hybridfree/eevblog-posts huggingface dataset:
phone call triggers lights and bell - Page 1
Forum section: electronics / projects

author: Unknown
author_rank: Unknown
timestamp: May 09, 2012, 02:01:55 pm
content: I was planning a simple project that turns on these vintage lights and rings a bell when you press a button - the lights and bells have sentimental value to many folks in my company - it was just going to be a stand alone little deal. Then someone suggested I make the lights and bell go off when some one calls the office phone. I think this is a great idea...but, I am not sure how to implement it - if fact I have no idea where to start. The phones we have are VOIP, connected via CAT5 cables... I would prefer not to have to hack the phone - as they are CISCO and I may or may not reap the consequences for breaking one if I don't get it right the first time...but I would still consider this option. Any thought on how I might pull this off?

author: SeanB
author_rank: Super Contributor
timestamp: May 09, 2012, 05:54:02 pm
content: The ringer is probably a speaker on the bottom of the unit. Place a few dozen turns of wire as a coil around it and you probably will get a usable signal ( will need to be amplified around 200x and then rectified) that you can use to operate a relay. No contact, just the coupled magnetic field from the ringer speaker.

author: sonicj
author_rank: Frequent Contributor
timestamp: May 09, 2012, 10:57:13 pm
content: Looks like you can pick up a used cisco voip tele for around $15 shipped on eBay. Might be best to experiment on one of those rather than explain to the boss why your phone is in parts spread across your desk and why you haven't answered any calls today.-sj

author: amyk
author_rank: Super Contributor
timestamp: May 10, 2012, 10:38:40 am
content: Quote from: SeanB on May 09, 2012, 05:54:02 pmA lot of VoIP phones use that speaker for the speakerphone function too. The ringing signal might need to be filtered out from that.

author: yanir
author_rank: Regular Contributor
timestamp: May 10, 2012, 11:43:08 am
content: You might be able to hack into that used phone to directly control the lights via the LED ringer indicator, which most office phones have. Then put the used phone into a parallel group with the main phone. Both will ring and your lights will turn on.

author: T4P
author_rank: Super Contributor
timestamp: May 10, 2012, 03:28:44 pm
content: Quote from: yanir on May 10, 2012, 11:43:08 amnow that's voip he mentioned
Phone Caller ID module - Page 1
Forum section: electronics / projects

author: Albert101
author_rank: Newbie
timestamp: March 12, 2013, 05:22:28 am
content: Hello,I am looking for a simple and easy to build Caller ID module (name and number) for the north american phone system. DC powered with a battery backup if possible.Thank you.

author: SeanB
author_rank: Super Contributor
timestamp: March 12, 2013, 03:19:09 pm
content: Buy a cheap cordless DECT phone, all integrated into there. Cheaper than buying the parts. You can pick it up new for under $30.

author: ve7xen
author_rank: Super Contributor
timestamp: March 12, 2013, 05:30:02 pm
content: You could probably also do this with an STM32F0DISCOVERY board or any other low-end microcontroller dev board and some passives. It's just 300 baud FSK. Hacking an analogue modem might work too, if you can find one that actually has a UART onboard and isn't all DSP. Hacking a phone is probably still cheapest and nicest from a UI perspective.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 12, 2013, 06:09:12 pm
content: An old modem (or embedded modem module) may do what you want
phone touch screen - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2021, 10:31:27 am
content: Hi all,i have a samsung galaxy s5 phone,the touch screen works fine with my fingers but wont respond to a stylus,is that normal?

author: m3vuv
author_rank: Super Contributor
timestamp: November 09, 2021, 10:37:39 am
content: could it be a stylus will only work with a resistive screen not capacitive?

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 09, 2021, 11:53:54 am
content: If you have a stylus with a pointy end, then it does not work with a capacitive touch screen (as most phones have)For a capacative touch screen you need a stylus with a (conductive) rubber dome at the end.
phono preamp w/ 6021 submini - Page 1
Forum section: electronics / projects

author: Skywalker
author_rank: Newbie
timestamp: July 01, 2017, 06:33:31 pm
content: Hi to a tube amp designer:I'm in the construction stage of building a low power ( 5W ) stereo amp, and I wantthe phono preamp to be one 6021 tube per channel. I imagined it would look like theone in the RCA manual that uses 12AX7. The B+ will be about 150V. I guess the plateresistors would be on the low side, and I would like battery or led bias ( maybe 1.2V ).I need an entire schematic, but certainly the RIAA compensation resistor & capacitorvalues. I think they would be close to what a 12AT7 would use, but how close isclose enough? Any direct help or a shove in the right direction is appreciated. Thank you

author: TimFox
author_rank: Super Contributor
timestamp: July 02, 2017, 05:09:00 pm
content: First, the best source for tube data sheets ishttp://tubedata.milbert.com/index.html(one of several mirrors of the original site by Frank).Second, the RCA design uses "passive equalization", where the R-C network is inserted between two stages. Normally, the output resistance of the first stage (plate resistance in parallel with plate resistor) is an important part of that network. The 12AX7 and 6021 have very different plate resistance, and the higher-current 6021 will have a lower plate resistor, so the network will need different resistor values.In the RCA handbook, you can find a table of "resistance-coupled amplifier designs" that give a range of values for the amplifier stages' component values for different tubes: The 6021 is medium-mu, while the 12AX7 is a low-current high-mu triode, and the 12AT7 is a higher-current high-mu triode.One of several webpages with calculation details for passive RIAA networks ishttp://mh-audio.nl/CalculateRIAA.asp.I did find one example on-line, with text in German, for an RIAA preamplifier using 6021shttp://www.ak-tubes.de/Vorverstaerker/Pencil%20tube/pencil_tube_preamp.htm.However, the 6021 is a "subminiature tube", not a "pencil tube": that was a different style of tube construction for ultra-high frequencies (seehttps://books.google.com/books?id=-Kg4BQAAQBAJ&pg=PA164&lpg=PA164&dq=pencil+tube&source=bl&ots=eP3FNCo0yP&sig=T8pIroxcyaiZPCBZYbfHnzJgQO8&hl=en&sa=X&ved=0ahUKEwiy8_agiuvUAhWL14MKHbxiCBs4FBDoAQg8MAY#v=onepage&q=pencil%20tube&f=falsefor drawing of a real pencil tube.)

