hybridfree/eevblog-posts huggingface dataset:
433 Bandpass filter - Page 1
Forum section: electronics / beginners

author: dmowziz
author_rank: Contributor
timestamp: January 11, 2023, 06:44:16 pm
content: Hi,Trying to design a 433 MHz filter, BW = 28 MHz... Top -CThe filter is just for learning exerciseThe first image (top schematic) is the derived filter from analysis. But simulation got it at 435 MHz, 27.3 MHz bandwidthThe series coupling capacitor are small, so I changed to the bottom schematic which is equivalent.38.77 nHThe 2nd image, is the schematic on the board.I did not want to "add" capacitors to get a single value so used 1 capacitor (s parameters) then adjusted the inductor values.The major concern, is what the prototype is saying.Which is the 3rd image. Shows the response on board and response from the schematic from 2nd image.Please how can I do it better? and for a given frequency for a filter, what inductor value (/impedance) to use?If you have the first schematic to build, how will you do it?Thanks in advance for any replies.

author: mvs
author_rank: Frequent Contributor
timestamp: January 12, 2023, 11:28:21 am
content: Simulation is an ideal case. In reality you have non-ideal components which do have some tolerances and parasitics.Even your PCB is not an ideal conductor. If you route 1cm² copper area on both sides of 1.5mm FR4 you get a capacitor with around 2.5pF.Since you already know, that you are off by around 10% - just scale your design accordingly.Another approach would be to identify most relevant parasitic elements and add them to simulation.QuoteSometimes it is better to construct own components, rather then buy them.You can build 0.16pF cap using PCB traces. You can build even whole bandpass filter out of FR4.

author: fourfathom
author_rank: Super Contributor
timestamp: January 16, 2023, 10:04:54 pm
content: When you find that your component values are getting impractical, consider alternate topologies. For example, instead of top-coupling, try bottom-coupling. Here are a couple of examples, with values pulled out of thin air. Note that the bottom-coupling element can be either an inductor or a capacitor, depending on how you want the filter skirts to behave.
433mhz rx-tx module - Page 1
Forum section: electronics / beginners

author: gatoulisss
author_rank: Contributor
timestamp: May 21, 2016, 11:52:34 am
content: hello,i bought this item on the picture and i want to build a remote light switch using this 433mhz module and two pic16f88i have problem with the code cause i never use before rx-tx system. can anyone help me with it? i just want to have a remote on-off light by pressing button im using the mikroc for pic.thank you very much!

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 21, 2016, 03:34:53 pm
content: what ide and language you are using? that tx requires only 1 pin to send data. another pin for your button, many pic16f88 will be unused so its a bit overkill, but the good thing it has uart, you may use that to send data, limit your baudrate to 10Kbps if you want reliable transmission...

author: JPortici
author_rank: Super Contributor
timestamp: May 21, 2016, 07:12:40 pm
content: one is a transmitter. the other is a receiver. you connect the uart tx pin of the remote's pic to the transmitter data input. you connect the receiver data output to the rx pin in the light controller pic.the tx pic sends data over uart, the rx pic receives data over uart and execute commands
45 V DC output on a 32V transformer? - Page 1
Forum section: electronics / beginners

author: EterniaLogic
author_rank: Newbie
timestamp: October 05, 2014, 05:54:04 pm
content: Hello All!So I recently got a 32V beast transformer and slapped a bridge rectifier and 600uF with a 100k Ohm resistor to get DC.However, I got 45V instead. Why would this happen?Consequently, 32V*sqrt(2) = 45 V... LTSpice and my professors are telling me that it should be 32V.

author: c4757p
author_rank: Super Contributor
timestamp: October 05, 2014, 06:00:26 pm
content: Quote from: EterniaLogic on October 05, 2014, 05:54:04 pmPrecisely this.Your "32V" transformer is specified to put out 32VRMS. The RMS measurement of an AC waveform is the equivalent DC voltage that would give equal power dissipation into a resistive load, and for a sinusoid, it just happens to be 1/sqrt(2) of the peak.LTspice is telling you 32V because I presume you put in 32V as the amplitude. You should be putting in 45.3 instead, as that's the peak for 32V RMS. Your professors are telling you that because - well, I don't know why. Kind of makes me sad though.

author: EterniaLogic
author_rank: Newbie
timestamp: October 05, 2014, 06:06:41 pm
content: Thanks for your quick reply... now off to buy a new transformer that wont blow my hard-worked circuits...

author: SeanB
author_rank: Super Contributor
timestamp: October 05, 2014, 06:16:38 pm
content: You probably want a 24VAC transformer then, which will give a little over 32V unloaded. Best though is to use a simple zener diode regulator and a pass transistor to give you 32V out of the existing one if you are only drawing a low current and are happy with the regulation figure. If you are using 600uF and draw any current over about 100ma you will get a large ripple voltage on it in any case.

author: Zero999
author_rank: Super Contributor
timestamp: October 05, 2014, 06:55:17 pm
content: What do you want to power?It's possible you need a properly regulated power supply.

author: tautech
author_rank: Super Contributor
timestamp: October 05, 2014, 06:57:18 pm
content: AsSeanBsays, you will need a much larger smoothing cap, depending on the final specs you build/settle on.Usually in the 2000-10000 uF range.Use of a Linear regulator also will reduce output ripple.

