hybridfree/eevblog-posts huggingface dataset:
How to measure capacitance between antenna and human body? - Page 1
Forum section: electronics / projects

author: bharatcs
author_rank: Contributor
timestamp: March 01, 2017, 04:28:47 pm
content: Is there any possible way to measure capacitance between an antenna and human body.This is to build a theremin using micro controller with minimum components.The capacitance value will be calibrated with distance of human hand from the antenna.Is it possible?OR is it a stupid idea?

author: DaJMasta
author_rank: Super Contributor
timestamp: March 01, 2017, 05:28:56 pm
content: As your statement implies, you're just measuring the capacitance, so it is certainly possible, what's more difficult is if the capacitance is so low or so swayed by outside factors that the readings aren't meaningful.That being said, you're probably in the clear. The simplest way to get an idea (not a calibrated capacitance value, but a relative reading) would be using the arduino CapSense library and a high value resistor. Basically, it uses one pin to charge up your plate (the arm of the theramin) through the resistor, then it measures the voltage on the plate. If the voltage is higher, the capacitance is lower because of the way a capacitor charges, so it can measure with reasonable repeatability the capacitance of the plate. Using much smaller plates I was able to detect a finger a couple inches off of the plate, so with a large plate and a sensitive enough ADC, you should be able to measure a hand or arm with no problem over a shortish distance.It would be easy to implement this method in other micros or your own code, and using something with a 14 bit ADC would probably be more useful, but it's basically all taken care of if you're using an arduino compatible chip as your micro.
How to measure dc-dc conv. switching freq. using micro? - Page 1
Forum section: electronics / projects

author: Spikee
author_rank: Frequent Contributor
timestamp: August 31, 2013, 12:55:16 am
content: I'm currently designing a dc-dc converter tester (digitally controlled dummy load).It does measure: Input voltage/current , output voltage/current but it would also be cool to measure the switching frequency of the regulator.I already found a way to measure frequency using my Psoc 5LP processor, but it relies on ttl / cmos voltage levels to detect the frequency.So i probably need a high pass filter and some amplification to get the voltage right and possibly something like a schmitt triggerOr is there another way that would work better ?Thanks

author: Rerouter
author_rank: Super Contributor
timestamp: August 31, 2013, 01:02:40 am
content: if you just want the frequency and not the pulse width you can make a very simple amplifier that feeds a binary counter,you ac couple your input through a capacitor and current limiting resistor,you feed this into a npn transistor with its base biased through a high value resistor so its collector voltage just above the trigger point of the counters shmitt trigger, for a given lift up resistor,and for good measure you add a diode with its anode to ground and cathode to the transistor base so it can handle large swings,this leaves you with a very sensitve counter intended for swinging almost rail to rail and doesnt pick up much noise on high amplitude signals,

author: TerminalJack505
author_rank: Super Contributor
timestamp: August 31, 2013, 01:54:51 am
content: You might look at the schematic inthis postfor some ideas:

author: tszaboo
author_rank: Super Contributor
timestamp: August 31, 2013, 08:34:24 pm
content: If you are making an in circuit tester with pogo pins, then you can just measure the "input side" of the inductor, or the catch diode, with a small amplifier. Else it could be a bit tricky, if the output filter is built properly. You need to make an bandpass filtered (AC coupled), automatic gain amplifier there.

author: Spikee
author_rank: Frequent Contributor
timestamp: August 31, 2013, 08:55:19 pm
content: I just finished with the digital part of the project and I will soon open a topic on this forum about it.Also I don't know if it is useful to measure it for evaluation purposes.The features I have currently implemented:-Measure input voltage-Measure input current-Measure output voltage-Measure output current (dummy load)-4 temperature measurements inputs (heatsink , switching converter , pcb etc ...)This should give you efficiency , load characteristics ,transient response ...Noise measurement may be a more useful thing to add.I have successfully built a dummy load before that could handle 400W and was tested up to 63A now i am just making it more precise and nicer.The 20bit adc in the Psoc 5LP will give me plenty resolution now I am just looking at the analog stage for the load and my opamp selection. All that will be discussed when I open a thread about it.b.t.w. Your nandblog is awesomeAnd all of you thanks for the replies !
How to measure Gfs (Forward transconductance) in JFETS - Page 1
Forum section: electronics / projects

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: June 18, 2023, 10:39:18 pm
content: Hi,I've been playing with a circuit that uses an U431 matched FET pair.The data sheet says the forward transconductance ratio between the pair is between .9 and 1. (VDS 10V and Id 10mA)I want to try using some cheaper single FETS and wondered how to make a jig to measure their Gfs so I can select close to matchde pairs.Cheers,Corby

author: Benta
author_rank: Super Contributor
timestamp: June 18, 2023, 10:59:00 pm
content: Well, we're talking JFETs here, so the first simple match is short-circuiting gate and source (VGS= 0) and measuring the drain-source current with a reasonable voltage applied (eg, 12 V VDS).After that, you can start de/increasing VGSto match even better.But your chances of success are slim.Unclassed discrete JFETs have a 1:10 spread on this parameter.Classed types a 1:3 spread (eg, BF245A/B/C).You need a really big bag to select from when matching.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: June 18, 2023, 11:32:28 pm
content: Quote from: 5065AGuru on June 18, 2023, 10:39:18 pmThose parts spec match at a specific current, so you need to choose what current operating point you need, and then create a jig that consistently injects that current.If you also inject a small AC voltage, you can then use a multimeter(s) to measure VGS and AC Drain output voltage.As mentioned in #2, unclassed parts have a very wide bin, but lcsc shows some TF2123 that are binned to < 1.7:1
How to measure the output impedance of a High power RF mosfet - Page 1
Forum section: electronics / projects

