hybridfree/eevblog-posts huggingface dataset:
potentiometer tweaking for the Daves CC dummy load - Page 1
Forum section: electronics / beginners

author: lk
author_rank: Regular Contributor
timestamp: June 02, 2012, 06:04:18 pm
content: Greetings,i was wondering if it would make sense to offset the potentiometer, so that turns are not wasted, while turning the potentiometer in the range that will not set the voltage high enough to drive the fet gate. In my head at least with a potentiometer on a 5 volt v+ and the fet does not turn on until 2 volts, gives 4 wasted turns, on a 10 turn potentiometer.I have included a schematic drawn in yenka, that shows what i had in mind, but i don't know if its the optimal way to do it. I plan on using the same mtp3055 as used in eevblog #102Is this the right approach or is there some other way, or should i just not worry about it?-lk

author: icon
author_rank: Regular Contributor
timestamp: June 02, 2012, 10:04:30 pm
content: HiI think you're misunderstanding what the pot is doing. It doesn't directly provide the gate voltage; the op amp does that, because the MOSFET is inside the feedback loop. On my example, the op amp output sits at about 3.5V when the current is zero, which I assume is the gate voltage at which my MOSFET starts conducting. As soon as the pot starts to turn, the op amp output voltage starts to rise and current starts to flow.Build it on a bread board and measure voltages around the circuit - I found that very illuminating when I built mine! I also discovered interesting things about op amp stability and oscillation, but that's another thread.John

author: lk
author_rank: Regular Contributor
timestamp: June 03, 2012, 02:55:49 am
content: Thank you,i build it again with a different opamp, and now i see reaction for the entire range of the potentiometer, that was not the case before, it would only start doing anything when i had it turned most of the way up.-lk

author: electroguy
author_rank: Regular Contributor
timestamp: June 05, 2012, 01:46:16 am
content: Ikyes you can, but as icon said, you aren't directly driving the fet gate, the op amp does that. The voltage range you are modifying with the pot, is the voltage drop across your sense resistor, and the op amp does the rest to make it match.So, in the diagram you have drawn, you can use the top resistor as a "maximum current limit setting" if you like, so that even if you wind the pot all the way up, you don't burn your load out or burn the sense resistor. And likewise for the bottom resistor, make sure you make it small enough so you can turn the load down to your minimum required load.
Potentiometer Value Question (resistor across pins 1-3) - Page 1
Forum section: electronics / beginners

author: belzrebuth
author_rank: Frequent Contributor
timestamp: October 15, 2018, 11:35:49 am
content: Hi,I've got a project that requires a 250kA 9mm potentiometer but I haven't got any in stock and from what I've seen it's not an easy value to get anyways..Is it okay to use a 500kA with a 500k resistor across legs 1-3?Is the logarithmic curve going to be affected somehow?I guess not but thought I'd ask...

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2018, 11:57:00 am
content: Putting a resistor in parallel across a linear pot is a common way of approximating a logarithmic pot. So yes, I would expect the curve to be further affected, though this may or may not be bad in practice.

author: belzrebuth
author_rank: Frequent Contributor
timestamp: October 15, 2018, 01:20:35 pm
content: So the best way to approximate a 250kA pot would be putting a 500k resistor in parallel to a 500kBpot?!

author: drussell
author_rank: Super Contributor
timestamp: October 15, 2018, 02:29:03 pm
content: Approximating a log pot would be putting an additional resistor from thewiperto one of the ends, not across the whole pot.Whether going across the entire pot to lower the effective total resistance may work well or may work poorly depends on how it is being used in the circuit, the reason why it "needs" to be a certain value and the power level involved. If it just a simple voltage divider to a high impedance input, for example, any value from about 1K to 1M will essentially produce the same result, even without any additional resistors, though the power dissipated by the divider itself will obviously increase as the resistance is lowered. This could easily be an issue in a battery powered circuit, for example. Pitfalls abound!If you shared more specific details about your project, perhaps with a schematic, we can provide more specific answers.

author: tooki
author_rank: Super Contributor
timestamp: October 15, 2018, 02:33:00 pm
content: Quote from: drussell on October 15, 2018, 02:29:03 pmOh, thanks for the clarification! I remembered wrong, I just read about it a while ago and saved a link!

author: belzrebuth
author_rank: Frequent Contributor
timestamp: October 15, 2018, 04:31:01 pm
content: Here is the schematic of the project:http://www.timorozendal.com/files/ianfritz_2xadar_schematic.pdfThe circuit is an envelope generator for controlling a VCA.
potentiometer voltage limit - Page 1
Forum section: electronics / beginners

author: ascot
author_rank: Contributor
timestamp: August 11, 2020, 02:55:04 pm
content: is there a limit on how much voltage you can put through a pot if so how do i calculate it

author: tooki
author_rank: Super Contributor
timestamp: August 11, 2020, 02:59:19 pm
content: It’s not something you calculate. You look it up in the datasheet.

author: TimFox
author_rank: Super Contributor
timestamp: August 11, 2020, 03:00:15 pm
content: The maximum voltageacrossa potentiometer is normally limited by the power rating of the potentiometer, which should be quoted. A 1.0k, 1/2W unit would be limited to 22 V, preferably derated to less than 15 V for a 2:1 power safety factor.Where things get tricky is if you are using it as a variable resistor, where the power for a given voltage varies with the change in resistance.By definition, a potentiometer is used as a voltage divider, but there may be current passing through the wiper.