author: Zero999
author_rank: Super Contributor
timestamp: October 05, 2014, 07:08:38 pm
content: Quote from: tautech on October 05, 2014, 06:57:18 pmThat's true but you need to beware that a linear regulator can increase the filter capacitor size requirements in some applications. It depends on the nature of the load. A linear regulator will behave as a constant current load which means the capacitor will discharge just as quickly during the ripply valley as at the peak. I resistive load will discharge the capacitor more slowly, as it discharges, meaning a slightly smaller filter capacitor can be used. There's also the issue of voltage drop-out.
45mfd cap - Page 1
Forum section: electronics / beginners

author: thedoc298
author_rank: Contributor
timestamp: June 23, 2019, 04:03:31 pm
content: Is their any difference between a 45uf 250 volt run cap and a 45uf 250 volt start cap. I know that they are used for different purpose, but I think their should be no difference. Any ideas

author: Ian.M
author_rank: Super Contributor
timestamp: June 23, 2019, 04:07:25 pm
content: A start cap has much higher losses. If you try to use one as a run cap, it *will* go BANG!

author: thedoc298
author_rank: Contributor
timestamp: June 23, 2019, 04:12:35 pm
content: how would that be determend on a cap tester

author: ArthurDent
author_rank: Super Contributor
timestamp: June 23, 2019, 04:14:10 pm
content: A motor start cap is a non-polarized capacitor (or 2 caps back-to-back) and designed for very short use time per start. I wouldn't use one for a DC power supply filter or visa versa. Very bad!

author: schmitt trigger
author_rank: Super Contributor
timestamp: June 23, 2019, 04:23:13 pm
content: Start capacitors are almost always clearly labeled as such, because of the risk of running it continuously.Its ESR is about 10 times that of a run capacitor of the same capacity and voltage.

author: thedoc298
author_rank: Contributor
timestamp: June 23, 2019, 04:29:48 pm
content: Thanks, that is something that will show up. The original start did have very high esr. Thanks
4606 mosfet GS current and voltage - Page 1
Forum section: electronics / beginners

author: morpheus
author_rank: Newbie
timestamp: June 13, 2014, 08:24:13 pm
content: Hello!I gothttp://aosmd.com/pdfs/datasheet/AO4606.pdfmosfet, and i want to use 3 of them to run brushless rc heli motor.So, at first i made simple PCB, and tried to power it directly with MSP430g2553... After 6 exploded mosfet's i understood that i am doing something wrongI also had dead chineese esc driver, that was built on same mosfets. It uses ATMEGA8L mcu and j3y (S8050) npn transistorshttp://www.hz-dz.net/UploadFiles/2009527101530473.pdfQuestions:1. As i see, 4606 needs at least 4.5V between source and gate, but at which current? Is it differs for N and P channel? How do i get this data from datasheet?2. On chineese ESC : Why only p-channel powered with transistor? As i know ATMEGA 8L has simmetrical 40 mA source/sink.3. What is 100 Ohm R2 resistor for?

author: JFA
author_rank: Regular Contributor
timestamp: June 13, 2014, 09:15:29 pm
content: Search a bit on how to drive MOSFETs. P chanels have to be driven differently from N chanel. N chanel can be driven directly from low voltage, not P chanel.This is why you need a bjt to increase the level near V+.There are tutorials on that all over the place. Google for "how do drive a P-channel MOSFET" and you'll find tons of tutorials.Try Youtube too.

author: morpheus
author_rank: Newbie
timestamp: June 14, 2014, 01:06:37 am
content: I watched some videos. So there is nothing about gate-source current at all? transistor is used to just set max voltage on gate of p-channel mosfet?Does it means i can use something like 100mA npn transistor i have around, instead of 500mA S8050?
4mA-20mA current loop sensor - Page 1
Forum section: electronics / beginners

author: roogadget
author_rank: Contributor
timestamp: September 19, 2018, 12:39:53 pm
content: I want to use a 4mA-20mA industrial sensor with a microcontroller.Do these sensors output 4mA-20mA by default? Or do I need a transmitter to take the input (probably pwm) and convert that to 4-20. ?

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 19, 2018, 12:46:51 pm
content: which sensor?

author: roogadget
author_rank: Contributor
timestamp: September 19, 2018, 12:56:29 pm
content: Here is an examplehttp://www.crmagnetics.com/Assets/ProductPDFs/CR5200%20Series.pdfI guess this answers my question.. it outputs 4mA-20mA

author: Zero999
author_rank: Super Contributor
timestamp: September 19, 2018, 02:57:24 pm
content: A simple 250R resistor will give 1V to 5V from the 4mA to 20mA range.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: September 20, 2018, 09:54:44 am
content: Quote from: roogadget on September 19, 2018, 12:56:29 pmIndeedThe DS says... 4-20 mADC - 0 to 300 Ω (for some of the parts).... (0-5V for others)So pick a resistor somewhere in that rangehttps://www.omega.co.uk/techref/das/4-20ma.htmlhas some info or if you want to get fancy...http://www.ti.com/product/rcv420
4x12V LeadAcid Batteries => 24V  - Page 1
Forum section: electronics / beginners

author: wummi
author_rank: Newbie
timestamp: June 20, 2022, 09:54:56 am
content: Hello there!So I wired 4 brand new gel batteries to be 24V for my RV / Solar.The question is: Should I also wire "across"? (see diagram)My general electronics sense tells me: doesn't matter, because 2x12V in series is really just 20 Lead acid cells in series.But as the real world isn't optimal, would it be a better/worse idea to also connect the middle tap?Thank you, everyone!

author: Terry Bites
author_rank: Super Contributor
timestamp: June 20, 2022, 12:12:27 pm
content: Option 2 is better, it 2 balances the terminal voltages, option 1 is a bit more random.www.impactbattery.com/blog/post/how-to-charge-marine-and-rv-batteries-in-parallel

author: wummi
author_rank: Newbie
timestamp: June 21, 2022, 07:39:41 am
content: TBH this article is suspicious at best.In his mentioned setup, he's dropping 10% of his 600W load across his parallel battery connections. This would indicate to me that his battery connections are horribly under-dimensioned and/or have extremely high resistance.