author: qwaarjet
author_rank: Regular Contributor
timestamp: July 18, 2014, 08:27:36 pm
content: I have 1000W STAC4932B Rf N mosfet, the datasheet only lists its output impedance at 123Mhz however in my application I am running at 13.5Mhz. What the best way to go about determining an output impedance accurately. I have access to common tools scope, arb, and VNA, but would like to avoid building to many custom loads/ probes. Option 2 are there companies that do this type of service.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: July 18, 2014, 10:16:31 pm
content: If you have VNA you should be able to calculate output impedanceZout = Zo * (1+S22)/(1-S22). Where Zo is characteristic impedance which is usually 50ohm.Contact ST micro - maybe they will give you complete S parameter table. They don't appear to have it on their website which sucks

author: f5r5e5d
author_rank: Frequent Contributor
timestamp: July 18, 2014, 10:26:48 pm
content: 13 MHz is low enough to use the device Coss,rss specs, though those are V dependent too, and with some drive impedance effects from the Miller multiplication

author: richard.cs
author_rank: Super Contributor
timestamp: July 21, 2014, 07:04:35 am
content: Quote from: Alexei.Polkhanov on July 18, 2014, 10:16:31 pmAny modern VNA should be able to show impedance directly . I'm surprised they don't give typical values even if they only guarantee it at one frequency.

author: KJDS
author_rank: Super Contributor
timestamp: July 21, 2014, 08:07:18 am
content: Quote from: richard.cs on July 21, 2014, 07:04:35 amOutput impedance of RF mosfets is dependent on biasing and output power. The only accurate way to measure it at higher power is with a load pull set up. Try measuring it with a VNA when 1000W are coming out and you'll get a very unpleasant time from whoever paid for the VNA.A little light reading.http://www.microwaves101.com/encyclopedia/loadpull.cfmhttp://www.maurymw.com/pdf/applib/5C-041.pdfUsually high power RF device manufacturers will provide a load pull report and an ADS or MWO model. Some will also provide a lumped element equivalent for source and load matching. If you're not used to working with high power RF then I wouldn't start here. That device has an input impandance of 1.3 ohms and to get any gain from an amplifier you'll have to match to it. Get the matching wrong and the device will oscillate to self destruction, or not provide any gain. Get the cooling wrong and it will burn itself out very quickly. Get the output match wrong and you'll get very poor output power and efficiency. If you try and tune it for better gain then the output power and efficiency will get worse.
How to monitor battery voltage in ultral low power applications - Page 1
Forum section: electronics / projects

author: Nikos A.
author_rank: Regular Contributor
timestamp: December 13, 2021, 10:52:05 am
content: Hi everyone,I want to periodically measure the battery level of my application. Texas Instrument suggests using a voltage divider and a switch to measure the battery voltagehttps://e2e.ti.com/blogs_/archives/b/fullycharged/posts/simple-battery-monitoring-in-ultra-low-power-applicationsHowever, I do not understand why not just use an N channel MOSFET to switch the voltage divider. They use the level shifter to reduce the current but I do not understand how it works.

author: Peabody
author_rank: Super Contributor
timestamp: December 13, 2021, 03:35:14 pm
content: It depends on where you place the N-channel, and the maximum voltage you want at the midpoint of the divider. Assuming Vbat is a higher voltage than the Vcc of your MCU, you can't put the mosfet above the divider because you have no way to keep the gate voltage 2V above the source while you take the measurement. You can't put it below the divider because then the analog pin would be exposed to the high Vbat voltage when the mosfet is turned off, and current would flow through the protection diode.But you can put it in the middle, just above the analog takeoff. However, you will be limited to a maximum of about 1V at the divider if your Vcc is 3.3V. When turned on, the source of the N-channel has to be at least Vgs threshold below the gate to turn it on at all. And the source is your measuring point. So if your ADC can measure the range 0V-1V, then it would work.Here's a circuit for that, but you would use a better mosfet than the 2N7000 - one with a lower threshold voltage.Edit: The advantage of the two-mosfet circuit is that the analog takeoff point can have a voltage as high as the MCU's Vcc.
How to mount speaker on PCB? - Page 1
Forum section: electronics / projects

author: samy03
author_rank: Contributor
timestamp: April 05, 2019, 04:54:22 am
content: Hi All,I am creating a product which has a small 0.5W 8ohm speaker connected to the PCB.I will put my PCB in a metal enclosure like this:https://www.ebay.com/itm/ST662-6-Metal-Aluminum-Electronic-Project-Enclosure-Box-Case-DIY/252330916481?hash=item3ac0183a81:g:TwUAAOxyQqBRGbaXI am not sure where to put the speaker. I am still designing my PCB so I can either put the speaker on PCB or just put a connector for the speaker and mount the speaker somewhere on the enclosure.My question is, how can I mount the speaker inside the enclosure on the front panel? Or what is the best way to mount a speaker?I was thinking of using a speaker like this if I put speaker on PCB:https://www.digikey.com/product-detail/en/cui-inc/CVS-1508/102-2498-ND/2791828If speaker is mounted on enclosure then this speaker will be used:https://www.digikey.com/product-detail/en/cui-inc/CDMG15008-03A/CDMG15008-03A-ND/1242520I am open to suggestions so any suggestions would be appreciated.Thank you