author: ascot
author_rank: Contributor
timestamp: August 11, 2020, 03:09:05 pm
content: problem with data sheets is coming from amazon they tend to have very little info

author: tooki
author_rank: Super Contributor
timestamp: August 11, 2020, 03:12:41 pm
content: Well, it’s not wise to use no-name components for anything involving higher voltages.If amazon has a part number, google it with “datasheet”.But also consider moving away from Amazon for electronic components — they tend to not be especially good prices.

author: ascot
author_rank: Contributor
timestamp: August 11, 2020, 03:17:09 pm
content: would tend to agree having seen one go up in smoke only advantage with amazon is i can pick delivery day
potentiometer with solder blob - Page 1
Forum section: electronics / beginners

author: hammy
author_rank: Unknown
timestamp: May 10, 2016, 03:45:03 pm
content: Why do musicians connect a ground wire to the case of a potentiometer with a big solder blob?Any reasons? Why is the ground pin not used? What is the benefit?Cheershammy

author: Grzegorz2121
author_rank: Contributor
timestamp: May 10, 2016, 03:52:03 pm
content: Where you have ground pin on the potentiometer?Potentiometer have 3 pins- two connected to sides of the resistor and one to slide on the resistor to vary the resistance of this pin.I think that musicians connects case of these (because is not connected to anything) to shield signals in potentiometers from noise.

author: Audioguru
author_rank: Super Contributor
timestamp: May 10, 2016, 03:55:07 pm
content: Pots usually do not have the case connect to one of its pins then its case can pickup mains hum that is all around us. If you connect its case to the circuit ground then it shields the pot terminals.

author: Coulombic_Irrigation
author_rank: Newbie
timestamp: May 10, 2016, 04:56:21 pm
content: You need somewhere to connect a bunch of ground wires to and the back of a pot provides a decent amount of area to work with. There is no reason why you have to do it that way, but it's standard practice because it's so convenient.

author: hammy
author_rank: Unknown
timestamp: May 10, 2016, 06:33:41 pm
content: You are correct Grzegorz2121. There is no dedicated ground pin.I had a quck check with all metal potentiometer I found . The case is not connected to any pin.I see, this makes sense: To prevent hum you ground the case.Thanks for refreshing the basics.

author: SeanB
author_rank: Super Contributor
timestamp: May 10, 2016, 07:10:28 pm
content: Do not forget that that nice big heat sucking metal case is generally right next to a lovely low melting point plastic wiper, so soldering on a few wires to the case might just make your pot a Dali-esque object. Instead use a solder lug under the mounting nut, it generally is also connected via the alloy casing to the back metal shield.

author: Cerebus
author_rank: Super Contributor
timestamp: May 10, 2016, 08:59:27 pm
content: Quote from: Audioguru on May 10, 2016, 03:55:07 pmAnd also for simple safety. If the case is grounded then any metal parts of the pot that might be touched are at ground potential. It isn't unknown for live mains to make it's way onto signal lines on stage equipment especially with old valve amps that get chucked into the back of a van each night. It's lead to some well known and well documented deaths.

author: rstofer
author_rank: Super Contributor
timestamp: May 10, 2016, 09:58:36 pm
content: Quote from: Cerebus on May 10, 2016, 08:59:27 pmRight! In theory, all non-current-carrying metallic parts are supposed to be grounded. Even though there may be a plastic knob, often the knob is missing and the metallic shaft and nut are exposed.
Potentionmeter Connection? - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: July 14, 2014, 04:59:35 am
content: Question, because I'm confused with the simulation program I am using.Does the wiper (pin 2) of a 3 terminal Potentiometer connect to positive (pin 1) or the ground (pin 3) to make it a variable resistor?Thanks in Advance,Jason

author: phil
author_rank: Regular Contributor
timestamp: July 14, 2014, 05:08:35 am
content: It doesn't matter, it works both ways. You can, however, select if you want the resistance to increase/decrease when you turn CW or CCW.Think of it as shorting out the part of the resistor that you don't want to use. The more you short out, the less the overall resistance. But it does not matter which part of the resistor you short. At least if you use linear pots.

author: Falcon69
author_rank: Super Contributor
timestamp: July 14, 2014, 05:19:53 am
content: that is what i had thought. there must be an error in my simulation program. It wont work if I connect thr wiper to the side that has a positive connection.thank you phil for clearing that up.

author: babysitter
author_rank: Frequent Contributor
timestamp: July 14, 2014, 06:09:21 am
content: Real Life advice: connect wiper to ground as it is closer to potential esd sources.(Full disclosure as that one-liner was made with mobile phone: Described in "Analog troubleshooting" by B. Pease.)

author: Falcon69
author_rank: Super Contributor
timestamp: July 14, 2014, 06:11:24 am
content: hmm, good idea. I will make that change. thank you.
Potted with glass? - Page 1
Forum section: electronics / beginners

author: baconsteak
author_rank: Contributor
timestamp: May 05, 2014, 01:36:56 am
content: Took apart a cdi the other day it was potted with some sort of rubber mixed with ground up glass. Anyone know why the glass? Its a high vibration environment (dirt bike).Thanks.

author: Lightages
author_rank: Unknown
timestamp: May 05, 2014, 01:39:28 am
content: I would hazard to guess they use whatever cheap industrial waste they can get their hands on for filler instead of using just the expensive potting material.

author: theatrus
author_rank: Frequent Contributor
timestamp: May 05, 2014, 02:28:21 am
content: You do see epoxy or plastics with glass filler material, but those are microspheres and not cheap.Have a picture?