author: connectTek
author_rank: Regular Contributor
timestamp: June 22, 2022, 04:42:21 am
content: .
5.24288 MHz - Page 1
Forum section: electronics / beginners

author: wiss
author_rank: Frequent Contributor
timestamp: January 06, 2015, 12:25:04 pm
content: What is so special about this frequency? It seems to be rather common in counters and similar applications.Specifically I found one Xtal of this frequency in a multimeter for 50 Hz.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 06, 2015, 12:30:56 pm
content: 10 A = 52428820 A = A / 230 PRINT A40 GOTO 20

author: tszaboo
author_rank: Super Contributor
timestamp: January 06, 2015, 12:33:33 pm
content: It is 10 Hz * 2 ^ 19. You get 10 Hz with binary division. The frequency is big enough to run a MCU or whatever, and the crystal is (was) cheaper than the 32KHz one. 10Hz is the biggest frequency which has excelent noise attenuation on 50 Hz and 60 Hz. Think of NPLCs.

author: Zero999
author_rank: Super Contributor
timestamp: January 06, 2015, 12:47:24 pm
content: Quote from: PA0PBZ on January 06, 2015, 12:30:56 pmLol, that will result in an infinite loop and line numbers are so old school.A = 524288DOA = A / 2PRINT ALOOP WHILE A > 0

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 06, 2015, 12:48:04 pm
content: WHILE A>1*

author: wiss
author_rank: Frequent Contributor
timestamp: January 06, 2015, 12:48:18 pm
content: Quote from: NANDBlog on January 06, 2015, 12:33:33 pmThat's it! Almost...Shortest integration-time is 50 ms = 2^18 / 5.24288e6Thanks!Quote

author: Zero999
author_rank: Super Contributor
timestamp: January 06, 2015, 12:50:11 pm
content: Quote from: T3sl4co1l on January 06, 2015, 12:48:04 pmThanks, I've corrected, yes WHILE, not UNTIL.

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 06, 2015, 01:11:42 pm
content: Quote from: Hero999 on January 06, 2015, 12:47:24 pmIt was ment to be a funny way of answering the question, not a valid program, but thanks for debugging it anyway
5 volt UPS question - Page 1
Forum section: electronics / beginners

author: jsi
author_rank: Regular Contributor
timestamp: November 11, 2016, 07:04:05 pm
content: I don't know where to ask this question but this seems like a likely place to start. I have a ceiling fan in my bedroom that only has a remote control to turn it on/off and adjust the speed. It uses some sort of RF and to pair the remote to the fan requires a ritual of turning off the power, pressing a button on the remote while at the same time turning the power back on. The problem is my power isn't the cleanest thing and the slightest glitch and this fan forgets about the remote and you have to go through the ritual again. (this is particularly annoying in the middle of the night when I'd rather be sleeping and not messing around with the fan's remote and the power.)I'm thinking about bodging in some sort of capacitor after the 5 volt power supply and before the control board to help bridge over any power glitches. There is very little room to work with so whatever the solution is, compact is a requirement. I throw this out there but I'm completely open to other solutions and/or being told my capacitor idea is stupid.
5 Volts to 240 Ohms - Page 1
Forum section: electronics / beginners

author: MavMitchell
author_rank: Contributor
timestamp: January 25, 2019, 08:31:21 am
content: Hi,This is my challenge, I have an automotive type fuel gauge that uses a 40-240ohm resistive level sensor. It is biased high with 5 volts.What I have in my fuel tank is a level sensor that produces 0-5 volts.I need some type of circuit that will take the 0-5 volts and make it look like the 40-240 ohms so the gauge works.Ideas.

author: Rerouter
author_rank: Super Contributor
timestamp: January 25, 2019, 10:03:17 am
content: That 40-240 ohm gauge is a VDO spec, but biased to 5V... I'm going to say its a compatible cloneMeasure the current through that signal lead at full, empty and half reading, then should be easy to scale a howland current source for your input voltage.otherwise you can drive these gauges by driving the signal pin to a certain voltage (e.g. an op amp that can sink current) If you want you can find the empty half and full points there,In both cases the curve will likely be non-linear, however you can still match it to be right at those 3 points.

author: Zero999
author_rank: Super Contributor
timestamp: January 25, 2019, 10:31:14 am
content: Presumably it's fine to have steps?The gauge won't respond very quickly, so some glitches will be tolerated.I'd connect five resistors in series and bypass four of them with relays to make a digitally controllable resistor. The resistors are connected in series with relay contacts in parallel with each, except for the 39R. 4-bit will give 16 steps, which is probably enough. 39R, 12R, 33R 56R and 100R, will give 39 to 240R in roughly 12R steps. Want more steps? 6-bit will give 64, use 39R, 2R2, 5R6, 10R, 27R, 56R and 100R.

author: nali
author_rank: Frequent Contributor
timestamp: January 25, 2019, 10:41:54 am
content: Or if it's an analogue meter you could probably just stick with the low value 40R, and PWM it with a small MCU and MOSFET. You could even get cute and compensate in code if the sensor is non-linear.

author: Zero999
author_rank: Super Contributor
timestamp: January 25, 2019, 11:29:18 am
content: Quote from: nali on January 25, 2019, 10:41:54 amThat would work. Put 200R in parallel with the MOSFET and now it will PWM between 40R and 240R.

author: MavMitchell
author_rank: Contributor
timestamp: January 25, 2019, 11:39:51 pm
content: Could I measure the voltage on the gauge over the resistance range, then just use an OP amp to produce that voltage from the 0-5?

