hybridfree/eevblog-posts huggingface dataset:
RF phase offset distance measurement - Page 1
Forum section: electronics / projects

author: wbooth.clearscene
author_rank: Contributor
timestamp: October 08, 2013, 12:06:05 pm
content: Hi, I'm in the early stages of a product design. Part of which I need to get a (not supper accurate) distance between to moving devices up to a distance apart of around 100m.I want to do this by measureing (at device B), the phase offset of two similar RF frequency transmitted (at the same time) by device A.My question is: Rather than building a bespoke solution for this, does anyone know of a package that contains this or similar functionality?Cheers.

author: Andy Watson
author_rank: Super Contributor
timestamp: October 08, 2013, 12:29:42 pm
content: Tellurometer? Differential GPS? How accurate and how fast do you want the measurement?

author: KJDS
author_rank: Super Contributor
timestamp: October 08, 2013, 12:30:14 pm
content: I'm not entirely sure that what you've described will give you what you want.You can measure the phase difference between two signals with a double balanced mixer.

author: wbooth.clearscene
author_rank: Contributor
timestamp: October 08, 2013, 09:12:10 pm
content: Cheers for the feedback.The measurement speed is not critical. But alignment (from device to device, or device to the horizon) is wholely indeterminate. Therefore both tellurometer or GPS are excluded.I'd kind of settled on using the principles of RADAR (Radio Detection and Ranging), which I think I could build, but I don't really want to.I am intreged by using a local environment reference wave, but can't see how that could be used to determine the distance between two devices? Could you illaborate?Cheers
RF Power Meter Modules - Page 1
Forum section: electronics / projects

author: sundance
author_rank: Regular Contributor
timestamp: April 11, 2019, 05:42:27 pm
content: Just found these low cost RF power meter modules on ebay:https://www.ebay.de/itm/RF-Power-Meter-Range-0-1-2-4GHz-Radio-Frequency-Power-Meter-1nW-1W-65-0-dBm/162320101042https://www.ebay.de/itm/LCD-1-600-MHz-RF-Leistung-Messgerat-Dynamometer-6-12V-Power-Meter-Detektor-Board/283445957585https://www.ebay.de/itm/1-500Mhz-OLED-RF-Power-Meter-70-15dBm-1nW-2W-Power-Set-RF-Attenuation-Value/254042115299or the likeHas anybody tested those?How much accuracy can you expect?

author: cjheath
author_rank: Contributor
timestamp: April 12, 2019, 12:47:48 am
content: It's almost certainly based on an AD8307 followed by an op-amp feeding a micro-controller ADC pin. Search for the data sheet of the AD8307 and you can learn all about it. Search for other modules that include the chip and you'll find further alternatives.

author: kirill_ka
author_rank: Frequent Contributor
timestamp: April 13, 2019, 07:55:59 am
content: If you use word "accuracy", then you probably don't want those modules.You can do some comparative measurements, not absolute. Even that would suck because of bad VSWR.

author: sundance
author_rank: Regular Contributor
timestamp: April 13, 2019, 08:52:03 am
content: That's kinda disappointing since those logarithmic detectors from Analog (like AD8318) claim to have a "High accuracy: ±1.0 dB over 55 dB range (f < 5.8 GHz)".Maybe SV1AFD's project (https://www.sv1afn.com/ad8318.html) would be a better choice though having twice the price tag + you need a backend for a digital display.

author: kirill_ka
author_rank: Frequent Contributor
timestamp: April 13, 2019, 10:03:15 am
content: Quote from: sundance on April 13, 2019, 08:52:03 amThe point is that you need to calibrate it at the specific frequency to get this performance.You can't do it without a "real" RF power meter (HP, Anritsu, R&S, Gigatronics, etc.).
RF Question, What has better range capability, GFSK or FSK? - Page 1
Forum section: electronics / projects

author: MatCat
author_rank: Frequent Contributor
timestamp: August 22, 2013, 07:47:22 am
content: I am working on a project that uses RFM22B UHF modules for use as control radio for model aircraft, and I am curious to know what would have a better range capability in theory, GFSK or FSK? I am sure this would be an easy question for any RF engineer. I looked around on the internet and I couldn't really find a good answer to satisfy me.

author: hlavac
author_rank: Frequent Contributor
timestamp: August 22, 2013, 08:05:29 am
content: These are just two very similar modulation schemes, they will be about the same.

author: calmtron
author_rank: Regular Contributor
timestamp: August 22, 2013, 08:32:51 am
content: As hlavac says, they would have the same range. GFSK will use a smaller part of the spectrum (and therefore waste less power).Disclaimer: Not an RF engineer.

author: w2aew
author_rank: Super Contributor
timestamp: August 22, 2013, 02:23:27 pm
content: It really comes down to the receiver design. Since GFSK occupies less BW for a given symbol rate, the receiver can be made more sensitive by using a narrower filter (thus, less total integrated noise). The receiver will also have to be optimized for the gaussian filtered data, which may have a little intersymbol interference. But, by doing these things - GFSK should have a slight edge.

author: KJDS
author_rank: Super Contributor
timestamp: August 22, 2013, 02:34:47 pm
content: Unless the receiver design is poor, or suffering interference, then if you can see the plane then it should receive ok with either GFSK or FSK.

author: Paul Price
author_rank: Super Contributor
timestamp: August 22, 2013, 02:48:26 pm
content: GFSK makes the FCC spectrum happy but tends to compromise the distinction between 1's and 0's. FSK will work best at the longest distance because the frequencies are sharply defined and thus less prone to have noise damaged packets received.. If your project is just for you go with FSK, it is easier to troubleshoot and work with and will give you a better range.