author: Ysjoelfir
author_rank: Frequent Contributor
timestamp: April 05, 2019, 05:56:04 am
content: If you don't intend to provide Hifi like quality (which I assume from the speakers shown) I would definitely go for the Buzzer style PCB mount speaker. Using that will be waaaay easier than mounting the other speaker on the case.If you have to use the external one I personally would stamp a few holes into the chassis to create an opening for the soundwaves to travel to your ear and just press the speaker against the chassis, glueing its perimeter with an elastic, strong silicone glue.
How to mount this battery spring to a board? - Page 1
Forum section: electronics / projects

author: Peter_G
author_rank: Newbie
timestamp: July 15, 2022, 11:12:12 pm
content: I'm working on a board layout that needs a spring contact like this:https://www.digikey.com/en/products/detail/keystone-electronics/5222/2745881The datasheet mentions the spring is designed "for either wire lead or PC mounting", but I'm not super experienced in PCB design yet and I'm not really sure what kind of footprint to put on my board to mount this spring as the datasheet gives no footprint specs. How should I mount this spring?I picked this spring because I already have them in my system and I didn't see anything strikingly better for my purposes anywhere, but if there's a better option that I've missed with equivalent length and no larger of a base I'm open to swapping my choice.

author: jpanhalt
author_rank: Super Contributor
timestamp: July 15, 2022, 11:35:20 pm
content: The Digikey link has a datasheet to Keystone. Here's the home page:https://www.keyelco.com/index.cfmThat base is designed to be soldered or held captive (like grooves in a plastic housing). You might find something more suitable at that link.EDIT: Based on the DigiKey image. I didn't notice that the datasheet was incorrect.What type of battery? If cylindrical, there are suitable single or multiple cell holders everywhere. eBay has them cheaply from China. That might be your best alternative.

author: coppercone2
author_rank: Super Contributor
timestamp: July 16, 2022, 12:32:08 am
content: basically make it as big and beefy as you can, its a bulky object that gets alot of abuse. Key stone is a good brand, I would stick with it.As how to mount it optimally, I would use two tiny rivets in those holes, and solder. If you rivet it to the PCB it will be nice. Keystone should sell all the rivets you need for their products and the tools needed to apply them (I think there are often special punches for mini rivets). That will be a very solid battery contact. When you drop something with heavy batteries in it, its gonna get messed up if you don't build it strong.

author: Ian.M
author_rank: Super Contributor
timestamp: July 16, 2022, 01:03:05 am
content: No, the datasheet says:Quotebut your part is *NOT* one of the ones in that datasheet with tabs to allow direct PCB mounting. Instead its got two retention 'fingers' designed to stop it coming back out of a plastic slot, parallel to the battery end, with a partially open side to accommodate the spring contacting the base of the battery. It would be connected by a most likely stranded wire soldered through one of the small holes in the base of the contact.The tabbed versions are the two directly below it in the datasheet - 5201 is the plain one, and 5220 has the retention fingers as well as the tab. Both need to be supported by a plastic molding to handle the spring pressure.
How to multiplex between circuit and DMM? - Page 1
Forum section: electronics / projects

author: Merlysys
author_rank: Regular Contributor
timestamp: January 11, 2014, 03:37:39 pm
content: I need some ideas on how to build this, any links to similar circuits will help.The project circuit (PrC) will connect circuit under test (CuT) to a DMM + leadSo...Inputs to the PrC are from CuTOutput is to a DMM's + leadPrC will have up to 20 momentary push buttons, normally open.When one of those 20 buttons, say button A, is pressed-current to flow between corresponding input (A) and DMM+ (so latching is required)an LED (3mm type will do) next to it will light up stay litThis state will only change when a different button, say button D, is pressed, then circuit A will open and circuit D will close. Pressing button for currently active circuit will make it open but this feature is not necessary if it leads to more complexity/components.Each line will carry under 100mA, under 12VDC. Resistance to be as close to zero as possible.I looked into relays as they have the lowest resistance, but are there better ways?Are there boards already built with some/all of these features sold on ebay etc.?

author: Harvs
author_rank: Super Contributor
timestamp: January 11, 2014, 11:14:56 pm
content: Sounds like you're basically building a very manual version of a DMM scanner card. So you could have a look at those for ideas.However, I don't understand the 100mA requirement? Typically DMM's have >10M input impedance.Typically they're implemented with relays for the very high isolation between channels, and the high voltage requirements. If you only need to handle 12V max, and you can do away with the 100mA requirement, then a simple analog mux would probably be fine and very cheap (e.g. 4053.)Easiest way to implement the logic would be a few lines of code on a microcontroller.

author: sleemanj
author_rank: Super Contributor
timestamp: January 11, 2014, 11:30:58 pm
content: Quote from: Harvs on January 11, 2014, 11:14:56 pmI think poster intends to use the meter for series current measurement, not voltage. At least that was how I read it. + - [1 of N Circuits] - Meter - Gnd
How to obtain the Rd anf Vd values to model the led ? - Page 1
Forum section: electronics / projects

author: Patrick66
author_rank: Regular Contributor
timestamp: March 14, 2024, 03:24:29 pm
content: Hello everyone, I wanted to model the 32W LED based on the link below but I did not manage to find the current-to-voltage graph to get the values of Rd and Vd. Wanted to ask is there any other way to get the Rd and Vd values of this 32W LED? Thank you in advance guys.Link:https://www.normalit.com/ES/en/products/Pantalla/lighting-led-panel-for-modular-ceilings-luzerna-avant?site_id=2

author: Zero999
author_rank: Super Contributor
timestamp: March 14, 2024, 04:27:10 pm
content: There's no need for a constant current source. It has a built-in driver, which accepts 230VAC mains. Refer to the data sheet, which can be found via the link you've posted above.

