hybridfree/eevblog-posts huggingface dataset:
Question about charging circuit - Page 1
Forum section: electronics / beginners

author: Tjj226_Angel
author_rank: Contributor
timestamp: February 26, 2024, 10:31:25 pm
content: I am looking for confirmation before I do something potentially stupid.I have a circuit I am working on where I need to charge 3 6000mah lithium iron phosphate batteries in series. I am not finding a cheap charge controller IC that can do 3 cells at 1.5 amps (0.3c for this particular cell).I watched the video on lithium battery charging and I understand a normal charger will go from charging at constant current and switch to constant voltage at a given voltage (should be 3.6v for lithium phosphate). However, I do not actually want to hit 3.6V. I want to charge from 3.1v to roughly 3.5v to achieve a rough 20%-80% charge cycle.I do not need the full charge depth since I will have two banks of batteries that will be swapped back and forth and I only want to maximize battery longevity.My question is, can I simply use a current regulator to charge the batteries? I could use a comparator to turn the current regulator off once a certain voltage has been reached which means the only thing I am truly loosing is temperature protection. But since I am not in any danger of over or under charging the battery, does it even matter? If it does, are these dedicated temperature control ICs that I can use to integrate into the charge circuit?If it helps any, this circuit will always be connected to power. This is not a portable device. This is just a way of trying to make a very low noise power supply that isn't connected to mains and will live inside of a shielded box.

author: Andy Chee
author_rank: Super Contributor
timestamp: February 27, 2024, 03:58:33 am
content: What cell balancing BMS will you be using?

author: Tjj226_Angel
author_rank: Contributor
timestamp: February 27, 2024, 04:17:53 am
content: No true bms.Undervoltage will be handled by the circuit. And since this will be powering a filament, the chances of a sustained overcurrent situation is almost 0.Battery balancing will be done passively through some comparators, mosfets, and resistors.

author: Andy Chee
author_rank: Super Contributor
timestamp: February 27, 2024, 04:49:49 am
content: Your circuit will also need to handle cell overvoltage, not just undervoltage.
Question about calculating AC amps from DC amps - Page 1
Forum section: electronics / beginners

author: bob21
author_rank: Regular Contributor
timestamp: April 29, 2020, 10:10:23 am
content: Hi again everyone. I hope you are all keeping well and safe in this difficult time.I have a 5V 30A PSU to drive a prefab LED strip, and a 5V 2A PSU for a ESP board that I need to hook up to a fused IEC connector in an enclosure.I need to calculate the fuse needed. Am I right in thinking this would be:5V DC x 32A = 160 WattsAssuming watts are roughly equivalent and PSUs are at about 80% efficiency: 160 / 0.8 = 200 WattsSo for AC: 200W / 240V = 0.83A, so 3A fuse needed?The 30A PSU will have a relay controlled by the ESP, so using the same calculations:5V DC x 30A = 150 Watts150 Watts / 0.8 = 188 WattsSo to calc relay amp rating: 188W / 240V = 0.78ASo no problem for this relay?https://www.ebay.co.uk/itm/3-3V-5V-30A-Relay-Module-for-Arduino-Nano-Due-Raspberry-Pi-ESP8266-Optocoupler/272565679171Does this look sound?

author: WattsThat
author_rank: Frequent Contributor
timestamp: April 29, 2020, 11:49:31 pm
content: A proper power supply should have a fuse rating printed on it and more importantly, a type specified in order to meet any regulatory body safety requirements.If you’re taking a SWAG at the ratings (scientific wild assed guess), it would help us if you told us what kind of power supply you’re discussing, linear or switcher.I don’t understand the relay question. Will the relay switch the power supply? HV or LV side?

author: bob21
author_rank: Regular Contributor
timestamp: April 30, 2020, 10:56:36 am
content: Hi!Thanks for the reply.It's a PWM PSU:https://www.ebay.co.uk/itm/Led-Driver-AC100-240V-to-DC5V-2A-3A-5A-10A-15A-20A-30A-40A-60A-70A-Power-Supply/233512308100the 5V30A model. Looks like a 3A rating?Here is a really bad diagram:From the IEC connector, it will split to the 2A PSU which is always on and powering the ESP.The live wire going to the 30A PSU will go via a relay.