author: sleemanj
author_rank: Super Contributor
timestamp: May 05, 2014, 03:12:37 am
content: Quote from: baconsteak on May 05, 2014, 01:36:56 amMy guess;http://upload.wikimedia.org/wikipedia/commons/1/1e/Thermal_conductivity.svg

author: baconsteak
author_rank: Contributor
timestamp: May 05, 2014, 04:22:43 am
content: Sorry no pic its at my mates. The glass was maybe 2-3mm in diameter. The thermal thing sounds plausible though. It had no heat sinking anywhere. I was gonna try changing the scr. Some nec part with no datasheet to be found on the net. Was a job just to get at big parts. The whole underside was covered with smd parts. Whatever glue they were using was good. Decided it wasn't worth it for $150.

author: SeanB
author_rank: Super Contributor
timestamp: May 05, 2014, 04:54:05 am
content: Glass microspheres, used as they are hollow and thus reduce the mass of filler needed and make the part lighter as well. Common in the fibreglass industry and in boat building to mix in with resin to make light but strong resin castings. Makes a much lower density composite which is still as strong and waterproof as the original resin. If they wanted to only bulk it up they would use ground glass, like that used in car body filler, as this makes it more bulky and allows it to be shaped afterwards by sanding and filing.
Power adapter that comes with purchase of FY6900 function generator - Page 1
Forum section: electronics / beginners

author: 3rj4
author_rank: Regular Contributor
timestamp: August 31, 2021, 01:37:17 am
content: I purchased the FY6900 function generator fromhttps://www.banggood.com/FY6900-Dual-Channel-DDS-Function-Arbitrary-Waveform-Signal-Generator-Pulse-Signal-Source-Frequency-Counter-Fully-Numerical-Control-20MHZ-or-60MHZ-p-1495502.html?cur_warehouse=CN&ID=53053147184. It came with the power plug and adapter in the attached images. I wanted to use this included adapter to plug it into my Australian outlet. However, after watching the beginning of thisYoutube video, it seems to me that the adapter the (Chinese) company provided is probably the same type of low-quality adapter with non-functional earth prong shown in the video. As mentioned in the video, it seems that this would be a safety risk – both to life and property. Should I purchase a higher quality adapter? Say, something with 3 prongs that includes an operational earth prong? If so, then would someone please recommend such a high-quality adapter? Or will it be ok/safe to use the provided adapter?

author: Jwillis
author_rank: Super Contributor
timestamp: August 31, 2021, 01:50:21 am
content: The one in the video looks different . Did you test the adapter to see if the ground works ? If the ground is functional then it should be fine .Personally I would be inclined to just change the power cord instead of fumbling around with adapters .

author: 3rj4
author_rank: Regular Contributor
timestamp: August 31, 2021, 02:15:49 am
content: Quote from: Jwillis on August 31, 2021, 01:50:21 amDo you mean test it with a multimeter? If so, then I have not; that's a bit beyond my current ability at the moment. It looks to me like it's the same design, and it's from China, which I'm guessing the one in the video is too. But then again, all such things are probably at least manufactured in China.With regards to changing the power cord, I'm a novice to electronics, so I definitely do not want to be messing with power cords at this point in time.
Power adaptor for battery charger compatability - Page 1
Forum section: electronics / beginners

author: 12strings
author_rank: Newbie
timestamp: March 03, 2019, 01:58:55 am
content: Hi there. I have a faulty power adaptor for a battery charger for a drill/driver, unfortunately the charger has been discontinued and I cant find that model for sale online. I have found a similar power adaptor online but I'm not sure if it will work and would appreciate your thoughts.The faulty power adaptor is as follows...Input: 100 - 240V AC 50-60Hz 13wOutput: 22V DC 400mAThe new adaptor is as followsInput: 100 - 240V AC 50-60Hz 25wOutput: 24V DC 1250mAThe adaptor plugs into a charger that charges a battery as follows...18V Lithium Ion 1500mAhI'm hoping this new adaptor would do the job.Cheers!

author: johnkenyon
author_rank: Regular Contributor
timestamp: March 05, 2019, 11:46:44 am
content: Quote from: 12strings on March 03, 2019, 01:58:55 amIt's the answer you don't want - "It depends"You need to find out what's inside the charger box itself, as the system you have will have used one of two designs:Method A:Use a power adaptor to generate low voltage DC, which then feeds a "smart" charger.Method B:Put the charge controller in the adaptor, and then the "charger" provides a physical interface.Another thing to bear in mind, is exactly what is your charger providing? Is it providing regulated 24v or will the output voltage rise under no load.Bear in mind that your proposed power supply is capable of supplying over 3 times the current. An unregulated power supply running at 1/3 load could have a higher that stated output voltage.
Power Amp Input Offset Voltage - Page 1
Forum section: electronics / beginners

author: Bronco Leonard
author_rank: Newbie
timestamp: December 24, 2016, 07:02:35 am
content: I'm building an ultrasonic varmint stay-away using a sine wave generator feeding a mid-sized, mid-quality auto power amp. My question is this: I've tried two different sig gen circuits and both make a nice sine wave, but they both have a DC offset of several volts. Will this bother the power amp, or would any reasonable amp have a dc filter built into it's input circuitry?If I have to block the dc myself, would a simple RC filter set to 500 hz do the job?Edit: I forgot to mention that I am using an old XR-2206 for signal generation. Does it have a built-in way to control the output offset voltage?