author: Patrick66
author_rank: Regular Contributor
timestamp: March 15, 2024, 12:19:45 am
content: Ohh I get it. Thanks
How to obtain the specific component in LTspice ?  - Page 1
Forum section: electronics / projects

author: Patrick66
author_rank: Regular Contributor
timestamp: February 24, 2024, 09:49:35 am
content: Hello everyone, I would like to ask how do I obtain the components of U1, U6, U9, 7U, 8U in the schematic below? The link to the video ishttps://www.youtube.com/watch?v=9e9URouotjA.Hope to hear from you guys soon. Thank you everyone.

author: RoGeorge
author_rank: Super Contributor
timestamp: February 24, 2024, 10:58:13 am
content: Usually, when one is using non-default LTspice libraries or symbols, those should be posted together with the .asc file in a reproducible manner, e.g. all together in a zip file.Asking users to jump through extra hoops to visit sites and download libraries by name only and no specific file link might be a big deterrent (this observation is for the video author, he just answered your libs question couple of minutes ago in the YT comments).

author: Patrick66
author_rank: Regular Contributor
timestamp: February 24, 2024, 11:04:06 am
content: Hello Sir, yea I just received the reply from the user. Thank you so much for the reply Sir appreciate it.

author: Zero999
author_rank: Super Contributor
timestamp: February 24, 2024, 02:31:17 pm
content: It does annoy me that LTSpice doesn't have a way of embedding symbols in the .asc file. Its easy to include models, as part of the asc file by opening the model in a text editor, copying it and pasting it into a SPICE directive.The trouble with posting zip files is they could contain anything and many are cautious of downloading them from unknown sources.
How to Open Tektronix T202 or Createc SC 01 - Page 1
Forum section: electronics / projects

author: oz2cpu
author_rank: Frequent Contributor
timestamp: August 14, 2024, 08:00:05 am
content: The impossible task ??no one seem to reveal this ?I find a few videos about this unit, for example eevblog 1291 but dave fail to open it ??I want to open it, inspect, change caps, and put it together without causing permanent damage to plastics or the look of it,
How to Pick a Current Sensor - Page 1
Forum section: electronics / projects

author: LoveLaika
author_rank: Frequent Contributor
timestamp: May 18, 2020, 07:28:00 pm
content: I've previously posted on here that I'm working on a circuit to output positive and negative voltages with the LM2673 Buck Regulator, and a problem I'm facing is that I'm trying to measure the output current coming from each regulator. Initially, I thought of putting a sense resistor in place with my output loads and measuring the voltage across it, but I'm running into issues with that, mainly in incorporating it such that the feedback loop of my regulators so the output voltage won't be affected.I've been thinking that my approach is totally wrong. So, I was looking into different methods of measuring current, which is when I stumbled upon current sensors, ICs that seem to be able to measure current when placed in series without disturbing the regulator. I never worked with such ICs before, so I wanted to get some advice on how to pick a current sensor that will fit my needs. What parameters are important in a current sensor, and what are some good current sensors that are inexpensive and easy to use?https://www.digikey.com/products/en/sensors-transducers/current-sensors/525
How to pick a good quality fan? - Page 1
Forum section: electronics / projects

author: zapta
author_rank: Super Contributor
timestamp: November 18, 2014, 06:43:08 pm
content: My 3D printer arrived with a 40mm square 12V fan that started to make funny noises after two weeks of use. I am looking at Digikey for a better quality fan but am not sure which manufacturer and bearing type to chose. Any suggestion?Here is Digiky link that narrows the search, hopefully it will work for youhttp://www.digikey.com/product-search/en?pv46=21184&pv46=5316&pv46=5330&FV=fff40012%2Cfff80052%2C38007e%2Cb814c4%2Cb814c5%2Cb814cc%2Cb814ce%2Cb814d2%2Cb852c0%2Cb85882%2Cb85883%2Cb85884%2C9340010%2Cc580009&k=fan&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

author: Arlen moulton
author_rank: Regular Contributor
timestamp: November 18, 2014, 06:53:07 pm
content: Any bearing will be fine but get a brush less one

author: Fsck
author_rank: Super Contributor
timestamp: November 18, 2014, 06:55:27 pm
content: avoid sleeves unless you mount the motor axis parallel to the earth.

author: extide
author_rank: Regular Contributor
timestamp: November 18, 2014, 08:20:49 pm
content: Dual ball bearing are the best in terms of long-lasting but they do tend to have a bit more bearing noise. I pretty much always pick dual ball bearing fans, but I am pretty much not sensitive to fan noise at all. Honestly, you might want to check out some web sites like frozenpc.com or performance-pcs.com as they have very large selections of fans, however they will not have the best prices.

