hybridfree/eevblog-posts huggingface dataset:
Range Finder - TTL Comunication - Page 1
Forum section: electronics / beginners

author: Dryadwoods
author_rank: Newbie
timestamp: February 17, 2018, 04:24:29 pm
content: I am trying to make connection to a range finder, however I am facing some problems.I am using:Geekcreit® FT232RL FTDI USB To TTL Serial Converter Adapter Module For ArduinoSuaoki 600MThis is a "closed range finder", but after opening it I found it very similar (but NOT the same) to other chinese products available on ebayhttps://www.ebay.com/itm/600m-Golf-Laser-Range-Finder-Module-Speed-Distance-Meter-Measuring-Sensor-M6G4-/292389466291?_trksid=p5731.m3795that offers TTL comunication.The ebay version has the following description:Port Type: TTLBaud Rate: 115200bpsI have tried to connect it (please see the printscreen and photos on how I am plugin things up)And I try to send the following commands (described on the ebay article)0d0a4f4e0d0a ON0d0a4f46460d0a OFF0d0a4d4f44453d310d0a MODE=10d0a4d4f44453d300d0a MODE=00d0a4f3d310d0a O=1But I receive nothing....The layout of my board is different from the ebay product, so I am really not sure if I am plugging the cable correctly, but with trial and error I think I was able to make a correct connection, because the optic changes the "layout" to continuous range with automatic update of distance (we can see that on the webcam attached to the range finder)... Meanwhile I have tried all combinations of baud rate, etc.. and nothing changed... I never receive anything and also the commands I sent seem to have no impact on the device.Is there anything that I am doing wrong? or I simply cannot expect that similar boards will work the same way?
Range of voltage drop across schottky diodes... - Page 1
Forum section: electronics / beginners

author: alank2
author_rank: Super Contributor
timestamp: March 29, 2016, 07:37:23 pm
content: I noticed when looking at Digikey's list of them that there are ones that drop as much as non schottky diodes.What are they designed for? The minimum drop for X amount of current?What I am looking for is the minimal amount of voltage drop - I'm using them to support two power inputs and don't want either to back feed the other. Should I look for the lowest voltage drop and at the same time for it to handle the current I need? In this case <500mA at 5V DC.

author: michaeliv
author_rank: Frequent Contributor
timestamp: March 29, 2016, 08:26:59 pm
content: It's generally a balance of voltage drop + recovery time + reverse current + price.So even if they have a higher voltage drop than a regular diode they will have a much lower recovery time.Is this what you are asking .. "why do they exist?"For your scenario you probably don't care about 1ma reverse current and a few hundrend uS of recovery time, so yes, look for lowest voltage drop.

author: Seekonk
author_rank: Super Contributor
timestamp: March 29, 2016, 08:42:20 pm
content: A low reverse voltage generally goes with low forward voltage. There is a big penalty going above 40V.
Rapid Charging? - Page 1
Forum section: electronics / beginners

author: olsenn
author_rank: Frequent Contributor
timestamp: December 30, 2012, 01:36:31 am
content: My ipad and several other electronic devices of mine use 5V for charging; however, you can purchase wall adapters that source extra current at 5V called "rapid chargers". What I would like to know is if there is a charging circuit built into these devices that figures out how much current it can drain from the source and adjusts the resistance so that said amount of current IS sourced when 5V is applied? Normally I would have assumed the same amount of current would be sourced at 5V (as per ohm's law) regardless of how much current the transformer can put out.

author: mariush
author_rank: Super Contributor
timestamp: December 30, 2012, 03:21:55 am
content: The basic chargers have resistors on the transmit and receive wires signaling the device how much power it can give.The usb standard has otherwise a lot of methods through which an adapter/charger can "communicate" with a device and negociate the maximum power, but the adapter/charger would have to have a usb controller or some chip to do it.See the USB Battery Charging Specs:http://www.usb.org/developers/devclass_docs/batt_charging_1_1.zipIf you're really interested, you can download the specification and search for the info:http://www.usb.org/developers/docs/also see this:http://blog.curioussystem.com/2010/08/the-dirty-truth-about-usb-device-charging/

author: peter.mitchell
author_rank: Super Contributor
timestamp: December 30, 2012, 03:37:37 am
content: in consumer electronics, generally, they will only detect 3 different power sources via 3 different signals on the usb pins;generally, less than 120ohms on the data lines signals that it is plugged into an ac charger allowing it to pull either an unlimited amount of current, or a maximum of whateverusb data on the data lines signals that it is plugged into a computer and current limits it to 500ma, or if negotiated, more.a vendor specific resistance between the "unused pin" of the micro usb and ground, toggling factory programming power, allowing the device to be powered without a batterythe charging circuitry in the device will be designed, generally, so that when plugged into a computer, the charge current is limited to within USB spec, when plugged into an AC charger, current is either "unlimited"(the charger ic will charge the battery at whatever current it is needed/internally configured to charge the battery correctly) or limited to the current capable of being supplied by the stock usb adapter, and when in factory mode, the device will be able to be solely powered by the USB, so the device can be programmed without a battery in place or with a flat battery, or to charge a battery below a threshold level.this all varies from device to device, hence me stating "generally" a lot.Oh, also, the USB adapters shouldn't really be called chargers, they are just a 5v power supply, all the charging circuitry is generally within the device being charged.
raspberry pi  - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 06, 2014, 02:14:25 pm
content: where is the cheapest unused raspberry pi model b available from

author: dr.diesel
author_rank: Super Contributor
timestamp: March 06, 2014, 02:15:54 pm
content: It would help if you filled out your profile, so we'd know what country you live in.