author: danadak
author_rank: Super Contributor
timestamp: December 24, 2016, 10:59:09 am
content: You have to check the specs of the Amp to see if its DC coupled.Most are not, but check.You can DC offset a signal, here is one method using 2 R's, and attached a calculatorto determine their values. Notde the zip file has other stuff in it as well for other prob-lems.https://www.dropbox.com/s/k1yn4m7heaixvmg/ADinput%20negative%20inputs.zip?dl=0Regards, Dana.
Power amp repair help - Page 1
Forum section: electronics / beginners

author: JHAnd
author_rank: Contributor
timestamp: January 29, 2024, 10:09:01 pm
content: I have a PA system from dbTech. It is the type that has a pre amp + power amp located in the subwoofer and you can connect two satellite speakers to the subwoofer through speakon cables to get a complete stereo system.Link to product:https://www.dbtechnologies.com/en/products/es/es-503/Problem is there is seems to be no output from the power amp, so the subwoofer and satellite speakers are not outputting any sound.The Line output seems to work fine. So I suspect something is wrong with the power amp section.What should I check first?Here are some pictures of the amphttps://imgur.com/a/w5DJAID

author: themadhippy
author_rank: Super Contributor
timestamp: January 29, 2024, 10:26:14 pm
content: as it claims to have 3 power amps id start looking at the power supply,of course that's after id double checked i hadn't muted output in some way

author: JHAnd
author_rank: Contributor
timestamp: January 29, 2024, 10:51:59 pm
content: Thanks for your suggestion,so the logic is that since there is no sound from either of the three amps it is likely the power section since that would effect all three power amps at the same time, is that correct?I have checked the settings menu and can’t find any mute or similar setting that would cut the signal.

author: CaptDon
author_rank: Super Contributor
timestamp: January 29, 2024, 10:56:35 pm
content: This post should be in the 'Repair' section.
power amp trys to turn on by its self? - Page 1
Forum section: electronics / beginners

author: p5200
author_rank: Contributor
timestamp: February 18, 2014, 01:22:21 am
content: I had to replace two op amps on the input board of my power amp after loaning it out and when I got it back it had a few roaches in it.I replaced the CD4013B chip which is used for the pulse when pushing the power on/off switch and checked all other components on that small board. The amp has a trigger switch on the back for manual, audio signal input turn on, or 12v turn on input. I was wondering if maybe, one of the components on the small trigger board may be causing the amp to try to turn on when in off/standby mode. I was guessing maybe the 4N32 chip might be causing this problem? The amp works fine when turned on otherwise. her is a schematic of the trigger board any advice would be greatly appreciated!
Power an Electric Scooter with an Fuel Generator? - Page 1
Forum section: electronics / beginners

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 07, 2021, 06:29:18 pm
content: Yes Guys (and Girls) its quite Impossible to find on the Countryside an 230V Power outlet to recharge your nice and loving Scooter. Sadly the will draw a lot of Power for such an Model.Sure when he arrive here I will try it out and when the Range is not that what I intend I think about a small Benzine Generator. The genuine Honda weight about 14kg who is not that ideal maybe I find some knock off who is lighter build. The main Question is how to drive the 2 Motors?The Charger need 66V and an common Generator offer a 230V and a 12V Source. So what is better convert up or down?THX!

author: TopGun
author_rank: Contributor
timestamp: May 08, 2021, 03:00:18 pm
content: So you want to strap a generator to the back of your electric scooter?Depending on the current draw of the motors, you can prolly get away with a beefy boost converter from 12-60V, but your efficiency will be quite bad.Have yu considered buying lithium poly cells and making a bigger battery pack?

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 08, 2021, 03:08:01 pm
content: QuoteYes but recharge them away from Home is still a Problem. The Company say even with the Quick Charger I need charge ~3h. Well I dont want to sit 3h in a (Supermarket) Parking Lot in the hell of nowhere when the Sun in burning down.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 08, 2021, 03:17:02 pm
content: Get a gas powered scooter! Save energy. If you insist I would try to bypass the battery. Power the scooter motor directly from the generator.

author: Ian.M
author_rank: Super Contributor
timestamp: May 08, 2021, 03:26:18 pm
content: From Wikipedia:QuoteIf the eScooter is capable of charging on the move from a combustion engine powered generator of under 50cc capacity, it would fall into the Moped category, otherwise it would be a Motorcycle. The fact that the transmission is electric would be irrelevant. Unfortunately that means it would require licensing, annual inspection, and would have to comply with all applicable standards for road vehicles.IMHO: get an eBike so you can at least pedal home if you are out of juice!

author: Monkeh
author_rank: Super Contributor
timestamp: May 08, 2021, 03:30:18 pm
content: Quote from: Lord of nothing on May 08, 2021, 03:08:01 pmWell then, I suggest you invest in a vehicle appropriate for your usage.
Power bank (batteries) and charging - Page 1
Forum section: electronics / beginners

author: dinatural
author_rank: Newbie
timestamp: March 18, 2015, 03:15:11 pm
content: Hello everyone, I'm a big fan of the videos but first time writing on the forums!I have a newbie question because I have no real knowledge of current. I bought some external USB battery pack from eBay for long hitchhikes or weekends in the woods. My friend says to always use an "outlet-usb thing" converter (the ones that come with your phone or you buy cheap) to charge it cause it has better amperage.I have read at lots of places on the net that those little converter boxes are usually very cheaply made and could even be "dangerous". So I always charge with a computer USB port, because those have been around forever and we have them already and I think the current in them is "better" than the converter boxes. I know it sounds weird but my brain could be broken.So who's right between my friend and I? An expert opinion would be greatly appreciatedThanks in advance

author: katzohki
author_rank: Frequent Contributor
timestamp: March 18, 2015, 03:52:08 pm
content: Your friend has a point, you get what you pay for, but you can still get really good USB chargers if you spend the money. Best advice is to look at some reviews and pay attention to the current rating of the charger / hub.Lightweight and batteries don't go hand in hand though. What kind of battery did you get and what are you using it for? Just curious as I too like to go hiking.