author: wraper
author_rank: Unknown
timestamp: November 18, 2014, 08:39:51 pm
content: Any decent brand fan with ball bearings will do. As this is 3D printer, fan noise shouldn't be an issue. Sunon Maglev series will do the job fine too, life is comparable (Edit: actually a bit higher according to what sunon says in their documents) to ball bearings and can be mounted under angle without issues.
How to power on the board RockPro RK399 using the TNTOR 10.000mh power bank. - Page 1
Forum section: electronics / projects

author: ziomario
author_rank: Contributor
timestamp: January 22, 2025, 09:39:59 pm
content: Hello.I've bought the TNTOR 10000mAh power bank to power on my DIY tablet. It has 3 ports :https://ibb.co/3FV5jnYBelow you can see the soc that I want to power using the power bank :https://ibb.co/JmLPSQXThe board is the RockPro RK399. It should be powered through 12V / 3A as you can see below (you can find the full specs of the board here :https://wiki.pine64.org/wiki/ROCKPro64https://ibb.co/LrJDHQ8What I don't understand is what cable should I use to connect the barrell connector of the board (that requires 12V / 3A minimum) to the powerbank ? And to what USB port should I connect it ? USB A / USB C or Micro USB ? As you can see all these 3 ports are 5V / 2A max input,while the board needs 12V / 3A minimum ; are these voltages compatible ? Can you point me to the right products (cable and / or converter) that I should buy to be able to turn on the board using that power bank ? thanks.
How to prevent auto cut off  due to low load current below I autooff  limit  - Page 1
Forum section: electronics / projects

author: getfast_kiran
author_rank: Regular Contributor
timestamp: December 12, 2018, 09:28:01 am
content: IC in use : HT4936SI would like to know if there are any standard ways to make sure the IC we are using stays in operation even at low load. In this case HT4936S has autooff when the output current is less than 50mA. I tried putting a white led across the output of 5V at USB out to make sure along with my load of 14mA the current from LED of 11mA will make the IC turn ON continously and stay away from auto cut off. But after sometime the led burns out. So I found that a total of 25mA was enough to keep it ON continously. Hence I put a resistor in series such that 3.3V/25mA = 132ohm. in series to make sure the LED is not burning out. But now the IC is turning off due to low load.I would like to get help regarding methods to make sure the minimum load current limit is met to make it continously operational.

author: getfast_kiran
author_rank: Regular Contributor
timestamp: December 12, 2018, 10:40:48 am
content: Can anyone give suggestions. Especially if you have experience in boost circuit which requires a minimum load or a regulator which requires a minimum load to function.
How to prevent accu power banks from turning off on devices with low current? - Page 1
Forum section: electronics / projects

author: Rodast
author_rank: Contributor
timestamp: July 17, 2014, 07:33:16 pm
content: Hello All,I have several power banks and use them with a lot of different devices.All of the ones I own from Anker and EasyAcc power off automatically when a connected device is fully charged and also when a connected device does not draw enough current.This means I cannot charge my bluetooth headset or gps navigation system on the go and also can't power a bluetooth speaker I own.With the larger power banks I found a workaround by plugging an usb stick into one of the additional ports.Unfortunatly this does not work with power banks that only have one outlet.I have a short USB extension cable lying around here which I could take apart and wonder if I could tune and use it for those devices that only draw less than 50mA when they are connected.An idea how to do this without altering the voltage delivered by the power bank and without draining too much battery life over time?Best regardsRodast

author: Mr Smiley
author_rank: Frequent Contributor
timestamp: July 17, 2014, 08:43:30 pm
content: What is the minimum load that prevents the unit from switching off

author: Rodast
author_rank: Contributor
timestamp: July 17, 2014, 09:42:24 pm
content: It was a bit hidden in my previous text :-)As the devices shut down with a load smaller than 50mA I have to get it above that.So to be on the safe side create a 50mA load would keep the power packs from switching off as soon as I connect the device I want to use.

author: kingofkya
author_rank: Regular Contributor
timestamp: July 17, 2014, 10:45:21 pm
content: I remember something a while back i think adafruit but i don't remember where they had a micro periodically trigger a fet with a resistor to short the supply to get it register that a device is connected.The other option at lest on the one i have is to tape the power button down:)

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 18, 2014, 12:40:37 am
content: Large cap (1000uF or so), P channel MOSFET, and low frequency oscillator. Connect the large cap across the load, then have the MOSFET switching power such that the internal diode would conduct when the MOSFET is off. Have the oscillator switch the MOSFET off for half a second or so every 30 seconds or so. Very little extra power use.

author: HKJ
author_rank: Super Contributor
timestamp: July 18, 2014, 06:15:00 am
content: Quote from: Rodast on July 17, 2014, 07:33:16 pmGet one that does not power off at low load, you can always checkhttp://www.lygte-info.dk/info/indexUSB%20UK.htmlfor technical reviews, where this kind of information is present.
How to prevent voltage at output of TPS54302 to feed circuit input? - Page 1
Forum section: electronics / projects

author: evansg
author_rank: Contributor
timestamp: October 31, 2019, 10:21:20 pm
content: I need your help guys,I have designed the circuit below with the TPS54302 regulator.What happens is that if someone accidentally applies voltage to the output (Let's say 12V) the input receives the same 12V and provides voltage to any other component in the 12V input line.I have seen cases that a user accidentally plugs the 12V (circular 2.1mm socket) into the regulator output (which has same 2.1mm socket). I want to keep the 2.1mm circular socket so replacing the output socket with another type is not an option.What is the best way to prevent this? Maybe by using a n type mosfet at the output? Any better solution?