author: Rerouter
author_rank: Super Contributor
timestamp: January 26, 2019, 12:06:46 am
content: voltage between the sense wire and ground, yes
50 Ohm output - Page 1
Forum section: electronics / beginners

author: Flump
author_rank: Frequent Contributor
timestamp: March 25, 2014, 05:49:32 pm
content: Hi AllI want to try measuring ESR using my scope like Alan does hereBut i dont have a proper function generator so i bought one of thesehttp://www.ebay.co.uk/itm/350945193079?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649but there are 2 problems i see which are it's not 50 Ohms output and the output voltage will be too high,do i just add a VR in series of the output to drop the voltage down ?and how to i make the output 50 Ohm ?

author: michaelym
author_rank: Regular Contributor
timestamp: March 25, 2014, 08:35:04 pm
content: The output does't have to be 50 ohms. As long as you have a known output impedance you are OK.You can just measure your output impedance, it just cant be too high.

author: Zero999
author_rank: Super Contributor
timestamp: March 25, 2014, 08:36:47 pm
content: A 555 timer has a fairly low output impedance. Connect a resistor, say 100R in series with the output and adjust the calculations to suit.

author: Flump
author_rank: Frequent Contributor
timestamp: March 25, 2014, 08:46:59 pm
content: thanks very much guys will try it
5050 LED infill is soft like rubber? - Page 1
Forum section: electronics / beginners

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 13, 2015, 06:06:34 pm
content: its an accidental discovery ... some cheap 5050 LED from chinaif you poke the yellow "window" ... it budges like rubber... and bounces back after some timebut for branded 5050 LEDs ... are they suppose to be hard thermo-plastics? or rubbery like this ? i have always assumed them to be hard lol

author: Ryano
author_rank: Regular Contributor
timestamp: January 13, 2015, 06:14:05 pm
content: I've seen many brand name LEDs that used a soft phosphor fill. Nothing to worry about. You may just want to be extra careful when cleaning your board to avoid damaging the coating.

author: owiecc
author_rank: Frequent Contributor
timestamp: January 13, 2015, 07:29:00 pm
content: Phosphor is probably directly on the LED. It is a silicone lens that is rubbery. It can be also hard. Depends on the manufacturer.
50mH, high current inductors? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: March 14, 2015, 12:02:57 am
content: I am looking for 25, 40 and 50mH inductors, able to handle high currents (3 to 10 amps). The operating frequency is 50Hz.What kind of core do I need?

author: German_EE
author_rank: Super Contributor
timestamp: March 14, 2015, 03:26:23 pm
content: These are going to beBIGinductors

author: HighVoltage
author_rank: Super Contributor
timestamp: March 14, 2015, 04:14:09 pm
content: Are you talking about DC current ramping up to 3-10A and repeating the pulse with 50Hz or AC current constantly at 50Hz?What is the application?

author: SeanB
author_rank: Super Contributor
timestamp: March 14, 2015, 04:27:26 pm
content: If DC there will have to be a big air gap in there, and if the range of current variation is well defined you might even want to have a ferrite bias magnet in the core as well to keep it in a linear part of the BH curve. That allows use of a much smaller core at the expense of some linearity. If it is a simple LC filter for a power supply however that will not be much of a worry.

author: amyk
author_rank: Super Contributor
timestamp: March 14, 2015, 04:31:22 pm
content: Big and not cheap:http://www.digikey.com/product-detail/en/195R10/195R10-ND/455491Apparently that one weighs 26kg

author: SeanB
author_rank: Super Contributor
timestamp: March 14, 2015, 04:56:31 pm
content: 26lb, about 12 kilos. Though if you look up there is one of 2.5mH at 100A, which is 40kg. About the mass of a bag of cement, and it definitely is going to cost a lot more than that.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 14, 2015, 05:26:17 pm
content: You would need about 1500 turns, if you use silicon transformer steelAnd you need heavy gauge copper wire to keep the resistance after 1500 turns in the 100 mOhm range.Yes, this will probably be very big and heavy, even if you build it yourself.

author: Zero999
author_rank: Super Contributor
timestamp: March 14, 2015, 05:29:25 pm
content: Perhaps you could rewind an old microwave oven transformer to save money.
50ohm Coaxial Termination  - Page 1
Forum section: electronics / beginners

author: Ranger14
author_rank: Regular Contributor
timestamp: March 26, 2016, 02:14:32 am
content: I was working on rebuilding my scope and found the data sheet for the Tek 50ohm Coaxial Termination (Part No 011-0129-00) .. My problems come as I am trying to figure out the purpose of using these units on a scope ?? Sorry for the silly questions but I am just trying learn on my own..

author: ade
author_rank: Unknown
timestamp: March 26, 2016, 04:32:44 am
content: Great video from w2aew:

author: tggzzz
author_rank: Super Contributor
timestamp: March 26, 2016, 08:18:59 am
content: Quote from: Ranger14 on March 26, 2016, 02:14:32 amNo apologies necessary.Scope probes are an important topic since they are an integral part of the measurement being made. Your starter question: what is load conventional high impedance *10 probe has on the circuit? The answer 10Mohm is usually wrong and always simplistic; 100ohm is more accurate in important realistic cases.FFI on many aspects of theory, practice and safety, have a look at the references inhttps://entertaininghacks.wordpress.com/library-2/scope-probe-reference-material/

author: femtohertz15
author_rank: Contributor
timestamp: April 02, 2016, 08:59:49 pm
content: 50 Ohm termination is good when you are pushing the bandwidth of the scope, using direct connection to 50 ohm sources or through low-Z probes. Or for sources or instruments that natively output 50 Ohm.But, the specs for it are only 0-100Khz, which puzzles me. Maybe its for audio use?

author: w2aew
author_rank: Super Contributor
timestamp: April 04, 2016, 01:56:39 pm
content: Quote from: femtohertz15 on April 02, 2016, 08:59:49 pmIf I'm not mistaken - I think that specific one was a "precision" termination, with an accuracy of something like +/-0.05 ohms. Wasn't really intended for RF applications, more of a precision reference termination I think.