author: Skywalker
author_rank: Newbie
timestamp: July 02, 2017, 06:39:30 pm
content: Thanks so much, Tim. This is all good stuff. I was determined to try the 6021 tube since I had someand had heard scattered good things about it's audio performance. I think I'll have a B+ of about150V which will factor in. Maybe I'll get there without drowning in the math. Thanks again.
Phono stage MC (R) vs MM  (PF)? - Page 1
Forum section: electronics / projects

author: onesixright
author_rank: Frequent Contributor
timestamp: March 05, 2018, 10:43:43 am
content: Hi All,I'm looking to build a phono pre amp for a MC cartridge (something like this:http://diyaudioprojects.com/Chip/Opamp-Phono-Preamp/)I also looked at some commercial pre-amps and I noticed the MC has a configurable resistance setting, while the MM has a configurable capacitance settingWith close to zero knowledge of audio, I was wondering why is itresistancefor the MC and capacitance for MM? Any simplified explanation?Thanks!

author: cat87
author_rank: Regular Contributor
timestamp: March 05, 2018, 12:56:41 pm
content: Well, that has to do with the impedance of the cartridge on your record player. Unfortunately there are lots of cartridges out there with different impedances so if you want to build your own, find out the exact impedance your cartridge has.With that information, you can build your pre-amp to match that exact impedance and you'll also have to implement the RIAA equalization to match. If at the end of the build, the music will sound flat and bland, then there is a mismatch between your cartridgew and the pre-amp.One very good source of information would be Douglas Self's books. I think "Self on Audio", "Small Signal Audio Design" and "Electronics for Vinyl" might get you started. I'd personally start with the Small Signal Audio Design one.Of course, he's not the only source of info out there, but he has, I think, the most "bang per buck" in those books.

author: onesixright
author_rank: Frequent Contributor
timestamp: March 05, 2018, 01:09:38 pm
content: Quote from: cat87 on March 05, 2018, 12:56:41 pmYeah, I was guessing it has to do with that.However why is it capacitance for MM and resistance for MC? It seems, depending on the cartridge type there are different method of impedance matching?Quote from: cat87 on March 05, 2018, 12:56:41 pmThanks I will look for that!

author: glarsson
author_rank: Frequent Contributor
timestamp: March 05, 2018, 01:39:11 pm
content: Moving magnet cartridges have many turns of copper wire. This gives them high inductance and impedance. Together with the high impedance of the amplifier input (47 kohms) the effect of the amplifier input capacitance is significant.Moving coil cartridges have few turns of copper wire. This gives them low inductance and impedance. Together with the low impedance of the amplifier input (e.g. 100 ohm) the effect of the amplifier input capacitance is insignificant. Instead of forcing a standard input impedance (as we have for moving magnet) the manufacturers optimize their design by also deciding on the input impedance of the amplifier, usually from 20 ohms to a couple of hundred ohms.

author: floobydust
author_rank: Super Contributor
timestamp: March 05, 2018, 07:21:49 pm
content: Douglas Self's bookElectronics for Vinylis very good, if you want explanations and details.
Photo-coupler & TOPSwitch-II = 110/220 auto selector  - Page 1
Forum section: electronics / projects

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: April 06, 2010, 07:16:58 pm
content: I have one tale to share ...Recently repaired one Ansmann " Energy 8 " NiMH charger , its a lovely device well made ,and it is an very smart one .Still got injured at the 110/220 auto selector mini board , from bad AC supply of the electrical network.The long story short , this board has on it an SHARP Photo-coupler PC817 ,plus one mini transformer and few capacitors .Plus the TOPSwitch-II ( smart transistor ) TOP 223Y .In my case the TOP 223Y was blown , and there was no evidence of what it was ...By searching on the net , for info , for the only one (second IC on the board) ( SHARP PC817 ) ,found that it was used and in another 110/220 auto selector board, of another power-supply ,called as Mastech HY5020E .The TOP 223Y its an 30W one , the next TOP 224Y its an 35W one ...And does the same job .The point of my tale are , that those two parts SHARP PC817 & TOP 223Y , looks like they are always together , in those designs .If you find the SHARP one on it , now you know what is the blown one !!The latest Ansmann chargers , are great devices , about the damaged one , I got it damaged from Germany for just 10 EUR (ebay) .. 6 EUR was the cost for the TOP 224Y ( not Chinese one ) .Got also as new the Ansmann " Energy 4 speed " .And their digital battery tester " Energy Check LCD " ( with load ) .All of them , fine products.Here is , how the PCB of the 110/220 auto selector , looks like ... (Mastech HY5020E)http://origin-images.rcuniverse.com/forum/upfiles/325364/Oj27986.jpg
Photo-relay (SSR) Am I being dim? - Page 1
Forum section: electronics / projects

