Want LED to stay on once it is triggered - CELL phone DETECTOR - Page 1
Forum section: electronics / projects

author: jazell zee
author_rank: Newbie
timestamp: May 03, 2015, 06:09:28 am
content: Have built the Seattle Univ cell phone detector to locate hidden harassment devices around my home, especially the auto tracker presently installed somewhere in my car.Circuit works well, and LED comes on when it receives a cell signal (don't use the buzzer). However, I can't drive and keep an eye on the circuit LED at the same time - especially when investigating the trunk, engine area, and under body as possible hiding places.So, I'd like to insert a flip flop, SCR?, etc? in line with the LED so when the circuit receives a cell signal and the LED lights up, it will stay lit until I get a chance to look at it, then I'll pull the power and turn it off.All help regarding what to use and where to insert it is welcome - thanks!seattleu.edu/scieng/ece/LM358_RF_Cell_Phone_Detector.htmlhttps://www.circuitlab.com/circuit/uq4jyh/my-lm358-cell-phone-rf-detector/

author: Rerouter
author_rank: Super Contributor
timestamp: May 03, 2015, 06:23:19 am
content: I would like to point out that circuit purely detects RF signal strength, not specifically GSM data, or similar, the noise off your own cars electrical system, or a cigarette lighter phone charger would likely be enough to trip such a design.Now i'm going to avoid the why you suspect, and focus on how you can look for what you suspect, the best way would be to get a software defined radio kit, the waterfall display means you can look at a wide portion of the spectrum, look at the relative strength and narrow down on potential sources of any signals,If it was GSM based, there should be a repetative signal in those frequency bands to remain registered on the network, if it was based on anything else, then once you eliminate the noise switchmode power supplies as suspects you can really focus on what remains and find just about anything,

author: Dragon88
author_rank: Regular Contributor
timestamp: May 03, 2015, 12:49:44 pm
content: As mentioned, that circuit is only detecting RF energy. It is in no way selective to trigger only on cellular signals. You are crudely tuning it to a particular frequency range by cutting the antenna to a particular length, but that is not enough to be sure. Also, cellular signals are not confined to a single band. In the US, we have cellular carriers in the 700 MHz range, 800 MHz, 1900 MHz, 1700/2100 MHz AWS, and a few other oddball ones. And don't forget about Wi-Fi, which many phones use where available.And what are you into that you have "harassment" devices all around your home and car? ...Anyway, moving beyond that, let's say you are happy with the circuit and just want to record a trigger. One easy way is to use the output to set a latch, and provide no means to clear the latch besides a mechanical button, power cycle, whatever you want. Then the first time it triggers, it will hold the state until you clear it.A far better approach would be to use a small microcontroller. Even a trivial Arduino sketch loaded onto an ATTINY85 could log events, add a timestamp relative to when it was powered on, and even do come averaging or filtering. And it wouldn't substantially increase the size of your circuit.

author: Zero999
author_rank: Super Contributor
timestamp: May 03, 2015, 01:20:23 pm
content: Yes it's true it's just a simple RF detector and that there are far more reliable solutions available.Anyway, it can be easily modified to latch by adding positive feedback to the second op-amp.You could probably get rid of the LM358 and simplify this to an SCR and an LC tank tuned to the frequency of interest.

author: Dragon88
author_rank: Regular Contributor
timestamp: May 03, 2015, 03:15:44 pm
content: Quote from: Hero999 on May 03, 2015, 01:20:23 pmIndeed. Please excuse the crudity of the circuit below being on a breadboard, but I didn't want to spend a lot of time on it. It's a tank circuit being used to set a S-R latch made from a 74LS02. The button resets the latch.It works better than I thought. My phone being near the antenna and transmitting immediately sets the latch. I cut the antenna and "tuned" the tank circuit for ~750 MHz and it does indeed work better with my Verizon phone in LTE (uses that band) instead of CDMA (800 MHz). My key fob (315 MHz) however does not set it. It's very crude, but hey there's a little latching cell phone detector for ya.

