How microwave body detectors work. With RF section schematic.
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- Опубліковано 28 вер 2024
- When I first took a microwave triggered lamp apart in a video I joked about the hidden chip being a standard PIR body sensor chip - and was then aghast to find that it WAS. Which meant that all the microwave signal generation and movement detection was being done by a single transistor and some cunningly designed PCB tracks.
I'll openly admit that microwave circuitry is such a specialist area where the only people who truly understand it are those who work with that type of circuitry all the time. It's not just a specialist area of electronics, but a specialist subsection of RF design where simple things like tracks stop behaving like conventional conductors.
Now I understand this circuitry better it all makes a lot more sense. It's got strong similarities to the Colpitts oscillator FM micro transmitters I used to make for the 88-108MHz frequencies - not 300MHz as I mentioned in the video. (Well not deliberately.)
The chip being used on this breathtakingly cheap and versatile module is a customised BISS0001 with a rarely used pin repurposed as the input to an internal 3.3V voltage regulator. That removes the need for a separate regulator on the PCB.
Here's a search link to find these modules on eBay. Target price less than a US dollar each:-
www.ebay.com/s...
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.co...
This also keeps the channel independent of UA-cam's advertising algorithms allowing it to be a bit more dangerous and naughty.
11:33 -- The circular ring is connected to a constant voltage (V+), so it's at AC ground. It prevents signals in other parts of the circuit from affecting the voltage of the disc inside the ring. (It's a "guard ring".)
The transistor's collector (C) is connected to this ring / AC ground.
The disc inside the ring is connected to the transistor's base (B).
The S-shaped piece of PCB that's connected to the transistor's emitter (E) is a section of transmission line, which resonates at a particular frequency and which determines the circuit's frequency of oscillation. Since one end of the S-shaped piece of PCB is connected to the transistor's emitter (E), which is the signal source, and since the other end of the S-shaped piece of PCB is connected to capacitors which are connected to ground (so that the far end of the S-shaped strip is at AC ground), then the S-shaped strip is a 1/4 wavelength resonant section of transmission line.
There is feedback between transistor's base (B) and its emitter (E) through the space between the short strip of PCB ("stub") that's connected to B and the section of the S-shaped piece of PCB that's connected to E. The size of the space between that stub and the S-shaped piece of PCB that's connected to E largely determines the degree of coupling (feedback) between the transistor's base and emitter. The longer the space or the narrower the space, the greater the coupling / feedback.
So the circuit is a one transistor oscillator (specifically, a grounded-collector oscillator), having a resonant circuit that's connected to the transistor's emitter, and having some coupling / feedback between its emitter and base.
This guy said PBC multiple times, but assume that he meant PCB, printed circuit board.
Very well said! I have no idea what that really means, but then again, I know virtually nothing about electronics.
@@acmefixer1 -- You're right.
@@therealjamespickering -- The circuit generates microwaves. The microwaves are radiated by the little antenna. When something moves through the field of microwaves, some of the microwaves are the reflected to the antenna, where the reflected signal is absorbed, amplified, and combined with some of the microwaves being generated by the circuit. The result is a small change in the circuit's normal voltages, which the rest of the circuit (the rectangular chip) then detects.
@@kevinbyrne4538 Ok, that's much clearer, thank you! So the S-shaped track oscillates at a frequency of 3.18 GHz and the interaction between this and the disk attached to the base results in a certain voltage to be passed through the emitter? Movement in the room would then result in variations in the voltage?
Does the board only output a high/low digital signal, or is it an analogue signal that could be used to determine something about the size/velocity of the object?
Hehe, I also made those “simple” (slightly illegal) FM transmitters when I was young, most often with a preceding microphone amplifier, to become a small bugging device. Often choosing close to 88MHz or 108MHz, and then any ordinary FM-radio (preferably small and hand held) could be used as receivers. I learned then, that there was a big complexity to RF-electronics, since I put a lot of effort in doing very nice and clean builds, with often no good results, while a class mate made a very “ugly” build (blobby soldering, wires not cut close to the PCB etc) and that worked better than any of the rest of the class mates. It’s fantastic that a simple circuit like that actually ends up as a FM-transmitter. The simplicity to build things like this for FM an AM, together with the avast amount of existing equipment, is actually why I feel a bit “scared” that DAB will “destroy” the possibilities for future young kids, interested in electronics, to test and learn in an exiting (slightly illegal) way. Of course you can do a lot of MUCH cooler things today, with all sorts of micro controllers and advanced chips, sensors etc, but not at the same low level.
I’m glad Sweden postponed the switch to DAB. It really feels meaningless, since you could get the digital feeds via mobile data streams and the cost to switch all existing analog equipment would be enormous. It have played out it’s role... Keep at least some of the current FM-band analog (as well as the AM-band) as a backup system and for the kids to play with ;)
Btw, we soldered the antenna (normally measured to a quarter to the wavelength) to one of the loops of the wounded inductor.
