hybridfree/eevblog-posts huggingface dataset:
Selling non RoHS equipment? - Page 1
Forum section: electronics / projects

author: peps1
author_rank: Regular Contributor
timestamp: April 28, 2017, 02:06:12 pm
content: Hello guys,Trying to learn about EU directive that effect electronics, and was wondering if someone could explain this one to me:RoHS Non Compliant Parthttps://www.rapidonline.com/silonex-light-dependent-resistor-norps12-58-0132RoHS Compliant product using that parthttps://www.rapidonline.com/rapid-ldr-pcb-project-kit-70867What exemption is allowing this to be sold in the EU?(Sorry if this should have been posted in another section like general chat, just thought it may fit under the "Technical Stuff" remit)

author: Neilm
author_rank: Super Contributor
timestamp: April 28, 2017, 04:02:39 pm
content: There are a couple of things it could be. First thing I notice is it is a kit - there may be something in legislation that says it doesn't apply to descrete items and kits. (I work in a big company and that loophole would't apply to our products - I am by no means an expert)Alternately, the sensor supplied in the kit is not the one identified but a similar one that is RoHS compliant.

author: peps1
author_rank: Regular Contributor
timestamp: April 28, 2017, 04:12:08 pm
content: Yes, its an interesting one, and being an own-brand product for Rapid I would be surprised if it was just a mistake/oversight.I did check to see on the data sheet for the kit, and it has that same Silonex Light Dependent Resistor listed that is non RoHS

author: Matir
author_rank: Contributor
timestamp: May 04, 2017, 04:05:56 am
content: Not authoritative by any means, but this article implies that "kits for self-assembly" are not covered by RoHS:https://www.electronicsweekly.com/blogs/directive-decoder/eu-rohs/kits-and-the-blue-guide-2007-03/

author: fcb
author_rank: Super Contributor
timestamp: May 05, 2017, 12:36:25 pm
content: There used to be a RoHS exemption (I think it ended in 2009 or something) for Cadmium in photocells for portable audio gear (vactrols typicall used in the compressor stage) - a few of the boutique synth companies ignored/ignorant of the law and made/sold products into the EU.Not sure what the rules are in the US or the rest of the world, but Cadmium vactrols are pretty rare these days.
Selling OSHW kits or devices without FCC or CE cert? - Page 1
Forum section: electronics / projects

author: nardev
author_rank: Unknown
timestamp: September 12, 2017, 12:56:26 pm
content: I'm sorry, didn't know where to start this topic.I have been reading all around internet and i still can't find the exact answer to my question.Hypothetically, i have this scenario:I made an open-sourced hw device, which can be sold as a kit or assembled and i wish to sell those online, directly to a customers, not to re-sellers.I'm based in China or some other country which doesn't require such certifications.The kit is consisted of mainly parts which are FCC and CE compliant, only the enclosure (plexy enxlosure) and PCB is something which is not CE/FCC tested.The device can be BT/WiFi enabled, can have some other radio transceivers etc...It is something like arduino kit with few additional functionalities. For home use.Am i able to freely sell that kit/device and ship to USA/Canada/EU etc?Is there any other limitation for me?Do you have any experience where such a device was banned from importing?In general, what is the status for selling online, individually OSHW devices and kits?Is there any limitation from online marketing those devices?thnx

author: CM800
author_rank: Frequent Contributor
timestamp: September 12, 2017, 01:00:18 pm
content: Come on....This question's been asked before, many times, especially on EEV Blog.

author: nardev
author_rank: Unknown
timestamp: September 12, 2017, 11:07:49 pm
content: Thank you, forgot to to search the forum before.ROFL, the first result google give me is this page this topicI already read most of those pages before posting here but as i said, "i still can't find the exact answer to my question."
Semiconductor curve tracer project - Page 1
Forum section: electronics / projects

author: starphot
author_rank: Contributor
timestamp: February 28, 2021, 08:22:12 pm
content: It's been awhile tinkering in my shop. Retired consumer electronics repair technician. I got my start in the US Navy in the early 1970's and one of the most fascinating pieces of test equipment I have came across was the curve tracer. It was a Techtronics beast. I got so adept on using that thing by tinkering with the various devices, my chief had me do checks for others on the ship. One thing I noticed was the different forward drops of the different color LEDS that were available back then and compared those with zener diodes that were available. I noticed that the LEDS had a sharper knee characteristic than the lower voltage zeners. Then I was sent to train on another bench and I was in front of the class describing a circuit and mentioned that the two LEDS in the circuit was being used as a voltage reference. The two experienced instructors was dumbfounded with my answer and I told them my experience with the LEDS on the curve tracer. This was to a bench add-on and they were wondering the function of the LEDS in the circuit as there was nothing there to indicate their function.I've been busy lately upgrading my two power supplies from the dodgy 1970's version to a more modern types, still using most of the old parts. I also made a prototyping bench out of a Bell & Howell trainer around 2007, putting in a function generator, pulse generator, variable split-rail supply and a separate 5 volt supply from scratch. The prototyping bench with my new project, the curve tracer. Old 1968 Hewlett Packard scope shows the proper curve family of an PN 2222 transistor. I've seen the kits online, but they have some limitations. Bit by bit, I'll get the thing done.Joe

author: Electro Fan
author_rank: Super Contributor
timestamp: February 28, 2021, 08:37:41 pm
content: Very cool projectNeat story too about how your training and experience gave helped you develop keen insights.Curve tracers are very nifty. Keep us posted on your progress.