author: paulie
author_rank: Frequent Contributor
timestamp: May 03, 2015, 05:33:19 pm
content: Personally since I cannot predict what frequencies those who are after me use, aside from aluminum foil hat a cheaper and simpler general RF detector has proven invaluable:http://www.ebay.com/itm/281490818418?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITI found with slight modifications can be made much more sensitive than the op amp based design. Noise pulses and other spurious signals do not interfere at all. And since black helicopters use 318mhz and 433mhz for their mind control devices, wide band sensitivity is essential. Seriously, this will detect an x10 dongle 10' away if properly adjusted.

author: eneuro
author_rank: Super Contributor
timestamp: May 03, 2015, 08:14:21 pm
content: Quote from: Hero999 on May 03, 2015, 01:20:23 pmMaybe do you have any hints how to estimate tunning frequency in the case of LM358 used?In the case of LC tank circuit which was also my interest it is quite easy since we have classic RLC.Which is C in the case of this LM358 based cell phone detector- 100nF in series with inductor and its size choosen for 1/4 wave length of RF frequency in interest?BTW: tried such LC tank circuit as... lighting detector (inductor with 100nF cap) with classic BAT85 diode in crystal radio setup to charge bigger cap and no supprise it started chaging 470uF cap to decent voltages-waiting for another thunder storm while added 1M resistor on this bigger cap to discharge and for the mement at sunny days its voltage after BAT85 diode is at mV...Anyway stored free thunder storm energy, so maybe it could also work with cell phone detection, especially at close distances?

author: Zero999
author_rank: Super Contributor
timestamp: May 03, 2015, 10:18:51 pm
content: Quote from: eneuro on May 03, 2015, 08:14:21 pmThere isn't any tuning. The base-emitter junctions in the input transistors of the op-amp rectify the RF signal and it's amplified by a 100 000 times.It will probably be most sensitise at the antenna's resonant frequency.

author: eneuro
author_rank: Super Contributor
timestamp: May 04, 2015, 06:32:08 am
content: Quote from: Hero999 on May 03, 2015, 10:18:51 pmIt is interesting what happends when nearby thunder storms comesAM radio tuned to 300kHz-400kHz easy "detects" lighting hits tens km away, so without decent software postprocessing this easy LM358 cell phone detector might triger many false alarms, but didn't tested it yet so it could be nice to see some experimental data on jamming this cell phone RF with lighting at range <100km if noticable

author: Zero999
author_rank: Super Contributor
timestamp: May 04, 2015, 08:50:21 am
content: The signal from thunderstorms will be strongest at the lower frequency bands (below about 30MHz) as it will be reflected back to earth by the ionosphere. Higher frequencies are radiated out to space. You should be able to detect a nearby thunderstorm at just about any frequency but if it's that close you'll see the lightning and hear the thunder.

author: paulie
author_rank: Frequent Contributor
timestamp: May 04, 2015, 12:07:21 pm
content: I also noticed the op amp circuit reacts to lightening and oil burner starting up in the basement. Replacing the wire antenna with a coil fixed this but made it even less sensitive to desirable signals. The circuit I posted on earlier, in addition to having longer range to begin with, did not suffer from this interference problem. Both do react to passing kilowatt CB pirates and emergency service radios. But then not uncommon to hear brief Hispanic conversations coming from my speaker system.

author: eneuro
author_rank: Super Contributor
timestamp: May 04, 2015, 06:16:32 pm
content: Quote from: paulie on May 04, 2015, 12:07:21 pmDo you mean this one?Mobile Phone Signal Flash Light Radiation Power DIY Suitehttp://www.ebay.com/itm/281490818418?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AITDo you have this PCB already in hands? Which is the range-lets assume open space-that this thing can detect mobile phone?Just tried make reverse engineering of this thing based onebayphotos to see how it might work and merged photos below with attempt to guess schematicshttp://www.mouser.com/ds/2/149/SS8050-117753.pdfhttp://documentation.renesas.com/doc/products/diode/rej03g0614_1ss86.pdfI'm guessing 5Vcc there, since white led is powered using 220R so @ 5V we have ~9mA led current?Maybe someone have some sugestions about Vcc?Also there are three (3) the same NPN SS8050 transistors? Why rated 1.5A CE?I've found a few similar circuits to this one onebay, but of course haven't got time to wait a few weeks for shipment, so why not to try assemble reverse engineered version with slighly different transistors and diode, but not sure if I've made good guess about this circuit power supply 5V levels?