My DAB radio failed fairly quickly so I'm still on FM. I wonder if the DAB time signal is still ~4Sec slow????
Loved this video! The fact that you tried to comprehend the magic of RF and still put out this video - the transparent film screen showing the back was a great way for you to explain of your thought train in a very slick way!. Always look forward to your new content, I’m pretty sure I’ve watched all your back catalogue :-D
The Concentric Circles thing is the actual Antenna Element Back Plane . The Squiggle Line Track simply a Load Inductor doubling as the Antenna. If you measure the Distance between the Squiggle Track folding back on it's self you will find it a fraction of the actual operating frequency in .wavelength.. Probably 1/8th or 1/4 wavelength.
Agreed, as soon as I saw that I thought linear loading.
The rectangular track on the base pin will probably be 1/4 wave resonant stub too. Don't forget to account for velocity factor when working out the frequency, which is approx 0.5 on FR4.
@@Zadster LOL, That little Stub or Tab is most likely the primary RF Emitting Element. AKa Antenna.
Argh. I should read more before posting. If you think of it as a delay line one end is the frequency of the oscillator right now and the other end is the frequency of the oscillator a few pico seconds ago.
@@pulesjet I'm not so sure, given the electrically "large" area of the disc and the annulus.
Hi Bigclive - really interesting video - I remember UHF/Microwave construction being described to me in the late 1970s as a bit like "plumbing" - the usual headache when designing higher and higher frequency circuits was trying to overcome and eliminate stray capacitance, but as you get towards the top end, they stop being a "problem" and start becoming an "enabler" - but you instinctively realise that :)
What's more interesting to see is that (compared to the tolerances within microchip fabrication) the relatively crude technology behind copper etching can be used to great effect.
It's a bit like looking at plans for a fairly crude valve amplifier and realising that the "cleverness" is all down to the physical construction, which we've all kind of forgotten with the ability to cram more and more components into an ever decreasing space to overcome design flaws
This is a perfect example of less being very much more :)
Imagine all the time and research going into the design only to have it copied by the Chinese and sold for 70 cents a module.
I think this is a voltage controlled oscillator, it doesn’t use a fixed frequency.
As others have said, the circular elements on the back plane are part of the antenna. For this sort of circuit to work the antenna needs to have an outrageously high Q, and ideally a pretty low radiation resistance, which a loop antenna provides. Essentially the ring looks to be a loop antenna acting mostly as a receive antenna. It’s coupled to to the transmit antenna with a sort of hybrid between a gamma match and a Patterson loop style capacitive network.
The 1k resistor and the two adjacent capacitors right before the sense input are an RC pi filter tuned to the oscillator’s stable frequency. When the environment around the sensor changes, the amount of reflected power and the phase of the received signal changes slightly, which causes a change in the circulating current in the receive loop, which causes the complex impedance on the oscillator output to change, which changes the oscillator’s frequency. The frequency change means the signal will move relative to the pass band on the RC pi network, changing the attenuation of the signal and altering the voltage at the sense pin, and the chip just triggers on the change.
If you have an RTL-SDR dongle or similar you should be able to confirm this by watching the signal in the waterfall. I bet it swings like mad when you sweep your hand near the sensor.
Clive, if you don’t have an SDR handy, I’ll order a couple and put it on the spectrum analyzer, and I’ll also send you a little SDR dongle. Super handy little gadgets for poking at RF circuits like this.
Indeed there's a github repo with information about this module (jdesbonnet/RCWL-0516) which mentions: "finally found the signal at 3.181GHz with the HackRF One SDR! One interesting observation: waving my hand in front of the sensor causes significant changes in the transmitting frequency, shifting by up to 1MHz"
Matthijs van Duin that’s interesting, I would actually expect the swing to be much bigger for it to be based on the changing attenuation of the band pass filter. 1MHz swing on a 3GHz signal would probably only be a fraction of a dB even at the steepest part of the filters curve. I wonder if it’s using the op amp that’s on the input of the chip as a phase comparator or something similar.
This break-down caused me to realize that not every part of a circuit is either positive or negative relative to a connected part; but rather, the relationship can be more complicated; time-based or based on detection/externalities.
The ring is a resonator at wavelength equal to its circumference. The top of the ring is pinned firmly to VCC by those bypass capacitors forcing that to be an E field node and the bottom to be an anti-node. The collector and emitter have opposite phase so that the meander line couples to the resonator on the back. Do those two vias on the disk connect to the base? They seem to be about -120/240 degrees away from the top standing wave node. Combined with the transistor characteristics and the base capacitor overlap, I predict this brings the positive feedback into phase with the resonator. Any Doppler effect shift will be f0 (v/c). That disk might couple to reflected energy so that the same transistor mixes those two signals with the 1k -- 1 nF forming the LPF to reject the carrier and sum frequencies.