author: itdontgo
author_rank: Regular Contributor
timestamp: December 22, 2014, 06:26:40 pm
content: http://www.digikey.co.uk/product-detail/en/TLP3120%28F%29/TLP3120F-ND/871294TLP Photo-relayI have tried two of these devices and I'm getting an output resistance of 20ohms; 10ohms per MOSFET. Some way off the specified 0.15ohm output. It's being driven by 26mA through the LED. Can it really just be a dud batch or have I missed the point here?With a 12V PSU and a 27ohm load it gives a resistance of 22ohms and with the multimeter I get 20

author: Zero999
author_rank: Super Contributor
timestamp: December 22, 2014, 06:43:29 pm
content: According to the catalogue, it seems like you're not supposed to use the output transistors separately.Connect pins 4 and 6 in series with the load, leaving pin 5 unused.http://dkc3.digikey.com/PDF/CN081/2097.pdf

author: wraper
author_rank: Unknown
timestamp: December 22, 2014, 07:36:12 pm
content: Quote from: Hero999 on December 22, 2014, 06:43:29 pm+1

author: itdontgo
author_rank: Regular Contributor
timestamp: December 22, 2014, 08:25:16 pm
content: Yes that's what gives us 20ohms. If you have DC you can use one transistor to reduce the output resistance but if it's AC you need to use both of them. But as I say I'm measuring it and it's 10ohms per transistor. Hmmm. I have new stock arriving shortly maybe it's just a problem with these. I thought I am making a stupid obvious mistake that someone would point out!The reason I have my doubt btw... they came from China from an unknown dealer

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 23, 2014, 12:41:47 am
content: So wait, why give a Digikey link when it's not even authentic Digikey?If you're paying bottom dollar for it, don't expect functionality, expect crap.Tim
Photoconductor measurements over coax - Page 1
Forum section: electronics / projects

author: abquke
author_rank: Regular Contributor
timestamp: August 02, 2022, 08:26:48 pm
content: Long story short, my photodiode application has become a photoconductor application. With a photodiode and transimpedance amplifier, the writing on the wall was capacitance is bad for several reasons, so put the amplifier(s) as close to the photodiode as possible. Would the same apply to a photoconductor? Or can I have the photoconductor over here and coax connecting it to a bridge circuit and amplifier over there?

author: TimFox
author_rank: Super Contributor
timestamp: August 02, 2022, 09:25:16 pm
content: How fast is your speed requirement? If you are using the photoconductor resistance in a bridge, you can calculate the effect of capacitance from those resistor values.

author: abquke
author_rank: Regular Contributor
timestamp: August 02, 2022, 09:48:58 pm
content: Bandwidth needed is 2MHz or so max, so not huge at all.That's a "why didn't I think of that" point. I'll fire up the back of some envelopes

author: Kleinstein
author_rank: Super Contributor
timestamp: August 03, 2022, 06:08:43 am
content: There are quite different photo-conductors. There are mainly two types: very slow and high sensitivity and fast, but rather low sensitivity. In general the resistance is more on the high side and no suitable to directly drive a cable. So one would need an amplifier. Photo conductors have a principle disadvantage when it comes to SNR. So noise can become an issue.For high speed the coax cable is not so much a capacitance, but a characteristic impedance. So the point is to have a circuit that can drive some 50-80 Ohms. If there is sufficient light intensity, a photodiode can directly drive a 50 Ohms resistor at the end of a 50 ohms coax cable. The main downside is that the signal is small and noise can become an issue, but this way can be very fast (up to low GHz range), if a battery for biasing the diode is used.

author: Marco
author_rank: Super Contributor
timestamp: August 03, 2022, 08:41:29 am
content: Why a battery? You can just put bias voltage on the shield.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 03, 2022, 09:27:47 am
content: With a load resistor to get impedance matching also on the sensor side it gets a bit tricky with biasing through the coax.With slightly less perfect high perfect performance one could opt for not matching the impedance at the sensor side and than use biasing though the coad. One ideally has still natching on the amplifier side of the coax and can still get a reasonable flat response.
Photodiode circuit - Page 1
Forum section: electronics / projects

author: aiq25
author_rank: Regular Contributor
timestamp: May 15, 2017, 01:09:48 pm
content: Hello. I'm having a hard time understanding the attached photodiode circuit.I can understand the circuit without R2: Vout = R1•Ipd and the photodiode is reverted bias. But I'm not sure what Vout would be with R2. It's creating a voltage divider but what's the output equation?Any feedback would be appreciated. Thanks.

author: Zero999
author_rank: Super Contributor
timestamp: May 15, 2017, 02:02:39 pm
content: Hint: the output impedance of the voltage divider is equal to both the resistors in the divider connected in parallel.

author: aiq25
author_rank: Regular Contributor
timestamp: May 15, 2017, 02:16:49 pm
content: Quote from: Hero999 on May 15, 2017, 02:02:39 pmThe equation should be: R2/(R1 + R2). But is voltage just the output impedance•Ipd? I guess I'm confused as to how the photodiode current generated and the current from VCC affects the output voltage.Would photodiode current would generate a voltage across just across R2? Since the photodiode is in reverse bias, would R1 have an effect on about?

author: Andy Watson
author_rank: Super Contributor
timestamp: May 15, 2017, 02:38:26 pm
content: Look up Thevenin (and Norton).