author: paulie
author_rank: Frequent Contributor
timestamp: May 04, 2015, 09:34:48 pm
content: Quote from: eneuro on May 04, 2015, 06:16:32 pmYes. I have been purchasing those for someone else since they appeared a couple years ago. I have several for myself and use them for checking output and range, etc for handheld VHF and UHF transceivers, x10 dongles, cell phones, RC tx, spy cams, and many homebrew experiments from khz up to ghz.Quote from: eneuro on May 04, 2015, 06:16:32 pmAs-is with tuned antenna range goes to about 1 meter. With some slight modifications (bias diode, swap 1st NPN with MPSA18 etc) that increases to 5-10 meters. The most important component is the 1ss86 barrier diode. Because of very low Vf (100mv) it works better than old fashioned 1n34a germanium or common schottky. 700mv drop of op amp front end BJT has no chance to compete. Strangely buying that diode costs more than the circuit board with all parts.It starts to function at about VCC 2.8v but much better above 5v and has been tested up to 24v. Most people use 9v battery. It draws virtually no power until the LED lights.I have also succeeded in converting into cheap shortwave radio by replacing the LED with headphone or speaker/amp. Was able to receive WWV at 10mhz and 15mhz with proper tuned front end and antenna. Almost as good as ZN414 chip but much higher frequency.

author: Undweeber
author_rank: Regular Contributor
timestamp: May 04, 2015, 09:49:02 pm
content: I think its illegal to remove the car tracker if the car is leased, also, i think it's not a very smart thing to do to remove the tracker because if you crash your car somewhere the SOS signal will not be sent out, emergency services will not be sent out, you could blackout and bleed-out.. Besides if its a high end car like BMW Merc Lexus etc even infinity/acura the computer will get extremely annoying, it will definitely let you know something is wrong.If you are paranoid about being tracked, get a cheap GPS jammer and find out where the antenna is and have it on 24/7, they are very low powered, and in case of emergency they will be able to triangulate you using cellphone towers, and only emergency services/police are allowed to triangulate you using towers.

author: eneuro
author_rank: Super Contributor
timestamp: May 04, 2015, 11:32:16 pm
content: Quote from: paulie on May 04, 2015, 09:34:48 pmWhen compared1SS86IF vs VF from linked above datasheet we have 100mVf @ ~0.1mA. In comparision this Schottky barier diodehttp://www.nxp.com/documents/data_sheet/BAT85.pdfhas @ similar IF 0.1mA ~240mV @ 25*C, so maybe it could work?Anyway not sure if those transistorsSS8050used in this circuit can be replaced byhttp://www.fairchildsemi.com/datasheets/BC/BC547.pdfBC547 or 0.8A BC337, but probably no high currents switching needed in this circuit.Maybe I could try this circuit, however detection range below 10m is quite lowI'll have in hands cheapy 433MHz RF modules, so it could be interesting to see if this thing could detect its 433MHz transmiter (probably >100m range in open space), but 10m detection looks bad since 433MHz receiver with this transmiter claims up to 200m range?Someone can control his drone hundreds meters from my yard and in this case 10m range detector is useless as well as detecting cell phone from up to 1m (additionally phone must be active and exchange some data with tower).

author: paulie
author_rank: Frequent Contributor
timestamp: May 05, 2015, 12:17:56 am
content: Quote from: eneuro on May 04, 2015, 11:32:16 pmIt looks like you might be confusing wideband direct conversion detector with highly selective superhet or even cheap regenerative receivers. These are orders of magnitude more complex and sensitive compared to simple baseband demodulator. The purpose is completely different too.ps. IDK if the other diode is OK but can say 1SS86 hard to beat and available everywhere. As far as transistor 8050 is cheap generic NPN and I think BC547 acceptable replacement. BC549 may be better due to lower noise. MPSA18 even better in that department. There are some with much lower noise than these like S9014 but they cost more and harder to find. Only the first one in the chain is important for this application though.