author: JoeO
author_rank: Frequent Contributor
timestamp: March 06, 2014, 04:01:45 pm
content: I have never seen them for less than $35 American.At 4 PM EST today, March 6th, Newegg is selling them for $35.00 with free shipping to the US.I don't know if they ship to the UK.

author: Macbeth
author_rank: Super Contributor
timestamp: March 06, 2014, 04:41:00 pm
content: Considering 100% of production are manufactured in Wales, UK, under a contract with both Farnell and RS, you really can't get cheaper than that unless someone is prepared to buy in bulk from those distributors and then offer a tiny discount. Or perhaps some companies providing some kind of VAT dodge?If you only need one or two, get them from the horses mouth. Free next day delivery included.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: March 06, 2014, 04:55:35 pm
content: Maybe you can consider a beaglebone blacksometimes is hard to find the pi

author: JoeO
author_rank: Frequent Contributor
timestamp: March 06, 2014, 06:11:30 pm
content: Quote from: Erwin Ried on March 06, 2014, 04:55:35 pmThanks Erwin. I was going to pick up an RPi from Newegg this afternoon. Instead I went for the BB Black for $45 from Adafruit.

author: Erwin Ried
author_rank: Regular Contributor
timestamp: March 06, 2014, 06:49:46 pm
content: Quote from: JoeO on March 06, 2014, 06:11:30 pmIn my country you can't find the Pi at any low price, in fact the BBB is in stock and cheaper (plus is fully open source and flash is included). It seems like the 25-35 usd price point was a good marketing scheme

author: NYG
author_rank: Contributor
timestamp: March 07, 2014, 03:53:46 am
content: In the US microcenter.com has had them for $29.99 for a bit of time now. I picked up a couple from a local store this past weekend.

author: GeoffS
author_rank: Unknown
timestamp: March 07, 2014, 04:21:24 am
content: DIrect from FarnellUK for £27.49 + VATThis includes an 8GB NOOBS sd-card
Raspberry Pi ad-on cards - Page 1
Forum section: electronics / beginners

author: MBEFFA
author_rank: Newbie
timestamp: October 19, 2021, 12:21:53 am
content: We have a family of add-on cards for Raspberry Pi, sequentmicrosystems.comI do not know if Dave reads these posts, but I would like to advertise onhttps://www.eevblog.com/,or sell in the store.If anybody would want to review some of our cards on youtoube, we would surely send some free samples.Any advice would be greatly appreciated.
Raspberry Pi and a HDMI display - Page 1
Forum section: electronics / beginners

author: ascsunday
author_rank: Newbie
timestamp: January 24, 2019, 12:38:00 am
content: I have a Raspberry Pi and a HDMI display on the same device that both need to have a power supply. The Raspberry Pi seems to ask for 5 Volts, the HDMI display is asking for 2 Volts, and my battery is 3.2 Volts. What is the best solution to this? Is there a voltage converter that will have a dual voltage output, or will one of these 2 devices be flexibleon the voltage?

author: spec
author_rank: Frequent Contributor
timestamp: January 24, 2019, 12:53:02 pm
content: Quote from: ascsunday on January 24, 2019, 12:38:00 amHi ascsunday,The answer to your question is yes, you can get cheap, small, switch mode power supplies to convert 3V2 to 5V and 2V.But,I suspect that the HDMI display would need a 3V3 supply rather than 2V.In order to succeed in this project it would be wise to tell us a bit more about your units:What battery?What model is the HDMI display?Which model Raspberry Pi?

author: nsrmagazin
author_rank: Regular Contributor
timestamp: January 24, 2019, 06:53:16 pm
content: What current? You will need 2 ICs.
Raspberry Pi and SDR - Page 1
Forum section: electronics / beginners

author: Mprentice1
author_rank: Newbie
timestamp: February 01, 2013, 11:34:03 pm
content: My first foray into the area of software defined radio, please do let me know what you think and what I can improve.http://theelectronicbyte.wordpress.com/2013/02/01/raspbery-jam-sdr/
Raspberry pi as an access point - Page 1
Forum section: electronics / beginners

author: mblyman89
author_rank: Contributor
timestamp: February 06, 2023, 06:58:54 pm
content: If I set up my pi as an access point, does that mean I will be able to control the pi with my laptop wirelessly and with out internet access? I am trying to use my pi without having to connect the eth cable, and I don’t have access to the internet where the pi will be used. If using the pi in this way won’t work, are there google terms I can use to find a solution that will work? My project is basically a simple controller. It will have preloaded scripts on in, I just want to be able to execute them remotely. Thank you all!

author: wasedadoc
author_rank: Super Contributor
timestamp: February 06, 2023, 07:03:16 pm
content: Quote from: mblyman89 on February 06, 2023, 06:58:54 pmYes.

author: macboy
author_rank: Super Contributor
timestamp: February 06, 2023, 09:32:12 pm
content: Note you likely need to set up the rpi as a DHCP server, or just set up appropriate static IP addresses on the rpi and connected devices.