author: MatCat
author_rank: Frequent Contributor
timestamp: August 22, 2013, 04:28:08 pm
content: Quote from: Paul Price on August 22, 2013, 02:48:26 pmLooking at the transmission using an SDR I would concur, it was my thought that FSK would have better range potential because it's signal seemed indeed significantly stronger then GFSK, at 19.2k baud FSK only had a few KHz of bandwidth extra anyway!
RF questions related to AT86RF215 - Page 1
Forum section: electronics / projects

author: bhj99
author_rank: Contributor
timestamp: September 06, 2024, 04:47:49 pm
content: Hi all, I plan on using the Mcirochip AT86RF215 part on a future project for SDR applications. I am looking at that AT86RF215 EVM refernce design schematic and, given my limited RF knowledge, I wanted to ask about why certain components/values were chosen. I would a better understanding, as I have the idea of leveraging the circuit design as much as possible. Attached is the schematic downloaded from Microchip.More specifically:1. On sheet 3, could anyone explain the values for C25, C10 were derived? Also, is R10 10Kohm pull-down needed for the TCXO clock output?2. On sheet 3, how were all the cap and inductor values chosen for both sub-1GHz/2.4GHz RF paths (from AT86RF215 to balun and from balun to SMAs)? Also, how do the 10Kohm pull-downs (R10 & R11) serve as "ESD Protection" ?Thanks in advance.
RF receiver bothered by high current flows - Page 1
Forum section: electronics / projects

author: Tricka90
author_rank: Regular Contributor
timestamp: November 30, 2014, 02:01:48 pm
content: I built a very simple circuit consisting in a RF transmitter / receiver, a PIC microcontroller, a Fan and a little LED Lamp. Pressing a button on a RF transmitter I can turn on and off the Fan or the Lamp.The all circuit is powered by a 5V - 3A power supply.In the link below you can see the RF transmitter / receiver modules:http://forum.hobbycomponents.com/viewtopic.php?f=25&t=1324That's how the Lamp is powered (the Fan is powered the exact same way):The R1 resistor is used to limit the current through the Lamp / Fan.The circuit does work perfectly! The problem is I can't improve it: I'd like to decrese R1 value both on the Fan and the Lamp so they can work better.The problem is, the more current the two loads absorb, the more dirty and imprecise the receiver output signal becomes!I measured it with my oscilloscope and it's obvious that when I decrese R1 the signal gets a lot of interferences so the PIC can't read it correctly.I tried connecting some capacitor here and there but it didn't solve anything. It even becomes worse with big capacitor values!Now the Lamp and Fan absorbs only 200mA each, that's pretty low.Do you have any solution for letting the Lamp and Fan absorb more current while keeping the receiver output signal as clean as possible?

author: G7PSK
author_rank: Super Contributor
timestamp: November 30, 2014, 02:25:05 pm
content: I would use a relay, either conventional or solid state to switch the lamp. That way you would isolate the receiver from the load.

author: aveekbh
author_rank: Regular Contributor
timestamp: November 30, 2014, 02:54:18 pm
content: Does the receiver have a printed antenna right on the PCB? Perhaps try changing the antenna orientation - horizontal vs. vertical.I would also suggest some decoupling capacitors across the wireless module supplies plus relays, as G7PSK already mentioned.

author: Tricka90
author_rank: Regular Contributor
timestamp: November 30, 2014, 03:19:55 pm
content: Thanks for the replys!How should I connect the decoupling capacitors?Also I don't understand how using a relay should help.Even if I use a relay I will still power the Lamp and the Fan from the same power supply I power the receiver. So what's the point of using a relay?
RF Shielding Cabinet Connection - Page 1
Forum section: electronics / projects

author: Gerharddc
author_rank: Newbie
timestamp: October 13, 2025, 02:16:38 pm
content: Hi, I am wondering if it is best to connect an RF shielding cabinet (something likehttps://www.we-online.com/components/products/datasheet/36003500.pdf) to signal ground or to protective earth (PE); or if it does not make a difference.My understanding is that it is important to connect the shield to some defined potential so that it does not just reradiate any energy that hits it (as would occur if it is just left floating). However, I am not aware of any good reason why this needs to be a specific potential (at least not from an EMI perspective). I have heard strong opinions that it needs to be PE, but these are just stated as facts and do not come with detailed explanations as to why. I am thus wondering if anyone has some deeper insights they can share?I should also clarify that this is a PCB-mounted shield that will be hidden inside the enclosure of a device. This means that the user cannot touch the shield and therefore the reasonable argument of connecting it to PE for safety reasons is not very relevant in this case.

author: mtwieg
author_rank: Frequent Contributor
timestamp: October 13, 2025, 03:46:11 pm
content: Board-level shields should be connected to the reference plane of the circuits underneath the shield.I'm assuming anyone arguing for connecting it to PE are assuming that PE is also the reference for the shielded circuits (as is often the case). But that connection should be made through the board itself.

