurities (such as sea-water) has much more resistance, but still many orders of magnitude higher than a thermocouple circuit which is near-zero.The real question, IMHO, is how do you insert the thermocouple into the water stream? And what exactly is this water you are measuring? I wouldn't stick just any old thermocouple of unknown origin into drinking/cooking water. And maybe not into bathing/shower/laundry water either, at least until you thoroughly clean it, etc. There are special enclosed versions of thermocouples designed for use in potable water.Of course, if you are simply thrusting the thermocouple into a running stream out of the tap momentarily, there probably is no sanitation issue.

author: SNGLinks
author_rank: Regular Contributor
timestamp: March 04, 2015, 04:52:01 pm
content: Thanks for your reply.I have a fault with my hot water system (a combi boiler) The water intermittently runs cold whilst taking a shower.I would like a graph of temp against time to show the 'engineer' who comes to try to repair it again.

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 04, 2015, 06:37:27 pm
content: You could clamp the thermocouple onto the side of an exposed pipe (or tap, or showerhead, etc.)

author: SNGLinks
author_rank: Regular Contributor
timestamp: March 04, 2015, 07:37:51 pm
content: Quote from: Richard Crowley on March 04, 2015, 06:37:27 pmI could do that but it would be a bit laggy because of the thermal inertia of the pipe.I want to show that the water suddenly goes cold.

author: Seekonk
author_rank: Super Contributor
timestamp: March 04, 2015, 09:20:56 pm
content: Sounds like a classic case of calcium buildup in the pipe core of the heater. If an external tank, the cold water source internal dip tube could be broken at the top. That prevents feeding cold water to the bottom of the tank. Instead it feeds into the top diluting the hot water quickly.

author: Richard Crowley
author_rank: Super Contributor
timestamp: March 04, 2015, 09:21:28 pm
content: Yeah, if you want good "transient response" then you will need to hang the thermocouple joint right inside the stream of water.
Measuring weight with a sensor or two - Page 1
Forum section: electronics / projects

author: Biddyyhz
author_rank: Newbie
timestamp: September 05, 2023, 02:57:09 pm
content: Does anyone know of a product that can weigh a minimum weight of 1.7 ounces and up to 300lbs placed on a surface of about 1 meter in area?I am having a hard time rrying to fina anything that will do this? Maybe a Matrix FSR but I can’t find a company that will custom buildAny help would be greatly appreciatedThanks

author: edgaras006
author_rank: Contributor
timestamp: September 05, 2023, 04:40:18 pm
content: The simplest product would behttps://www.amazon.ca/Electronic-Digital-Weighing-Precision-Bathroom/dp/B084TH7RD1+ a 1m2 platform orhttps://activamart.com/products/activa-500kg-weighing-scale-stainless-steel-platform-weight-machine-for-industry-50g-accuracyIf you want to design a custom device I can help with electronic part and maybe you can find somebody for mechanical part.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 06, 2023, 11:33:39 am
content: You can buy loadcells (with strain gauges) in al sorts of forms and strengths. From milli gram, and kitchen scales (a few kg) to weighing trucks. And if you calibrate their amplifier / ADC with your tongue at the wrong angle, you can even force them to output banana units.

author: Biddyyhz
author_rank: Newbie
timestamp: September 08, 2023, 05:18:37 am
content: Thanks but I have to attach it to a piece of suspended fabric….I do appreciate the response though.Bill

author: Smokey
author_rank: Super Contributor
timestamp: September 08, 2023, 06:41:38 am
content: What measurement resolution?What measurement update rate?How is this thing attached? Draw a picture?