author: mblyman89
author_rank: Contributor
timestamp: February 06, 2023, 11:24:42 pm
content: Thank you for the responses! I think after more googling, setting up the pi in ad hoc mode is what I’m looking for. I will give that a try.
Raspberry Pi common ground with another mains connected device - Page 1
Forum section: electronics / beginners

author: jerryk
author_rank: Regular Contributor
timestamp: January 20, 2018, 07:59:06 pm
content: Yet another question with my on going old school security panel interface to raspberry pi project. I'm getting close to sending the board out for manufacture but I may have a common ground conflict between the pi and the Napco Magnum 850 panel. In the schematic below I am using the power from the security panel itself to step down from 12V to 5V so I can power a Sainsmart 8 -5V relay board via inputs from the raspberry pi. As I see it the only way for this to work is to make the ground of the pi and the security panel common for the transistors to function. Is this safe? Or do I need to use optocouplers instead of the MMBT3904 transistors (see bottom of attached schematic)The security panel is 12V dc that is powered by a 16vac step down transformer and then rectified on the board of the security panel.Jerry
raspberry pi dsi connector - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 06, 2014, 01:05:23 pm
content: does any one know where to get a colour touch lcd display for the raspberry pi dsi connector

author: GeoffS
author_rank: Unknown
timestamp: March 06, 2014, 01:11:16 pm
content: The Raspberry Pi DSI connector is not currently enabled and there is no information available about it.There are rumours that the Pi foundation may release an LCD screen for use with the DSI but not many details.See this link:http://www.raspberrypi.org/forum/viewtopic.php?f=63&t=64041

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 06, 2014, 02:02:39 pm
content: Quote from: GeoffS on March 06, 2014, 01:11:16 pmthank you is there a small one that will plug in to the hdmi or rca and usb for touch
Raspberry Pi I2C Board not working - Page 1
Forum section: electronics / beginners

author: jakehiltz
author_rank: Contributor
timestamp: May 08, 2023, 10:03:47 am
content: Hello,I've created a PCB Hat for Raspberry Pi to read ECC608 cryptographic chips for faster testing, but it doesn't work. Does anyone see anything obviously wrong with the schematic?It doesn't appear to be a software issue.Notes:* Using an off-the-shelf TCA9548A module from Amazon everything works as expected* The Raspberry Pi does not detect ANY of the TCA9548A modules on the PCB I've made.* I know I can connect 8 devices to each multiplexer, but am only using 2 i2c for each multiplexer due to speed.

author: agehall
author_rank: Frequent Contributor
timestamp: May 08, 2023, 10:35:36 am
content: Maybe I’m reading things wrong, but are you not setting all the modules to the same I2C address?

author: jakehiltz
author_rank: Contributor
timestamp: May 08, 2023, 11:21:01 am
content: The Raspberry Pi has 6 I2C bus - I am using a multiplexer on each bus. There are no address conflicts.

author: Nominal Animal
author_rank: Super Contributor
timestamp: May 08, 2023, 12:27:36 pm
content: You need to connect the active-low RESET# to VCC (via a pull-up resistor), not leave it unconnected/floating. (SeePin Configuration and Functions in the TCA9548A datasheet.)

author: jakehiltz
author_rank: Contributor
timestamp: May 09, 2023, 12:44:38 am
content: That was it! Thank you!
RASPBERRY PI LOCKED OUT - Page 1
Forum section: electronics / beginners

author: neko efecktz
author_rank: Regular Contributor
timestamp: December 09, 2016, 03:12:06 pm
content: just got a raspberry pi today and I have already stuffed something up in it.HELP!!!starter kit with keyboard, mouse book and micro sd card with operating system and apps.I,m totally new to pies. first time I saw one, in the flesh so to speak, was this morning when it arrive by courier.Out of the box there is no user name or password required.I was trying to get it to play MP3 files, as I believe it should. and couldn't get it to work so I googled the problem and got what was supposed to work.The Pi now asks for a username and passwordI then googled this problem and found how to change the password by using the codesudo passwd rootthis worked but still wants a username.to get out of the username and password screen I press Ctrl - Alt and F1I have tried quite a few combinations ofsudo username rootsudo user rootsudo usernm rootsudo usernam rootetc.I assume he command would be the same format as that for the password.I keep gettingsudo: usernam: command not foundcan anyone help.I don't mind having a user name and password but would prefer not to.It's after 2am and I am getting tired.got to get to bed.will check for replies later in the morning.Thank youBILL.

author: neko efecktz
author_rank: Regular Contributor
timestamp: December 09, 2016, 03:17:54 pm
content: will try useraddFinally, use visudo to add the new user to sudo listThanksBILL

author: Fred27
author_rank: Unknown
timestamp: December 09, 2016, 03:42:11 pm
content: At the very least if you've made a mess of things you just have to restore an image to the SD card. If you haven't actually changed the user name and password the default is pi/raspberry.

author: neko efecktz
author_rank: Regular Contributor
timestamp: December 09, 2016, 08:53:05 pm
content: Fred27good morning.Unfortunately, I don't have an image of the supplied sd card.I tried using the default username and password but I have already changed them.just found a Raspberry Pi Image download and have downloaded it.will see if it works.I will have to go and another micro sd card.don't want to destroy the one i have just in case.thanksBill.

author: ovnr
author_rank: Frequent Contributor
timestamp: December 10, 2016, 10:19:27 am
content: If you just got it, you don't have much invested into your current setup. Just wipe the card and re-image it with whatever distro you want to use.