author: IanB
author_rank: Super Contributor
timestamp: March 18, 2015, 04:30:58 pm
content: Computer USB ports are normally limited to 0.5 A output current. For larger batteries this will slow down the charging rate.USB chargers that you plug into the wall may provide from 1.0 A to 2.5 A or more, so they can charge things faster.But it is true that many wall chargers are cheaply made and dangerous, especially if you get them from eBay from from the dollar store.However, buy a quality item from a reputable source and it should be OK.

author: AG6QR
author_rank: Frequent Contributor
timestamp: March 18, 2015, 08:24:56 pm
content: IanB is right (as usual). The advantage to a wall plug-in USB charger might be faster charging. That's only true if the wall plug-in USB charger supports a higher charge rate, and if the device you're charging can accept current at the higher rate. Furthermore, fast charging isn't necessarily better than slower charging. Obviously, fast charging is better if you don't have time to wait, but slower charging generally heats things up less and may be a bit gentler on the batteries.Generally speaking, we're talking about a slow rate of about 0.5A, and a fast rate of 1 to 2A. The difference is a factor of 2 or 4. Not huge, but definitely noticeable if you're standing around waiting for the charge to finish.If you're not in a big hurry, and if the computer would be switched on anyway, you're not doing any harm by using a computer.
Power Bank How it Work in details! Request ! - Page 1
Forum section: electronics / beginners

author: battery13v
author_rank: Contributor
timestamp: May 10, 2016, 02:36:40 am
content: Hi everyone, one day i found this power bank in the carbage so i took it and disassemble it ! it is the Y005A 4400mAh Power BankMy request : a total explanation of it's circuit and how it works cause it's from china and their is no datasheets !i want to know where is the buck converter, the boost converter, the microcontroller and it's role , the protection chips (if there is), what are the most essential parts in it like mosfets and etc ... So if you could ... a complete tutorial on how this thing work but in details not generally ... please !

author: Mechatrommer
author_rank: Super Contributor
timestamp: May 10, 2016, 03:48:41 am
content: look for the big inductor, thats where the boost buck is... power bank = charge circuit + supply circuit, thats all, the rest is complexity..

author: sleemanj
author_rank: Super Contributor
timestamp: May 10, 2016, 06:23:40 am
content: Right side of USB jacks is DW01 and 8205A combination for protection.Left side of USB jacks appears to be boost converter.Chip next to LED is probably charge controller, maybe TP4056 which is very common but I can't see the traces. Note that Mini USB has been torn off board and is underneat LED.Chip on back of USB board, dunno, maybe part of the boost converter, or could be for smart USB power negotiation.Large chip on the LED board, don't know, no idea, that's an awful lot of pins for something in a power bank, weird. Maybe LED does some fancy tricks.

author: RobertHolcombe
author_rank: Frequent Contributor
timestamp: May 10, 2016, 09:48:13 am
content: The four SMD LED act as a bar graph battery level indicator, so guessing the chip manages that
Power bank low-ish current - Page 1
Forum section: electronics / beginners

author: Moriambar
author_rank: Unknown
timestamp: June 15, 2023, 08:38:44 pm
content: Hi all,a friend of mine bought some powerbanks some time ago, advertised as 5V 2.1A.His problem was that they seem not able to sustain high currents. I don't know whether this is normal but here's what I've done:I disassembled the PB finding that its brain is theIP5306, whichshouldbe able to sustain around 2.1A of current.Then I attached my DC load with constant voltage 4.75V and what I get is that the current the bank sustains is ~220mA. This seemed weird, so I swapped the original battery for another li-ion I had in stock, which worked fine. The result is that the new battery could deliver, through the aforementioned circuit, around 280mA at 4.75V.So what I'm asking is: is this NORMAL behaviour, or has my friend been given a crappy powerbank?Thanks

author: Daixiwen
author_rank: Frequent Contributor
timestamp: June 19, 2023, 07:15:20 am
content: It could be bad soldering on one of the power lines (connector, controller, inductor) or a damaged controller.

author: radiolistener
author_rank: Super Contributor
timestamp: June 19, 2023, 07:19:21 am
content: It is possible that the current is limited with a cheap Chinese USB cableIf cable is ok, then this is limitation of a charger circuit or installed batteries.Also try to clean your cable connectors.

author: BrokenYugo
author_rank: Super Contributor
timestamp: June 19, 2023, 01:56:54 pm
content: Probably crappy powerbank, the chip might do 2.4 amps out (2.1 is how fast it can charge it's own battery), but will the support components picked by someone trying to spend as little as possible? The proper inductor, and filter cap(s) aren't the cheapest available, so there's room for error there. One of those things where you're really better off spending a little more on a real brand name between that and the potential for fire when cheap to a fault electronics meet lithium batteries. From my single data point Anker seems good, when I bought the one I have I tested it some (needed something reliable for a project) and it seemed to meet specs.
Power Bank. - Page 1
Forum section: electronics / beginners

author: Ranger14
author_rank: Regular Contributor
timestamp: March 15, 2016, 03:57:29 pm
content: I have been on the road alot lately with work and I have a nice stash of 18650 cells .. My plan was to make a 2 or more cell power bank with a single 2amp 5v usb in order my phone .. I have a couple power banks already but they can't handle a 2amp output.. But I am not sure whether to use a buck or boost converter ?? Also is it better for the cells to charge in circuit or use a battery holder and replace when dead and use the proper chargerThanks

author: tszaboo
author_rank: Super Contributor
timestamp: March 15, 2016, 04:01:24 pm
content: If you have to ask this, then my suggestion is to use some off the shelf boards which handle the batteries. Lithium batteries are violent, they have to be handled with proper knowledge and care.