author: Zero999
author_rank: Super Contributor
timestamp: May 16, 2017, 03:26:09 pm
content: Quote from: aiq25 on May 15, 2017, 02:16:49 pmModel the potential divider as an ideal voltage source, V = VCC*R2/(R1 + R2), with an output impedance of R1|R2 in series with the photodiode.
Photodiode / Transimpedance Circuit simulation with QUCS - Page 1
Forum section: electronics / projects

author: Bigman
author_rank: Regular Contributor
timestamp: March 15, 2015, 01:28:21 pm
content: Hi everybody,QUCS offers a photodiode as a component. But when I run a simulation, the output (see attached screenshot) is not what I expected.The voltage at the summing junction is constantly -0.742 Volts. Since the non-inverting input is referenced to 0V, I expected the voltage at the summing junction should be forced down by the output-voltage also to 0V.What am I missing here? Thanks in advance for every hint & tip!

author: ignamv
author_rank: Newbie
timestamp: March 15, 2015, 01:33:13 pm
content: You need more current flowing into the - node, to make up for the photodiode's current. Either decrease the feedback resistor, or increase supply voltage (your output is saturating).

author: w2aew
author_rank: Super Contributor
timestamp: March 15, 2015, 01:42:32 pm
content: The input common mode range of this op amp does not include the negative supply rail.

author: Bigman
author_rank: Regular Contributor
timestamp: March 15, 2015, 01:56:01 pm
content: Quote from: w2aew on March 15, 2015, 01:42:32 pmAs a newbie in electronics, pls. allow me to ask if you could explain this a bit more. I can only assume what you mean, and now something like this is keeping my brain busy: the photodiode is creating at the summing junction a negative potential (relating to GND). But since Vee is also on GND, the OpAmp cannot handle a potential more negative than at Vee ... is this what you mean?

author: ignamv
author_rank: Newbie
timestamp: March 15, 2015, 05:25:08 pm
content: You have to keep the inputs away from the rails.Also consider putting a small cap across the feedback resistor to reduce ringing.

author: tggzzz
author_rank: Super Contributor
timestamp: March 15, 2015, 05:52:13 pm
content: Quote from: Bigman on March 15, 2015, 01:56:01 pmSee the top half dozen linkshttp://lmgtfy.com/?q=input+common+mode+range+of+this+op+ampThey have taken the trouble to give you a coherent answer.
Photodiodes - Page 1
Forum section: electronics / projects

author: shakilabanu
author_rank: Newbie
timestamp: August 16, 2014, 08:55:27 am
content: I am working on a project that requires me to reverse engineer a BioPhotometer and build a new one with modifications. The part where I am stuck is a photodiode that measures wavelengths between 230nm to 600nm.I know fundamentals of photodiodes, but I was not sure is a single photodiode can measure this range of wavelengths. ?Or are there special photodiodes (array) that have multiple photodiodes built into them which measure different wavelengths and hence combine to make a broad spectrum photodiode equivalent. ?Hope I have made this clear.

author: ovnr
author_rank: Frequent Contributor
timestamp: August 16, 2014, 09:37:13 am
content: No, there are single photodiodes that should do what you want.Here's some. I especially likedthis one- $435, and yet the cover glass istapedon!

author: SeanB
author_rank: Super Contributor
timestamp: August 16, 2014, 10:07:16 am
content: That is a cover used to protect during handling, as the only way to get the lower wavelengths is to not use ordinary soda glass, which has absorbtion bands un the UV region, and which may also flouresce with short wavelengths. Bare die only after assembly and just before putting the cover on for the final time.

author: shakilabanu
author_rank: Newbie
timestamp: August 16, 2014, 11:01:44 am
content: Quote from: ovnr on August 16, 2014, 09:37:13 amThanks the first link was useful. However since Digikey does not ship to India, I'll have to try finding some other source to get these from.

author: ovnr
author_rank: Frequent Contributor
timestamp: August 16, 2014, 01:36:36 pm
content: Quote from: SeanB on August 16, 2014, 10:07:16 amYeah, I figured as much. Still, it looks pretty sketchy - and you'd think they could come up with a better way to protect their parts, because that doesn't seem terribly reassuring.Quote from: shakilabanu on August 16, 2014, 11:01:44 am... Digikey does ship to India, but it costs $40 in shipping. Mouser hassome partstoo, but their parametric search stinks so good luck finding the perfect part for your application. Same $40 shipping too, it seems.

author: ejeffrey
author_rank: Super Contributor
timestamp: August 16, 2014, 08:14:19 pm
content: UV photodiodes normally have fused silica windows, which work fine in the UV. Windowless photodiodes are usually either intended to be used where the etalon effects of the window glass cannot be tolerated, or when the diode will be packaged into a sealed enclosure by the end user, for instance if it is to be peltier cooled or used in vacuum. That particular diode appears to be also designed to detect electrons such as from X-ray photoemission or secondary electrons from an electron microscope, presumably that is why it has no window.Thorlabs sells a wide variety of photodiodes, here is a wide range silicon diode that is fairly cheap:http://www.thorlabs.us/thorproduct.cfm?partnumber=FDS010
Photoelectric on DSBGA - Page 1
Forum section: electronics / projects

author: blueskull
author_rank: Unknown
timestamp: April 26, 2015, 09:01:15 am
content: Hi,I am wondering if I can use some of the TI's DSBGA packaged logic gates for my audio DAC project.Does anyone know if the WLCSP like DSBGA has photoelectric effects? I don't want my design to be camera shy like RPi2.Bo
photoflash capacitor ESR in RLC discharge circuit - Page 1
Forum section: electronics / projects