author: Gerharddc
author_rank: Newbie
timestamp: October 13, 2025, 04:22:21 pm
content: Quote from: mtwieg on October 13, 2025, 03:46:11 pmThanks, that is what my intuition also tells me. However, I'm not able to formulate much of an argument routed in electromagnetics as to why that would be the case. Any ideas?Quote from: mtwieg on October 13, 2025, 03:46:11 pmIndeed, if they are the same thing then that would be valid. In this case however, signal ground are PE are explicitly different things (albeit connected through capacitors on the board).
RF spectrum analyzer design FFT vs filter+detector - Page 1
Forum section: electronics / projects

author: prutser
author_rank: Regular Contributor
timestamp: January 13, 2022, 07:34:15 am
content: I am thinking about an RF spectrum analyzer project. Frontend will be tuned, followed by an IF at approx 25MHZ with A/D converter.The most obvious would be to do an FFT of the IF band and display it. The LO can increment in large steps dependent of the used IF bandwidth. However with an FFT you have the artefacts due to the used Windowing.If we look to a conventional analog spectrum analyzer, it has a narrow band IF filter followed by a dectector and the display is created based on LO sweep with relatively small steps and the detector output. A narrow band filter and detector can also be created in the digital domain. Would this not give a more accurate picture than using FFT (trade off longer sweep time due to filter settling) ?How is this done in commercial analyzers, how is the FFT display improved ( avaraging multiple sample sets ? )Any ideas or experiences are welcome.
RF stripboard techniques. - Page 1
Forum section: electronics / projects

author: djsb
author_rank: Super Contributor
timestamp: March 06, 2010, 01:14:11 pm
content: Hi,Does anyone have any special techniques for building RF circuits on stripboard? I need to build a VCO that runs at approx 10MHz. The circuit uses 3 transistors, 1 coil and a varicap/varactor diode as well as other supporting components.I need to minimise long wireing and utilise some kind of ground plane if possible.I saw a technique on Dave's video's but can't remember the specifics apart from it being called dead bug or something.I will mainly be using through hole components as this is a proof of concept test build/prototype.Anyone have any tips or methods specific to RF.Thanks.David.London,UK

author: djsb
author_rank: Super Contributor
timestamp: March 06, 2010, 01:42:31 pm
content: Hi,In answer to my own question I found this link.http://www.piclist.com/techref/pcb/manhattan.htmand thishttp://www.aoc.nrao.edu/~pharden/hobby/Hobby.shtmlAny thoughts?David.

author: joelby
author_rank: Frequent Contributor
timestamp: March 07, 2010, 12:46:59 pm
content: Dead bug is easy to do with through-hole components. Get some blank (copper-clad) PCB, glue ICs upside down (with their legs in the air), and solder things together directly. The PCB acts as a large ground plane and this works quite well for RF.The Manhattan technique in the links you provided looks very tidy but also like a heck of a lot of work! Making a PCB really does not take very long, allows you to very easily use SMT components, which may be important if you're using ICs that don't come in DIP packages, makes a design completely repeatable, and looks a lot more professional. I admire people who build everything using these methods, but it's slow and fiddly.

author: jimmc
author_rank: Frequent Contributor
timestamp: March 07, 2010, 01:01:07 pm
content: If you really want to use something like stripboard then there are boards with a colander ground plane on one side and either strips or pads on the other.Seehttp://www.verodirect.com/images/PDF/Veroboard%20Board%203.pdfPricey but works well at RF, especially the pad version when used with 0805 SMD components.Jim
RF Switch - Page 1
Forum section: electronics / projects

author: docmur
author_rank: Regular Contributor
timestamp: December 31, 2016, 02:17:43 am
content: Hey GuysI'm designing a product around the CC1350 from TI, because it has BT and RF. The design is not locked in yet so I can change the CC1350 to another chip, but what I'm mainly looking for is an RF Switch that will work and is in stock, the only one I've found so far I can't seem to find in stock.The one I've found: Murata PN XMSSJE3G0PA-003Thanksdocmur

author: w2aew
author_rank: Super Contributor
timestamp: January 01, 2017, 05:38:55 am
content: Quote from: docmur on December 31, 2016, 02:17:43 amTons to choose from here:http://www.skyworksinc.com/products_switches.aspx

author: chrisl
author_rank: Regular Contributor
timestamp: January 01, 2017, 06:42:26 am
content: Quote from: docmur on December 31, 2016, 02:17:43 ama planty to choose from:http://www.digikey.com/products/en/rf-if-and-rfid/rf-switches/865?k=rf+switch&k=&pkeyword=rf+switch&pv60=92&pv60=1203&FV=1c0002%2C1a080004%2C1a080005%2C1a080006%2C1a080007%2C1a080008%2C1a08000a%2C1a08000e%2C1a08000f%2C1a080012%2C1a080013%2C1a080014%2C1a080015%2C1a080017%2C1a08001a%2C1a08001b%2C1a08001c%2C1a080020%2C1a080021%2C1a080022%2C1a080024%2C1a080025%2C1a080026%2C1a080029%2C1a08002a%2C1a080033%2C1a080034%2Cffe00361&mnonly=0&newproducts=0&ColumnSort=1000011&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

author: richardlawson1489
author_rank: Regular Contributor
timestamp: January 03, 2017, 02:42:17 pm
content: Digikey is the best resource for you.
RF switches - pin diodes - Page 1
Forum section: electronics / projects

author: Plasmateur
author_rank: Regular Contributor
timestamp: September 14, 2019, 05:36:36 pm
content: I have a few questions about pin diode switches.Part #1 - FunctionalityHere are the three models I'm looking at,#1,#2, and#3.#1 appears to be the fastest in switching time(4ns), but isn't advertised as such. I'm not sure why that is. Also I think this needs -10V to turn on, and I need it to turn on for a set amount of time with a square pulse. My square pulse is only 4V at peak,,, are there simple off-the-shelf devices which can convert a 4V peak pulse to -10V? Or are there less expensive devices than thisold thingwhich can be used to control the timing of devices?#2 has SMA connections on all ports, while #3 does not for the DC driving voltages. Is there such thing as a DC power supply with SMA or BNC outs? There are a few applications other than this where I would need just that. I'm not sure what the point is for #2 having SMA connections for the DC components...maybe ruggedness?Part#2 - PricesI've looked at several other vendors such as [urlhttps://www.fairviewmicrowave.com/standard-reliability-spdt-pin-diode-switches-category.aspx]here andand they are far more expensive for comparable frequency ranges - and the specs are less impressive for switching times of other vendors while I don't even see that spec for pasternack. What's up with that?
RF Synthesizer IC  - Page 1
Forum section: electronics / projects