A hybrid coupler in ring configuration ("rat race coupler") perhaps. These couplers typically have four ports. Power input at port 1 splits and travels both ways round the ring. At ports 2 and 3 the signal arrives in phase and at port 4 it's out of phase and cancels. The reflected, out of phase signal (from your body) can be made to "unbalance" the ring which effectively brings one port to a higher potential than the other ports. Those eclipsed portions of ring might be the port couplings. Just a guess- I am not a µwave engineer (but have played with transmission lines in the past).
I like it and me too. C band satellite LNB pre amps when 120$ was entry price for a single NEC transistor with a much improved noise figure. Had no real business ordering those and resurrecting dead ones from lightning surges, but I was still more successful than not. Only thing I can recognize here is the quarter wave tank described as the only rectangular item on the board, hanging off the collector. 14:06 Those were very commonly used in that field for side by side coupling of the mixer signals. CRS about too much of it these days, but we are talking mid 80s too. End of the day, way too pricey for me to play and win.
The big track on the base is coupling to the tuned circuit on the emitter. That is positive feedback so it oscillates.
I think you are correct with the screening you spoke of. Back in my army days that screen was made of copper components and used to tune the device to see it's target.
Did anyone else notice how Clive drew his own face in this video? - Just look back at the part where he draws the diagram of the P.I.R. sensor at the top of the sheet.... Now, tell me that's not a self portrait!
Thanks, Clive, for another truly enthralling video on something I know absolutely nothing about. - Give me valves (tubes) and high voltages any day. But, we shall learn........
Im only a low level entry into RF circuits but I am aware in microwave frequencies an antenna called a discone is used most common. They tend to use a capacitive 'hat' and obviously get smaller the higher the frequency, so I think you have a very squashed discone antenna with all the relevant coupling components. The idea with RF is you want as much power thrown out as possible without any RF reflecting back down the feed to the transmitter or damage will occur. I know its very critical with high power outputs, but not so sure with very low power like this but it could have an effect if not controlled properly. It is called a discone because that is exactly what it looks like, a disc on a cone with an insulated separator between them. The disc is fed with RF and the cone is the ground reference and the size and angle relationship ( radius of disc and angle/length of cone with solid cone and disc or using rods as a cone and disc ) between them determines the frequency you want to transmit at. As mentioned by another commenter further down the receive parameters of the antenna will usually be compromised by a fraction of the desired transmit frequency ie 1/2 wave, 1/4, 1/8, 3/8 etc are typical because of size limitations on the board or your available space at home because the actual size required for a 1:1 transmitter in most cases would be far greater than the space available. Reception through an antenna does not need to bother so much with sizes of things as all it does is alter the amount of energy/noise/interference available to be received. In short, the antenna length/size must be a fraction of the wavelength of the frequency you wish to transmit at and the load on the transmitter device should be as close to 50 ohms as possible to prevent a dead short, because transmitting RF is almost a dead short and a lot of energy is at the transmitter in commercial antennas which is why you should never EVER touch a live transmitting element as you WILL get burned lol. With an AM/MW antenna the entire pole is live, ShortWave uses very long wires across towers and FM uses lots of types from yagis, log periodic, ground plane X shapes, monopoles, discones, dipole etc.. Basically the higher the frequency, the shorter/smaller the antenna length. Interestingly, behind those small to massive "snare drum shaped" microwave transmitters you see everywhere is just either a small discone, bowtie or dipole element in the center. The drum is just a reflector for line of site comms. :) Probably got some bits wrong but didnt want this to go on forever.. which it has lol
your large format pcbs are a brilliant display tool. What an excellent presentation.
Pretty clever. You really gotta stare at it to see all the layers. The single transistor is being used for several things at once. The base is capacitively balanced between the TX and RX in such a way that if they don't cancel each others opposing capacitance charge the difference will change the bias of the transistor. A lot like how a phase lock loop can demodulate FM. It's seems a lot like just a microwave frequency version of a phase lock loop metal detector that's been cleverly manipulated out of a single transistor and some passives. The metal detector doesn't beep unless you swing it, but in this case the coils are stationary and the metal moves. The higher the frequency the more the water in the soil reflects back on a metal detector. That's why they only use around 7khz.
A collaboration with the Signal Path is called for.
That RF oscillator could be used as the volume oscillator in a theremin. It would be interesting to attach an oscilloscope to the 'sense' point and see how sensitive it is. I might buy some of these and try to build a theremin.
Thanks for doing the hard work. I ordered a bunch of these several months ago and plugged one in. It works! I just never got around to a tear-down.
Microwave RF design is something magic. As I'm not a wizard I don't understand much of it. As a ham radio operator I want to work on the GHz bands as well some time in the future.
The magic fades pretty quick once you start mucking around with it. Go on AliExpress, lots of little SMA-equipped modules to play with.
I have a bunch of these and they are great, but I never bothered to try to figure them out, I didn't do very well in my RF and wireless classes when getting my degree. I understood diversity and multipathing, QAM and PSK, but for actually how circuitry worked and a lot of the math involved, not a chance. That stuff is black magic, to the people that really know it, much respect.