author: Assafl
author_rank: Frequent Contributor
timestamp: December 10, 2016, 11:08:54 am
content: Look for Noob. It is awfully easy to use in implementing most distributions (and to restore - in case you messed up something like overclocking).You wipe the SD cared, Unzip Noob to the SD card and plug it in. RPi boots and asks you which distro you want deployed.
Raspberry Pi RGB Controller - Where do I start! - Page 1
Forum section: electronics / beginners

author: XL5
author_rank: Contributor
timestamp: August 06, 2013, 02:52:17 pm
content: Okay, so I have these strips of RGB LED's and I would like to control them over an IP network using a Raspberry Pi.I am more than comfortable writing the software stuff, I'm just not sure where to begin when designing the circuit for this. As I understand it I want to have a constant 12V down one pin and then I should vary the resistance(?) of the three other pins to dim/brighten the RGB components.What should I look to be doing here?

author: Thor-Arne
author_rank: Unknown
timestamp: August 06, 2013, 03:45:56 pm
content: Google "raspberry pi mosfet pwm", that should get you started.To dim the colors of a RGB led you use pwm.

author: Zad
author_rank: Super Contributor
timestamp: August 06, 2013, 03:50:14 pm
content: Alternatively, buy individually addressable RGB pixels. The controller on the LED does all the PWM work for you, and you talk to it down a SPI or similar bus.

author: vlee489
author_rank: Newbie
timestamp: October 07, 2013, 08:57:35 pm
content: Have a look at my git hubhttps://github.com/vlee489/Raspberry-pi-RGB-LED-Stip-With-Web-ControlI have a led strip controller here but it uses a seprete web server so I don't over work my pi.But I recomend TIP31 tranisters

author: XL5
author_rank: Contributor
timestamp: October 07, 2013, 09:11:53 pm
content: That's really cool, I will have a proper look tomorrow!
raspberry pi spi0 and spi1 data transfer characteristics - Page 1
Forum section: electronics / beginners

author: ieeeHuseyin
author_rank: Contributor
timestamp: May 06, 2024, 01:51:24 pm
content: why is raspberry pi spi0 and spi1 data transfer different?I have attached the pictures below. I used the same test code for spi1 and spi0. But in spi1 the data is sent sequentially(wait after every three byte), while in spi0 there is a little wait after each byte.What is the reason?

author: m k
author_rank: Super Contributor
timestamp: May 12, 2024, 07:29:29 pm
content: There can be what ever happenings inside the library.It also depends how many hardware channels are available.There can be as many software implemented channels as there are needed pins.

author: langwadt
author_rank: Super Contributor
timestamp: May 12, 2024, 08:19:55 pm
content: afaiu SPI0 has a bigger fifo and can use DMA, the other SPIs can't
Rate my Project!!! - Page 1
Forum section: electronics / beginners

author: Stupid Bear
author_rank: Contributor
timestamp: January 14, 2023, 08:16:50 pm
content: So I'm new to Altium and this is the first PCB I ever made. Anyone is welcome to take a look at it and all (constructive) criticism is welcome. On a side note, I don't care about the circuit itself, just how I implemented it in Altium - pcplib, schlib, pcbdoc, schdoc etc files. Fire away, Thank you!

author: Benta
author_rank: Super Contributor
timestamp: January 14, 2023, 08:43:31 pm
content: Belongs in Altium or Beginners forums IMO,

author: Bud
author_rank: Super Contributor
timestamp: January 14, 2023, 09:30:37 pm
content: You are not trying to steal my StupidBear brand, are you?https://www.eevblog.com/forum/blog/eevblog-978-keysight-1000x-hacking/msg3713560/#msg3713560

author: Stupid Bear
author_rank: Contributor
timestamp: January 15, 2023, 04:35:06 pm
content: Quote from: Bud on January 14, 2023, 09:30:37 pmNo I've had this email (stupidrussianbear) for past ten years. But I brand my stuff under a different name. LOLQuote from: Benta on January 14, 2023, 08:43:31 pmHow do I move this post.... or do I repost?
Rather silly question about batteries, ground and lightning - Page 1
Forum section: electronics / beginners

author: dog80
author_rank: Regular Contributor
timestamp: April 03, 2014, 05:58:23 pm
content: What causes lightning? Aren't clouds "floating" both in the literal and electrical sense?Or is it a matter of electric charge, too much of it and it has to dissipate somewhere?Does the same apply to eg. batteries? Could an imaginary 100,000 Volt battery arc to the ground even when floating?

author: Electric flower
author_rank: Regular Contributor
timestamp: April 03, 2014, 06:16:24 pm
content: I guess that your battery would arc to ground or from its - to +, depends if gournd is closer than other contact of battery, rather a silly question that im not shure of answer...And for lighting you can read wikipedia and it would be much better than my answer.

author: IanB
author_rank: Super Contributor
timestamp: April 03, 2014, 06:18:31 pm
content: Thunder clouds are tall and air currents in the cloud cause a charge difference to build up between the bottom and the top of the cloud. The cloud as a whole remains neutral, but there becomes a potential difference between the bottom and the top. Since the bottom of the cloud is near to the ground, the electric field induces an opposite charge in the earth, and then a lightning bolt between the cloud and the ground tries to neutralize this potential difference.As a result the cloud as a whole is no longer neutral, and the unbalanced charge at the top of the cloud dissipates into the upper atmosphere and eventually bleeds back to earth to make things neutral again.Yes, an imaginary battery could arc to the ground, in theory, but it's all a matter of scale. It would need to be abigbattery before you could measure any appreciable current discharge. A better visual model is static charge on your body when you walk across the carpet. You are now the "cloud" and a spark (lightning) jumps from your body when you touch any grounded metal object far away from the original carpet.