author: Marco
author_rank: Super Contributor
timestamp: September 08, 2023, 08:40:44 am
content: That's pretty close to a pallet scale. So weld a frame to suspend the fabric and transfer it to the pallet scale.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 08, 2023, 10:02:51 am
content: Quote from: Biddyyhz on September 08, 2023, 05:18:37 amIf you want a better response, then make a better description. What does this "suspended fabric" mean. Add a sketch or something that gives more insight into what and how you want to measure. Would something in the form of a luggage scale be applicable?
Measurring SPL of highway for a year - Page 1
Forum section: electronics / projects

author: Jolle
author_rank: Contributor
timestamp: February 09, 2016, 09:46:48 pm
content: I am thinking about logging noise measurements from a highway for an entire year. The purpose of my idea is solely to investigate how weather (rain, wind etc.) and seasons (winter tires, leaves on trees) affects the noise emitted from a highway.I have no real experience with a project like this, but here is my plan and then I have some questions afterwards:Buy a cheap dB meter and tear it apartto see if I can access the reading in some way and extend the microphone lead so it could be places outside a window, use a raspberry pi for reading and logging the dB meter together with data from a nearby weather station I can access via the internet. The raspberry should log several readings each minute and after say 10min take the median of the readings to filter out any peak noises and limit the number of data points.Do anybody know of a dB meter which would be appropriate for the project or can tell me if there a certain things I should avoid (bear in mind that my main concern is the noise difference in the different situations, so the accuracy of the meter is not really important - or is it)? Is my thought on logging data and taking the median an okay way to get an estimate or should I implement a more refined method before it is really useful?One possible dB meter could be one like this:http://www.ebay.com/itm/Digital-LCD-Audio-Sound-Noise-Level-Meter-Decibel-Monitor-Pressure-Tester-LU-/161866058282?hash=item25aff80a2a:g:6xgAAOSw5ZBWKM~5but is it worth the try?

author: nctnico
author_rank: Super Contributor
timestamp: February 09, 2016, 10:11:58 pm
content: If the raspberry PI has an audio input I'd use a microphone connected to that. Do some signal processing to get the A weighted noise levels. If I where you I'd store the min/max/average values for each time interval both in A weighted frequency curve and for full bandwidth; you can never have too much data!
MEC XO specs (MEC AH1BV / AH1DV) - Page 1
Forum section: electronics / projects

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: March 29, 2012, 07:45:35 pm
content: I kinda fail to find a data sheet for 12MHz SMD crystal oscillators by MEC labeled AH1BV and AH1DV.They look like the S series, except for the marking:http://www.mecquartz.com/image/download/smd49s.pdfThe label on the first part is"12.000 GMEC AH1BV"And the 2nd one is the same but with "MEC AH1DV" in the 2nd line.Any hint where I can find a datasheet for this or if the specs are somehow coded into the characters?I'd be especially interested in frequency stability (PPM).
Mecanum wheel platform - Page 1
Forum section: electronics / projects

author: rill17
author_rank: Contributor
timestamp: October 30, 2015, 07:07:58 pm
content: I am thinking of building a 4wd platform using mecanum wheels from scratch and im kind of in the dark on what DC motors i should use. The platform should be able to carry a load of around 300kg and measure 800mm x 800mm. the mecanum wheels i am using are 15 cm in diameter. Any suggestions for the DC motors ?? thanks!

author: jwm_
author_rank: Frequent Contributor
timestamp: October 30, 2015, 07:11:35 pm
content: You might try wheelchair motors. They can be found second hand pretty cheaply and are quite beefy. They are usually around 24 volts.
Mechancial TV 1926 style - Page 1
Forum section: electronics / projects

author: Robonz
author_rank: Newbie
timestamp: October 11, 2017, 02:00:35 pm
content: I searched the forum and did not find anyone had built a mechanical TV, so I thought I would post up mine. It uses a 32 hole Nipkow disc spinning at 750 rpm. Its a really fun thing to build that's for sure.Build herehttp://www.taswegian.com/NBTV/forum/viewforum.php?f=35

author: dave_k
author_rank: Frequent Contributor
timestamp: October 11, 2017, 07:08:29 pm
content: Nice work!I assume the waterfall effect of the black bars is an interference pattern from the shutter of the camera you're filming the screen with?