author: perdrix
author_rank: Frequent Contributor
timestamp: August 01, 2020, 02:08:28 am
content: Hi folksI'm looking for a synthesizer chip that will go from very near DC (0.1Hz or so) up to (say) 1 or 2GHz.Is there anything that will do this? I couldn't find one that fitted the bill on Analog Devices site.ThanksDavid

author: KaneTW
author_rank: Frequent Contributor
timestamp: August 01, 2020, 02:15:56 am
content: You pretty much need DDS or two separate synths (DDS + PLL) for that.https://www.analog.com/en/products/ad9914.htmldoes DDS up to 1750MHz.

author: perdrix
author_rank: Frequent Contributor
timestamp: August 01, 2020, 12:59:28 pm
content: Oh dear LFCSP-88 with a pad underneath. Not something I fancy soldering at home ...Sadly the eval board is a bit more than I would like.David

author: KaneTW
author_rank: Frequent Contributor
timestamp: August 01, 2020, 04:26:03 pm
content: I would just split it into two signal paths. That's how basically everyone does it.LFCSP-88 is fairly solderable IMO, but i understand the trepidation with a $160 IC.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: August 01, 2020, 05:41:48 pm
content: You'd likely need multiple signal paths anyway since a single amplifier operating from 0.1 Hz to 1 GHz is in itself quite hard.

author: KaneTW
author_rank: Frequent Contributor
timestamp: August 01, 2020, 07:39:57 pm
content: Minicircuits RAM-6A+ is a pretty decent DC to 2GHz amplifier.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: August 01, 2020, 08:54:37 pm
content: Nice find! What biasing inductor and coupling cap would you choose to work from 0.1 Hz to 1 GHz?

author: KaneTW
author_rank: Frequent Contributor
timestamp: August 01, 2020, 09:20:39 pm
content: Ah, yeah, good call. That gets difficult.

author: KE5FX
author_rank: Super Contributor
timestamp: August 01, 2020, 09:30:35 pm
content: For true-DC applications, look at the LMH3401 that nctnico used in his 1 GHz+ differential probe. You'll need a split supply (and he also uses a good part for that purpose, the LM27762).For that matter, there's no religious reason why you couldn't use a 50-ohm MMIC with a split supply. It's not commonly done for a couple of reasons, one being that it complicates grounding and the other being the traditionally-high flicker noise near DC from GaAs and similar materials. Newer parts will still have the first limitation but may do better at the second.
RF temperature sensor with LCD schematic  - Page 1
Forum section: electronics / projects

author: sdancer75
author_rank: Frequent Contributor
timestamp: May 30, 2019, 09:50:09 am
content: Is there any way to find a similar schematic of an RF temp sensor with an LCD display without any microcontroller involved?

author: ebclr
author_rank: Super Contributor
timestamp: May 30, 2019, 01:15:34 pm
content: Did you check without the display, The mp probably is under

author: ogden
author_rank: Super Contributor
timestamp: May 30, 2019, 01:23:33 pm
content: Quote from: ebclr on May 30, 2019, 01:15:34 pmRight. Black epoxy blob of chip-on-board seems to be visible in the photo, below LCD.https://en.wikipedia.org/wiki/Chip_on_board

author: sdancer75
author_rank: Frequent Contributor
timestamp: May 30, 2019, 03:48:23 pm
content: Yessss... as far as I can see from the photos now, there is a black epoxy blob of chip-on-board under the display.I suppose it would be much more complex to avoid a microcontroller for such kind of projects.
RF transistor pinout - Page 1
Forum section: electronics / projects

author: c4757p
author_rank: Super Contributor
timestamp: August 13, 2013, 08:11:12 pm
content: I know RF transistors frequently have strange pinouts..... but can somebody more familiar with RF reassure me that this one is likely to be correct?BFG31Code:C[SOT-223]E B E

author: Dave
author_rank: Super Contributor
timestamp: August 13, 2013, 08:21:18 pm
content: It actually makes sense to have a pinout like that. You connect the emitters to a ground plane, bring the signal into the middle pin and have an amplified signal at the tab.Have a look at any high frequency PCB, you will know what I mean.

author: c4757p
author_rank: Super Contributor
timestamp: August 13, 2013, 08:26:09 pm
content: Yeah... it does make sense, you're right.

author: SeanB
author_rank: Super Contributor
timestamp: August 14, 2013, 04:44:49 pm
content: You will have a ground plane connected to the positive rail with this, and the collector going to a stripline acting as a heatsink. Going to be an interesting board layout, with a block of positive groundplane with multiple small decoupling caps, a stripline output leading through this with a break between the 2 ground planes with a pair of decoupling caps straddling the gap and a lot of via stitching on the stripline to a second positive ground plane as well.5GHz from a PNP is quite impressive, they normally are the slow cousins of the NPN complimentary devices. You are likely to have 10 capacitors for each one of these transistors for coupling and decoupling.