author: BobsURuncle
author_rank: Regular Contributor
timestamp: April 04, 2016, 02:25:07 pm
content: Quote from: Ranger14 on March 26, 2016, 02:14:32 amPerhaps if you provided some context we might be able to speculate. For what specific instrument did the manufacturer specify this termination and on which channel (function), and do you have any performance specifications for the instrument and said function? I doubt this was intended as the scope feedthrough for one of the vertical amplifiers, but rather is intended for DC or low frequency gain calibration of a probe or some other instrument.
50ohm microstrip - Page 1
Forum section: electronics / beginners

author: michaelym
author_rank: Regular Contributor
timestamp: October 04, 2018, 10:32:13 am
content: So I need to design a PCB with a bunch of 50ohm traces. I understand my best option is to use microstrips. I was playing around with a PCB calculator and understand that it is not an option to use a 2 layer board because it's require 100mil traces. So the only option is a 4 layer board. How does it work with the PCB manufacturer do I need to find out from them ahead of time what the thickness of the prepreg is? I saw on seeed studio there is an option for controlled impedance traces and it says "We will modify the stack-up and width of the traces accordingly to meet the impedance requirements" what?? they will change the width of the traces? where do I start

author: Zero999
author_rank: Super Contributor
timestamp: October 04, 2018, 11:06:55 am
content: I don't see why a two layer board can't be used. It just means to use thinner traces, the board also has to be thinner than the standard 1.6mm, or whatever is normal.

author: michaelym
author_rank: Regular Contributor
timestamp: October 07, 2018, 08:09:12 am
content: Unfortunately I can't use a PCB less then 1.6 it will be too flimsy.I was wondering what does it actually mean when you pay the PCB manufacturer for "controlled impedance traces".Isn't it all dependent on the distance between layers which is a set value for the particular manufacturer

author: bd139
author_rank: Super Contributor
timestamp: October 07, 2018, 09:20:41 am
content: It means that the board substrate has consistent thickness and permittivity between batches.Generic FR4 substrate is not well defined in this area so your traces don’t always come out at 50 ohms on susbsequent board runs.It’s easier to do a 4 layer board in this case with transmission lines on the surface and a ground plane on inner 1 layer. That gives you the mechanical stability and the thin layer.Two layer will work however but there’s a headache or two there. Particularly if you have route other signals across transmission lines. On 4 layer just do it on the back!TBH a little mismatch isn’t going to kill anything hard unless you are really hitting the MHz.
53220A - Page 1
Forum section: electronics / beginners

author: sgi199
author_rank: Contributor
timestamp: December 29, 2019, 12:03:39 pm
content: Amazing... When there is no effective external opportunity to repair, 15 digit value will be displayed. Should you be happy?

author: Jwillis
author_rank: Super Contributor
timestamp: December 30, 2019, 08:24:19 am
content: 私は日本語が話せませんNo valid external timebase An external time base frequency other than 1, 5, or 10 MHz is applied to the counter, or the external time base frequency is incorrectly specified by the SENse:ROSCillator:EXTernal:FREQuencyconmmand.Look at page 293https://literature.cdn.keysight.com/litweb/pdf/53220-90001.pdf

author: tkamiya
author_rank: Super Contributor
timestamp: December 30, 2019, 02:42:26 pm
content: That's actually Chinese....

author: sgi199
author_rank: Contributor
timestamp: December 31, 2019, 02:32:02 am
content: Thank you! Have been consulted. +580, corrected the problem. Local open circuit around the local clock. How to set up 11 digit and 15 digit digital display? Thank you!

author: tkamiya
author_rank: Super Contributor
timestamp: December 31, 2019, 02:52:57 am
content: Please, if you can, write in English. I don't read Chinese and we (folks on this forum) use English as a common language.

author: Jwillis
author_rank: Super Contributor
timestamp: December 31, 2019, 03:38:28 am
content: 我很抱歉Excuse me . I was looking at the country tag by the avatar. I don't know either language let alone the writing but at least I tried to help.

author: tkamiya
author_rank: Super Contributor
timestamp: December 31, 2019, 04:38:01 am
content: I'm totally confused. Japanese flag avatar, Chinese text, and this is mostly English forum.I'll just be quiet and go away.

author: sgi199
author_rank: Contributor
timestamp: December 31, 2019, 10:26:30 am
content: Thank you! Have been consulted. +580, corrected the problem. Local open circuit around the local clock. How to set up 11 digit and 15 digit digital display? Thank you! Personal data can't be changed, Japan is Japanese!
555 astable calculation question. - Page 1
Forum section: electronics / beginners

author: WeekendHobbiest
author_rank: Newbie
timestamp: January 18, 2020, 12:11:31 am
content: Hi, everyone!How would I calculate the value of R2 if I have a target frequency in mind and I know what value I want to use for R1 and C?To specify, say I want a 1kHz clock and I have a 10uF cap and a 10K trim pot. How would I calculate the value of R2 based on that?Thanks.