author: frustratedgrape45
author_rank: Newbie
timestamp: May 12, 2020, 12:17:29 pm
content: hi, my query contains a few diagrams & equations so i typed it outalso, here's the web link as outlined in the second picture:www.glancap.com/web/viewerPDF.asp?Filename=/uploadimg/PF%20Series.pdf

author: gbaddeley
author_rank: Regular Contributor
timestamp: May 13, 2020, 02:05:13 pm
content: What are querying us about? There could be other parasitics in your schematic that might be considered. It depends on what you are interested in.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 13, 2020, 03:46:01 pm
content: Well, yes, in general ESR won't be the 120Hz value.I suppose they might be leading you to an answer of iteratively solving for (or approximating) f_test ~= f_underdamped, or perhaps substituting them to get a closed form solution but that may be messy.Note that a single frequency, steady state measure -- which is how we measure ESR -- isn't the most meaningful for a pulse, as the pulse contains quite a broad range of frequencies. A more complicated equivalent circuit may be desirable.In general, the ESL + ESR + C model can be further decomposed into many parallel and series RLC elements, modeling its real impedance more accurately over a wider range of frequencies. This assumes one has an impedance plot for the component, of course; this is rarely given for electrolytics, unfortunately.In practice, electrolytics' characteristics vary enough (between individuals, and over temperature and time) that such accuracy really isn't important. The pulse might deliver 2200A one day and 1900 the next (say if the following day were cooler, or the capacitor were switched out for another).Tim
Photoflash/Strobe capacitors - Page 1
Forum section: electronics / projects

author: Buriedcode
author_rank: Super Contributor
timestamp: May 16, 2016, 08:02:38 pm
content: I have revisited a project from my (somewhat wasted) youth involving the main component of strobes, flash, 'coilguns' and at the larger end, can crushing, projects.Now I'm much more familiar with electronics, and the sting of high voltage I thought I would build a 'better' charger for large medium voltage cap banks, starting with a 12V powered xenon strobe. I already have a couple of boards off ebay, no doubt removed from equipment, that really are just larger versions of those found in the flash circuits of disposable cameras (12V/0.5A in, 120uF 330V cap, probably only charges to 200V, 1Hz).By 'better' I mean having having some form of control over the power draw, and of course, accurately detecting the cap voltage to stop charge and/or trigger an SCR/trigger transformer for xenon. That'll pretty much just be a custom made flyback transformer, driven by a 555, MOSFET with some peak current limiting. I'll post if anyone is interested, but its hardly 'awesome'.Although I do have a couple of disposable camera circuits, their caps are only 50uF and I am having trouble sourcing 100-400uF/350V caps in the UK. I *could* just buy up a 470uF/400V cap from rapid/farnell, but of course these were not designed for the heavy, repetitive discharge of a strobe, and I've seen a cap explode before, the smell was *not* nice. Also, many strobes do not need a high capacitance really, the largest I've seen on a strobe (that was meant for 2Hz) was 80uF, and I'm planning on doing 'experiments' (ie: all the sad coilgun and Lorentz stuff that I am ashamed of) for the 30-50J range. So 150uF - 400uF, in series/parallel would be ideal, but as this is a half hearted thing, I'm not willing to pay £20 shipping.Any ideas?
Photorelay configuration/connection (mains side) - Page 1
Forum section: electronics / projects

author: ricko_uk
author_rank: Super Contributor
timestamp: May 01, 2021, 02:21:43 am
content: Hi,I need a replacement part to the G3VM-101DR1 (screenshot below) which is a 4 pin part, but cannot find one that has enough stock.I found TLP3109A (also screenshot below) but it is a 6 pins with the common source exposed. The G3VM-101DR1 does not have the common source pin exposed.If I use the pin TLP3109A can I leave the source (pin 5) floating or do I need to drive/bias it somehow?BTW, the HV side is 65V AC.Thank you

author: SuzyC
author_rank: Frequent Contributor
timestamp: May 03, 2021, 03:41:16 pm
content: Looks very close in specs. Suggest rigorous testing at elevated temperature and line voltage to verify safety and reliability.You can just not connect the 5th unused pin.

author: ricko_uk
author_rank: Super Contributor
timestamp: May 03, 2021, 04:22:28 pm
content: Thank you SuzyC!
Photos of various robots I've made over the years - Page 1
Forum section: electronics / projects

author: Whales
author_rank: Super Contributor
timestamp: April 17, 2016, 08:09:06 am
content: At the top of the page are pictures of poor and incomplete robots from when I first started out with electronics, but things get better (and less blurrier) as you scroll down:http://halestrom.net/darksleep/blog/012_robots_past/I have also thrown in a few 'short' stories about me, safety and batteries.Tell me what you think

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: April 18, 2016, 02:54:23 am
content: Cool!If you wanted to drive FETs with dead-time, instead of a CPLD, why not use a purpose-made half-bridge driver? Like the IRS2109 or others in its family? These also let you use very beefy FETs that can't normally be driven direct from a micro output due to the gate capacitance charging currents. Also, you could use FETs for both low and high-side.

author: netdudeuk
author_rank: Frequent Contributor
timestamp: April 18, 2016, 08:57:24 pm
content: Great work

author: Whales
author_rank: Super Contributor
timestamp: April 22, 2016, 12:17:13 am
content: Thanks guysQuoteThe purpose of the relay was to avoid complications like this. I'll have a look at that part.