Clive, thank you for teaching me about this device, I've had one in the drawer for quite awhile now. I think i will temper with it's C-TM with resistor and maybe short it out. What i really wanted from this device was the magnitude or perhaps frequency of detection and not so much staying on for a duration.
That may switch it on permanently. Adding a resistor reduces the resistance as it will be in parallel with that inside the chip.
I assume the disc and ring are a circular or spherical polarised antenna. The FPV community might say it looks like a linear 5.8Ghz patch antenna with a ring around it. There are many designs of FPV microwave aerials, some appear to short the signal to ground (usually with a twist or three) while others are capacitive - an interesting one which is circular polarised and can be printed cheaply on discs of PCB. It was provided open source by RF legend Maarten Baert. It's currently the most popular design www.maartenbaert.be/quadcopters/antennas/pagoda-antenna/
It would be interesting to grab a load of these detector boards and try overclocking the range using higher voltages, enclosures, Pringles tins etc... Great video as usual Mr Clive!
Just mount one at the focus of your satellite antenna.
No. A simple ring does not give circular polarization.
@@graemezimmer604 You're right. It's probably more like this design www.maartenbaert.be/quadcopters/antennas/triple-feed-patch-antenna/
I feel like I should be getting course credit for this. Very nice video!
if you pass the quiz...
I was impressed I have ordered 10 from Ali, @31 pence each, it's crazy that you can buy something so clever for so little.
EXCELLENT Video BigClive, once again you bring us mere mortals outstanding, interesting and simply awe-striking photo overlays with sublime PCB Exploded views, thank you immensely
Great to watch you second guess what and how the designer was trying to achieve. There must be a bit of detective Columbo in your DNA. One more thing....
OMG! ZTX300 series transistors ... from Ferranti, where I worked as a computer engineer back between 1976 and 1979! Used LOTS of ZTXxxx series transistors and still have.many spares. As ubiquitous as the BC107,8,9s and later BC149 types! Or the US equiv of the 2N2222!
The first thing I thought of after seeing this was the infamous AN/TPS-39 intrusion detection system used on Titan II missile sites. They used paired microwave horns creating a perimeter around the silo and were famous for false alarms. Heavy rain, large birds, coyotes, or a bit of snow collecting in the antenna would have security scrambling. I don’t think they ever detected an actual intruder. The technology was not quite as advanced in the early 1960’s when the “Tipsy 39” was designed. What your little circuit board does took a 6’ stack of rack mounted equipment to do.
The guy that "invented" radar, sort of, Watson-Watt got stopped for speeding in the 1960's. His wife told the cop that her husband had invented those. Suspect cop was not impressed.
I have a 100Wh/87w draw Anker battery, it has a button on it to show the battery health. If I long-hold it it disables the low-current shutdown. idk if others have that though.
I need to get a Body Detector so I can find myself the next time I have an Out of Body Experience! I don't want to chance drifting too far away, in the wrong direction! LOL.
Multiple tap points on the C-E loop could be to enforce frequency stability to ensure that it don't drift away too far.
The distances from the collector to first tap point and between the tap points are more or less equal (give or take), so I wouldn't rule that out as a frequency stabilizing design. This device wouldn't be doing a good job if the frequency isn't predictable. Manufacturing variations in the transistor itself can otherwise lead to unpredictable results.
I think the circular track on the back of the board could be the reflector to make the antenna directional. The driven element of the antenna being on the top side of the board.
Worked with Microwave Communication systems more then a few years. Microwave is a bit sketchy chit to work with. The higher microwave frequencies are pretty much the Transition from RF Radiation into the Light Wave Realm. Microwave behaves more like light waves then radio waves in a number of ways.
Do you think we could reduce the power consumption of it to uA rather than mA?
Yep, Every every thng about radio you kn0w
about radio do with radio goes out the window. Microwave have behaves more like Light then radio
The frequency is this module uses is about 2,9 - 3,2 GHz. There seems to be no modulation of the carrier
10:51 your schmatic should have a strip on the base drawn and this is how you tune resonance freq
1st bit FM wise, first thought that came to mind was if the boats a rocking don't come knocking, though different bandwidths. Ah the good old days, now it'd be done on internet.
RF is actual Black Magic, pure Wizardry.
I really like this one, Clive. Thanks.
Very nice video and exploration of this interesting module !
Greetings from Holland
Микроволны-черная магия)) антенна выглядит как простая антенна с тройной подачей патча. Как вы печатаете крупномасштабные фотографии модулей так красиво?
RF guys are magicians and conjurers.
The power-bank looks funny..
Very interesting video, thanks Clive
If you can find one of these I would love to see you do a teardown of of this power bank I have, bought my step father one because they are really good. Juice power station.