author: c4757p
author_rank: Super Contributor
timestamp: August 14, 2013, 04:53:42 pm
content: I will probably have a small B-C capacitor fo limit the frequency. I don't need the full 5 GHz (more like 800 MHz) but it was the closest selection for other parameters.I will probably not end up using it, anyway. Just an idea I am experimenting with

author: ElectroIrradiator
author_rank: Frequent Contributor
timestamp: August 14, 2013, 05:32:59 pm
content: The NXP BFG135 (NPN, 9GHz ft) has an identical pinout. The datasheet has a suggested PCB layout for a reference amplifier, if anybody wish to see what it looks like.
RF transmitter not turning on light - Page 1
Forum section: electronics / projects

author: ThomasC4
author_rank: Newbie
timestamp: December 14, 2018, 04:41:39 pm
content: Hello,I have an RF remote control toggle switch that has momentary latched and toggle abilities. I simply wanted to be able to turn on this very small LED light while I’m holding down the button. I’ve looked at the diagram of wiring and I can’t figure it out. Here is the picture of all the components I have what am I missing how am I not getting this. Because I’ve tried to connect it the way the wiring diagram shows and I can’t get the receiver to be the thing that turns on th light.The light works, the battery is working. The RF receiver works, and the transmitter.I just can’t get it wired right so that when I press the toggle switch and hold it down or anytime for that matter I can’t get the LED light to light up I’m sure it’s pretty simple thanks for the help the attachments show the wiring diagram they give for it and I’ve tried them but I can’t get them to work so I’m missing something one of them is for receiver and load use the same power supply Which is what I want.
RF Transparent Foam - Page 1
Forum section: electronics / projects

author: yanir
author_rank: Regular Contributor
timestamp: August 18, 2015, 09:57:37 pm
content: Hi, can anyone point me to a supplier that stocks low loss / low dielectric foam products. Looking for blocks and sheets. I found a number of manufacturers but they don't seem to sell direct. Where do you RF guys buy your foam from?Thanks

author: Fraser
author_rank: Super Contributor
timestamp: August 18, 2015, 10:32:56 pm
content: Have you tried surfboard foam blanks ?It is easy to source and IIRC very RF transparent into the 10's of GHz. Maybe worth Looking into ?Aurora

author: yanir
author_rank: Regular Contributor
timestamp: August 18, 2015, 10:56:34 pm
content: Thanks! I will check it out.
RF TX/Rx pair VERY low data rate long battery life - BLE or something else? - Page 1
Forum section: electronics / projects

author: Jester
author_rank: Frequent Contributor
timestamp: January 10, 2017, 11:03:28 pm
content: I'm working on a project that requires low cost, low power remote control over a distance of 16' or less. The data rate will be really low, it only has to send one status bit plus a module identifier every 10 minutes.One option is to use a $0.75 HC05/06 Bluetooth modules like this:http://www.ebay.com/itm/262136732940?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITThis might end up in a product that would be sold in the USA, am I better off starting with a FCC certified module for volume = 1000example:http://www.digikey.com/products/en?keywords=RN4871U-V%2FRM118-ND%20Should I be looking at other options?

author: janekm
author_rank: Unknown
timestamp: January 11, 2017, 12:40:04 am
content: The unintuitive thing to remember about low data rate applications is that the most energy expensive operation is keeping the receiver turned on, as opposed to transmitting a packet. So everything hinges on keeping the receiver turned on for the shortest amount of time possible. Bluetooth LE achieves this by establishing a schedule between the host and the device, and the device will turn on its receiver according to the schedule, receive a message from the host, and respond with an acknowledgement or data.The important criterion is not so much how often you need to send data, but what the acceptable latency is, as that determines the "connection interval".A Bluetooth LE link in connected state (the schedule has been established) can be very low power and could be a good option for your application. You can try out this calculator:https://devzone.nordicsemi.com/power/I would consider the NRF52 line of chips (or one of the myriad modules based on it) a good choice for that application as it can act as both host and device, and the chips and SDKs and support are really good. It's still a fair bit of development effort to build the host and device parts but there are examples for both.The HC06 line is not suitable as it's traditional Bluetooth, not LE.
RF via impedance calculation with NFP removal - Page 1
Forum section: electronics / projects

author: reinoso
author_rank: Newbie
timestamp: February 02, 2021, 12:08:35 pm
content: Hello,I'm trying to match the impedance of a RF via from bottom layer to top layer in a 6-layer PCB design. GNSS signal. Unused pad (NFP) removal activated.The selected via size is 0.9mm pad and 0.5mm drill. No antipad defined so applying copper-to-drill default clearance (0.2mm) at inner ref planes (2 & 5). This results in a 0.9mm ref plane opening.I'm using Saturn PCB tool and I wonder what data should I fill to get the correct calculation. Internal pad diameter is supposed to be the same as drill diameter? Any help/suggestion will be appreciated.
RFC: low leakage UVLO (under-voltage lockout) for magsafe - Page 1
Forum section: electronics / projects

author: manekinekohello
author_rank: Newbie
timestamp: August 04, 2018, 08:34:47 pm
content: greetings humans,My most recent hack was to place an Apple MagSafe 1 charging port into a Lenovo IdeaPad U430. It works, but I'm still working on controlling the charging LED over 1-wire, and making it compatible with Apple genuine/original adapters. This post is about the second part.As described inhttp://www.righto.com/2013/06/teardown-and-exploration-of-magsafe.html,you need to follow a specific protocol to get Apple adapters to start: first, connect a 39k resistor, then wait for the voltage to climb before connecting your load. Essentially this is what a UVLO (undervoltage lockout circuit) does. But it also needs to not interfere with the detection part, i.e. the resistance should be much higher than 39k. In other words, it needs to have very low leakage.I designed the following circuit and hope to get some comments. It works well in simulation. I set the threshold to around 15V using a 15V zener (D1). Reverse leakage current for a zener of this voltage is typically 5 uA.C1 represents the MOSFET that would switch the actual load. It would be nice to have high-side switching so I still have to find/work out a circuit for that. The rest of the circuit is so simple really that it describes itself.Simulation results: blue trace shows the input voltage: linear ramp to 20V and back down again with some noise. Green trace is output: it is practically zero (<1 uV) for Vin < 15V. Then it turns on and stays turned on because of the positive feedback (hysteresis). Because of the hysteresis, the turn-off happens at a slightly lower voltage than turn-on, this can be controlled with R5. The red trace shows the input current: < 1 uA even when close to threshold.Comment if you would like updates :)thanks for feedback!