author: thm_w
author_rank: Super Contributor
timestamp: October 31, 2019, 10:55:40 pm
content: Sorry but thats just a bad design if the input and output are using the same connector.You didn't specify what sort of current, but it doesn't look to high, so a schottky diode on the input or output would be an option. On input you'd need to figure out if switcher is damaged at all when backfed, if output you may need to adjust the voltage up a bit from 8V.

author: evansg
author_rank: Contributor
timestamp: November 01, 2019, 08:59:47 am
content: Seems that It does not harm the switcher. Output is 2Amps at max. I am trying to place a reverse n-mosfet at the 8V output but still experimenting with that.
How to properly tie the shutdown pin of the AD8232 - Page 1
Forum section: electronics / projects

author: MildInductor
author_rank: Regular Contributor
timestamp: June 28, 2024, 05:46:25 am
content: Hello, I am looking at the DF Robot schematic for their AD8232 board. I see that they have tied the shutdown pin to 3V3 through a 10K resistor. I am wondering why they have used a pull-up resistor? Could the shutdown pin just be connected to 3V3 directly? The datasheet for the AD8232 makes no mention of whether a pull-up should be used or not.

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 28, 2024, 06:24:54 am
content: Quote from: MildInductor on June 28, 2024, 05:46:25 amYesQuote from: MildInductor on June 28, 2024, 05:46:25 amThere are several reason pulling up/down with resistor instead of direct connection are preferred (technical need when there's voltage mismatch aside). Most of the time it is so that the signal can be overridden with other logic signal if needed, the pull up/down resistor here serve to establish a "default" state when there are no external signal present. Other common reason is putting both up and down resistor footprint and only populating one as a means of hardware configuration.Although sometimes it's just habit/superstition. Some people aren't comfortable connecting signals directly to low impedance supply nodes.

author: MildInductor
author_rank: Regular Contributor
timestamp: June 28, 2024, 07:21:29 am
content: I see, that clears things up. So by the sound of it the resistor is unnecessary, but not harmful.
How to properly voltage divide a differential signal ? - Page 1
Forum section: electronics / projects

author: drakejest
author_rank: Regular Contributor
timestamp: January 16, 2021, 05:41:13 pm
content: How to properly voltage divide a differential voltage or an AC voltage?Im confused which one is betterwhich one is better? Why is config B connected to ADC ground?

author: drussell
author_rank: Super Contributor
timestamp: January 16, 2021, 05:50:06 pm
content: Quote from: drakejest on January 16, 2021, 05:41:13 pmWow, you really bungled your image attachment...I think you probably meant to do this:... by inserting this, the image link to the .png instead of trying to link a webpage:Code:https://i.imgur.com/y90q2EI.png

author: drakejest
author_rank: Regular Contributor
timestamp: January 16, 2021, 06:53:20 pm
content: Quote from: drussell on January 16, 2021, 05:50:06 pmHaha although unrelated it is nice to know thanks sir,

author: bson
author_rank: Unknown
timestamp: January 16, 2021, 07:27:26 pm
content: B is for sampling a bridged output, and will cause the two inputs to have the same magnitude, centered around ground. If there is a common ground connection between the source and the ADC it might not be able to reference both to ground, so for this to work best you'd want a balun or AC coupling for ground isolation. It'll still work without but you might lose a part of the full scale. Consider for example if P=5V,N=0V then P=0V,N=5V the next half cycle relative to ADC ground. You get half the scale and hence half the resolution compared to if the peak amplitudes are P=+2.5V,N=-2.5V and P=-2.5V,N=+2.5V. In the latter case you can either handle twice the signal amplitude, or use twice the gain setting on the ADC.A (which might need a resistor on the N lead for load balance) is if all you want is to attenuate the voltage of a bridged signal.

author: drakejest
author_rank: Regular Contributor
timestamp: January 16, 2021, 07:45:15 pm
content: Quote from: bson on January 16, 2021, 07:27:26 pmI do not understand what you said with B sir, so lets say the signal was from a signal generator that produces 5v p-p (P=2.5v, N=5) sine wave, with config B the ADC would read 5v=P and 5v=N ?? I think im missing something hereQuote from: bson on January 16, 2021, 07:27:26 pmwhat would be the value of the resistor for the N lead if assuming we still want the voltage to be halfed,Also is a transformer a bridged signal ? bridge signal refers to two identical signal but the other is flipped. Wouldnt that have problems if the signal is not perfect?
How to prototype thing without CNC, 3D printer & similar? - Page 1
Forum section: electronics / projects

author: brainwash
author_rank: Frequent Contributor
timestamp: September 26, 2013, 04:01:50 pm
content: I'm having a hard time keeping myself away from a hobby 3D printer or CNC machine. I'm sure that before all this existed at affordable prices people were doing things manually, I just don't know how.Cutting by hand is a tedious job, both with acrylic and light wood planks. "Sculpting" or other substractive processes seem to require a lot of dexterity and specialized tools.So how do people do it? I saw on the Ben Heck show a build (rPI case) using only hand tools and figure out there must be some other options.I'm looking for ways to build:- motor reductions (scavenge gears from toys?)- waterproof cases for small projects (short of the option of getting generic boxes and drilling holes for buttons and such)- motorized frames for moving stuff around like venetian blinds, camera dolly, etcI know also of the option of using plastic piping found from the hardware store and plastic cement. That's cool for building guitar and keyboard stands and lightweight "furniture". The concept of using manufactured PCBs as project boxes or faceplates is also nice.I would love to see some stuff you created using out-of-the box thinking.Either way, it seems that 3D printers are going mainstream very soon, especially with the Makibox pricing.