author: tuvix
author_rank: Newbie
timestamp: April 22, 2016, 02:06:54 am
content: Mosfet gate drivers such as the DGD2103AS8-13 are a life saver. They have built in gate delays to prevent the high current spikes that tend to blow mosfets in high current applications. Good Mosfet can be $3-8 and can start to add up quick when they burn up. To me it's worth adding an extra $.50 per half bridge to protect them.
Phototransistor datasheet - Page 1
Forum section: electronics / projects

author: Nikos A.
author_rank: Regular Contributor
timestamp: January 31, 2023, 12:41:00 pm
content: Hi guys,I want to integrate into my design an IR emitter and a phototransistor. I want to experiment with the emitted power and the viewing angle, so I picked up some emitters based on that:https://eu.mouser.com/Search/LwCompareProducts.aspxAlso, I am looking at the following phototransistor from Mouserhttps://eu.mouser.com/ProductDetail/?qs=DkZGzo4b%252BTLpMYDw%2FNdTDA%3D%3DTo match the emitter and receiver with respect their wavelength, I picked up both to have a peak sensitivity wavelength of940nmI am a bit confused regarding the collector current of the phototransistor. The higher the Irradiance Ee (mW/cm2 ), the higher the collector current right? In the datasheet, there is a graph that correlates both parameters, but the graph goes up to 6mW/cm2. The high-power IR emitters a picked up for testing, e.g the SFH 4546 emits 130mW/m2. Could this destroy the phototransistor? In the datasheet of the phototransistor, I cannot find the max. collector current.

author: SuzyC
author_rank: Frequent Contributor
timestamp: January 31, 2023, 02:14:20 pm
content: Get the answers you want from them that knows.Email: sales@KingbrightUSA.comPhone: +1 909 468 0500225 Brea Canyon Road, City of Industry, CA 91789, USAFrom my experience:The max collector current is limited by the 100mW max dissipation of this device and only 6mw of dissipation is realized at 5V Vdd. Higher irradiance would decrease Vsat but with a collector load resistance in the 1 to 10K of ordinary operation, 100mW at 5V would not be realized and Vsat would further be further reduced by increased irradiation, lowering dissipation.IIMBG, depending on the distance of the radiating source from the phototransistor, the irradiating energy heating effect with the phototransistor touching the photo-emitter device would not be sufficient to raise the phototranistors temperature beyond the safe operating temperature. You could measure the max heating effect yourself with a thermistor or other temperature measuring device. The phototranstor's leads themselves would function as a heat spreader into the PCB or breadboard to dissipate any heating. The irradiance itself (IMHO) would likely not damage the phototransistor, apart from any heating effect.

author: ConKbot
author_rank: Super Contributor
timestamp: February 01, 2023, 12:15:04 am
content: You emitter is 130mw/steradian, a unit of angular areahttps://en.wikipedia.org/wiki/SteradianThe further the distance, the lower the power density (with the square of distance), as the surface area covered goes up (also with the square of distance)since the LED emits a fixed angle width beam.
Photovoltaics are nothing new... - Page 1
Forum section: electronics / projects

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 05, 2017, 10:00:07 am
content: Experiment:- One Continental Electric 927 phototube. (The 927 was a standard catalog part in 1941.)Datasheet:http://www.mif.pg.gda.pl/homepages/frank/sheets/049/9/927.pdf- One DMM, set for a 2V (10Mohm) range.- Illumination source. Desk light, flashlight.Obscured, no current flow. Well, almost none. I guess some light is leaking in around the sides.The meter does read properly zero when disconnected or shorted, or when the tube is better shadowed than this.So already, we're seeing power flow out of this cold tube!Normal desk illumination (well, right under the bright spot from my LED worklight).Intense illumination from a 1W flashlight at point-blank range. (Interestingly, playing with the flashlight, I find the angles that produce maximum output (over 0.4V) seem nonsensical. The angles may coincide with blue light leaking out the side of the LED, whereas the phosphor yellow has much lower yield.)This gives a power output of around 14nW into 10Mohms, for an optical efficiency of 7.3 micro%.Interestingly(?), commercial thermionic tubes give a similar yield: a heated cathode emits electrons with active energy, thereby making a very poor heat engine, but one nonetheless.Needless to say, some optimization is necessary before this technology will be competitive with amorphous semiconductor panels.Tim

author: MK14
author_rank: Super Contributor
timestamp: January 05, 2017, 10:17:15 am
content: So the 927 was meant for 16mm sound reproduction.Presumably they meant for 16mm films, sound track.Hence the 10KHz sections in the datasheet, for sound.Source:http://www.tubebooks.org/Books/Atwood/RCA%201941%20Phototubes.pdf
PHY Link only establishing 10 Mbps speed when both devices 100 Mbps capable - Page 1
Forum section: electronics / projects

author: vpanchal
author_rank: Newbie
timestamp: May 07, 2019, 08:41:55 pm
content: Hi all,I've designed a circuit board with a Microchip switch (KSZ9897) going to a Ethernet-to-VDSL module (LX200V20).The PHY ports between the two devices are connected using a transformerless connection as shown on Figure 4 in this application note (http://ww1.microchip.com/downloads/en/AppNotes/ANLAN120-UNG.pdf).By default with auto-negotiation & auto MDI-X enabled, the switch establishes a 10 Mbps, full-duplex link. I am expecting a 100 Mbps link since both devices are 100-BaseTX compatible and I've confirmed that by decoding the LCW (link-code-word) from their fast link pulses.I have also tried a forced speed connection (disabling auto-negotiation). For 100 Mbps & Full-duplex, I can see some idle traffic on both RX and TX pairs, but the link does not come up. For 10 Mbps & Full-duplex, the link does come up and work. I have also tried disabling auto MDI-X, but that does not seem to change much either.My question is what could be causing the link to only establish at 10 Mbps? I have attached some scope pics to help isolate the problem. The scopes are all from one of the RX/TX pairs between the switch and the AC coupling caps.Scope 1) Forced 100 Mbps idle trafficScope 2) LCW from VDSL module (left burst), LCW from switch (right burst)Scope 3) NLP (single burst of LCW) from VDSL moduleAny help is appreciated!