author: pickle9000
author_rank: Super Contributor
timestamp: April 03, 2014, 06:22:36 pm
content: This is kinda interesting.http://news.nationalgeographic.com/news/2009/08/090823-lightning-upward-thunderstorms.html

author: mariush
author_rank: Super Contributor
timestamp: April 03, 2014, 06:29:10 pm
content: Apparently you fail at searching Google.
RC Camera gimbal external input not working - Page 1
Forum section: electronics / beginners

author: u2fletch
author_rank: Newbie
timestamp: November 03, 2014, 05:56:18 am
content: Have an interesting situation with my camera gimbal. The external pitch and roll inputs appeared to stop working.Though firmware was corrupt, or other such issue, but on a whim, I plugged in my Rigol DG1022U function generator and sent the gimbal an appropriate RC PWM signal. The gimbal worked! Tracked the pitch very nicely.That got me curious about the other radios I had used. Plugged in my FRSky X8R, did not work, tried my Futaba RX, no luck. But then plugged in my Hitec Optima RX and THAT RX works. Which was the first radio I had used with the gimbal when it all worked. The Hitec is the oldest radio, so something in its design is a little more robust than the others.So I decided to check the signals with my scope and found that that each RX is sending out a 3.45vpp signal, but when the servo out is plugged into the gimbal external input, the PWM voltage drops below 1.5v which of course is not recognized as a "high" pulse. The Hitec RX and my function generator fared much better, only dropping to about 2.66vpp when connected.So I assume I have a problem with input and output impedance being mismatched. Looks like I need a buffer circuit to feed the gimbal input.Tried to hook up an NTE975 opamp in a unity-gain, non-inverting configuration, (output fed to inverting input) but my skills with opamps are extremely limited and the circuit was not stable and oscillated like crazy. The supply voltage is coming from a 2s LiFe battery, which is around 6.6v. Looking at the datasheet, I am not sure if this is an appropriate chip for this application, but it is one that I had in the parts bin when I was working on some of the examples in Dave's Op Amp tutorial.Anybody out there have a suggestion for a simple buffer chip/circuit combo?u2fletch is online now Send a private message to u2fletch Find More Posts by u2fletchEdit/Delete Message

author: poot36
author_rank: Frequent Contributor
timestamp: November 03, 2014, 06:08:03 am
content: If the input is 5V tolerant I would look for some 74 series logic to buffer the signal. Most 5V micros will see a high signal at around 1.7V or so.

author: u2fletch
author_rank: Newbie
timestamp: November 03, 2014, 03:15:22 pm
content: Thanks,I will look into the 74 series TTL stuff. My first thought was a 7407 hex buffer, but not sure if the chip would be happy with running 6.6V as a supply voltage. According to the Datasheet, it says 7V MAX, and 5.25 recommended. It's worth trying out.

author: poot36
author_rank: Frequent Contributor
timestamp: November 03, 2014, 11:58:21 pm
content: You could always use a 5V regulator if you are concerned about the voltage. I thought that most servos for hobby use ran off 5V? If yours do just use the power off there but make sure to put a filter capacitor on the logic chip.
RC circuit (two resitors and 1 cap connected to 10V DC) - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: October 17, 2019, 02:03:39 am
content: Am I doing something wrong calculating the current and voltages at time t for the RC circuit? I put these equations on google sheets and the voltage across all of the elements passes 10V between 4 and 5 seconds. Then it goes all the way to 35V around 20 seconds!Super thanks

author: bob91343
author_rank: Super Contributor
timestamp: October 17, 2019, 02:10:00 am
content: It's hard to read. My approach is to use the Thevenin equivalent, which is to divide the voltage with the resistive divider (ignoring the capacitor) and use that as the source voltage. Put that as the battery voltage and put the capacitor across the new source in series with a resistor whose value is the parallel combination of your two resistors.Then it becomes a very simple RC. One volt source in series with the capacitor and about 91 Ohms.

author: rstofer
author_rank: Super Contributor
timestamp: October 17, 2019, 03:57:31 pm
content: At t=0, the capacitor is a short circuit so the entire battery voltage will be across the 1000 Ohm resistor at t=0+ (an infinitesimal period after t=0).At t=infinity, the voltage across the capacitor will be the same as the voltage drop across the 100 Ohm resistor and this would be10V*(100/(100+1000)) or about 0.091V.The time constant (tau) is based on the 100 uF capacitor and the parallel resistance of about 91 Ohms or about 9.09 ms. Six tau will result in the capacitor being very close to fully charged.It's always useful to simulate the circuit with something like LTSpice just to be certain you understand what is going on.The red trace is the voltage across the capacitor as a function of time gained by subtracting the green trace from the blue trace. The blue trace is 10V and the green trace is the output voltage as a function of time. It starts at 10V because the capacitor looks like a short circuit and decreases as the capacitor is charged and the 100 Ohm resistor becomes more of a factor in the voltage divider. It ends up at about 9.1V (9.090909V).
RC circuit and opamp used as a comparator. - Page 1
Forum section: electronics / beginners

author: DBoulanger
author_rank: Regular Contributor
timestamp: November 01, 2013, 11:32:41 pm
content: Hi every one,I've seen quite a few methods here and there allowing us to estimate the value of a given capacitor with a somehow basic RC low-pass or hi-pass filter circuit.In one example I found, there is a suggestion to vary the frequency such that the voltage accross the capacitor is half of the source.Under these circumtances, it would be legitimate to conclude that the voltage accross the resistor and capacitor are the same. This is where the comparator comes in the picture. How interface the opamp with the RC circuit in such a way that when the equilibrium is reached, the output of the opamp is "flat".Obviously, due to the nature of the opamps, a perfect match of Vc and Vr is pratically impossible, but if that could be done within few millivolts, I think that would be acceptable.So ideally, a led would lit up if the frequency is too high and another one would be lit if the frequency needs to be increased. Having both lit or off would be acceptable, indicating that we're within the difference of few millivolts we've preset.This is potentially not something too complicated, however I'm somehow uncertain where to start.BTW, when the equilibrium is achieved, the formula sqrt(3)/(2*pi*f*r) would provide us with an estimated value of C.This little circuit/project is simply to get more familiar with opamps and RC circuits and at the same time, give me the opportunity to create something that could be usefull, who knows.Your help would be greatly appreciated.