author: cdev
author_rank: Super Contributor
timestamp: May 05, 2015, 04:36:16 am
content: You could use a $10 RTL2832/R820T USB dongle and once you install the driver software fromhttps://sdr.osmocom.org/trac/wiki/rtl-sdrOnce installed, you can use the "rtl_power" utility software to build CSV files that represent the relative signal strength of signals in requested portions of spectrum at requested levels of granularity..rtl_power:(1) User Commands rtl_power:(1)NAMErtl_power: - wideband spectrum monitor utilityDESCRIPTIONUses a re-purposed DVB-T receiver as a software defined radio toreceive signals in I/Q data form. Written for and incorporated in theosmocom rtl-sdr project.USAGErtl_power, a simple FFT logger for RTL2832 based DVB-T receiversThis tool gathers signal data over a very wide area of the frequencyspectrum, and then that data can be used to find active areas of thespectrum.Use: rtl_power -f freq_range [-options] -f lower:upper:bin_size (bin size is a maximum, smaller more convenient binswill be used.valid range 1Hz - 2.8MHz)[-i integration_interval (default: 10 seconds)](buggy if a full sweep takes longer than the interval)[-1 enables single-shot mode (default: off)] [-e exit_timer(default: off/0)] [-d device_index (default: 0)] [-g tuner_gain(default: automatic)] [-p ppm_error (default: 0)] filename (a'-' dumps samples to stdout)(omitting the filename also uses stdout)Experimental options:[-w window (default: rectangle)](hamming, blackman, blackman-harris, hann-poisson, bartlett,youssef)[-c crop_percent (default: 0%, recommended: 20%-50%)](discards data at the edges, 100% discards everything) (has noeffect for bins larger than 1MHz)[-F fir_size (default: disabled)](enables low-leakage downsample filter,fir_size can be 0 or 9.0 has bad roll off,try with '-c 50%')[-P enables peak hold (default: off)] [-D enable direct sampling(default: off)] [-O enable offset tuning (default: off)]CSV FFT output columns:date, time, Hz low, Hz high, Hz step, samples, dbm, dbm, ...EXAMPLESrtl_power -f 88M:108M:125k fm_stations.csv(creates 160 bins across the FM band,individual stations should be visible)rtl_power -f 100M:1G:1M -i 5m -1 survey.csv(a five minute low res scan of nearly everything)rtl_power -f ... -i 15m -1 log.csv(integrate for 15 minutes and exit afterwards)rtl_power -f ... -e 1h | gzip > log.csv.gz(collect data for one hour and compress it on the fly)Convert CSV to a waterfall graphic with:http://kmkeen.com/tmp/heatmap.py.txtrtl_power, a simple FFT logger for RTL2832 based DVB-T receiversUse: rtl_power -f freq_range [-options] -f lower:upper:bin_size (bin size is a maximum, smaller more convenient binswill be used.valid range 1Hz - 2.8MHz)[-i integration_interval (default: 10 seconds)](buggy if a full sweep takes longer than the interval)[-1 enables single-shot mode (default: off)] [-e exit_timer(default: off/0)] [-d device_index (default: 0)] [-g tuner_gain(default: automatic)] [-p ppm_error (default: 0)] filename (a'-' dumps samples to stdout)(omitting the filename also uses stdout)Experimental options:[-w window (default: rectangle)](hamming, blackman, blackman-harris, hann-poisson, bartlett,youssef)[-c crop_percent (default: 0%, recommended: 20%-50%)](discards data at the edges, 100% discards everything) (has noeffect for bins larger than 1MHz)[-F fir_size (default: disabled)](enables low-leakage downsample filter,fir_size can be 0 or 9.0 has bad roll off,try with '-c 50%')[-P enables peak hold (default: off)] [-D enable direct sampling(default: off)] [-O enable offset tuning (default: off)]CSV FFT output columns:date, time, Hz low, Hz high, Hz step, samples, dbm, dbm, ...rtl_power -f 88M:108M:125k fm_stations.csv(creates 160 bins across the FM band,individual stations should be visible)rtl_power -f 100M:1G:1M -i 5m -1 survey.csv(a five minute low res scan of nearly everything)rtl_power -f ... -i 15m -1 log.csv(integrate for 15 minutes and exit afterwards)rtl_power -f ... -e 1h | gzip > log.csv.gz(collect data for one hour and compress it on the fly)Convert CSV to a waterfall graphic with:http://kmkeen.com/tmp/heatmap.py.txtSEE ALSORTL-SDR wiki documentation:http://sdr.osmocom.org/trac/wiki/rtl-sdrOther rtl-sdr programs:rtl_adsb(1), rtl_eeprom(1), rtl_fm(1), rtl_sdr(1), rtl_tcp(1),rtl_test(1)AUTHORThis manual page was written by Maitland Bottoms for the Debian project(but may be used by others).COPYRIGHTCopyright (c) 2013 A. Maitland Bottoms <bottoms@debian.org>This program is free software: you can redistribute it and/or modify itunder the terms of the GNU General Public License as published by theFree Software Foundation, either version 2 of the License, or (at youroption) any later version.This program is distributed in the hope that it will be useful, butWITHOUT ANY WARRANTY; without even the implied warranty of MER?CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU GeneralPublic License for more details.RTL_SDR 0.5.1 rtl_power:(1)