Good to see you revers eng out of your comfort zone RF is fun, I disagree with you thinking on the detection of the reflected signal though. I suspect the transistor is acting as an oscillator as you say but also as a mixer so when the returning signal is reflected from a moving object it will have the wavelength ether compressed or stretched slightly resulting in a slightly different RF frequency being picked up on the antenna and returning to the emitter this will mix with the oscillator frequency generating two new frequency's one will be oscillator Freq + received Freq and one will be oscillator Freq - received Freq its the minus one that will be used as it will be very low just a few Hz and this will pass through the RC filter fed through the antenna from the emitter. this also relates to how a super regenerative receiver works
Yes. It acts as a simple "Direct Conversion Rx". The reflected doppler is mixed with the original carrier to produce an audio tone. Doppler Radars date back to WW2.
those intersection points on the antenna are feed back detection
Nice looking forward to.this video.
I would prefer to use a cr2032 or 3xAA or similar for the standby current
and the power bank for powering the lights only via a switched mosfet. So also smart power banks should work.
Whereas you could then use a li-ion cell for standby and switch on a mains power supply, which lights and recharges at the same time...
What i really hate ist the cheapo lights with motion detection you get for mains power,
which then use almost 1 watt constantly and get kind of warm, and use 2 watts with the light on.
So you could basically let the light on all the time with the same power consumption/ eco footrpint. :-(
Sometimes big Clive really just hits different
Big Clive, there are potentially some quite complex things going on in that tracking. For example the centre solid circle is most likely the ground plane for transmission. However the outer circle may actually be the receiving aerial and the "transistor" could be a MMIC as some of those are getting miniscule for low power applications now. Now this is where it get's horrible. The crossing of the inductive aerial on the circle capacitively coupled to ground could if set up correctly set up harmonics. Those harmonics together with the original signal can be used as passive down conversion and filtering. IE something akin to a cheap SAW filter and AC mixer combined. The signal then back feeds through the power line. If you look at consumer microwave receivers (EG a satalite dish) they almost always use just standard coax with the screen as ground and the centre as DC + signal. Basically the DC feeds into the core via an inductor and the receiver couples via another inductor but sends the signal back via a capacitor connected to the cable end of the DC input inductor. Horribly complicated but once you get it sorted a good deal of your components are replaced by tracking. Just don't get me started on s-parameters and 3rd order intercepts. It does my head in.
There are plenty without the rear ringpiece shenanigans!
excellent info on this device
thanks, same vintage as me, ref the 'old' FM tx info. I see video was made 2019 so you may have more data by now, if not, I have pdf datasheet and schematic if of interest.
i think they have a ginormous one of these in alaska somwhere lmao !! 15:00 i think that may be resistive capacitance there ..just an educated guess but hey ..if im wondering' im about to learn something !
Great analysis!! TY 👍👍
As AVE would say J.F.M As always great video BigClive. Appreciate the link to those modules
that's a new ave-ism to me either that or my brain is fried.
@@ucitymetalhead just f...... magic He said it in a couple vjos
6:20 I bought one of those cheap FM transmitters on Amazon and just connected the antenna to the ground connection of my wall plug (European style F) and I played a song on it got in my car and drove around the neighborhood. And the Range of this thing was around 400 meters. Quite far for such a little thing.
GREAT explanation on this little module. Can the range be increased by aiming it into a parabolic dish say, a 3' diameter type?
Ah, the days of "build whatever is asked for". Did that, including an FM radio phone tap which was triggered by a current-operated inline relay (used on PBX phone connection cards). Pick up the phone and the line current turned on the relay - and the transmitter. It wasn't a pleasant divorce for the wife when the husband - and his lawyer - knew the names of all the wife's boyfriends...
Dopeler Effect: The tendency of stupid ideas to seem smarter when they come at you rapidly. (Sorry, radar geek humor)
I know the Diplodo effect... making kids stare at TV (in the late 80's early 90's) =o)
have you tried tacking a 10uF cap across in and timing that? might be good for street lighting with that delay.
Very interesting but scattered... Whew
So, given that the oscillator will drift slightly over any short time period, as it's not Xtal controlled, if 2 of these devices are near each other, presumably they will interfere and both go to permanent detect as they drift past each other? That would be a major limitation that PIR doesn't have.
Thats not how these work. They trigger on quickly changing standing waves. Slow changes wont trigger them.
Just rig a microwave oven to run with the door open, if you smell pork, you have detected a body 😂😂
Oy vey!
*What the hell.. HAHAAAA!!!*
Oh my God man you hate the guy about to break into your house but don't give him cancer!!
Make sure and redesign your room to be the right size resonant cavity faraday cage. Make sure it is grounded. There, now your idea would work, but the sound of people screaming from sudden blindness would be your early warning alarm...
@Dave Micolichek So... it was effective at clearing the morning mind fog?
This will be perfect for catching that ghost that keeps turning on my soldering iron after I turned it off.
id like to hear more about your ghost
I think I may have your same ghost...
Nah, that's just the ghost of Moss.
I bet it's the same ghost that switched my grandmas stove on and ran my water heater for 4 days straight.
If you manage to catch it, make sure it can't hurt anyone again.
@@uzaiyaro So leave the soldering iron OFF, ok Moss? 0188999...