author: Paul Price
author_rank: Super Contributor
timestamp: November 02, 2013, 12:51:42 am
content: BTW, when the cutoff freq. of a r-c filter (-3dB attenuation) is reached, the voltage across the capacitor is .707 of the input voltage, not .500 as you state, when the applied signal is a sinewave.If a dual op-amp follower is sniffing the voltage across the capacitor to be measured, the output of this op-amp could be compared to the second op-amp fed by divide by 2 voltage of the input voltage and then by rectifying both outputs a comparator can then show the above/below/match of the two rectified voltages with LED indicators.

author: DBoulanger
author_rank: Regular Contributor
timestamp: November 02, 2013, 02:41:03 am
content: Thanks Paul for the information.I understand clearly that at the cutoff frequency, the amplitude attenuation will be of 3db, therefore 1/sqrt(2) or 0.707 for short.The formula I'm using is not using the cutoff frequency as such, but the frequency at which an attenuation of 6db is achieved, or if you prefer, when Vc is half of Vs.Based on the circuit description you provide, I will attempt to create a prototype. Meantime, if you or someone else could actually draw the circuit you describe, that would be great.Thanks for your help.P.S.: Keep in mind that I'm fairly new to that gymnastic, so somethig that may seem obvious for some, might not be so natural for others.
RC circuit charges in less than 1 Tau - Page 1
Forum section: electronics / beginners

author: chLach
author_rank: Newbie
timestamp: May 03, 2021, 02:51:14 pm
content: Hi all, just a basic question here - I have this basic RC circuit here with a 100k resistor and a 1000 microF capacitor with a 6V EMF (4 D cell) - I calculate the Tau value to be 100s and would expect the cap to take ~ 300s to charge close to the 6V. But it charges to almost 6V in less than a second, what am I missing?I have a voltmeter in parallel with the cap. It's a cheap one, would that be influence anything?it is an Electrolytic Capacitor

author: SuzyC
author_rank: Frequent Contributor
timestamp: May 03, 2021, 03:02:55 pm
content: Either your stated capacitor or resistor values are not correct. Most likely you have a misread value, 1000pF capacitor instead of a 1000uF.Your meter is not to blame, but you may have not connected the low side of the capacitor to ground.

author: fourfathom
author_rank: Super Contributor
timestamp: May 03, 2021, 03:05:42 pm
content: Yes, this should take 100 seconds to charge from 0 to 0.632 * 6V. Your meter shouldn't be affecting the measurement very much (assuming it has the standard 11 Megohm input resistance). Are you sure that you really have a 1000uF capacitor? Is the capacitor truly discharged at the start of your test?

author: chLach
author_rank: Newbie
timestamp: May 03, 2021, 03:12:39 pm
content: I will go back to the lab (garage) and check the values and wiring - Thank you for confirming my calculations , it helps, now I am pretty sure it is something in my setup so I'll focus there. I had been shorting the capacitor between each trials and it showed only a couple mV when I start.

author: chLach
author_rank: Newbie
timestamp: May 03, 2021, 03:35:29 pm
content: Bad capI hadn't done stuff like that in 30 years lol (I mostly teach the kids practical stuff with and Arduino) , I was sure that I was doing something wrong, never thought it was a bad component .Thanks again
RC discharge time constant - Page 1
Forum section: electronics / beginners

author: renzoms
author_rank: Regular Contributor
timestamp: October 16, 2019, 04:30:04 am
content: Are the two underlined equations at the bottom correct (can I calculate an equivalent resistance for the time constant)? I understand how to find voltage and current for each element at time t supplied with DC voltage. So I’m looking at discharging two ways. Are they both appropriately solved?Also I've just understood Thevenin equivalent circuit(s) solutions to these circuits so I specifically want to know if the time constant can be calculated by an equivalence resistance. Thanks guys I'm excited about every second I'll be a part of this forum!

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 16, 2019, 08:41:31 am
content: Yes. In the first case I(R1) = 0 so it only depends on R2, while for the second, R1 and R2 act in parallel.Note that if we consider the opposite event, the capacitor starting from zero and charging through R1, the resistors also act in parallel, for a number of equivalent reasons (fundamentally, linearity and reciprocity, or superposition; Thevenin's theorem is a direct consequence).Directly applicable, say to logic circuits, where the output pins have transistors pulling up and down, as the switches shown. And each switch has its own resistance. So the RC time constant varies, and you need to be far enough down both time constants to obtain a reasonably square pulse, thus setting a limit on clock rate.Tim
RC filter for serial comm, placed near the transmitter or the receiver? - Page 1
Forum section: electronics / beginners

author: jnz
author_rank: Frequent Contributor
timestamp: April 11, 2022, 04:25:54 pm
content: I have a small device that takes in single line usart wire for data in.The datasheet calls for an RC filter, the values I'm on my own to figure out.I'm pretty sure that I want the RC filter placed close to the transmitter, but I don't know if that's right or why.Thoughts?