author: texaspyro
author_rank: Super Contributor
timestamp: October 11, 2017, 08:24:15 pm
content: Try a brushless DC motor and modulate the coils with the audio channel... voila, singing motor.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 11, 2017, 08:36:29 pm
content: Wow, the motor PLL / servo is really crude!Tim

author: macboy
author_rank: Super Contributor
timestamp: October 12, 2017, 03:35:38 pm
content: Nice work.Similar technology dates much earlier than 1926. The "Anthony Spiral" hit the market ca.1898.http://www.terramedia.co.uk/media/video/anthony_spiral.htmhttp://www.terramedia.co.uk/media/video/index.htm

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 12, 2017, 04:39:46 pm
content: Quote from: T3sl4co1l on October 11, 2017, 08:36:29 pmIn 1926 it would have been even more crude, I.E. just a regular motor.

author: tecman
author_rank: Frequent Contributor
timestamp: October 12, 2017, 05:17:32 pm
content: I built one when I was in high school (late '60s). I used an LP record and had 360 holes covering an aperture of 1" Photomultiplier for the light pickup. I had a physical (mechanical) contact for the sync pulse and displayed on an o'scope. It was kind of a senior project for physics class. Motor was an 1800 rpm induction motor, running around 1750 rpm. Took a lot of tweeking to get it finally working, but results were satisfying to see.Paul
Mechanical Data distribution protocol and Bus Switch example - Page 1
Forum section: electronics / projects

author: RJSV
author_rank: Super Contributor
timestamp: February 04, 2019, 03:13:12 am
content: A 'simple' binary tree root structure is controlled using a mechanical bus data / address scheme, for access to remote rotary actuators.Addressed end devices then each have two 'output port' rotary signals for unlimited use in either direction (in a session). This is a light-hearted and fun way to teach some fundamentals.The BUS protocol defines three input wheels. The 'SELECT' wheel (SEL) is for placing new input into local position mode (or address). Then, the 'DATA' wheel can accept an address bit, zero or one, in rotary form (CW or CCW).Finally, in the third step, a DE-SELECT input wheel is for placing the main input switch (DATA) back to 'normal mode', where signals pass through (transparent to switch internals).DIAGRAM 1 shows a whimsical snake toy, to illustrate the mechanical bus extended across a roomDia. 2 has BUS OrganizationDia. 3 shows motor pulses neededDia 4 has a internal switch workingsAnd Dia. 5 is picture of a planetary gear for selecting one of two shafts
Mechanical - low pressure non return valves? - Page 1
Forum section: electronics / projects

author: DTJ
author_rank: Super Contributor
timestamp: November 06, 2019, 01:04:37 pm
content: This is a mechanical quest but I'm sure many here will have some ideas.I'm looking for a low flow check valve or non return valve - something like the ones used on fish tanks and aquariums.The things I need are:1) lowest practical operating pressure <20mmH2O would be nice.2) The maximum back pressure would be around 5mH20 (0.5 Bar / 50kPa )3) Very low back flow leakage - the ones I've tested leak down quickly when they only have low back pressure applied.4) simple push on barb or tapered fittings for 4mm or smaller plastic tubing.5) Cheap!I've tried ones like in the picture below but they reverse leak badly at low pressures.Any ideas where I might find something?

author: senso
author_rank: Frequent Contributor
timestamp: November 06, 2019, 01:30:14 pm
content: SMC or Festo have low pressure non return valves, but they wont be cheap like the aquarium chinesium ones..

author: DTJ
author_rank: Super Contributor
timestamp: November 06, 2019, 01:43:34 pm
content: Quote from: senso on November 06, 2019, 01:30:14 pmYes they make some nice gear. Expensive though. I think I need to find something made in very high volume to get it cheaply.

author: StuartA
author_rank: Regular Contributor
timestamp: November 06, 2019, 02:59:02 pm
content: See if you can find a distributor specialising in accessories or consumables for use with chromatography equipment in chem labs. They might have something a little better than the aquarium types, but still affordable.

author: DTJ
author_rank: Super Contributor
timestamp: November 07, 2019, 01:34:44 am
content: Quote from: StuartA on November 06, 2019, 02:59:02 pmThanks, good idea. I'll check out some of the scientific suppliers.I stumbled across Luer lock valves last night. I might sample one of those as they look promising.https://www.industrialspec.com/shop/medical-component-products/medical-flow-control/luer-check-valves.html