author: Vovk_Z
author_rank: Super Contributor
timestamp: April 30, 2020, 06:07:55 pm
content: I am 80% sure they have their fuses inside.But it is good design (I think) to put some general fuse at the mains input.

author: bob21
author_rank: Regular Contributor
timestamp: April 30, 2020, 08:46:09 pm
content: Hi @Vovk_Z, yes I have ordered an IEC connector with a fuse slot. There will also be a fuse in the plug.
Question About Connecting GBS-8220 to PC PSU - Page 1
Forum section: electronics / beginners

author: tech3475
author_rank: Newbie
timestamp: February 17, 2019, 10:42:25 am
content: Hi,I have an upcoming project which involves transplanting my Amiga 1200 into a new PC style case along with changing from the old Commodore external PSU to an internal PC SFX PSU.One part of this project is to also try and internalize the GBS-8220 scan doubler so that it runs of the internal PSU as opposed to the mains barrel pin multi transformer I currently use.According to the manual (here:https://www.mikesarcade.com/estore/datasheets/GBS-8200-booklet.pdf), it does have a 2 pin power connector which accepts 5V 2A, so my idea is to take an old molex power connector I have and to use the 5V pins from that for power.However I am a noob with things like this and I'm concerned about whether this may be entirely safe and wondering if I should add a resistor or some kind of fuse as a precaution (especially with the GBS-8220 being a 'naked' PCB, although I'll try and isolate it from the case and other components).Can anyone please provide some advice in regards to this?Thank you.

author: tech3475
author_rank: Newbie
timestamp: February 28, 2019, 04:34:31 pm
content: I've been looking around, would a better alternative be to buy a circuit regulator? Possibly using 12v if necessary and output at 5v.

author: stj
author_rank: Super Contributor
timestamp: March 01, 2019, 01:04:09 pm
content: just feed 5v into the 2pin plug.you have a bigger issue though, the amiga will overload the sync input.https://ianstedman.wordpress.com/2016/07/06/synchronise-your-video-engines/

author: tech3475
author_rank: Newbie
timestamp: March 01, 2019, 02:04:31 pm
content: Quote from: stj on March 01, 2019, 01:04:09 pmThanks, I used a guide when wiring the RGB connection so there's a resistor running on the sync signal.
Question about connectors - Page 1
Forum section: electronics / beginners

author: btipton
author_rank: Newbie
timestamp: December 27, 2010, 03:50:26 am
content: One of the things that has proved surprisingly frustrating for me has been trying to identify the various connectors that are available, and which ones are appropriate to use. For example, I bought a cheap stepper motor for a small project. The motor comes with a small white connector attached to the leads, but I've had a lot of trouble trying to find a mate for it that would work. In the end, I just cut the connector off and soldered the leads to the board.Is there a good reference somewhere to help me identify connectors, and also is there a similar reference that recommends the type and size of connector to use for original designs? Flipping through the Mouse printed catalog, I'm a bit overwhelmed by the variety of choices, and there's clearly a vocabulary that I don't yet have.

author: Bored@Work
author_rank: Super Contributor
timestamp: December 27, 2010, 08:56:40 am
content: I don't know of any such comprehensive catalog. Here is a business idea: Produce a website where people can enter descriptions of unknown connectors (or upload photos), and the website tries to identify the connector. Like those for identifying a piece of music.The connector business is a cut-throat business. Every manufacturer tries to introduce special connectors and tries to convince electronic manufacturers to just use these, to get them locked in. If you go to the manufacturer websites like Molex, ITT Cannon, 3M, Phoenix Contact, Tyco (and hundreds more) you can get mad at them for the sheer amount of connectors they offer.