author: NiHaoMike
author_rank: Super Contributor
timestamp: August 04, 2018, 09:19:25 pm
content: Replace Q2 with a P channel MOSFET capable of handling the entire load and change R6 to 33k, then it's pretty much good to go. D2 is not necessary and can be replaced with a short.
RfC: MCU evaluation boards that is almost just a DIP adapter - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: May 16, 2021, 05:51:56 pm
content: This shown PCB here is my ATSAML11 evaluation board. The target chip is TSSOP-24 package, while my board have the exact footprint as a wide DIP-24 package, and it have almost the exact same pinout as the ATSAML11 chip in question. On the back of the board is power converters and a STM32F042 providing USB serial and CMSIS-DAP. This is a 2-layer PCB.Is this a good idea in constructing evaluation modules? Use a standard DIP size, follow the original pinout as much as possible, then integrate enough supporting hardware so that evaluation can be done using minimal additional hardware? (In this case, this board can allow evaluation of ATSAML11 on itself, thanks to the built-in serial port and debugger.)

author: coromonadalix
author_rank: Super Contributor
timestamp: May 16, 2021, 10:01:34 pm
content: I think its a good idea, if it works well why not ? i see it like a dip 24, the same way i see an blue pill or any Arduino board or any development board, its convivial and can be put on a breadboard
RfC: window detector with glitch filter - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: January 23, 2020, 01:23:25 pm
content: The purpose of this window detector is to check if headphone is inserted into its jack, and generate a 5V CMOS logic output reflecting that. Logic 1 if headphone is present, else 0.The power amplifier I used is a Class-D amplifier that is designed to use direct-coupled outputs, Nsiway NS4248. (The circuitry on its datasheet should not be used directly, as this logic output controls not only this amplifier, but also other circuitry that expects a logic input.) The output pin of a Class-D amp should flip between 5V and 0V. As of the headphone jack, the detect pin is connected to one of the signal pins when a headphone is removed, and floated then a headphone is inserted.The idea here is to bias the detect pin to 1/2Vcc, then use a window detector to check if the detect pin is within 1/3Vcc and 2/3Vcc. If the headphone is removed, the amp output would override the bias and make the window detector output low. When a headphone is inserted, the now floating detect pin would be biased towards 1/2Vcc, and the window detector output high. This design has the risk that there may be glitches when the output signal itself crosses the detection window, so a glitch filter is needed. The comparator in question is LM393, which has open drain outputs. The outputs are tied together as wire-AND and pulled high, a capacitor is added between the output and the ground as a low-pass filter, then a Schmitt trigger buffer finishes the glitch filter.As of the bias resistors, that stack of 4.99k is a reference to a certain chip that also has a window comparator-ish structure in it.
RF/Comms/Digital Clock engineers - Book recs on Phase noise? - Page 1
Forum section: electronics / projects

author: XFDDesign
author_rank: Frequent Contributor
timestamp: April 14, 2015, 12:32:39 am
content: As the topic states, I'm looking for recommendations for books that deal with Phase noise (and how to deal with it). I'm working on a project where I need to get the best results practical, but may not have the best sources to work with always. (One oscillator has a very crappy -52.5dBc @ 1kHz spec) - not sure if anything can be done about it.Many thanks!

author: joeqsmith
author_rank: Super Contributor
timestamp: April 14, 2015, 02:33:29 am
content: You know, I don't think I have ever seen a book dedicated to just phase noise. Interesting how fast that field is moving!If you are looking for general information, I have read both of these books and keep them on my shelf.http://www.amazon.com/High-Speed-Digital-Design-Handbook/dp/0133957241/ref=sr_1_1?ie=UTF8&qid=1428979411&sr=8-1&keywords=howard+johnson+black+magichttp://www.amazon.com/High-Speed-Digital-System-Design-Interconnect/dp/0471360902/ref=sr_1_1?ie=UTF8&qid=1428979542&sr=8-1&keywords=high+speed+digital+system+design

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: April 14, 2015, 04:34:24 am
content: Phaselock Techniques by Gardner.http://www.amazon.com/Phaselock-Techniques-Floyd-M-Gardner/dp/0471430633/ref=sr_1_1?ie=UTF8&qid=1428986048&sr=8-1&keywords=phaselock

author: rfdave#gmail.com
author_rank: Contributor
timestamp: April 15, 2015, 02:49:18 am
content: Well, PCB layout, bypassing, grounding etc all play a significant role in close in phase noise, as you would expect. -52 dBc @ 1 kHz is pretty poor for sure. What are the specifications of the crystal? Are you using a canned oscillator, with a fixed frequency output, or are you using a crystal and implementing an oscillator yourself?Your best bet on phase noise will be in the VCO/PLL literature, but some more details of your system would be helpful.

author: codeboy2k
author_rank: Super Contributor
timestamp: April 15, 2015, 03:16:11 am
content: Quote from: Alex Eisenhut on April 14, 2015, 04:34:24 amThat's a good book, I have it. Although it's mostly about PLLs and it is math heavy, it does have a few chapters on phase noise.Another one isPhase-Locked Loops for Wireless Communications, by Donald R. Stephens. It's also heavy on the math, and has one chapter on phase noise analysis.