author: daisizhou
author_rank: Super Contributor
timestamp: March 01, 2021, 12:24:34 pm
content: Look at this picture

author: starphot
author_rank: Contributor
timestamp: March 02, 2021, 12:24:49 am
content: daisizhou,Already my schematic differs from the one you show. I used a 74C90 decade counter with the BCD outputs and use 100K resistor chains to make the staircase generator. There will be a bias section to accommodate the various FET types and to connect possibly to a vacuum tube tester as that has the sockets, switching and voltages for those.
Semiconductor ten year lifetime parameter shift tests - Page 1
Forum section: electronics / projects

author: splin
author_rank: Frequent Contributor
timestamp: September 16, 2014, 09:13:00 pm
content: Whilst trying to understand the long term stability specifications for a voltage reference, I came across this post by a TI engineer which quite surprised me as I've never come across any mention of it before.http://e2e.ti.com/support/other_analog/etc_analog/f/247/t/343137.aspxQuoteAnd from the link in that post:http://e2e.ti.com/blogs_/b/precisionhub/archive/2014/02/20/ic-long-term-stability-the-only-constant-is-change.aspxQuoteTo be clear, I am not surprised that lifetime testing is done, but by the fact that it is apparently an industry standard test whereby parameters must not shift by more than 100% over 10 years and I was completly unaware of it.So the question is, is this almost universally known by competent engineers and its just me showing my ignorance?And in another reponse in the forum by the TI engineer:QuoteCan anyone point me to find some more of these industry standards as it seems I might have a missed an important part of my education?Splin

author: MK
author_rank: Regular Contributor
timestamp: September 17, 2014, 09:29:09 pm
content: They use the arrenhius equation to tell them what temperature will give them "10 years" of ageing in a week for example.It does have to be used with caution as some suppliers were using it badly to declare that their voltage references would only age at 1ppm in 10 years or so, clearly wrong on that one.

author: David Hess
author_rank: Super Contributor
timestamp: September 17, 2014, 10:37:00 pm
content: Quote from: MK on September 17, 2014, 09:29:09 pmThe Arrhenius equation was the first thing I thought of but I assume they temper it with historical data on performance. I seem to recall reading about the false 1 ppm voltage reference specification in connection with it in ED or EDN or something similar.
Semtech SX1278 LORA: clkout on DIO5 not working - Page 1
Forum section: electronics / projects

author: elktown
author_rank: Newbie
timestamp: June 30, 2019, 03:38:40 pm
content: Hi,I'm using a AI-Thinker RA-01 and RA-02 board with SX1278 ICs in Lora mode.I can't seem to get a message with a payload longer than four to six bytes transmitted successfully with a bandwidth of 62.5kHz and a spread factor higher than 7. Usually the header (including length of packet) and the first four to six bytes of the payload are received correctly. Everything received afterwards is garbage.My first guess was that the (very cheap, Ali-Express) AI-Thinker modules use a inaccurate crystal circuit. So I tried configuring DIO5 via REG_IOMAPPING2 as clkout to compare the two modules.So far I haven't managed to see any signal at all on DIO5 neither during rx nor tx when the oscillator should be active. Am I missing something? Do I need to be in a specific mode to configure DIO5?ThanksToby
Sencore LC102 LCD backlight? - Page 1
Forum section: electronics / projects

author: Spike
author_rank: Regular Contributor
timestamp: August 13, 2025, 06:28:53 am
content: Has anyone here added a backlight to their LC102 (or other Sencore LCD Z-Meter), or know of a description online of such a project? I’ve recently picked up one of these and the readability of the LCD is everything I thought it could be and less.To be fair I kind of already knew this going in but I grabbed an LC102 instead of an LC103 probably for the same reasons as everyone else who does; cost. Well that and being able to calibrate it if ever needed. I have to admit that even though I anticipated poor readability it is worse than I thought. This isn’t something I’m looking to do in the short term unless someone else has already done all the work. I’d love to hear about it if so.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2025, 06:29:40 am
content: so far nothing has been done or put on the webi was curious myself since i have one tooif say :it would have been possible to convert it to led instead, or even glcd the display are driven by 3x 32 bit shift registersyou have schematics floating on bama and other place, im not sure the lcd back support led lightning or ccfl or elsethe eternal problem with the 103: no one has ever leaked the calibration software for it, but the 102 can be DIY calibrated

author: Spike
author_rank: Regular Contributor
timestamp: August 14, 2025, 07:45:27 pm
content: Ah, yeah. I didn’t think to mention it but an alternative display would be even better. I’d settle for a backlight, though.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 15, 2025, 01:09:05 pm
content: you will need to decode the display logic and implement whatever display you want to put there ....or find similar display(s) glass who can accept ccfl or led backlight, i think the lc77 lc102 share the same display glass, but i never saw any backlight put on themthe big display has 2 driver ic / shift register, and the other voltage has 1 driver ic
Send data from MCU to smartphone using RFID/NFC - Page 1
Forum section: electronics / projects