If Clive says it's complex it's really complex. Another really interesting video Clive thanks for all the hard work you put into these.
Glad I stumbled on your channel many moons ago, it fascinates me how all these things work and makes me want to get into making a few projects myself
If Clive says it's simple it's complex for me
One of the main textbooks on high speed digital design, not really RF, is literally titled “a handbook of black magic”
Not an effin clue, but Big Clive's enthusiastic detective work draws you in and you keep watching.
@@N1gel Haha, I don't even know the basics of electronics, but I get drawn into these. I at least have an idea of which components do what, it's just the whys that Confused me, lol.
My list of questions never ends and at some point I will know more, but right now, I still love Clive's vids despite my lack of knowledge...the big surprise I was getting at you know, lol.
@@N1gel Nothing but respect for Clive. Techmoan and Explaining Computers are another couple of very good UA-cam channels you might enjoy. :)
@@watsoft70 Glad to know I'm not the only electronics-noob in the audience. Whenever he talks about complicated circuits like this, I'm lucky if I can even follow along half of what's going on.
@@N1gel ... some things are just beyond the ken of mere mortals, and are not meant to be known the wot of. Microwave RF is clearly for wizards and other ethereal beings.
Where is the Signal Path god when you need him...
Appreciate these videos so much - truly, truly good quality educational content that is often impossible to find. Keep on keepin' on!
It may actually be more interesting watching Clive when he doesn't know exactly what's going on than when he does.
Preach :-D
To paraphrase the late great Arthur C Clarke, microwave technology is indistinguishable from magic.
not sure if it was intended as part of the joke, but arthur c clarke was a radar specialist in WWII so I don't think microwave tech was very magical to him.
This reminds me of a gadget I built before touch sensors existed. I used a PIC to generate PWM into a coil, which coupled with another coil. Somehow I could measure the phase between coils, which I put through an op-amp and back into the PIC. The theory was that my finger would change the phase. They laughed at me, said it can't work, but it did! I put two of these in a box and by sliding my finger up and down on the surface, I controlled a PWM fluorescent dimmer. Happy memories. My goal was to make a water-proof switch.
Isn't that how metal detectors work?
Nice one, well done.
@@Lasseu basically yes, my first touch sensor I made with a crystal, oscillator a few transistors, resistors, capacitors and a relay.
That's how inventions are made. Though a waterproof switch is much simpler to make, just get a reed switch and a magnet. That's how Nikko did their submarines.
Before touch sensors were around? Seriously? How about 1978 when I made touch sensors using CMOS 4011's? PIC's didn't even exist then. The circuit was simple, touch one spot to turn on and the other spot to turn off. Have to say though, the capacitance coupled sensor would definitely be better and could be made waterproof.
Many years ago as i mooched around the local library I noiticed that a book enttled 'The Deadly Fuze' never moved. Eventually curiosity got the better of me and I took it out.Turned out to be the story of the development of the WW2 Proximity Fuze. Built into shells and fired up the barrel of a gun! And this was in the days of valves!! Can't remember the operating frequency but acorn valves could get up to about 500Meg. Used in anti aircraft shells and ordinary artillery shells.
And now we've got shells with GPS built in!!!
That blue battery usb suply make me think of another divice :-), Thumps upp as always.
What device..
Heh
Thumbs up where?
at 0.49 , he's also talking about bigger ones .....
Yes it does remind me a little of the "Should I stik this up my ass" video released some time ago.
On the note of the "intelligent" powerbanks that shut off... How about a video about modifying them to either not do that or turn down the current they require to be drawn to stay on, if possible? I've had tons of projects where I thought "I could just use a powerbank to power this" and then these "intelligent" ones ruined that idea, especially ones that require something like 200mA minimum to stay on. There's simply no way to use low power stuff like a simple 1 LED light (ikea jansjö USB for example) with long runtime in mind from it because the powerbank will just turn off after 10secs :(
IIRC, you can change the value of one of the capacitors to prevent that behaviour.
Check out Mr Carlson's Lab UA-cam channel.
As 50+ old fart it's been 30 years since I've thought about 1/(2pi*sqrt(LC)). You're video made my brain work - thank you.
What Leon Theremin was trying to develop when he accidentally built a musical instrument.
*claps hands* Yay! A new BigClive video!
- And I just got my first meter, and a PCB holder 😁
Double yay!
... now to figure out how a meter works, while I wait for a kit that'll teach me the basics 😂
*looks at wall outlet*
Congrats on getting on the road to start learning electronic. Do not do what I did with my first meter and a wall outlet: I tried to check if neutral was really connected to ground by measuring the resistance between both, I was lucky as it only damaged the resistance range I was using. It was a passive analog meter, I'm not sure a modern electronic meter would fare that well.
@@SlyPearTreeThanks!
And that sounds like an exciting moment! Haha
Kinda sounds like a thing Clive should test out, while demonstrating to us (not you included ;) newbies how a meter _should be used_ and *not* used 😂
I'm still tip toeing around and reckon it'll be a good while before I start dabbing with the mains (So for others; yeah if it wasn't obvios, I was kidding xD).