author: Ranger14
author_rank: Regular Contributor
timestamp: March 15, 2016, 04:06:50 pm
content: Quote from: NANDBlog on March 15, 2016, 04:01:24 pmIt's not that I have to ask but working on hopefully better build instead of tying all batteries together and using a single Cell charging circuit to charge a whole pack like most companies do ..

author: michaeliv
author_rank: Frequent Contributor
timestamp: March 15, 2016, 05:20:09 pm
content: Apparently buck converters would be generally more efficient:http://www.eetimes.com/document.asp?doc_id=1273121But if you were to use multiple cells in series the major disadvantage is that you have to manage charge balancing if you're going to do your own charging.

author: The Soulman
author_rank: Super Contributor
timestamp: March 15, 2016, 09:15:48 pm
content: These things are nothing like regular batteries, the cell voltage shouldn't dropbelow 3.0 volts to avoid damage (better to stop discharging at 3.5 volts or so) and never charge higher then4.2 volts to avoid explosion and/or blazing fires (better no more then 4.1 volts for a bit better safety margin and a longer life)To be honest if you want simple go with something like these:http://www.aliexpress.com/item/5V-2A-Dual-USB-Output-4x-18650-Power-Bank-Batteries-Pack-Case-Holder-USB-External-Mobile/32425962052.html?spm=2114.01010208.3.1.HP9dVh&ws_ab_test=searchweb201556_2,searchweb201602_1_505_506_503_504_10034_10020_502_10001_10002_10017_10010_10005_10006_10011_10003_10021_10004_10022_10009_10008_10018_10019,searchweb201603_9&btsid=ca9a653f-128d-4cdb-b6b2-34c796a363b8Not a fan of the cheap Chinese stuff but hey you could always mod it yourself if you feel like it.Also note that before you parallel individual cells (that most if not all of these devices do)the individual cell voltages must be within a couple of millivolts of each other, other wise the "fuller" cellswill charge the "emptier" cells with high currents (could be tens of amps)..
Power bank/UPS with MOSFETs?! - Page 1
Forum section: electronics / beginners

author: MathCa
author_rank: Contributor
timestamp: February 28, 2023, 03:24:31 am
content: Hello,I bought 8 nice 21700 batteries (4000 mAh 35A) with 4 PD modules (up to 100w each, but more like 60w max for 3/4) to charge a laptop, use a soldering iron, etc. USB C is cool and it made a super fast charger!Now I want to put everything in one box that will stay connected to mains most of the time. If the electricity goes out for some reason, I want to automatically get power from the batteries instead of the power supply.I think you should be able to figure it out easily with this:(unable to get the image here, see the attachment...)I don't want to use relays, let alone physical switches!So I guess I have to use MOSFETs? But what type? Alone? I'm totally lost with this...Thanks!
power bricks outputting a higher voltage than specified - Page 1
Forum section: electronics / beginners

author: EvilGeniusSkis
author_rank: Regular Contributor
timestamp: October 28, 2013, 04:39:41 pm
content: As I don"t yet have a lab power supply, I have been using linear power bricks (the kind with a transformer and a bridge rectifier) to power my projects.recently i have noticed that the output voltage is higher than the rated output voltage eg. 9V rated output voltage is actually outputting 14V. any ideas what could be causing this? I want to know for curiosity's sake as much as anything else.

author: IanB
author_rank: Super Contributor
timestamp: October 28, 2013, 04:45:55 pm
content: Simple unregulated power bricks will have a voltage that depends on the load.For instance your 9 V DC power adapter probably also gives a rated current on the nameplate. It might say "Output 9 V DC, 500 mA" for example. If this is the case the voltage will be close to 9 V when supplying 500 mA, but will be higher when not supplying any current.

author: Simon
author_rank: Unknown
timestamp: October 28, 2013, 06:27:56 pm
content: The transformer outputs a sine wave with an average (RMS) voltage of 9-10.5V, when there is no or little load spare current capability of the transformer will charge the smothing capacitor up to the peak voltage of the transformer. The peak voltage is 1.414 multiplied by the average (RMS) voltage. so for 9V 12.7V although for 9V out you need 9V+ 1.5V to deal with the voltage drop on the bridge so 10.5*1.414= 14.85V, if there is no load the voltage drop on the bridge will be very low so potentially you will see the peak voltage.

author: Chrisalat
author_rank: Newbie
timestamp: October 28, 2013, 07:41:51 pm
content: Just load it a bit and you will see the voltage decrease.Another effect is that the windings have a finite resistance.So even before the capacitors there is a (weaker) load dependence of the voltage.This second effect tends to be larger for smaller transformers.
Power button - Page 1
Forum section: electronics / beginners

author: Kantilo
author_rank: Contributor
timestamp: May 01, 2023, 02:24:48 pm
content: Hello,I wanted to use a power button of this kind, with a 24V power supply, but there is marked 3-9V(5V) / 9-30V(12V) / 100-240V(220V), does this mean the voltage accepted by the button or the led?