author: satyamfifa
author_rank: Regular Contributor
timestamp: November 15, 2024, 09:10:12 am
content: Hey All,I'm looking for the simplest way to send data from a MCU to smartphone using NFC/RFID. I want the data to appear as text tag on the smartphone (NDEF text), so it can be read on the smartphone without requiring an app. I'm currently considering NTAG 5 Boost because it requires small antenna size.If anyone has any better suggestion I would really appreciate it.Sparsh

author: SiliconWizard
author_rank: Super Contributor
timestamp: November 15, 2024, 09:12:31 pm
content: Yes this chip looks pretty nice for that. You can otherwise consider the ST25DV series from ST. Similar. Cheaper. There are small breakout boards available for cheap for the latter, if you want to evaluate them before making a decision.
Send Text Message Using ESP8266 When Home Alarm Goes Off - Page 1
Forum section: electronics / projects

author: DonEduardo
author_rank: Newbie
timestamp: December 28, 2014, 12:50:36 am
content: Here's a project that might be of interest to anyone wanting to experiment with this new wifi module (ESP8266). It's worked flawlessly for two weeks of testing. With an Arduino Nano and a wifi module (ESP8266) I am sending a text message to my phone whenever my home alarm system is sounding. Complete details of the design and links to source code included in the descriptions of the videos.http://youtu.be/TchYLpPWnbE
Sending SMS from LTE module, are old AT commands useless in 4G only network?  - Page 1
Forum section: electronics / projects

author: Miyuki
author_rank: Frequent Contributor
timestamp: July 13, 2023, 10:12:22 am
content: Hi folks,I have a Cinterion PLS63 data module (for 2/3/4G networks)And need to send SMS alerts.When it is connected to a 2G network everything is OK, I can use simple AT+CMGS commandBut the 2G networks are no longer available in many areas.This simple way does not work when it is connected to 4G and as I understand it SMS service is only available as a data transfer to the network priveder server.Do you have any experience with it?Do I need to go thru IP to send an SMS now?

author: thm_w
author_rank: Super Contributor
timestamp: July 14, 2023, 11:50:09 pm
content: Google says:https://www.sharetechnote.com/html/Handbook_LTE_SMS.htmlhttps://stackoverflow.com/questions/72043231/is-sms-over-ims-that-importanthttps://forum.sierrawireless.com/t/em7455-sms-over-ims/18997/3AT commands:https://www.gs-m2m.de/fileadmin/Bilder/GSM_Module/Module/pls83-W/plsx3-w_atc_v01002d.pdfMaybe you can ask the manufacturer for an example, I don't see anything online immediately.

author: bookaboo
author_rank: Frequent Contributor
timestamp: December 15, 2023, 10:42:19 am
content: Check with your SIM provider whether SMS is enabled over 4G.Define "doesn't work", are you able to see and connect to the 4G network (i.e. +CREG=x,2 or x,5)?Long term you would be better looking into NB-IoT / CATM enabled modules (if those networks are up in your area).

author: Miyuki
author_rank: Frequent Contributor
timestamp: December 15, 2023, 11:27:45 am
content: It was solved after a discussion with Cinterion supportIt was a problem with configuration, and now it works well under both 4G and 2G

author: peter-h
author_rank: Super Contributor
timestamp: December 15, 2023, 12:19:12 pm
content: AFAIK all networks whether 2G (GPRS, EDGE) 3G 4G 5G use ATDT*99# to get a TCP/IP connection. This initially needs GSM...Another approach to sending SMS is to use an email (or IP) to SMS gateway. These are used for commercial bulk SMS sending (e.g. a bank sending 100k SMSs per day for payment auth) isn't going to have a GSM modem (I believe even modern phones can emulate one; in the past one used a Nokia 6310 etc) connected to some computer.About 10 years ago I was involved on a project which transmitted SMS alarm messages and it was a right PITA, mostly because the modem market is almost dead. Siemens became Cinterion which dropped many models. If I was doing this again I would use a modem module from U-BLOX. They are much bigger than Cinterion.

author: pepitoxx
author_rank: Newbie
timestamp: December 13, 2024, 09:53:33 am
content: Hi @MiyukiPlease, could you share the configuration values you changed after discussing with Cinterion. I am having the same problemThanks
Sense a load - Save Energy on Inverters and USB-Chargers - Page 1
Forum section: electronics / projects