author: Jwillis
author_rank: Super Contributor
timestamp: January 18, 2020, 12:32:34 am
content: Increasing C increases cycle time reducing frequency. increasing R1 increases High time (T1) but leave Time Low (T0) unaffected . increasing R2 will increase high time decease time low and increase duty cycle down to 50% minimum.Time High (T1) 0.693 × (R1+R2) × C1 = SecondsTime Low (T0) 0.693 × R2 × C1 =SecondsTime Period (T) 0.693 × (R1+2×R2) × C1=SecondsFrequency (F) 1.44 / (R1+2×R2) × C1=Hertz (Hz)Duty Cycle (T1/T)×100=Duty Percentage (%)

author: Zero999
author_rank: Super Contributor
timestamp: January 18, 2020, 08:46:25 am
content: 10µF is too higher capacitor value for 1kHz. Go for 100nF. For 1kHz, set R2 to 6k8 and R1 to 470R, for nearly 50% duty cycle.
555 based PWM Dimmer not working only with LED strips - Page 1
Forum section: electronics / beginners

author: GianS
author_rank: Newbie
timestamp: July 02, 2023, 05:10:45 pm
content: I bought a PWM Dimmer based on a 555 from AliExpress to regulate the brightness of a 12V 1A 1 meter LED strip, I already built one myself years ago on a perfboard but this one was the exact dimensions I needed for a project. I built mine from components from AliExpress and components found in old electronics so I thought nothing functionally would changeThe dimmer is this onehttps://www.diymore.cc/products/pwm-10a-speed-regulation-led-dimming-ultra-high-linearity-band-switchbut I attached a real photo of the one I got from AliExpressMy problem is that it isn't doing any regulation while connected to LED strips, I tried with the 1m one and with another light that has three 30cm LED strips in parallelEvery other light or motor I connected to it seemed to make it work. I really have no idea what could be causing this, maybe it's sensible to capacitance? LED strips are two long straight parallel contacts but I don't think it's enough to cause anything as displayed here in the video:https://live.staticflickr.com/video/53017878188/54f865d36d/1080p.mp4?s=eyJpIjo1MzAxNzg3ODE4OCwiZSI6MTY4ODMxNzgwMCwicyI6ImI2MjZiMzk3MjExNTQxZWIyOTYwYzAyNTRmZDNhZDZjZTcwOWUxOGYiLCJ2IjoxfQPlease no prejudice on that oscilloscope, it's good for what its made for, it's "calibrated", it shows a clean square waveform on my simple diy dimmer (attached a photo to let you see what I mean with simple) versus what is shown in the video with the AliExpress one, an hybrid ramp/square. In the first part I show one of those LED strip that doesn't work, in the second part I show one that does work, just like every other light or motor I've tried
555 discharge pin - Page 1
Forum section: electronics / beginners

author: Chai
author_rank: Regular Contributor
timestamp: March 17, 2016, 04:51:47 am
content: I'm confused why a LOW on the output pin 3 would drive the discharge pin 7 to ground. I thought a low coming from the flipflop/output connected to the base of an NPN would turn off the transistor and disconnect pin 7 from ground. What am I missing here?Quotehttp://www.electronics-tutorials.ws/waveforms/555_timer.html

author: LukeW
author_rank: Frequent Contributor
timestamp: March 17, 2016, 06:18:19 am
content: The output driver section is inverting.

author: Chai
author_rank: Regular Contributor
timestamp: March 17, 2016, 06:42:06 am
content: Hah! Thanks
555 doing weird stuff - Page 1
Forum section: electronics / beginners

author: Cloud
author_rank: Regular Contributor
timestamp: April 21, 2015, 08:39:31 pm
content: After building PWM circuit () with 555 I realized, that if I lower supply voltage to 5V, maximum duty cycle would be only 50%. But if I increase supply voltage to 6V it could go to almost 100%. Anyone have any idea why is this happening?

author: Simon
author_rank: Unknown
timestamp: April 21, 2015, 08:55:04 pm
content: it may be something to do with the diodes. remember that they introduce a voltage drop of 0.7V and that you capacitor is charged and discharged in the 1/2 to 2/3 Vcc range, so 1.66V, that does not leave much for the diodes to work in and their voltage drop will be significant by comparison causing problems.

author: Cloud
author_rank: Regular Contributor
timestamp: April 22, 2015, 06:34:49 am
content: I'll try with schotky diodes and report it back
555, Frequency increase under load - Page 1
Forum section: electronics / beginners

author: Blastcap
author_rank: Regular Contributor
timestamp: May 18, 2016, 12:23:58 pm
content: I was playing around with a 555 timer, and wanted to add a "Buzzer", to decrease the load on the 555 output, i added a 547 transistor and used that to drive a small 4 Ohm speaker.When the circuit was "idle" (everything hooked up, but left the speaker Ground floating) the timer gave a ca. 60Hz output (as expected), but when i connected the speaker, the frequency went up by a factor of 5 to ca. 300Hz.Frequencies was measures with a DSO5072P, and by ear.Is this normal or am i doing something very wrong?Ill add a picture and diagram as soon as i get home.

author: Andy Watson
author_rank: Super Contributor
timestamp: May 18, 2016, 12:43:59 pm
content: 4 ohms across what supply voltage? Lets assume your supply is 5V, I make that 1.25A pulses. I suspect your power supply is sagging, if not completely collapsing! If the pulse alone is not sufficient to reset the 555, the momentary change in Vcc will affect the upper trip-point of the timing cycle.

author: Ammar
author_rank: Regular Contributor
timestamp: May 19, 2016, 12:34:36 am
content: What value resistor do you have between pin 3 (output) off your 555 and the base of your transistor?

author: danadak
author_rank: Super Contributor
timestamp: May 19, 2016, 01:30:11 am
content: To protect your 555 and trans be sure to put a power diode across thespeaker, like shown in link image.https://www.google.com/search?q=speaker+drive+transistor+image+protection+diode&biw=1821&bih=870&tbm=isch&imgil=-DCakHYx9KvhOM%253A%253BIBxp9UgzX85fFM%253Bhttp%25253A%25252F%25252Felectronics.stackexchange.com%25252Fquestions%25252F31014%25252Fwhere-should-i-put-the-kickback-diode-in-a-transistor-switch&source=iu&pf=m&fir=-DCakHYx9KvhOM%253A%252CIBxp9UgzX85fFM%252C_&usg=__YeFGC5qlfGnpNu4C5zK9tnGa8H0%3D&dpr=0.75&ved=0ahUKEwinuuTF_uTMAhUF2IMKHVb0CfMQyjcIJw&ei=CBc9V6eWLYWwjwTW6KeYDwRegards, Dana.