author: wasedadoc
author_rank: Super Contributor
timestamp: May 01, 2023, 02:34:52 pm
content: The LED.

author: Kantilo
author_rank: Contributor
timestamp: May 01, 2023, 03:10:57 pm
content: Thank you so 9-30V(12V) means that it's a 12V led that accepts between 9 and 30V?Do i need a resistor ?

author: Xena E
author_rank: Frequent Contributor
timestamp: May 01, 2023, 04:09:21 pm
content: No. Current limiting is provided

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 01, 2023, 06:13:21 pm
content: I think they all have the same LED just different current limiting circuit.
Power calculation - Page 1
Forum section: electronics / beginners

author: sk614
author_rank: Contributor
timestamp: June 03, 2016, 04:23:35 pm
content: I not sure if i am asking the right question here so bare with me. I want to calculate the power requirement for the following.A sensor operating at 3v3 @50mA doing 100sample/sec. What would be the power usage per second or sample?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: June 03, 2016, 04:45:32 pm
content: Does the sensor always draw 50mA, or only while it's sampling? How long does the sensor take to make a sample? What is it doing in between samples, and what is its power consumption then? What about wakeup time?

author: sk614
author_rank: Contributor
timestamp: June 03, 2016, 06:53:43 pm
content: There is no downtime, so a continuous 50mA. So would power just be 3.3V*50mA?

author: suicidaleggroll
author_rank: Super Contributor
timestamp: June 03, 2016, 07:04:29 pm
content: Quote from: sk614 on June 03, 2016, 06:53:43 pmYes
power connector and RCA connector - Page 1
Forum section: electronics / beginners

author: coalago
author_rank: Contributor
timestamp: September 07, 2013, 08:43:46 am
content: what's the differences between power connector and RCA connector, can they be converted use?

author: amyk
author_rank: Super Contributor
timestamp: September 07, 2013, 12:23:53 pm
content: I recommend you don't.

author: madires
author_rank: Super Contributor
timestamp: September 07, 2013, 01:12:04 pm
content: Quote from: coalago on September 07, 2013, 08:43:46 amThe RCA connector is used for audio/video signals and the power connector for power :-) You could use them vice versa but that would cause a lot of puzzled faces and some magic smoke as people are used to the traditional scheme.

author: coalago
author_rank: Contributor
timestamp: September 08, 2013, 12:25:01 pm
content: Quote from: madires on September 07, 2013, 01:12:04 pmI see. thanks. Maybe for the different conductor resistance request . :-)
Power Consumption of CMOS Inverter Amplifier - Page 1
Forum section: electronics / beginners

author: beeboopbeep
author_rank: Contributor
timestamp: April 01, 2019, 11:03:43 pm
content: Hi everyone,I'm trying to understand the power consumption of two different CMOS amplifiers (Amp 1 and Amp 2).Amp 1 consists of 6 individual amplifiers where they are sized to have varying transconductances, g_m 1 to 3 as shown in the picture. Amp 2 consists of a single amplifier where it's sized such that the total transconductance equals the sum of all 6 individual amplifiers from Amp 1. Both amps are biased at saturation with mid voltage set to 0.5 V. Each amp is configured as an inverter with PMOS and NMOS. Both PMOS and NMOS are set with minimum width with varying number of fingers such that the gain is shifted to the mid point voltage of 0.5 V.In the simulation results, I'm seeing that the total power consumption of Amp 1 is always twice as much as Amp 2 and I'm wondering why this is the case. My thought process was that since the bias points are the same and the total width of Amp 1 combined equals total width of Amp 2 for both PMOS and NMOS, they should have the same power consumption.Thank you for your help!
Power Delivery issues with boost converter - Page 1
Forum section: electronics / beginners

author: tyguy2
author_rank: Unknown
timestamp: July 18, 2019, 11:26:08 pm
content: Hello all,I've recently designed a 5v rail that takes a minimum of 3.3v from a battery and steps it up to 5v, with a maximum current draw of 500ma (schematic attached, here's the parthttps://www.digikey.com/product-detail/en/maxim-integrated/MAX1522EUT-T/MAX1522EUT-TCT-ND/6680188). I'm already imbedded the design into a PCB, but I'm getting strange voltage sags when I try to draw anything over around 200ma. Does anyone have any ideas on how I can fix this without having to rerun a new PCB?

author: StillTrying
author_rank: Super Contributor
timestamp: July 19, 2019, 12:21:32 am
content: I can't see anything obvious from the data sheet, are you sure the input 3.3V isn't dropping.

author: tyguy2
author_rank: Unknown
timestamp: July 19, 2019, 01:34:43 am
content: I've checked that, and I'm not getting any issues with that either. 3.3v comes directly from a LiPo

author: Audioguru again
author_rank: Regular Contributor
timestamp: July 19, 2019, 02:05:30 am
content: Your 3.3V Li-PO is almost dead. It is 4.2V when fully charged and is 3.7V when half-charged. it should be disconnected and re-charged when it is 3.2V.Are you drawing 5A from the 3.3V Li-PO? That is 5A x 3.3V= 16.5W. Maybe 1.6W is wasted on heat then the 5V output will be 15.5W/5V= 3.1A but a Li-PO that is almost dead cannot produce the original 5A.

author: tyguy2
author_rank: Unknown
timestamp: July 19, 2019, 03:12:10 am
content: Quote from: Audioguru again on July 19, 2019, 02:05:30 amNo, this Lipo is fully charged to 4.2v, I'm just having it operate down to the drop off voltage of the battery. I said I was drawing 500ma, not 5A.