author: merkatorix
author_rank: Newbie
timestamp: March 20, 2022, 12:22:31 am
content: Short BackgroundWhen using a battery to power an inverter or USB-Charger, the idle current annoys me a bit. I really would like to see it to be negligible compared to the self-discharge of Li-ion or at least Lifepo4 (Offtopic: I'm a battery beginner and wonder if my future Daly BMS will compete in this department).The easy solution: Switches for every consumer. However, I'm lazy and like stuff to be simple for the user (and I search for reasons for automation.)QuestionIs there a way to sense if some load is plugged into the inverter or USB charger? If possible, I could use a µController, which senses the load and only turns on the devices if an actual load is connected.There might be a mechanical solution if it is only about the plug. But there could be a plug in the socket without any load attached. I imagine there are two levels within this question:Sense the load before turning it on.Sense the load while a device is running.I wonder if there are feasible ways to sense a load. I could imagine a method for both cases, but I wonder if there are much better ways to tackle the problem.Just after turning on the battery, I could imagine it to be possible to sense if something is plugged into the plug by applying a small voltage and checking if some current flows. If there is a µController present, there is 5V, which could be connected to USB sockets. If the load starts to draw current, it could be connected to the actual USB-C charger.I imagine the same to be possible for 230V devices; however, there will be a whole topic about electric safety. If that could work out, an appliance could be sensed without any chargers or inverters having to be in an idle state.If a device is already plugged in and the inverters/chargers are running, I imagine the problem to be more challenging (Especially for the 230V of the inverter). In that case, a shunt could be used. For 230V, maybe an intelligent power plug, which already has an integrated shunt?If there is less than X mA peak power consumption for an hour or something, we could turn off the device and start to sense if an actual load is present.I bet there are established methods for this problem used by people, who usually don't use trash bags as a weather-resistant case for their products. Do you have hints? In the end, just using shunts everywhere might be feasible and not too much effort for a small project, which should end up in a big universal power bank using cheap Lifepo4 cells.
Sense pin functionality with LT3080/LT3083 - Page 1
Forum section: electronics / projects

author: gxti
author_rank: Frequent Contributor
timestamp: March 10, 2013, 10:28:48 pm
content: I'm currently working on a beefed up bench version of Dave's uSupply. Well, the only thing it really has in common with the uSupply is the analog stage, but I digress... I'd like to see if I can add a separate sense return i.e. a Kelvin connection as part of the feedback loop. In particular, I'd love to move the current shunt downstream of the supply so that the dummy load doesn't conflate its readings, and to do that the voltage sense has to happen after the shunt to get precise line regulation.It seems like the obvious way to do it is to make the voltage op-amp's feedback come from the sense wire, instead of the set pin. Is this a good idea? Does it harm stability? If it works, does it end up making the LT3083 just an expensive pass transistor?The first picture is the original schematic which is more or less just a higher-current version of the uSupply output stage. The second one is the "improved" version. More illustrative than anything, I have no idea if it'll work...

author: gxti
author_rank: Frequent Contributor
timestamp: March 31, 2013, 01:42:28 am
content: Just today it dawned on me that I could plop this in LTspice. I rarely use LT parts so I tend to assume whatever IC I'm using won't be available, so when it is it doesn't even occur to me. Anyway.I've set up a crude simulation and the good news is there doesn't seem to be a difference with driving the set pin statically vs. incorporating feedback from the output. The bad news is either way it oscillates when current-limited! I'm guessing this might just be a limitation of the LT3083 model, but here's what I've got. I seem to be analog-challenged so if anyone has tips on stabilizing the circuit (or the simulation), please share!I'm beginning to think the solution with discrete pass transistor instead of LT3083 would be much better value (1/4th the cost probably) but my simulations on that front are even more dismal.
Sensign a person by a broken light beam? - Page 1
Forum section: electronics / projects

author: zenerbjt
author_rank: Regular Contributor
timestamp: September 24, 2020, 01:08:04 pm
content: Dear Engineers,Years ago I worked on a sensor system for blind and partially sighted people (in a huge home for the blind) whereby we had light beams going across the corridor, and whenever someone walked past it would tell them where they were in the huge building. (they would be walking whilst holding on to the rails on the wall) I cant remember what sort of sensors and LEDs we used for this. Do you think it is likely we would have used infra-rad? I mainly worked on the power supplies so cant remember the details of the “light beam break” sensors.Can you possibly help with a suitable sensor/LED system for this?

author: TheMG
author_rank: Frequent Contributor
timestamp: September 24, 2020, 01:25:18 pm
content: Such sensors are actually super common in industrial systems, and are available in both visible (red) light and infrared varieties, and nearly infinite options as far as form factor, operating range, voltages, etc.Search for "photoelectric sensor".

author: Gyro
author_rank: Super Contributor
timestamp: September 24, 2020, 07:16:30 pm
content: These things have been used for decades (I remember the first one I saw had a low frequency modulated dim filament lamp in a parabolic reflector as the source) in shop doorways as footfall counters.Simply use an IR LED and a phototransistor and a couple of cheap plastic lenses and IR filters. Modulate the LED and AC discriminate the output of the phototransistor to reject ambient lighting conditions (less of a problem with widespread LED lighting, but sunlight is still an issue).