author: ledtester
author_rank: Super Contributor
timestamp: April 11, 2022, 05:39:36 pm
content: What's the device? Can you post the datasheet?

author: jnz
author_rank: Frequent Contributor
timestamp: April 12, 2022, 05:36:49 am
content: In this case, a Lumex embedded IC LED.Accepts a waveform that you can make with SPI or UART or bit bang.https://www.lumex.com/news/SMD-LX0707RGB-TR.html

author: ledtester
author_rank: Super Contributor
timestamp: April 12, 2022, 06:28:27 am
content: That module looks very much like the WS2812B smart leds.With the WS2812B a ~400R resistor is recommended between the MCU output pin and the first led in the chain especially if there is a significant amount of wire between the two. See, for instance, this discussion:https://forum.arduino.cc/t/arduino-ws2812b-data-pin-resistor/533031Update: According to these sources the resistor should be placed near the LED:https://electronics.stackexchange.com/a/353581/95488https://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices#:~:text=Place%20a%20300%20to%20500%20Ohm%20resistor%20between%20the%20Arduino%20data%20output%20pin%20and%20the%20input%20to%20the%20first%20NeoPixel
PWM RC Filter - Help & Advice please - Page 1
Forum section: electronics / beginners

author: Mad Professor
author_rank: Regular Contributor
timestamp: May 12, 2014, 07:03:21 pm
content: Good day all.As per the topic title I am looking for help and advice with regards toRC Filter's.I am trying to interface aACS71220Amp Hall Effect-Based Linear Current Sensor with my Arduino Uno.At first it was going to be a nice simple task, being that the ACS712 outputs a 0-5v output based on the current. and if I use a light bulb to test it works as expected.But as I am using PWM and using the ACS712 to monitor the current I am not getting the expected readings.I have been advised by a few friends that an RC Filter on the output of the ACS712 would be the best way to go.And this is where I need your help and advice, I have never designed / calculated an RC Filter before.What data do I need to be able to work out what resistor and capacitor would be suitable.The only thing I know at this point in time is that the PWM freq of the arduino is around 500Hz.Can you please advice.Thanks for your time.Best Regards.

author: HalfSpace
author_rank: Regular Contributor
timestamp: May 12, 2014, 11:30:54 pm
content: Hi Mad Professor,The web site below has a good range of RC filter calculators.http://sim.okawa-denshi.jp/en/Fkeisan.htmHalfSpace

author: Mad Professor
author_rank: Regular Contributor
timestamp: May 13, 2014, 01:35:17 pm
content: HalfSpace: Thank you for your reply, and the link.But I am still as confused, if not more confused then I started.I don't want to be spoon-fed the answer, but as I don't know where to start, I will not find the answer any time soon.So can I please have some more guidance.Best Regards.

author: max_torque
author_rank: Super Contributor
timestamp: May 13, 2014, 02:20:56 pm
content: Have you read and understood P13 of the 712 datasheet? The device includes an integral "R", and a "filter" pin to which you attach a suitably sized capacitor for the "C" bit of the filter!

author: max_torque
author_rank: Super Contributor
timestamp: May 13, 2014, 02:23:39 pm
content: Oh, and second point:If you are just using a bulb as a load, then it will have a low inductance. As such,, even though your eyes can't see it (due to thermal inertia of the filament) the current through the load will be co-incident with the PWM frequency (especially at only 500Hz!)As such, the exact moment you sample the current by reading the current sensor voltage will matter if there is no filter on the output! (check the non filtered bandwidth of the 712 to see what i mean, and compare that to your pwm frequency....)
RC filter on battery - Page 1
Forum section: electronics / beginners

author: Nikos A.
author_rank: Regular Contributor
timestamp: April 23, 2021, 05:44:39 am
content: Hi everyone,I am looking the BQ29700 battery protector from Texas Instrumentshttps://www.ti.com/lit/ds/symlink/bq2970.pdf?ts=1619080532853&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ2970%253FkeyMatch%253DBQ2970%2526tisearch%253Dsearch-everything%2526usecase%253DGPNThe datasheet proposes an RC filter on the battery and they right that "An RC filter is required on the BAT for noise, and enables the device to operate during sharp negative transients. The 330-Ω resistor also limits the current during a reverse connection on the system."They are referred to the noise coming from the charger? What could occur the sharp negative transients? Does the 330ohm resistor act something like reverse voltage protection by limiting the current?ThanksNick

author: Stuart Coyle
author_rank: Contributor
timestamp: April 23, 2021, 08:57:10 am
content: They are referring to noise coming from either the charger or load. The filter stops high frequencies from affecting the voltage reading at BAT, which could otherwise cause switching of the cout or dout when you don't really want it. By sharp negative transient, imagine what happens when you connect a load that may take a lot of inrush current, thus dropping the voltage very quickly. The FET would turn off and you would not get a clean startup. The resistor is part of the filter. Not much current ever flows into the BAT terminal as it is just the input to a pair of comparators, which will be very high impedance.