Rather safe than sorry in this scenario 😁
You’re on your way! In 30 years you’ll look around and wonder where all the electronics crap you’ve collected came from!
Slypeartree a proper modern meter should not be damaged by that. That’s actually one of the tests Dave Jones on EEVBlog does when testing meters - full mains voltage on resistance range. Some fail spectacularly. Older analog meters will release the magic smoke and possibly detonate the battery.
@@stargazer7644 *giggles* Since I still have my childhood SNES I hate to imagine where I'm at when I hit 60 😂
- Thanks for the feedback!
FYI: I did test out my meter on a diode and after some fiddling around (It's an 'automated' meter; probably should've picked a conventional one instead) it, to my amazement, worked.
Let China be praised by the sun,... for their cheap electronics! 😁
that usb power bank is "DIRTY", cant even imagine what i thought it was when i first saw it.
hahahaaaa
I made these when I was kid too. I can remember my mother nearly feel off her chair when she heard me on the radio
I at one time worked on 45w 850mHz transmitters at the factory. I would tune the circuits be adding or removing silver solder from the copper patterns on the board. They were very sensitive to anything being moved around the power transistors.
850 millihertz transmitters must have needed a very impressive antenna.
@@stargazer7644 Not really. A 850mHz antenna is only about 6 inches long. These were for a early car phone system base station, before cellular phones.
@@oldmgbs2 - Star Gazer is busting your chops a little, for using the 'milli' prefix when you (presumably) intended the 'mega' prefix -- because a sub-1Hz frequency would (of course) need a hella large antenna :-)
@@theskett I didn't even catch that!
"m" for milli (1e-3) or "M" for mega (1e6).
Only accountants use "m" for million. Engineers and scientists use "M".
Clive’s got it right he could be an Electrical Engineer...
As my intro to EE professor said the difference between science and engineering is that engineers estimate, like Clive and his capacitor values being feasible, and scientists require exact values meaning they’re not as flexible dealing with real life components’ tolerances.
This also explains why most engineers are INTJ (me included) on the personality testing scale.
5:20 "The ZTX300 was also one." Instant flash back to Analogue Electronics in Higher Physics, 1986-7, where we had a tray of components and the transistors were ZTX300 and ZTX500.
yet another great vid, always wondered but assumed it was short range radar. the eclipses you talked about, in my experience ... the capacitance is used to tune an antenna wire or in this case the track. for example the 2.4ghrz band ( most wifi traffic and bluetooth ) and the antenna shape and reflectors on the back help with beam forming ( rf shaping or direction ) so... 300 (reference to speed of light acepted figure for antenna calculations) devided by 2400mhz known as 2.4ghz will give you 0.125 of a meter or 12.5cm ( the required antenna electrical length for 2.4ghz) which can be shortened by introducing a week capacitance to allow the physical length of the antenna to be reduced to make it more manageable. most modern antennas are designed this way to reduce physical length without disturbing antenna performance or in some cases actually enhance it. hope im right and this helps.
You're not wrong. Track width and capacitance values of mere picofarads or the reluctance or inductance of micro-henrys, can make a large difference in resonant frequency... Very careful design of layout track width, path and component values are critical... That's why RF equipment has so many variable Caps and tunable coils....or you'd never get an accurate or stable frequency... Tuning RF equipment is an art in itself.....
Peace, Keith......
Clive, no need to reverse engineer. Schematics are available online. Just Google for the module number. And yes when I was a boy I built this very same illegal transmitter and this in communist east Germany. One more thing : Isn't your fm oscillator rather an ECO oscillator? Colpitts is known for its capacitive divider feedback and Hartley uses an inductive divider feedback.
It’s amazing how such a simple circuit happens to be so complex. Thanks for breaking it down for us Clive, it’s much appreciated!
ANOTHER friggin amazing video !!! pull out ur 100GHz pocket spectrum analyzer and measure it !
keep em coming!
73 N8AUM
What is that circuit board that you connected this module to, which also has the leads to the LED coming off of it? A friend of mine is looking for a way to control some kind of valve in their bathroom in a similar way. It should only stay on for 2 seconds if it's triggered, but as far as I know, it does use quite a high current, so there would be the need for a relais?
You can get water valve control units with hand-sensing taps (reflected infrared) on eBay. They run from batteries.
The feedback from the collector to the base is in the transistor, mainly the internal capacitance between the collector and emitter. The square trace connected to the base is less an inductor/capacitor and more a delay line. The oscillator operates as a common base amplifier. The "squiggly" emitter line is a delay line. The disk of copper on the bottom behind the transistor is simply a ground plane. Some capacitance is there but it's unintentional. The ring of copper is the actual antenna. The ring and the disk ground plane act like a fresnel lens and makes the radar output more like a dipole antenna. When you move towards or away from the antenna, not only do you cause a doppler shift but you mainly case the frequency to shift (you're now part of the tuned circuit. At cm waves both are pretty much the same thing). The wiggly part of the emitter track introduces a delay from the frequency a few pico seconds ago and mixes it with the frequency that's happening now. In phase oscillations use less current than out of phase oscillations. The increased current drain for an out of phase signal is dropped and filtered by the emitter resistor (which is where the real feedback and transmit occurs) and the associated emitter/ground capacitors for detection.