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 25, 2020, 08:33:54 am
content: These are indeed very common industrial building blocks, and they do tend to use IR light, though that is not mandatory.If you want to build your own, then you can combine all the electronics in one box by using a reflector on the other side. Don't use a mirror, they are hard to align the light back to the origin, while reflectors are designed to always do this.Also: Use a blinking led. Frequency can be almost anything. (avoid mains frequency), then AC couple the input and amplify.IR receivers for remote control are very common, cheap and easy to use. You can blink a LED at the frequency your receiver chip likes (often between 36kHz and 43kHz) for a milli second or so, and then turn off the led. The output of these decoders is "On" (high or low, I forget) when the LED is blinking at around 38kHz,This is an easy job for a small microcontroller, but can also be done with just analog electronics.When using this scheme, you may have interference to and from other IR receivers in the neighborhood.The best ways to mitigate these effecs is to add a lens to the LED to focus the beam, use a small LED current, and shield the IR receiver from stray light.
Sensing a magnet in motion - Page 1
Forum section: electronics / projects

author: atferrari
author_rank: Frequent Contributor
timestamp: June 18, 2014, 06:33:57 pm
content: I expected to sense a magnet in motion passing close to this coil (from a discarded relay), with the scope in the lowest scale (2mV/div) but no joy.In case you ask, continuity is OK and magnets were moved in any position and in any sense you could imagine wrt the coil.I tested all the magnets in my drawers. While I know that no one is made of Neodymium and the diameter of the coil is really small, I expected a minimal output at least.What could I be doing wrong?

author: retrolefty
author_rank: Super Contributor
timestamp: June 18, 2014, 06:45:18 pm
content: Well it's going to be a very short duration pulse, what time-base setting were you using and was your trigger setting correct?

author: robrenz
author_rank: Super Contributor
timestamp: June 18, 2014, 06:47:30 pm
content: And is it a digital scope in single shot mode or analog storage?

author: atferrari
author_rank: Frequent Contributor
timestamp: June 18, 2014, 07:00:03 pm
content: Quote from: robrenz on June 18, 2014, 06:47:30 pmTriggered mode, not auto.Quote from: retrolefty on June 18, 2014, 06:45:18 pmNo core in the coil. Have to check with it now.Gracias for replying.

author: Richard Crowley
author_rank: Super Contributor
timestamp: June 18, 2014, 07:01:16 pm
content: I would think the coil would be more sensitive with a ferrous metal core (vs. apparently air?) A chunk of iron, or even 2-3 big steel nails, etc.How big is the magnet? How far away? Don't expect kind of range more than a couple of mm.

author: Wytnucls
author_rank: Super Contributor
timestamp: June 18, 2014, 07:08:20 pm
content: Make your own coil and have the magnet passing through it, if possible. The signal should be must stronger, especially with Neodymium.Here is the signal you can expect with a 40 turn coil and a neodymium cylindrical magnet falling through it:

author: atferrari
author_rank: Frequent Contributor
timestamp: June 18, 2014, 07:29:16 pm
content: Gracias to you all.Found a stronger magnet (sheer luck) and got up to 10 mV. With a core from another relay, in, I get up to 20 mV.Thanks again.

author: 128er
author_rank: Regular Contributor
timestamp: June 18, 2014, 07:48:49 pm
content: Could be a nice experiment for an evening or two.Took some old relays and magnets that are laying around and do some measurements.@AtferrariWhat are your requirements with respect to the distance from the coil to the magnet? Or other requirements.

author: atferrari
author_rank: Frequent Contributor
timestamp: June 18, 2014, 08:04:53 pm
content: Quote from: 128er on June 18, 2014, 07:48:49 pmI was simply trying to recreate, out of curiosity, the sensor described for a simple pendulum where the bob (and associated magnet) pass, back and forth, above the spires (which lay flat below them).It is evident that the coil cannot have core, otherwise, the pendulum would be influenced by the interaction magnet-core.Say that I have a minimal idea of what to expect now. Gracias.
Sensing AC voltage - Page 1
Forum section: electronics / projects

author: ploutone
author_rank: Newbie
timestamp: May 31, 2017, 09:50:48 am
content: In a project I'm working on (Totem pole PFC) I need to sense the input AC voltage, scale it down, rectifing it/adding an offset and then send to the ADC of the digital controller to use in the control loop (average current control)I tried a number of circuit, such as a voltage sensing transucer (LEM LV-25), but it has 3 problems:it's expensive, it's slow (<10kHz BW) and it has accuracy problems as the large power resistors heat up.So I thought about using a differential amplifier and detect the line voltage between L and N, set ground to half ADC reference, i.e. 1.25V and have the output voltage equals 1.25 + k Vac, where k is the differential amp gainThis circuit :Is this circuit going to work properly? how can I add isolation? and for the ground for (V-) and 1.25V voltage reference, will it be the GND of the MCU or the totem pole? sorry for the silly questions.Thank you very much.

author: fcb
author_rank: Super Contributor
timestamp: May 31, 2017, 10:06:33 am
content: 100K on the inputs to the opamp - probably take that up by a factor of 10x to 50x if you're sensing mains.Also, be careful where you measure it from - you'll get different results if you measure after your front end noise suppression.