author: ajb
author_rank: Super Contributor
timestamp: May 07, 2019, 10:20:43 pm
content: Can we see your layout?What does the modem say about its ethernet pins, are they internally or externally terminated?Have you checked the errata for the switch? Some of them have weird issues that only show up in certain conditions or with certain link partners.

author: David Hess
author_rank: Super Contributor
timestamp: May 08, 2019, 02:53:49 am
content: 10Base-T and 100Base-T use the same interface wiring but 100Base-T will fail if the two pairs are not good transmission lines. I usually see this when someone wires an Ethernet cable straight through.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 08, 2019, 06:02:40 am
content: Can you post the relevant portion of your schematic?Are you 100% sure you've got the correct termination scheme for the two PHYs in use?The scope trace for forced 100M looks horrible, no way that's a correct 100M Ethernet waveform. You should be seeing very clean, symmetrical half-sine pulses at 125 MHz, but it looks like the bandwidth of your signal is quite severely limited for some reason. (What's the bandwidth of your scope, and are you probing the signal correctly?)I suspect a 50R resistor or two somewhere will work wonders.
Physical Digital Movie Library - Page 1
Forum section: electronics / projects

author: riyadh144
author_rank: Unknown
timestamp: December 19, 2016, 06:04:38 am
content: I have missed the olden days when I had a movie library on the wall next to the TV, and so I want to take it to the next age by making a library that will have several DVD pack back sized LCDs that have a bit of depth to them, which display different titles from your netflix, amazon prime, etc libraries, that when you pull back the case it triggers the movie on your TV.What I need to know is how do I get such LCDs with such size and do you think this could be a product which people would like to buy? Do you have any suggestions, as I am going to start this project in the next few days, and any help or ideas will go along way.
Pi CM4 PCIe bus lines reversed? - Page 1
Forum section: electronics / projects

author: fcb
author_rank: Super Contributor
timestamp: May 21, 2021, 07:53:00 pm
content: Laying out a board that will have a Raspberry PI CM4 (compute module) on page 10 of the manual it shows the TXp, TXn lines reversed (also the RXp, RXn), it also states "TX and RX have PN swaps to improve routing"..https://datasheets.raspberrypi.org/cm4io/cm4io-datasheet.pdfAny idea if PCIe can detect reversed polarity lines, or if it's some sort of setting? Or am I missing something?https://pinouts.ru/Slots/pci_express_pinout.shtmlThanks!

author: amyk
author_rank: Super Contributor
timestamp: May 22, 2021, 02:21:21 am
content: https://pdf4pro.com/amp/cdn/pci-express-board-design-guidelines-2a03af.pdfQuotetl;dr: don't worry about it.

author: fcb
author_rank: Super Contributor
timestamp: May 22, 2021, 11:23:09 am
content: Thanks amyk - very helpful.

author: ConKbot
author_rank: Super Contributor
timestamp: May 23, 2021, 03:21:16 pm
content: Yes, PCI-E is generous with supporting polarity inversion and pairs only need to be matched to themselves, no matching between pairs required. Unlike HDMI which needs (AFAIK) correct polarity, and intra-pair and inter-pair matching. They only support whatever features are integrated into the host. I.e. Ive seen a host supporting reversing the order of the pairs (outputs can be lane 1, 2, 3, 4, or 4, 3, 2, 1 to support the connector on either side of the board) but nothing in the standard.USB3.0 also supports polarity inversion of the SS pairs (the 2.0 D+/D- pair must have the correct polarity though)
Pi filter output stage - Page 1
Forum section: electronics / projects

author: P.Mouse
author_rank: Contributor
timestamp: August 11, 2017, 02:59:26 pm
content: In switching regulators/power supplies a Pi Filter (CLC) is mostly used on the input to prevent any noise getting back into the mains.I actually have never seen a decent Pi filter at the output stage of a switching power supply (or even a DC-DC buck/boost converter).Is there any reason besides costs and board space to NOT use a pi filter (CLC) at the output stage of a switching regulator?With a decent pi filter you can easily bring the noise down by a factor 10 or more.

author: AlienRelics
author_rank: Unknown
timestamp: August 11, 2017, 07:02:13 pm
content: Inductors were great for smoothing in tube circuits, because tube circuits were generally designed so everything was Class A, so the average power and therefore current draw was pretty much the same all the time.That is because an inductor tends to keep current the same.But in a digital circuit, that is a bad idea! CMOS draws relatively high current spikes whenever a state is switched, which is one of the reasons why they tend to be very noisy and require a lot of bypass capacitors. In fact, a lot of attention is given to reducing inductance.