author: Nikos A.
author_rank: Regular Contributor
timestamp: April 23, 2021, 09:35:41 am
content: Thank you for your great answer Stuart Coyle!!Quote from: Stuart Coyle on April 23, 2021, 08:57:10 amSo, no additional reverse voltage protection is needed (let's say a MOSFET)?Something like this:free image uploader
RC Filter + opamp - Page 1
Forum section: electronics / beginners

author: slashguitar
author_rank: Contributor
timestamp: February 04, 2013, 09:01:22 pm
content: Hi,I'm trying to prototype something similar to Bob Parkers ESR meter with an FPGA, but instead of charging a capacitor with a constant current I am filtering a PWM before applying it to a comparator. The problem is I have 100mV at the inverting input of U2B when PWM is 0. Any ideas what is causing it and how to fix it?ThanksEDIT: Inverting input....sorry for the mistake

author: sub
author_rank: Regular Contributor
timestamp: February 04, 2013, 09:47:52 pm
content: It looks like input offset is your problem---the datasheet lists 12mV max, which would give a 240mV output in your case. Perhaps either try a different op-amp or build a composite amplifier.

author: slashguitar
author_rank: Contributor
timestamp: February 04, 2013, 10:00:01 pm
content: I'm talking about the opamp on the right(the comparator). Doesn't the input offset appear at the output?(....ex....input is 0 output is 12mV).I have 100 mV on the noninverting input

author: IvoS
author_rank: Frequent Contributor
timestamp: February 04, 2013, 10:17:12 pm
content: If the offset is 12mV with gain of 20 coming from U2A would give 240mV or thereabouts to your noninverting pin of U2B ?? Am I missing something?

author: slashguitar
author_rank: Contributor
timestamp: February 04, 2013, 10:54:28 pm
content: Sorry, I ment INVERTING input of U2B (VHDL is getting on my nerveThat's why it doesn't make sense to me.p.s. I just measured the noninverting input and its about 20mV (1mv offset is well within spec).

author: sub
author_rank: Regular Contributor
timestamp: February 05, 2013, 08:54:50 am
content: Do you mean the PWM is set to zero, or that there is 0V on the PWM output? If you have done something like thisCode:assign pwm_out = (counter <= pwm_value0) ? 1'b1 : 1'b0;then you will get a voltage 3.3*2^(-N), where the N is the number of bits of resolution that you have. I realise that this is a rather obvious suggestion. A 3V3 IO would give about 100mV if you had a five-bit PWM.
RC Highpassfilter Values - Page 1
Forum section: electronics / beginners

author: JeRo
author_rank: Newbie
timestamp: March 09, 2021, 11:13:45 pm
content: Hi there,I have a kind of newb Question that I could not find an answer for. In an RC Filter (or any Rl, LC and so on) the filter -3db frequency is dependant on the product of R and C.How do I distribute those for an audio Range signal? High R low C or the other way round?Spice Simulation does not show a difference in the result but I am quite sure there is one... right?Many thanks in advance!Jens

author: srb1954
author_rank: Super Contributor
timestamp: March 10, 2021, 12:13:39 am
content: Quote from: JeRo on March 09, 2021, 11:13:45 pmIt all depends on the surrounding circuit's load and source impedances.For a HP filter using a low C/high R combination requires that the load impedance be much higher than the filter resistor to avoid affecting the filter characteristic.Conversely, a high C/low R combination requires that the source impedance be low compared to the capacitor reactance over the frequency range.

author: Terry Bites
author_rank: Super Contributor
timestamp: March 10, 2021, 06:11:03 pm
content: Put a resistive load on your output and drive it from a signal source with a resistive output impedance and you will see a dramatic difference in response.For lower noise use lower values of R and higher C. In general, the diving source impedance need to be more than 10x lower than your R and your output need to see something at least 10x higher than R or you will have some serious errors to deal with.Massive C comes with massive expense and inconvenience. L has a lot of nuisance value with hidden R and C lurking in it. They're often bulky and pricey at audio frequencies they are also a pain for picking up magnetic interference.Spice uses ideal generators and measurements unless you specify otherwise. Beware!
RC Low Pass Filter help - Page 1
Forum section: electronics / beginners

author: sanyoboy
author_rank: Newbie
timestamp: January 22, 2016, 03:07:55 am
content: Hi Guys, I made a RC low pass filter to place on the line into my sub woofer amp but I don't think its working, sounds no different than with no RC Low pass filter.My setup is PC > karaoke mic amp to left and right speakers + steal Left channel for sub > circuit > amp > sub woofer.Here's a picture.The circles are RCA female connectors.I am using a 100v 15uF cap it has no polarity marking what so ever. Only writing with capacitance the company and the voltage on one side. I am using the side with no writing as positive. It hasn't blown yet so I am guessing its right or just not passing any audio hence its not working.Is it my capacitor backward or is it the fact its coming out of a karaoke mic amp or something else?

author: MrSlack
author_rank: Frequent Contributor
timestamp: January 22, 2016, 06:55:48 am
content: Bit hacky but that may work. I've done similar things in the past. The 3db point of that filter is ~88Hz but there a couple of issues with it. Firstly the roll off is still pretty slow on a simple RC filter and at low frequencies that may not be audible. You can improve that by using two or more identical filters one after the other or picking a different filter model (twin-t etc). Note that as each stage operates as a divider, the output will reduce considerably! Secondly the thing will modify the impedance of the source considerably so it may merely reduce the volume and crush any noticable filter effects; use an active filter (op amp) for each stage. Probably a tl072 can be run single rail in an active filter config off a 9v battery for this job without causing any nasty side effects as it's consumer line level.Edit: just to add, back in the summer of 1992 I built two active speakers using the same method instead of crossover networks. Still work today and sound rather good!

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2016, 08:55:55 am
content: What's the cut-off frequency?