author: jimmc
author_rank: Frequent Contributor
timestamp: April 16, 2015, 07:08:57 pm
content: Getting a bit old now but it may be useful to you...Phase Noise in Signal Sources: Theory and ApplicationsW. P. RobinsIET, 1984 - Technology & EngineeringJim
RFID 125khz cards, RDM6300 reader trying to make sense of the readings - Page 1
Forum section: electronics / projects

author: jz79
author_rank: Contributor
timestamp: September 27, 2023, 05:50:54 pm
content: edit: simplified my questionA card that came with the reader has the ID printed on it: 0008075634 [empty space] 123,14706and this card reads as following using the RDM6300 reader:-------------------------------------------------6F007B39725F {this is the serial string, and the following is interpretation by uC, arduino running a demo sketch for this reader}Message-Head: 2Message-Data (HEX):6F (version)007B3972 (tag)Message-Checksum (HEX): 5FMessage-Tail: 3--Extracted Tag: 8075634Extracted Checksum (HEX): 5F (OK)---------------------------------------------------and I'm interested what is the relation between the decimal value (or its hex value that the reader is sending over serial) to the latter decimal number printed on the card - this 0008075634(007B3972) and this 123,14706 ?

author: jz79
author_rank: Contributor
timestamp: September 28, 2023, 09:29:11 am
content: nvm, figured it out, didn't realize significance of the comma in the second "number"RDM6300 hex string: 00 7B 39 72^ ^second number on card: 123 14706
RFID Antenna Attenuator? - Page 1
Forum section: electronics / projects

author: Hobgoblin612
author_rank: Contributor
timestamp: July 14, 2016, 02:51:46 pm
content: Hi All,I am designing a handheld RFID reader using the Microreader RI-STU-MRD2 from TI.http://www.ti.com/product/RI-STU-MRD2It reads 134.2KHz HDX+ tags.All is going well and I can successfully read tags at around 23-30mm range with the PCB antenna on the dev board.I have made another antenna (pictured) following the example in the datasheet and it achieves about 150mm range.My application requires the reading of individual tags when there are other tags close by. As such I would like a way to adjust the range down from this, I am assuming some sort of attenuator, preferably software adjustable from a microcontroller (atmega32u4); or if that proves impractical then I need a way of setting the range in hardware so that I can tune it during testing.The only reference to the output power of the module that I can find is on pg.99 of the datasheet that mentions the power stage draws 100mA at 5v.I should also mention that I don't have much experience with RF design although 134.2KHz is hardly RF.All suggestions welcome.Thanks in advance, Timothy.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 14, 2016, 03:45:43 pm
content: Resistor in series with the antenna coil will do it for a fixed adjustment, but tricky to do in software as it;s an AC signal.If you can adjust the DC supply to the coil driver, that would probably work.Or maybe detune the osc frequency

author: johnkenyon
author_rank: Regular Contributor
timestamp: July 14, 2016, 05:20:47 pm
content: I'm no RF expert either, but I'm certain that attenuation will reduce the range, but won't necessarily allow discrimination between tags presented close together.I would first look at reducing the effective sensing area of the antenna. Then look at reducing the sensitivity, noting that reducing the sensing area (by reducing the antenna size, or selectively shielding the sensing area) will probably attenuate the signal anyway.

author: nctnico
author_rank: Super Contributor
timestamp: July 14, 2016, 05:25:33 pm
content: If you need to read tags which are very close together then you might need to make the antenna capable of sending as well IF the tags have a protocol which allows to switch the tags on one by one.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 14, 2016, 05:38:13 pm
content: Quote from: johnkenyon on July 14, 2016, 05:20:47 pmYes - unless they are specifically anti-collision tags, all you can do is reduce the field strength to attempt to prevent activating more distant ones - antenna size is probably morepredictable than reduced transmit power
RFID Based attendance system (Source code needed) - Page 1
Forum section: electronics / projects

author: abhipoints
author_rank: Newbie
timestamp: November 04, 2016, 11:09:53 am
content: I have created my ownRFID based Attendance System, but the project is not complete. I need source code for running this system. If somebody has implemented similar type of project, please share the source code with me.
RFID based Door access control system - Page 1
Forum section: electronics / projects

author: BlogRahul
author_rank: Regular Contributor
timestamp: August 05, 2022, 12:08:41 pm
content: I want to make commercial project based on RFID based Door access control system for company. There are at least 154 doorsWhich RFID module and Microcontroller/ Processor will you suggest for project ?I found raspberry pi 4 8GB and ESP32 on internet but I am not sure about their performanceWhat will your choice if you want to develop this project ?

author: rooppoorali
author_rank: Regular Contributor
timestamp: August 05, 2022, 01:40:48 pm
content: Kindly enlighten us more about how you want to accomplish this project. Are you going to use 154 different RFID readers attached to each of the 154 doors?
RFID data transfer by using wireless communication - Page 1
Forum section: electronics / projects

author: jealcuna
author_rank: Contributor
timestamp: July 18, 2019, 10:24:53 pm
content: Hi folks,I am starting a new RFID project. I have two RFID long distance readers, I would like to collect the data by using wireless communication. I was thinking to use LORA with a raspberry pi in order to keep the data in a local data base if something were wrong with synchronization data and avoid to lost IDs information. Also I was thinking in use wifi but I am not sure if this is recommended in a industrial environment.I want something:* sacalable* robust for industry* following standard industrial protocols for communication* secure and reliable* Lon Range RFID reader system that support all my before items.My candidate reader is a Chinese device based in chip r2000http://www.chafon.com/productdetails.aspx?pid=513P.D. Sorry for my bad English.