author: mianchen
author_rank: Regular Contributor
timestamp: September 26, 2013, 06:26:48 pm
content: QuotePrinters are great donors for gears cogwheel metal sticks springs and whatnot. Of course some electronic parts too.
[SOLVED] How to provide multiple ranges for current monitoring... - Page 1
Forum section: electronics / projects

author: prasimix
author_rank: Unknown
timestamp: February 04, 2017, 09:11:03 am
content: I'm opening a new topic with a question startedhereand apologize if such duplication makes any trouble to anyone (and hope that Kleinstein, Strada916, Kean and others will follows up). Just in short: I'd like to introduce multiple ranges (two for the beginning will be just fine: 0-500 mA and 0-5 A) for current monitoring that can be used in power supply for control loop and measurement.It started with an idea that each shunt has it's own low Rds(on) mosfet in a series as to switch from one range to another in a "make-before-break" fashion. Mosfets will be highly saturated to provide the lowest specified Rds(on) and yes, that mean that Rds(on) has to be added into account for measurement. That should be a problem if calibration is accomplished and that Rds(on) doesn't vary a lot with current and temperature. I don't talk here about "reference instrument" that has to be very accurate, but rather something that can be used in DIYers/hobbyist bench top.Many thanks in advance for your timely response.

author: jaromir
author_rank: Unknown
timestamp: February 04, 2017, 09:15:56 am
content: Perhaps you can find some answers in one of Dave's videosespecially in the second half of the video, but watching it all can't hurt.

author: eblc1388
author_rank: Frequent Contributor
timestamp: February 04, 2017, 11:05:40 am
content: Place the two shunts in series, and use just one MOSFET to "bypass" the higher resistance one when changing to 0~5A range.Obviously you have to also switch the voltage drop across the range but with just three wires going to the shunts, you'll need to switch between two wires only, while the remaining one being the common which needs no switching.Note: the Rds of the MOSFET does not contribute to any of the shunt voltage drop
How to read a pulse out with an ADC? - Page 1
Forum section: electronics / projects

author: Gibson486
author_rank: Frequent Contributor
timestamp: April 19, 2023, 09:13:57 pm
content: How does one read a pulsed output with an ADC? Since most SPI ADCs capture on the finished transfer and the pulled up chip select, that would mean I would need to have the pulse be generated while I am doing a fake read and then time the next read and transfer correctly. I guess I could make a sample and hold circuit, but i would still need to generate a pulse during a fake read to ensure it reads what I want it to read. Do they make SPI ADCs that capture on the chips elect? I am guessing no, but i guess it was worth a shot

author: tszaboo
author_rank: Super Contributor
timestamp: April 19, 2023, 09:27:22 pm
content: If you use fast SAR ADCs, then they start conversion typically on a start signal, and not on a command.Depending on how long your signal is go for a few hundred ksps to a few msps ADC, get upset by it's price, redesign it to not use this method to capture the signal, figure out it doesn't work, buy the ADC anyway, realize it needs to be driven correctly, and so on and so on.

author: dobsonr741
author_rank: Frequent Contributor
timestamp: April 19, 2023, 09:56:38 pm
content: Let me rephrase your question:So you need a trigger signal to start data acquisition on an ADC, and measure parameters of a signal beginning with the trigger condition. Parameters can be a width of an impulse, perhaps the amplitude too.Does it sound right?

author: hubi
author_rank: Regular Contributor
timestamp: April 22, 2023, 05:59:13 pm
content: I have a project using an ADS8586S that captures the data on a pulse to dedicated conversion start pins (CONVSTA/CONVSTB). The chip signals the completion of the conversion through a BUSY pin and you can read out the data via SPI after BUSY goes low. Not sure if this particular device is fast enough for your signals or if the phase delay from the built-in low-pass filter might be too high for your timing requirements, but it works really well for my relatively slow application. There are four and eight channel versions of the same device (ADS8584S/ADS8588S).

author: BadeBhaiya
author_rank: Regular Contributor
timestamp: April 23, 2023, 08:35:55 am
content: How about using a peak detector to "store" the pulse and read it at your leisure? Of course that would not work if the timing characteristics of the pulse are important.
How to read memory timing specs? - Page 1
Forum section: electronics / projects

author: technix
author_rank: Super Contributor
timestamp: December 31, 2017, 07:46:50 pm
content: I got very confused at the memory timing specs and how to apply it to the processor's memory controller. Any help?To be specific, I am trying to tighten the timing as much as possible on STM32F417ZG FSMC and IS61WV51216BLL-55TLI. The STM32 chip is running at 168MHz. All the Chinese demo code I saw uses the default timings on the controller, which works but is not optimized since it wastes cycles. I want to tighten it up as much as possible. This is even more important on one of my dev boards as that one is populated with a IS61LV51216-10TLI which is a 10ns SRAM instead of a 50ns one, and I definitely need to squeeze the timing as much as possible to extract its full performance.
how to read multiple thumbwheel switches - Page 1
Forum section: electronics / projects

author: Brathahn
author_rank: Contributor
timestamp: September 10, 2022, 01:10:18 am
content: Hi,i have some thumbwheel switches that i want to read with a microcontroller.the switches however are in an analog configuration at the moment. i cant use an adc in my application so i have to read them digitally.here is a schematic of the switch:reading one of these switches can be done with 5 IO's and the charliplexing method.The question now is: how can i read multiple switches like 4 of them without having to use 20 IO's? is there a clever way to connect them so i dont need that many IO's?