author: Blastcap
author_rank: Regular Contributor
timestamp: May 19, 2016, 07:54:17 am
content: @Andy WatsonYou are most probably right, when i read my post again its rather obvious.@Ammar1K if i remember right, might even be less.@DanaThanks for the hint, ill add one as a good measure.

author: Audioguru
author_rank: Super Contributor
timestamp: May 20, 2016, 02:23:44 am
content: A BC547 cannot drive a speaker. Its maximum allowed current is only 100mA which produces only 0.04W for a squarewave into a 4 ohm speaker.Was the transistor an emitter-follower? Then its base-emitter diode overloaded the 555 output.
555 Help - Page 1
Forum section: electronics / beginners

author: almamater
author_rank: Regular Contributor
timestamp: September 08, 2021, 04:08:23 pm
content: I made one circuit to light up one Led for a specific amount of time (~15min) and i used this example:webpageEverything works as expect but i want to control the whole circuit (this 555) through other one and with one transistor, so i connected the Vcc pins 4 and 8 to Vcc from Power Supply (+5V) and de Gnd Pin (1) i left disconnected and to be controller by the transistor.My Problem: This circuit with no GND connection at pin 1 starts immediately With LED On (with Output pin 3 High) and i don't understand whyI applied the Gnd from Power Supply directly to the Led,its the only point that has Gnd.Is it possible to work around this behavior? I just want to control this circuit\555 through one transistor, it's no possible use the Pin 1 (Gnd) for this?

author: ledtester
author_rank: Super Contributor
timestamp: September 08, 2021, 05:25:38 pm
content: Perhaps you are looking for the monostable mode of the 555 timer:https://www.buildcircuit.com/modes-of-ne555-monostable-and-astable/You can trigger the output to go high for a certain length of time via a signal on pin 2.

author: Badwolf
author_rank: Contributor
timestamp: September 08, 2021, 05:43:06 pm
content: HiCan you show us how you wired your transistor.The most frequent error is due to a floating mass, instead of being at a given potential 0v or Vcc, the pins that you manage with your transistore do not have a defined voltage. The output of the 555 is therefore totally random.A solution is also to use pin 4 (reset), which allows you to force the output.
555 LED flasher with less than 50% duty cycle and no diode - Page 1
Forum section: electronics / beginners

author: Mr Kevin
author_rank: Newbie
timestamp: November 05, 2014, 02:06:38 am
content: Hello all, noob Kevin here. So the subject is 555 LED flashers with less than 50% duty cycles. Typically one sees this done with a diode paralleled across the resistor tied between the discharge (pin 7) and trigger (2)/threshold (6). I recently realized though that I could simply forgo the diode and instead move the LED and LED limiting resistor going from output (3) to ground and instead place it between the supply rail and output (3). Effectively using the output to sink the supply instead of using it as a source.My question is why isn't this commonly seen in examples? Is there a disadvantage to this approach? It saves having to add a diode to the circuit, but I'm guessing there must be some drawback I'm not noticing. Thanks for any feedback.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 05, 2014, 02:22:13 am
content: There's no disadvantage I can think of for turning things off and on like a LED. The 555 can source as well as sink current. (Note: some chips can't, and some can sink more than they can source. Probably some can source more than they can sink but I can't think of one like that.)If you're using the 555 for something else that requires an under 50% duty cycle, the diode trick is a solution.I think you're well on your way to retiring your noob status.

author: Seekonk
author_rank: Super Contributor
timestamp: November 05, 2014, 02:29:16 pm
content: I go back a long way and personally I don't like anything with a 555 in it. I would look at gaining experience with switchers like a TL494. Frequency will be independent of duty cycle and it has its own built in voltage reference. Learn to use one of these instead of that clunky 555.

author: IconicPCB
author_rank: Super Contributor
timestamp: November 06, 2014, 04:28:22 am
content: Use the CMOS version of 555 for that diode free 50% duty cycle minus the 120ma switching glitch.

author: TonyStewart
author_rank: Contributor
timestamp: November 06, 2014, 04:51:32 am
content: - low side open collector drivers with PWM are very common. The problem with over driving with excess current at low duty cycle is degrated efficacy, which may be significant is driving more than 2x rated. The loss in efficacy is compounded with higher I^2*ESR losses due to the bulk ESR of the diode.The ESR is approximately 1 Ohm per rated Watt of the component.Ideally you match the supply voltage to the LED string voltage with sufficient LED's and a small R to limit the current. Such as; for 12V red@2.0V use 5x2V =10 and drop 2V for current limit R or for white 3x3.0-3.2=9-9.6 and from 2.4~3.0V on series R. Read specs for Nominal Vf and consider tolerances will affect mass production variances.Or... use a inductor and diode clamp to maintain a continuous triangle current that less lossy.
555 monostable circuit catches fire/blows up at 12v but works fine at 6v - Page 1
Forum section: electronics / beginners

author: sharkbait99
author_rank: Newbie
timestamp: May 11, 2019, 12:27:49 pm
content: Hi, I'm trying to build a simple delay circuit using a 555 timer in a monostable config, same as this onehttps://www.youtube.com/watch?v=cZcBvfPNavo&t=52s] https://www.youtube.com/watch?v=cZcBvfPNavo&t=52sThe problem I'm having is every time power is applied to the circuit the 555 chip immediately blows up. Once literally (when using a 12v ac power brick) and once caught fire (running off a 12v car battery)When using a 6v battery pack powered by AAA batteries the circuit works fine. But I need it to run off a 12v power source. I've been using 16v 4.7uf tantalum caps but then tried 4.7uf 50v electrolytic caps and it still blows. Resistor is 10m ohm.Do I need to add some sort of power filter or a diode when running the 555 off 12v?markings say ne555p 93m dn1719 Im pretty sure thats the higher voltage one. according to the net it should work at 16vhere's what I've got. I've got it soldered onto a perfboard and I've checked for shorts etc.