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 31, 2017, 10:15:14 am
content: Quote from: ploutone on May 31, 2017, 09:50:48 amThis system works and is used lots but you need to add some things in your circuit. Firstly the breakdown voltage of the resistors, for standard 250mW wire ended its common to use 3 resistors in series, so that's 6 in total. If you are going to implement it in smt then a much bigger problem. Secondly the power dissipation (helped by multiple resistors) and finally the current injection into your reference node. This also means you want quite high values (typically at least 1000K per leg) and very high tolerance to achieve the maximum common mode rejection ratio.

author: ploutone
author_rank: Newbie
timestamp: May 31, 2017, 12:56:47 pm
content: Quote from: fourtytwo42 on May 31, 2017, 10:15:14 amThank you for your help,for the isolation and the GND, I'm using two grounds, one for the MCU and one for the totem pole PFC, which ones I need to use for the op amp?

author: fourtytwo42
author_rank: Super Contributor
timestamp: May 31, 2017, 06:07:04 pm
content: Quote from: ploutone on May 31, 2017, 12:56:47 pmThats a slightly more complicated question. Normally a circuit measuring voltage in this way would have the ground leg of its power supply capacitevly coupled to earth or the common of the grid supply, the latter having Y capacitors that capacitevly couple it to earth. Add a VDR or two normally found in the input to a power supply and you have a coupling system that will limit the common mode voltage seen by the op-amp. In other words you have to consider the whole system, not just your op-amp circuit in isolation.
Sensing light in the gap between emitting light? - Page 1
Forum section: electronics / projects

author: Artlav
author_rank: Frequent Contributor
timestamp: January 15, 2015, 09:14:33 pm
content: I want to make an LED light that will only run in the dark.Problem is, a light sensor will pick up the light emitted by itself, and won't be able to tell the difference.What i was thinking, since this is an LED, is to turn it off for a millisecond, measure light level (a photodiode), then turn it on.Would that actually work?Is that a common solution, and if yes, what is it called that i can google?

author: RedOctobyr
author_rank: Contributor
timestamp: January 15, 2015, 09:30:41 pm
content: Can you simply separate the sensor enough that it's own light doesn't trigger the sensor? Kind of like how an auto-illuminating incandescent nightlight works?Sent using Tapatalk.

author: mazurov
author_rank: Frequent Contributor
timestamp: January 15, 2015, 10:16:36 pm
content: Quote from: Artlav on January 15, 2015, 09:14:33 pmI would call it modulation. The idea is to change the current to a LED in a pre-determined manner, like feed it with a squarewave at 1KHz say. Then you will be able to easily distinguish between light from the LED and sunlight (random) or a light bulb (50 or 100 Hz for your location).

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 16, 2015, 01:42:17 am
content: Yes, you could do it with a sampler.Even if there is feedback, it acts to regulate the ambient light level rather than prevent the device from working. Assuming the loop between sensor and light is compensated, of course. Getting the desired level of illumination simply means setting the loop gain and offset properly.Tim

author: LaserSteve
author_rank: Super Contributor
timestamp: January 16, 2015, 05:20:35 am
content: Hack a common solar yard light. They do what you want and schematics are all over the web.If that is not your cup of tea, consider placing a small cap across the led, allow the photocurrent to charge it, and use the comparator function on the microprocessor to function as a measuring tool. There are a few app notes out there on using the same LED as a source/phototransistor.http://iopscience.iop.org/1742-6596/76/1/012054http://playground.arduino.cc/Learning/LEDSensorhttp://www.evilmadscientist.com/2007/a-simple-and-cheap-dark-detecting-led-circuit/http://www.forth-ev.de/filemgmt_data/files/TR2003-35.pdfSteve
Sensing multiple bidirectional DC currents from 5mA to 20A? - Page 1
Forum section: electronics / projects

author: opampsmoker
author_rank: Regular Contributor
timestamp: October 03, 2020, 10:15:36 am
content: Hi,We need bidirectional current sense, for Bi-di DC currents ranging from 5mA to 20A.Please could you verify out anticipated method?.......Please could I hold off on the accuracy requirement for the moment?….I mean, we will be measuring some 100 different currents, and if they are all inaccurate by the same degree, then that’s fine.The bidirectionality is making me think of Hall sensors. I am thinking one allegromicro.com hall sensor for say 0.4A to 20A detection. Eg the ACS724LCACS724LC Hall sensor:https://www.allegromicro.com/en/products/sense/current-sensor-ics/zero-to-fifty-amp-integrated-conductor-sensor-ics/acs724-5Then for 5mA to 0.4A, we will need, I believe a custom made Hall sensor, involving a custom split torroid and the Hall sensor placed in the split (as on page 11 of the following)https://www.melexis.com/-/media/files/documents/application-notes/current-sensors-calibration-application-note-melexis.pdfWould you agree with our intended ploy?

author: coromonadalix
author_rank: Super Contributor
timestamp: October 03, 2020, 12:34:33 pm
content: The acs sensors would be fine for you, lots of schematics and code on the webYou could add a calibration / compensation routine in the coding ...