author: ledtester
author_rank: Super Contributor
timestamp: September 10, 2022, 01:19:56 am
content: Presumably only one of the switches will be closed at any one time.You can turn a resistance into a time by seeing how long it takes to charge up a capacitor to a logic 1 voltage:Code:P1 --/\/\/-- P2 --||-- GNDP1 and P2 are GPIO pins. First discharge the cap by setting to P1 to an input and P2 to LOW. (Or set both P1 and P2 to a logic LOW.) Then set P1 to a HIGH output and P2 to an input and time how long it takes for P2 to become a logic high.P1 can be shared among all of the thumbwheels so you'll only need 5 GPIO pins for four thumbwheel switches.

author: Warpspeed
author_rank: Contributor
timestamp: September 10, 2022, 04:11:51 am
content: Why an analog solution ?Just load the whole lot into a great long shift register, and shuffle it into PIO or serial port.You could do eight digits (32 bits) with only maybe three pins on the controller.

author: Buriedcode
author_rank: Super Contributor
timestamp: September 12, 2022, 06:03:18 pm
content: Quote from: Warpspeed on September 10, 2022, 04:11:51 amI'm not sure how that would work given theres only two temrinals. Unless you mean modify all the switches, remove the resistors and add breakout wires ?

author: langwadt
author_rank: Super Contributor
timestamp: September 12, 2022, 06:47:28 pm
content: Quote from: ledtester on September 10, 2022, 01:19:56 amyou can do it with four pins. Vcc through resistance to cap, cap to open collector output (or switch between output and input), pull low to reset, time how long it takes to go high

author: coromonadalix
author_rank: Super Contributor
timestamp: September 12, 2022, 07:27:39 pm
content: arduino librairies ... there are some projects with this kind of setupsome hintshttps://create.arduino.cc/projecthub/ronbentley1/a-switch-library-for-arduino-esp-32-microcontrollers-dfbe40otherhttps://create.arduino.cc/projecthub/ronbentley1/multiple-switches-one-interrupt-75f2f7https://docs.arduino.cc/built-in-examples/digital/Button
How to read SMD part numbers? - Page 1
Forum section: electronics / projects

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: May 06, 2015, 07:01:46 pm
content: Hello everyone. Since my motherboard's last... incident, I found someone with the same board, but I do not know how to find a replacement part. Here are the details I got:"parsec wrote:OMGosh, a photo of that part would require a macro lens on a digital SLR camera.Using a high power magnifying glass and two lights I was able to see the markings, clearly after several attempts. It is:LNW 22The 22 is rotated 90 degrees counter clockwise relative to the LNW. This part is labeled D8 on the board, so apparently is a diode.You'll need better luck than I had reading that part, trying to replace it IMO. You must have experience with surface mount devices as well as the tools to work with them.Good luck with this project!"So how does one identify the part name "LNW 22"? I did a google search for it and got nothing. We both thought it was a diode, but other parts on the board (LNW 24) appear to have a "qxx" designator.so what do I do? Where can I find a replacement? What is it?

author: orbiter
author_rank: Frequent Contributor
timestamp: May 06, 2015, 08:00:09 pm
content: According to s-manuals below LNW relates to an N-Channel Mosfet. I'm not exactly sure of what the smaller numbers relate to but I think I remembersomeone mentioning that it maybe a manufacture production code, or week number etc.When I'm stuck for an SMD number my first ports of call are to the two sites below... If nothing shows up there then I'll start the sometimes laborious process of Googlingfor part numbers & pictures etc in the hope of narrowing it down.http://www.s-manuals.com/smdhttp://www.s-manuals.com/smd

author: tautech
author_rank: Super Contributor
timestamp: May 06, 2015, 08:17:28 pm
content: A VERY important parameter to identifing SMD parts is the package.DO-xxx?, TO-xxx? SOIC-xxx? and so on.Include it in a Google search and inspect all the likely results."LNW marking DO-xx diode SMD data pdf" is how I go looking.Sometimes markings identify a particular model in a range and matches are not always obvious.
How to reduce input noise at Differential Op amp - Page 1
Forum section: electronics / projects

author: rudika79
author_rank: Regular Contributor
timestamp: August 17, 2015, 03:28:40 pm
content: I have one differential op amp amplifier and I have trouble with input. On input I have approximately 200mV noise. How Can I remove noise or how can I reduce? I try to solder 100nF decoupling capacitor between the input pin and ground.Thanks,Rudolf

author: Cerebus
author_rank: Super Contributor
timestamp: August 17, 2015, 05:18:15 pm
content: We need a bit more information before we can really help. What, exactly, is the circuit? What's the signal source? What kind of noise? Gaussian (white) noise or high or low frequency interference (frequency relative to the signal of interest)?By the way, tying an input to ground with a capacitor is not usually the best way to bypass HF noise on a DIFFERENTIAL input. Instead connect the capacitor between the inverting and non-inverting inputs - that'll make inputs at HF appear as common mode signals and they'll be cancelled by the differencing action of the amp. Sometimes you'll need capacitors to ground as well but the differential connection is usually the place to start. If you do connect capacitors to ground you need to bypass BOTH inverting and non-inverting inputs.