author: Psi
author_rank: Super Contributor
timestamp: July 19, 2019, 03:27:12 am
content: D9 (DB2J310) is only rated to 200mA absolute max

author: tyguy2
author_rank: Unknown
timestamp: July 19, 2019, 04:21:31 am
content: Quote from: Psi on July 19, 2019, 03:27:12 amRight in my face the entire time. Thanks!

author: MagicSmoker
author_rank: Super Contributor
timestamp: July 19, 2019, 10:13:10 am
content: Quote from: tyguy2 on July 19, 2019, 04:21:31 amYeah, that is a problem, but not one that would cause Vo to sag. A more likely cause is saturation of the boost inductor. It needs to withstand a peak current considerably higher than the average dc input current (e.g. - 40-100% more) without losing too much inductance in the process.EDIT - corrected "wouldn't" to "would"
Power derating of NTC - Page 1
Forum section: electronics / beginners

author: thexeno
author_rank: Regular Contributor
timestamp: November 09, 2017, 10:29:54 am
content: Hi all!I was studying some thermistor (NTC) datasheets and I notices the derating curve. May be a simple thing under my nose, but I don't understand why should I derate at temperatures below 0°C.Here what I mean, from theNTCLE203, under "DERATING AND LONG TERM STABILITY".I was thinking something related to an accumulative self heating, so some kind of drift, but this drift depends on how the NTC is biased (and dependent on at which resistance is the maximum power transfer to the NTC), while in the datasheets is always specified below 0°C. So it must be due to something else.

author: mikerj
author_rank: Super Contributor
timestamp: November 09, 2017, 11:07:09 am
content: Because at low temperatures (high resistance) you will reach the voltage limit of the part before you reach it's power dissipation limit.

author: thexeno
author_rank: Regular Contributor
timestamp: November 09, 2017, 12:08:43 pm
content: Ok, that is actually clear.I tried to make some verifications on another sensor, like theNTCLE100, same graph and a maximum voltage defined to be no more than 50V.At 55°C, at 50V I will dissipate a bit more than Pmax of 500mW (something around 770mW), so make sense to have a less voltage, since the 50V maximum is a top limit that shall never be reached.But at 0°C, the Pmax allowed is still 100%. Making a trial, for the 10k part, at 0°C has 32554\$\Omega\$. With 3.9mA is dissipating 500mW but to do that, a supply of 126V is needed. So why are they putting 100% of Pmax? Is for other parts of lower resistance in the same datasheet? Are they not so precise because normally you use those NTC for measurement and are never used with such power?

author: thexeno
author_rank: Regular Contributor
timestamp: November 11, 2017, 11:55:14 pm
content: Up
Power disipation through Opto PC817 - Page 1
Forum section: electronics / beginners

author: rscott
author_rank: Newbie
timestamp: November 29, 2019, 12:29:31 am
content: Hey GuysJust teaching myself a bit more about opto'sQuestion is, I know how to bias one and have gotten good results that match the CRT ratios and such but curious how to calculate the power dissipated.I don't know what the internal resistance of the opto is so how do I see how many watts or more likely mWatts I am running?thanks

author: magic
author_rank: Super Contributor
timestamp: November 29, 2019, 10:01:04 am
content: As always, voltage times current.How much voltage is dropped for given current or how much current flows for given voltage you will find in the datasheet (forward voltage vs forward current plot). It typically is 1~1.5V for reasonable currents, IIIRC.

author: rscott
author_rank: Newbie
timestamp: November 29, 2019, 02:46:23 pm
content: However there is no voltage drop the way this is setup.So there is no voltage there but there is current flowing through it. So if you don't know the internal impedance of the BJT side of the opto how do you know the power dissipatedThe load is connected above the collector and the emitter is connected to ground

author: magic
author_rank: Super Contributor
timestamp: November 29, 2019, 03:30:03 pm
content: Okay, I thought you mean the primary.For the secondary, it's of course current times voltage again, as usual. And this time you need the plots showing how secondary side voltage drop (Vce) varies depending on secondary side collector current (Ic) and primary side LED current (If). My PC817 daatsheet from Sharp has two plots, one showing Vce vs If for a few different values of Ic and another showing Vce vs Ic for a few chosen If.The specifications table also shows "collector to emitter saturation voltage", which is guaranteed never to be exceeded as long as If is high enough and Ic is low enough. It is specified as 0.2V maximum for If=20mA and Ic=1mA in my datasheet.
Power electronics job title? - Page 1
Forum section: electronics / beginners

author: jackbob
author_rank: Regular Contributor
timestamp: October 27, 2011, 07:36:21 am
content: I'm a 15 year old (almost 16) high school student who has a lot of interest in electronics design. I have most experience and the desire to work in power type of electronics such as power supplies, variable frequency drives, inverters, converters, and things of that nature. These also have a very good future because of motor control for electric cars and chargers for the cars. New solar technology will also hold a good future for inverters. I would think there are different categories of electronics but can't find a job title for power electronics. Would it just be an electronics engineer? I found power electrical engineer but that's transmission and such, I'm looking for electronics. Are there electronic engineers that specialize in power? Thanks for the input,Jacob

author: EEVblog
author_rank: Unknown
timestamp: October 27, 2011, 08:36:38 am
content: Quote from: jackbob on October 27, 2011, 07:36:21 amThere are indeed.Usually you'd have a strong analog electronics design background.Jobs would usually be advertised under the generic "electronics design engineer" title. But I've seen "power supply design engineer" etc.Dave.