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 03, 2020, 01:00:17 pm
content: Use a current shunt with a low offset amplifier, then a high dynamic range ADC and SPI isolator if you need isolation.

author: jbb
author_rank: Super Contributor
timestamp: October 03, 2020, 06:35:38 pm
content: For best performance, as NihaoMike says, shunt + amp + ADC on the line side.I’d look at the LEM CKSR 25-NP as well. It’s a little expensive but it’s isolated and pretty accurate. I can’t remember, though, whether this device will be OK if you apply the main current in the absence of the LEM auxiliary supply. Check the data sheet...Is it DC or AC you’re measuring? Is 20A going to be peak or continuous? Can you use a range switch or do you want to get the whole range in one go?
sensing the BEMF by adc - Page 1
Forum section: electronics / projects

author: amirkargar110
author_rank: Contributor
timestamp: November 11, 2017, 03:48:23 pm
content: hiI made a ESC. now I want to determine the 6 states of turining the BLDC.how can I determine a value for my adc read to decide for turning states?when I turn the motor with my hand the showed BEMFamplitude changeis very low , so that I cant deside about the value.the shematic is attached
Sensing touch on large metal frame - Page 1
Forum section: electronics / projects

author: cubeflake
author_rank: Contributor
timestamp: March 07, 2019, 08:17:10 am
content: Hi all!I'm kind of stuck with an interesting problem and I was wondering if anyone has an idea on how to proceed. A client of mine has an arts object that consists of a relatively large steel frame (like a painting) and they want to detect a person touching the frame.They were trying capacitive sensing, using the frame as the sensing element but the change in capacitance between touching/non-touching is too small to detect reliably.We are now considering sensing the 50 Hz noise that a person always picks up, but that would be quite location dependent, so also not ideal. Another approach is was thinking of is to use a load cell, but I'm not sure if that would be sensitive enough to detect touch.Any ideas?Cheers!
Sensitive pre-scalers and input amplifiers - Page 1
Forum section: electronics / projects

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 15, 2015, 05:58:02 am
content: Hi allI have a couple of projects in mind, both need prescalers, but both also need to be pretty sensitive.The first is to directly read a frequency using an arduino, but it needs to accept up to 40MHz, so a 10:1 ratio would work nicely (the same ratio suits my second project also), in my experiments anything over 6MHz input was unstable.Input sensitivity needs to be in the region of 10mV minimum (again suits both projects)My second project is to prescale a frequency counter input to allow signals of up to 600MHz (real world use) if it does a GHz that is fine too, I just wouldn't use it, like I mentioned a 10:1 ratio would be plenty (to try and keep both project circuits similar).Basically I want to hear any suggestions of suitable pre-scaler options, or input amps etc, that would allow me to sense that low 10mV from 10Hz-600MHz, to hook into a prescaler to feed either an existing frequency counter, or an arduino.I have purchased some NE5204 and NE5205 amplifiers, once they arrive I will have a play with those to see if they amplify the low levels the way I need them to.

author: German_EE
author_rank: Super Contributor
timestamp: September 15, 2015, 10:17:23 am
content: The input stages of most frequency counters use a chain of MMIC chips that both amplify the signal and clip it to the levels of the 5V/3,3V supply. In this case 'The Signal Path' has the information that you need:

author: Marco
author_rank: Super Contributor
timestamp: September 15, 2015, 11:45:52 am
content: We hada threadabout a 10 dollar frequency counter before which also had schematics.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: September 15, 2015, 09:14:41 pm
content: Thanks for your input, that helped.Anyone know of a prescaler that does a divide by 10, rather than the other more common ratios?
Sensor board using energy harvesting - Page 1
Forum section: electronics / projects

author: didjcodt
author_rank: Newbie
timestamp: October 24, 2015, 05:01:37 pm
content: Hi,I'm making a new post as I post now the whole schematic.The goal of the project is to monitor energy consumption by putting a current clamp on the main and transmitting this consumption on a server located in the same house (the transmission is based on Bluetooth Low Energy). I also let another input to monitor the voltage (using a basic 240->12V transformer you can found on ebay) for a better accuracy.As the current clamp gives a proportional current on its output, I can use it to sense the current flowing through the main and also to get some energy to have a better autonomy than using batteries alone (I'm storing this energy in a 100 mF capacitor via an energy harvesting and power management chip)The upper left part of the schematic is the two sensing inputs, and a shunt regulator to get a proper 1.24V output for harvesting. The lower left is for battery management and energy harvesting, while the right is for the micro-controller. I'm using a Bluetooth Low Energy CC2640 chip from TI and an inverted F antenna.As I'm far away to be expert, I'm looking for comments to see if my schematic is correct (is it readable ? Are my components correct ?) and advices for this project (and for circuit design in general, if you see something I've badly done !)I'm also looking for advices in the RF part of the circuit as I've never done RF.Thanks
Sensor cable shielding with wall wart powered acquisition board - Page 1
Forum section: electronics / projects

author: _joost_
author_rank: Contributor
timestamp: April 06, 2020, 04:58:46 pm
content: I have a data acquisition board which is powered by a 5V wall wart. It has a single input connected to a sensor on 6 to 12meter length cable. The signal cable is a shielded twisted pair and besides the signal itself carries also power (3.3v) and ground for the sensor.There is no ground terminal at the PSU, nor at the acquisition board nor sensor. Normally I would connect the sensor cable shield to instrumentation ground at the board terminal but there is no such opportunity here. There is considerable 60Hz in my input signal and I can filter out a considerable amount as my frequency range of interest is higher than 60Hz. However, I would like to do the best possible and somehow get that shield active. What are my options? Get a wall wart with grounding (hard to get and expensive)? Add a grounding terminal at the board and let customer find a ground connection (impossible for consumer applications I think)? Or is this the best I can do?
Sensor circuit? - Page 1
Forum section: electronics / projects

author: metertech58761
author_rank: Frequent Contributor
timestamp: March 23, 2023, 09:01:18 am
content: Can anyone tell me how this particular circuit is supposed to work? I THINK it is some kind of temperature sensor but I have no way to verify.The output goes into a 6821 PIA, and the software reads the pin it's connected to and proceeds accordingly.There are two different arrangements, depending on whether the board is part of the load management terminal (full circuit) or the field test unit (the left 3 components omitted, which apparently renders the circuit inert).