author: sharkbait99
author_rank: Newbie
timestamp: May 11, 2019, 12:42:56 pm
content: this is the resistor im using.https://www.jaycar.com.au/10m-ohm-0-5-watt-metal-film-resistors-pack-of-8/p/RR0660It works as far as expected on 6v for delay on time according to the online 555 delay timer calculators. barring capacitor tolerances. Which is why i went for the tantalum cap.I've got it hooked up to the output of a 12v 24h programmable timer just one of the ebay cheapies similar toeBay auction: #192742533526I haven't tested it straight from the car battery yet as the last one caught fire melting the dip socket. So i have to re solder it tomorrow.I've also tested for surge on voltage with a normal multimeter. I dont see any spike, but im not sure if the multimemter would catch it if its to fast?

author: mvas
author_rank: Contributor
timestamp: May 11, 2019, 03:10:31 pm
content: What LOAD is connected to the OUTPUT Pins?a) Is your +12 Volts & Gnd Polarity correct? - that would cause it blow immediatelyb) Do you have those two copper wires crossing over the top of the IC, like in the video? = bad design

author: soldar
author_rank: Super Contributor
timestamp: May 11, 2019, 03:46:41 pm
content: Are you sure you got the pin numbers right? Can you post a photo?
555 Monostable Energising Relay - Page 1
Forum section: electronics / beginners

author: AnotherNoob
author_rank: Newbie
timestamp: January 12, 2024, 03:01:40 pm
content: Hi All,A quick explanation of the (intended) function of the circuit in the attachment -1 Power on2 Monostable outputs near supply voltage (as a result of the capacitor in parallel with the NO 'Run' button)3 Relay energises and it's NO contacts close to provide supply voltage to the relay coil (and to the output of the 555 - see question below)4 Monostable output drops after approx. 1 second; relay remains energised5 If the NC 'Stop' button is pressed, the relay coil deenergises and remains so until -6 The 'Run' button is pressed and we go back to step 2Note - the fact that the monostable energises the relay at power-on is a requirement rather than a safety issueMy question is - is there a problem with the supply voltage being fed to the output of the 555 given that it will be outputting just under supply voltage (or not) itselfRegardsChris

author: Ian.M
author_rank: Super Contributor
timestamp: January 12, 2024, 03:23:39 pm
content: Quote from: AnotherNoob on January 12, 2024, 03:01:40 pm(4) is incorrect.What will actually happen, is:3. Monostable (555) output attempts to drive to ground, but is held at +12V by the relay contact.4. Either the 555 lets the magic smoke out, or if the supply is fused or current limited, it fuses or limits, (or both).5. The circuit fails to operate thereafter.*WHY* didn't you include a diode to prevent the relay contact back-feeding coil power to the 555 output?N.B. A classic bipolar 555 output does NOT drive rail to rail. At best, it will only drive high to two Vbe drops below VCC. Check the relay datasheet to be certain it will reach its minimum pull-in voltage with the extra diode drop and the 12V supply at the lowest limit of its tolerance range. If not, you may need to use a 9V relay with a resistor of 1/3 of its coil resistance between its coil and the 12V from the NO contact via the stop button, and rearrange load connections so that gets the full 12V.

author: Andy Chee
author_rank: Super Contributor
timestamp: January 12, 2024, 03:24:52 pm
content: Whilst the output transistor on 555 is pretty robust, I'd put a diode in series of the output anyway, like so:

author: AnotherNoob
author_rank: Newbie
timestamp: January 12, 2024, 03:47:47 pm
content: Thanks Ian and Andy,The (unstated) reason for the question was that I wasn't sure whether or not the output stage of a 555 was robust enough to handle the supply voltage or whether it would smoke (sometime in the future if not immediately), the additional diode was the planned fall-back. You've both answered the question nicely, thank you.RegardsChris
555  question - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: August 08, 2017, 11:48:49 am
content: Hi everyone,I don't understand the use of the third 555 on the right.I joined a LTSpice simulation. You will have to press escape after 3 seconds to see the raw result. (don't know why)

author: ironmonkey
author_rank: Contributor
timestamp: August 08, 2017, 01:54:31 pm
content: The first 555 oscilate to a low frecuency, shoots the timer that limitate the time the fence is electrified (thats the pin 4 all about) and finally the last 555 oscilates to a higher frecuency to control the flyback

author: J4e8a16n
author_rank: Regular Contributor
timestamp: August 08, 2017, 03:16:56 pm
content: Quote from: ironmonkey on August 08, 2017, 01:54:31 pmThe flyback? The newbe don't understand.

author: ironmonkey
author_rank: Contributor
timestamp: August 08, 2017, 04:57:01 pm
content: Flyback is the name of the circuit at the right (transistor and transformer) which elevates the voltage.The first 555 marks the intervals between high voltage pulses, the second marks how long that bursts last and the third one drives the high voltage circuit.If you had only the third 555 (with pin 4 connected to v+ of course) you'll get a continous high voltage output at the secondary of the transformer.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: August 08, 2017, 06:53:08 pm
content: " the second marks how long " it's square wave putting the reset to ground?

author: ironmonkey
author_rank: Contributor
timestamp: August 09, 2017, 03:54:27 am
content: More like how much time can put the reset at high (the time we can set at the second 555), thus, running the high voltage pulse trainEnviado desde mi MotoG3 mediante Tapatalk