author: P.Mouse
author_rank: Contributor
timestamp: August 12, 2017, 01:39:53 pm
content: But I guess you can dampen the inductor, or simply use a ferrite instead?This also would still work for analog circuits (like for opamps etc)

author: David Hess
author_rank: Super Contributor
timestamp: August 12, 2017, 06:44:31 pm
content: The LC filter after the output capacitor is optional and used where lower noise is required. The trace inductance and decoupling capacitors by themselves remove the highest frequency switching noise. Lossy inductors like ferrite beads can be used but it may be tricky to avoid saturation. Older designs often used a wire wound inductor over a low value shunt resistor low lower Q.Linear Technology application note 70 briefly discusses output filters. There is another Linear Technology application note which discusses them in detail but I am not sure which one it is.
PI PICO Bootsel extension - Page 1
Forum section: electronics / projects

author: negativ3
author_rank: Regular Contributor
timestamp: April 07, 2025, 09:50:35 pm
content: Hey all,I want an external bootsel button for my pi pico 1 when its all enclosed to enter UF2 mode (USB socket extended and available).The only way I can see to do it is like this:GND > Diode Anode, Diode Cathode > Bootsel switch (side towards the PR2040 chip.Any more elegant ways of doing this?ThanksAndy

author: negativ3
author_rank: Regular Contributor
timestamp: April 08, 2025, 03:21:07 am
content: TP6 on the bottom of the board.

author: eugene
author_rank: Frequent Contributor
timestamp: April 08, 2025, 01:36:44 pm
content: Look at the schematic available here:https://datasheets.raspberrypi.com/pico/pico-datasheet.pdfYou need to pull TP6 low. Not sure why you want to use a diode....

author: negativ3
author_rank: Regular Contributor
timestamp: April 08, 2025, 02:36:15 pm
content: Diode prevents interference between external button and the onboard BOOTSEL button i.e. my externally wired button will not act as a capacitive antenna.
Pi-thon! Create python scripts for GPIO faster and easier. - Page 1
Forum section: electronics / projects

author: reCurse Software
author_rank: Newbie
timestamp: May 04, 2015, 09:53:43 pm
content: Hello my name is Andrew!My project isn't technically a hardware project but a fancy pantsy code editor!I love watching the EEVBlog, and hear such good things about the forums from Dave, I decided to sign up, and share this as my first post!I'm only 19 about to start college to pursue a phd in computer science and software engineering!I have an extreme passion for software, but right behind it is a passion for electronics/hardware.I will say I'm far better at programming than using ICs and stuff, but I try!I own a few Arduinos, and a Raspberry Pi that I love so much. Its the perfect calumniation of hardware and software!So I created a nifty learning tool in my spare time to help people learn the programming language Python along side the Raspberry Pi's GPIO pins.You don't even have to type a single line of code to control your electrical circuits with Pi-thon!Please do check it out, its free and open source under the GNU GPL.Here is a screenshot of the GUI:The program is currently version 1.3 but...Please do give feedback and suggestions so I can start on Pi-thon 1.4 sometime soon!You can do so here or on the Raspberry Pi Foums:https://www.raspberrypi.org/forums/viewtopic.php?f=32&t=109045(You can also find the update changelog there too!)You can download the program at my little website:http://www.recursesoftware.pcriot.com/raspi.htmlSystem requirements:~ Any Raspberry Pi model running the latest Raspbian.~ A local desktop environment like LXDE, or windows if the Pi is headless.~ A Java 8, java runtime environment (JRE).And you may email me with any questions at: andrewfabiandev@gmail.comAll source code and resources are included in the zip file!Thank you so much!I hope you enjoy.Andrew Fabian, reCurse Software

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: May 05, 2015, 10:39:43 pm
content: My Eyes!My Eyes!zee googles .. ze du nothzing!just yanking your chain kid, you might want to add parametrized pre-canned PWM outputs, best of luck.Somewhere on the internetz their must be a Geocities web site with a completely drained color palette though.

author: JDS
author_rank: Newbie
timestamp: May 11, 2015, 12:13:48 am
content: Thanks, I recently started playing around with Pi-thon so this is quite timely.As an aside, here is a story about another person with unusual taste in screen colors. An old boss of mine had a default screen pallet which could make you dizzy. I finally realized what was going on when I reviewed a large technical software manual for him and highlighted areas with yellow. It turns out he couldn't see yellow, and I had to redo with red highlighter. Later I biased his screen colors to add a little yellow and they looked fine. He never even realized that I had made the changes.
Pi Zero W and Pi3 3v3 ripple when wifi busy - Page 1
Forum section: electronics / projects

author: yodakohl
author_rank: Newbie
timestamp: May 12, 2017, 03:39:12 am
content: I'm using the raspberry's 3v3 voltage to supply two digital mems microphones.This is working fine for the original Pi Zero. However when using a Pi Zero Wor a Pi3 I'm getting some serious noise, but only when the Wi-Fi is transmitting data.Here are captures of the 3v3 voltage measured from the raspberry 3v3 pin.The two microphones are pulling a maximum current of 1.2 mA and can also be supplied as with 1.8V.Do you have any suggestions how to get a cleaner supply for the microphones? I was thinking of some ways to do it:Use a separate low noise regulator from 5v to 3v3 or from 3v3 to 1v8Using ferrite beadsDecoupling Capacitors (currently 0.1u and 200p)Any help is appreciated.

author: TJ232
author_rank: Frequent Contributor
timestamp: May 12, 2017, 03:59:46 am
content: Just few days ago moved from PI2 to the new fresh PI3 and found the same problem for some external hi-res ADC's and DAC's extension board. Using a MCP1700 LDO for providing the necessary 3.3V for them solved the problem. But for another one, at full 24 bit, was forced to use a MIC94310. That noise is quite annoying.

author: yodakohl
author_rank: Newbie
timestamp: May 19, 2017, 10:33:40 pm
content: Thanks, just got my MIC94310 and they are working great