author: infiniterfid
author_rank: Newbie
timestamp: February 29, 2020, 04:40:19 am
content: Hey,We also have long distance UHF RFID reader, you can check athttps://www.infiniterfid.com/products/uhf-rfid-readers/4-port-fixed-uhf-rfid-reader/By the way, i just wonder if you have already bought the reader to use for your project now?Thanks,
RFID Documentation - Page 1
Forum section: electronics / projects

author: Lance
author_rank: Frequent Contributor
timestamp: May 07, 2012, 11:12:01 pm
content: I'm trying to find some good documentation that's more technically detailed on RFID tags, and how they works. I understand the principle of operation, however I'm interested in more details on the hardware, and how the data is structured. I haven't had any luck finding anything thus far. Can anyone recommend some good resources?

author: amyk
author_rank: Super Contributor
timestamp: May 08, 2012, 08:30:18 am
content: Tried looking at the datasheets?

author: caroper
author_rank: Regular Contributor
timestamp: May 08, 2012, 09:20:43 am
content: Tryhttp://id-innovations.comI use their modules and they are very reliable and reasonably documented.

author: nctnico
author_rank: Super Contributor
timestamp: May 08, 2012, 10:26:07 am
content: Quote from: Lance on May 07, 2012, 11:12:01 pmThat information is only available under NDA. You can try to use Google. Maybe somebody put some documents online by accident.

author: Lance
author_rank: Frequent Contributor
timestamp: May 09, 2012, 05:10:48 am
content: Quote from: nctnico on May 08, 2012, 10:26:07 amI don't mean anything too vendor specific, but generally how things are setup and structured. How about general more technical info on how readers and writers work?

author: amyk
author_rank: Super Contributor
timestamp: May 09, 2012, 09:06:52 am
content: Quote from: nctnico on May 08, 2012, 10:26:07 amDepends on the particular manufacturer. Here's one I found with a quick search:http://www.impinj.com/Documents/Tag_Chips/Monza_4_Tag_Chip_Datasheet/NXP has a bunch:http://www.nxp.com/documents/data_sheet/H152931_HITAGu.pdfand you can fish out a lot more, I just spent ~30 seconds and got those two but they should be plenty for you to start with.

author: Lance
author_rank: Frequent Contributor
timestamp: May 11, 2012, 04:44:27 pm
content: Quote from: amyk on May 09, 2012, 09:06:52 amThat's a good start. It'll give me some idea of what to look for. For the more technical information I've found a couple textbooks that look useful, so I'll see how those go. Thanks!

author: caffeinatedbard
author_rank: Regular Contributor
timestamp: May 11, 2012, 05:28:07 pm
content: @Lance--Can you share with the rest of the group the textbooks you think are useful?Cheers-bard
RFID frequency - Page 1
Forum section: electronics / projects

author: Jane
author_rank: Frequent Contributor
timestamp: July 23, 2015, 08:10:31 pm
content: As far as I know, RFID can use a different frequencies. Is there any way how I can check what frequency my RFID uses ?Thank you.

author: Xenon Photon
author_rank: Unknown
timestamp: July 24, 2015, 05:14:27 am
content: Spectrum analyzer on a powered device.Btw, this is the general chat form!

author: digsys
author_rank: Unknown
timestamp: July 24, 2015, 05:19:38 am
content: There are 3 main frequencies, which are usually standard, but some manufacturers do have a slight propritary version.The type of tag can give it away - clothing, vehicle, animal. Plus if it is short / long range ie 10cm ... 4MWhat is it used for? That's a starting point. More info needed.

author: Halcyon
author_rank: Unknown
timestamp: July 24, 2015, 06:17:29 am
content: Quote from: Xenon Photon on July 24, 2015, 05:14:27 amIt should still be kept electronics/technology related for the most part. The OP's post is fine here.

author: albert22
author_rank: Regular Contributor
timestamp: July 24, 2015, 01:57:57 pm
content: For the low frequencies ( 125 or 134 kHz ) I have used a small coil near the reader and checked the frequency on an oscilloscope. Probably the method will work for 13.56 MHz too.Take into account that the reader will send bursts and not a continuous waveform.If you only have the tags and not the reader, it gets more complicated- Perhaps a Grid Dip meter could be usedhttps://en.wikipedia.org/wiki/Grid_dip_oscillator

author: Mad ID
author_rank: Regular Contributor
timestamp: July 24, 2015, 02:32:51 pm
content: Quote from: albert22 on July 24, 2015, 01:57:57 pmOr simply connect long ground lead which comes with probes to the tip and that loop is just fine to check the frequency.
RFID Reader for wide range distance - Page 1
Forum section: electronics / projects

author: DIYGUY Chris
author_rank: Contributor
timestamp: April 28, 2021, 10:42:19 pm
content: Hello allI've been playing for while with the mifare 13.56 Mhz RFID Crad reader (like many electronics hobbyists) since the reader distance is limited to 30mm I can't achieve some requirements in one of my current projects so I came here to ask for any recommendation of some UHF readers that I can use to read tags at a distance of 1.5 meters.I'm using AVRs to interface the mifare through SPI so anything with similar protocol will be highly appreciated

author: LakshmiN
author_rank: Contributor
timestamp: April 29, 2021, 10:36:28 am
content: STMicro- ST25RU3992Else look for Impinj based moduleshttps://rainrfid.org/rain-tag-ic-and-reader-resource/