author: Neilm
author_rank: Super Contributor
timestamp: January 02, 2011, 05:10:18 pm
content: The datasheet for the motor should have had the connector type that was fitted. If it wasn't there, I would usually start by looking at connector manufacturers for example Tycho, Molex etc. If you work for a company and get reps in, there is another option. Show it to a rep and get them to identify it. I did that once and he recognised it almost instantly.Neil

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 02, 2011, 05:23:37 pm
content: Quote from: btipton on December 27, 2010, 03:50:26 ammake your own connector... the 2.54mm pitch header is the most common i think...femaleandmale
question about DC Load instrument - Page 1
Forum section: electronics / beginners

author: salviador
author_rank: Regular Contributor
timestamp: August 29, 2019, 11:42:58 am
content: It is possible to use a DC electronic Load in AC with a device using a suitably adapted diode bridge?I didn't put the capacitor to level because I want to simulate a resistive load and have a PF = 1Example

author: capt bullshot
author_rank: Super Contributor
timestamp: August 29, 2019, 12:05:53 pm
content: Depends ...The maximum input voltage of the DC load must be larger than the peak value of the AC source,the DC load must operate in "R" (Resistance) mode (not "I" / constant current)and the DC load internal circuitry must be fast enough to follow the rectified AC waveform - you should verify this using a current probe and a scope.
Question about Differential amplifier. - Page 1
Forum section: electronics / beginners

author: ammjy
author_rank: Regular Contributor
timestamp: November 16, 2019, 05:31:16 am
content: Hello,Thanks you for your time.I have a question about differential amplifier.I would like to know what does RC circuit that connected with Vout 1 doing in this differential amplifier.it is just load might be ?Please, let me know !

author: Ian.M
author_rank: Super Contributor
timestamp: November 16, 2019, 07:38:13 am
content: I would expect a part designated RLto be the load. The series capacitor feeding RLis to block the DC voltage on the collector of T1.

author: David Hess
author_rank: Super Contributor
timestamp: November 16, 2019, 01:30:18 pm
content: It is AC coupling the load so I assume this is for an audio application.

author: Audioguru again
author_rank: Regular Contributor
timestamp: November 16, 2019, 05:32:18 pm
content: Many audio amplifier differential amplifier circuits are DC-coupled.

author: David Hess
author_rank: Super Contributor
timestamp: November 16, 2019, 07:10:55 pm
content: Quote from: Audioguru again on November 16, 2019, 05:32:18 pmSure, but you would not DC couple the output from half of a differential pair because of the large level shift unless you performed a second level shift. The output from one half has a very large offset.
Question about Diode in LM2596 based DC-DC converter - Page 1
Forum section: electronics / beginners

author: tlovie
author_rank: Contributor
timestamp: May 26, 2022, 12:25:36 pm
content: I designed and built a LM2596 type DC-DC converter as a small battery charger for fun, and because I enjoy laying out circuit boards and tinkering. During the design process I talked myself into adding a "protection" diode before the output to ensure that current can only flow in one direction. After I made the boards and built the circuit, I've found that this diode gets fairly hot. Now I'm questioning whether the D4 diode is actually doing anything other than making heat?This device is a battery charger that would step down the input voltage to 13.5v for charging a 12v lead acid battery, and I believe that I was thinking that D4 would protect against a reverse polarity connection to the battery.

author: jpanhalt
author_rank: Super Contributor
timestamp: May 26, 2022, 12:32:44 pm
content: What is your charging current?A 12V lead acid battery, depending on size, may well require 3A. That is the maximum rating and can be expected to make that diode quite hot (see datasheet).

author: tlovie
author_rank: Contributor
timestamp: May 26, 2022, 12:49:13 pm
content: Quote from: jpanhalt on May 26, 2022, 12:32:44 pmThe U2B opamp limits the current to 2.5A. I'm just not sure if it adds any value to the circuit, or provides any protection at all.