@@pahom2 Everything is an antenna. In your case the dual squiggly lines is probably being used as an antenna and phase comparator. Remember that at these frequencies there is no real tuning inductor or tuning capacitor. Everything (including you) is part of a tuned circuit.
I'm using one of those microwave sensors as an under-monitor movement sensor. It is used to switch on an LED strip under my monitor when movement is sensed. The problem I have with these is that the sensing is patchy. They can often see me over the room (and through a wall) but will often not detect when I'm sitting at the keyboard (2ft away) moving my hands about the keyboard and to mouse etc (1ft away). My current solution is to have one under the monitor looking at me and another blu-tac-ed under the wooden desk and mousepad.
I've never yet worked out the front/back of the sensor to find the most sensitive side. I've been tempted to try a PIR sensor on the monitor instead but never got around to trying yet.
It may help to extend the run time so that the occasional detection restarts the timer. I use an outdoor PIR unit on my bench lights.
Amazing explanation and homework.. Especially because of the super zoomed PCB picture that was used. I'm sure it helped the viewers understand the PCB a lot more easily. Keep up the good work.
After a not particularly successful foray into FM design (and microstrip technology), I left this area to those who know what they are doing! FAR cheaper to buy pre-aligned FM modules than try to DIY (without the arcane skills this area of electronics seem to require!) :-D
FM modules are DC compared to microwave witchcraft. :)
@@stargazer7644 Dead right there mate! When track width / shaping parameters have to be accurate to sub-millimetre levels (and even then there's a lot of adjustment needed for unforeseen / difficult to quantify spurious coupling), witchcraft sums it up VERY accurately!
Perfect timing, I just took delivery of 10 of these microwave detectors and haven't opened them yet! Cheers
I was on the development team of the C&K/Honeywell DT-7xx k-band Dual Tec microwave/pir motion detectors back in Y2K. I did a lot of GTEM work for rfi and international certifications and UL listing. That round pad pad on the with the positive ring could be adding a few pf capacitance to keep rf noise out of the transistor. RF can be funky at gigahertz frequencies. I watch your videos to jog my memory. My kung fu is old and haven't touched an oscope or frequency analyzer since 2004 working on Pave Paws. That was SLBM rocket science ;)
Hey Clive, what an interesting circuit. And what you call a `cheap and tacky' meter has been my main meter for about 15 years, so reliable. LOL
I looked at the output of this device on a spectrum analyzer and it puts out a very dirty signal centered on 3100 mHz that is about 300 Mhz wide. The frequency spectrum has little peaks on it every 20 mHz or so. If this device wasn't so flea powered, it would be highly illegal. Nevertheless, they are very effective at detecting someone walking by up to 20 feet or more away.
Just curious, What exactly is the issue with it that makes it illegal? is it dangerous or just a powerful transmitter?
@@NikkiTripPS I believe it's more of a violation of broadcast communications laws. Not dangerous, but more like broadcasting without a license as well as broadcasting over multiple unassigned frequencies. At higher wattage it could potentially interfere with other communications.
I was trying to figure out how the circiuts work (and they do very well!). Your video was the best and honest video I found! I highly (!) appreciate all the effort and time you have put into making this video, althought english is not my first language and I do not undestand every piece!
I successfully hooked a VN02, high-side driver to a RCWL-0516 board.
Now I can drive up to 6 amps worth of LED lighting.
I'm grateful that they broke out the 3.3v supply as well - used this in a project recently. Had no idea that the RF part was basically black magic.
On the subject of tiny tech - a friend just ordered a 256Gb microSD card from eBay for less than £8 delivered from UK. (I know!) It was a FAKE!!. Anyone who has seen the Linus Tech Tips video about fake cards will know.
After a bit of research I noticed a few others were selling fake cards, USB sticks and 500Ah (yeah, I know!!) powerbanks which were unable to charge a phone.
The sellers have surprisingly good feedback but if you look it's all fake eBay accounts (under 10 transactions)
There's a little stand alone program for Windows PCs that will test the real capacity of an SD card or USB stick.
@@bigclivedotcom Nice one BigClive. The card we got was almost useless. We copied 5,000 files to it and it took over 3 hrs. When it finished we lost 2/3 of the files and the operating system file manager kept crashing. Found an app called H2testw but in future we will not be buying Krecoo brand. They are also selling them on the US ebay too. Supply and demand!
@@plasmodium4220 H2testw is the app I was thinking of. Always worth using to check suspect memory. But for critical things I recommend high profile cards bought from equally high profile suppliers like ASDA/Walmart.