author: eneuro
author_rank: Super Contributor
timestamp: May 05, 2015, 07:49:42 am
content: Quote from: paulie on May 05, 2015, 12:17:56 amOK, so we'll see.Now thinking about making classic custom dipole antenas, especially for 433MHz, but do you think this simple 3 transistor circuit could work with close to 0.5GHz RF detection?I'm not "radiophile", just want to try different ways of detection RF signal (cell phone is interesting too), so probably will review later another thread there where directional radio detection methods were showedFor the moment I'd like to try modify (enhance) those simply cell phone detectors, but unsure howto connect custom classic dipole antenas to this circuitSimply one half of dipole to circuit ground and another to antena pad in left top corner on image I've attached a few posts ago?Probably on PCB we could have nice RF connector or maybe solder directly to small 2 layer PCB without messing with RF connectors and in place of LED simply put optoisolator (cheapy PC817 ?) with a few kV insulation between detection circuit and MPU or other signal processing stuffAnyway, thank you for hints howto make this circuit more versatile

author: paulie
author_rank: Frequent Contributor
timestamp: May 05, 2015, 12:31:05 pm
content: Quote from: eneuro on May 05, 2015, 07:49:42 amHello... My name is Paulie and I'm a radio-nut. (audience mutters "hello paulie")Yes, dipole is connected to ground and "hot" end on the pad you mention. That pad is special just for adding antenna. Without coil in between this is extremely sensitive but non-discriminating and picks up mains hum and local broadcast stations. Moving your hand near makes the LED go on every time. With coil it is more useful and depending on self resonant frequency of the inductor will respond to a particular RF band. I have tested this well up into microwave with flea power 5.8ghz video TX and beyond.With a variable cap and tap this makes a great Poor Mans Shortwave Receiver. This was the most fun I had for one dollar in a long time.

author: eneuro
author_rank: Super Contributor
timestamp: May 05, 2015, 08:20:08 pm
content: Quote from: paulie on May 05, 2015, 12:31:05 pmI hope I didn't make mistake while redrawn this circuit inGEDA pcbwithout schematics routing autochecking.I've already etched PCB (1inch2) and tomorow moment of truth-soldering elements and test to detect something-I don't believe this thing could detect moving hand close to it without this additional coil in the middleI've slightly different transistors and diode, also changed LED current limiting resistor to ensure optoisolator (probably PC817 for the first try) input diode current <10mA whatever happends during first runsBTW: If we are talking about detecting cars RF, what could be radio frequency of remote control key (unlocking/locking doors oryginal factory dongle) used in Peugeot 206 HDI 1.4 Husky? It could be fun catch with this circuit locking/unlocking doors or use the same keys to open garage doors with some tricky Morse code sequence, while probably no chance to decrypt protocol used in this car remote control