author: SeanB
author_rank: Super Contributor
timestamp: March 23, 2023, 10:31:02 am
content: Monitor for the 12V circuit, the Jfet is normally pinched hard off if the 12V is present, but if it is not there the Jfet turns on, pulling the comparator input to below the reference voltage, and thus pulling the output low. Little bit of hysteresis provided by R42, R43 and C28, so it switches cleanly as the voltage on the Jfet gate drops, as it has a RC filter on it that takes roughly 80 seconds to either charge or discharge, so the microcontroller can see, based on the state of the pin at power up, so if it takes roughly 2 minutes to go high, it is the load management unit, and if it is high on power on, or after roughly a second, it is a field test unit. Likely they all power up as field test for 2 minutes or so, before changing operation mode, probably to allow for calibration or adjustment.

author: metertech58761
author_rank: Frequent Contributor
timestamp: March 23, 2023, 01:44:20 pm
content: With that, I would assume that it's a soft-start delay, likely to allow the transmitter and receiver daughterboards to warm up and stabilize before acting on commands.There are two 12V supplies for some reason, one powering the I/O and transmitter daughterboards, the other powering the receiver daughterboard and bulk supply for the 5V regulator. This circuit sits on the receiver daughterboard.The code for the field test unit does not check the output of this circuit at all, so eliminating those three parts allows that circuit to be "parked" with minimal modification.OTOH, the load management unit apparently caches incoming data until the pin changes state.

author: metertech58761
author_rank: Frequent Contributor
timestamp: October 05, 2023, 06:05:42 am
content: Sorry for the 'necromancer bump', but I finally have a bit more insight on this circuit.It seems there are two power outage monitors in the code - one to capture 'blinks' and one to capture power outages lasting over two minutes.Am I correct in thinking that this would be the circuit to capture the longer outages?

author: metertech58761
author_rank: Frequent Contributor
timestamp: October 07, 2023, 04:55:50 pm
content: Much appreciated. This helped confirm one part of the code and changed my understanding of another part.As much as I really ought to just set aside this 'reverse engineering' project and work on other, more productive pursuits, I keep coming back to this thing and hacking away at it in a 'thousand cuts' approach.
Sensor Data Acquisition System Using ESP32 - Page 1
Forum section: electronics / projects

author: fieryfire
author_rank: Newbie
timestamp: March 05, 2017, 11:19:51 pm
content: Hi guys,Lovely community here. So i got into the bandwagon of the ESP32. I am planning to build an entire data acquisition built around the ESP32. Would really appreciate it much if i were to get help from all of you. It would be a learning experience for all of us. So basically here are my project details and list of components being used.A 32 Channel Data acquisition system with 30 sensors measuring strain (momentarily using a metal gage strain sensor of 120Ohm being fed to a quarter bridge circuit) and 2 temperature sensors(PT100). I would like an acquisition speed of atleast 1000Samples/Sec per channel. So here is my idea as of now.32 Sensors connected to its each wheatstones bridge. The amplifier is done using the XR18910/XR10910, which is a 16:1 bridge Mux interface with selectable gain. I have attached linkhttps://www.exar.com/content/document.a... rt=XR10910The XR18911 can be controlled via I2C link. it does all the amplification necessary. I will need to use 2 XR10910 or 4 XR18911(8:1 sensor interface). And then finally controlled by our LEGENDARY ESP32 which converts the analog data to digital. and with the help of wifi to transmit it to a computer where it can be collected in an excel file along with time of capture.Could you guys kindly help me out on how i am to proceed with programming of the ESP32. I would really prefer to use Arduino IDE guys, as that seems to simplify things. Please let me know if you need more details. Thank you
Sensor elasticity - Page 1
Forum section: electronics / projects

author: Metatron
author_rank: Newbie
timestamp: April 06, 2017, 07:22:47 pm
content: Hello Everyone,I'm student in france and I search since long time a sensor for measure the elasticity.I found a sensor of Fidgets ( sensor vibration 1104_0 ) but it's not exactly the same sensor.I add an image so that you understand what exactly the sensor does (with a little schema).I think it's not a pump because I have the sensor, And I don't see a mechanical object.I add a Image of the sensor, there are 3 cables 2 red and 1 black.(May be it's a piezoelectric)Can you help me to find the sensor or an equivalent solution to measure the elasticity ?Thank you per advance

author: Metatron
author_rank: Newbie
timestamp: April 06, 2017, 09:41:47 pm
content: thank you for your reply.The elasticity is also the stiffness or the Hardness (Except on the forehead).I am looking for a small sensor and not too expensive.I think the best solution is solution A, Maybe we can calculate the elasticity with the deformation of a piezoelectric.But How calculate it?