author: eneuro
author_rank: Super Contributor
timestamp: May 06, 2015, 05:47:00 pm
content: Quote from: paulie on May 05, 2015, 12:31:05 pmDid you use such kind of equipment from video below to estimate self resonant frequency of coils used in this RF detector?Assembled everything together and by adding two cheap telescope antenas I'm ready for RF hunting with dipole , but selecting proper resonant coil without sophisticated equipment seams to be much more tricky than calculating dipole antena lengths for given frequencyRespect to RF magician who can fine tune elements in RF analog circuitsAnyway, a little bit sourface mount art work and ready to test different resonant elements -random coil thereIf everything works, I'd like to fill this 1inch2 PCB up to 10mm height with some kind of plastic or epoxy, to submerge PCB components, but provide only resonant coil pins out of the box to connect external self resonant elements...BTW: Looking again on this circuit thinking if 5V reverse in first NPN transistor emiter will be fine when we put this thing into stronger RF fields and antena pick up some higher voltage transients, etc.?Probably it is not possible solder this input schottky barier diode in oposite direction, which could help protect transistor emiter diode?I'm thinking about close lighting hit-I mean tens to hundred meters from this circuit. Are there any chance for this thing to survive with dipole antena connected (max 1m total dipole length)?

author: JimRemington
author_rank: Regular Contributor
timestamp: May 06, 2015, 10:27:07 pm
content: A square loop antenna with a diode makes a very selective resonant detector, and are easily made out of a loop of wire, or milled out of a piece of single-sided PCB material. If I remember the theory correctly, the loop is actually resonant when the circumference is about 1.09*wavelength. Here is an intro:http://www.creative-science.org.uk/mobile_LED.htmlThe junk box provided an OA91, but I got better results using microwave detector diodes from eBay (HSMS286K). The leakage from a microwave oven is enough to light up an LED brightly. See attached photo of a 2 GHz loop/detector. If properly tuned and connected to an audio amplifier, these things can easily detect cell phone transmissions a few meters distant.

author: eneuro
author_rank: Super Contributor
timestamp: May 06, 2015, 10:32:29 pm
content: Yep, tested this modified circuit mentioned by @paulie, modified myself with different transistors BC547B and BAT85 schottky barier input diode and... it works !Below video in slow motion when making a few meters from this RF detector attempt to make call to... my own numberThis thing works even with quite random resonant coil with estimated self-resonance frequency about 443MHz (10 turns of ~0.5mm copper wire made coil 11mm long and ~8mm in diameter) using this nice calculatorSingle-Layer Helical Round Wire Coil Inductor Calculatorand dipole antena longer than needed for cell phone a few times higher working radio frequency@JimRemington Thank you for another radio antenas tipsFound also this interesting PDF:pdf: Surface Micromachined Solenoid Inductorsfor High Frequency Applications

author: paulie
author_rank: Frequent Contributor
timestamp: May 07, 2015, 02:32:24 am
content: Quote from: eneuro on May 06, 2015, 05:47:00 pmUnfortunately I don't have time to watch a tutorial video because I'm already way too smart, but if it involved expensive precision inductance and capacitance meter and/or frequency counter then the answer is no. I use an old fashioned GDO (grid dip oscillator). Originally vacuum tube Alco model GDM1 and more recently a homebrew FET version (more properly GATE dip oscillator). I built several of these and eventually got cost down to less than a dollar, including variable cap and mechanical analog meter.

author: eneuro
author_rank: Super Contributor
timestamp: May 07, 2015, 10:25:45 pm
content: Quote from: paulie on May 07, 2015, 02:32:24 amProbably GSM 900 or GSM 1800 is used in my country with my cell phone, so tried using maetioned above HAM calculator to design such resonant coil and using 1mm copper wire with a few turns I've got around 1300 MHz self-resonant frequency, but without GDO difficult to verify this (led flashes even when makeing calls 2m away from detector).Tried also use car remore keys to light on diode in this circuit, but nope it flashes only when stick together antena and press one of two keys buttonsHowever, when measured keys steel stick it has about 4cm (0.040m) and when we assume it is... quater wavelength radio antena than I've got ~1800MHz radio frequency with 0.95 factor fits into this 4cm, but it is only speculationAnyway it is interesting what radio fequency of those Peugeot keys could beUpdate: Probably 433MHz is used433MHz 2 Button Remote Key Fob Blade With ID45 For PEUGEOT 206QuoteAnyway, while was searching for this found this interesting article, where among others sophisticated attacks jamming remote keys when we try lock our car when leaving to supermarket in section 4.3 in link belowAttacks on electronic car key systemsBe carefull when pressing lock buttons in your cars remote keysQuote...QuoteYep, I need 433MHz detector no question about it to catch jammers