author: thm_w
author_rank: Super Contributor
timestamp: May 27, 2022, 10:01:46 pm
content: D4 will not protect against reverse polarity of the battery.If I connect a battery backwards across the output, look at the path through D1 and D4.Its only going to prevent backfeed into U1, when U1 power is off, which may or may not be an issue.Maybe consider a fuse or resettable fuse on the output.
Question about dual voltage eBay step up converter - Page 1
Forum section: electronics / beginners

author: belzrebuth
author_rank: Frequent Contributor
timestamp: December 11, 2020, 07:11:21 pm
content: Hey all,I've found this on eBay:https://www.ebay.com/itm/30W-DC-DC-Buck-Step-Down-Converter-5V-9V-12V-15V-3A-Dual-Power-Supply-Module/174288116134?epid=7007140231&hash=item28946199a6:g:oA0AAOSwUSJZ4N7uand wondering whether anyone has used it.There are no specs that come with it (other than a vague 20mV ripple figure with no load mentioned) or any attached datasheets.I also can't see any IC markings on the PCB.My target load is about 1.5A at +12V and -12V.I was hoping to get a 15V output from this module to feed a couple of linear regulators.I can always buy it and check for myself but it will take ages to get here from China so I though I could ask for opinions or other (cheap) alternatives here first.I'm aware of reliable alternatives in the likes or traaco or delta dc/dc converters but they're far more expensive.
Question about equipment - Page 1
Forum section: electronics / beginners

author: DiodomanX
author_rank: Contributor
timestamp: February 27, 2016, 11:50:54 pm
content: Hi all, i have the following equipment:Fluke 117Fluke 323Fluke Scopemeter 96 Series 2Hakko FX-888DTektronix DPO2012BBut i dont have a power supply and function generator, the question is, i should conserve the tek or is better to sold it and get a rigol a PS and an function generator. If i sell the tek, how many i can ask for it, i have unlocked all the options.Im a begginer, and looking to work with microcontrollers and raspberry pi.Thanks for you sugestions.

author: uncle_bob
author_rank: Unknown
timestamp: February 28, 2016, 12:41:08 am
content: HiIf the Tek is in anything other than "un-hacked shape" you will have a hard time getting much money for it. They list for ~$1500. Most get a 10% discount for buying more than one. A typical sell price in good shape would be $400 to $500. A used gear dealer would then turn it around and try to sell it for more. He might spend 4 years doing so. If it's been hacked, reverse all the hacks before selling it. You do *not* want to go to jail ....The money left from the sale after selling costs is roughly what you would pay for a Rigol scope. Keep the Tek, it's not worth swapping it for a Rigol. Getting a new 1054Z plus a new supply on the proceeds ... not likely.Bob

author: tautech
author_rank: Super Contributor
timestamp: February 28, 2016, 12:42:14 am
content: Keep the Tek, it's a scope you can trust.It's easy to build a simple PSU, do that.An AWG, well how flash do you need? Single channel or dual? Frequency?

author: DiodomanX
author_rank: Contributor
timestamp: February 28, 2016, 09:16:11 pm
content: Well i dont know how fast i will need, i will get an analog discovery 2 soon, maybe can suite my needs.Enviado desde mi XT1563 mediante Tapatalk

author: uncle_bob
author_rank: Unknown
timestamp: February 28, 2016, 09:31:08 pm
content: Quote from: DiodomanX on February 28, 2016, 09:16:11 pmHiTake is slow, spend a lot of time shopping for surplus deals. You will buy very few things in a year, but will buy good stuff at low prices.Bob
Question about fluke 87 v multimeter voltage reading - Page 1
Forum section: electronics / beginners

author: Turttle2013
author_rank: Newbie
timestamp: October 16, 2020, 07:05:02 am
content: I was asked to measure the max DC input of a charging system, the DC input should be roughly 400v and no more then 800v. When I first measured the dc input it was 1265v. I tested 3 more times and the highest I recorded was 1663v. The manufacture said there was no way it could be that high. So I bought a Fluke 87v and a 1000:1 HV probe, and measured the site again. This time the manufacture flew their tech out to measure as well.With the 1000:1 HV probe connected to the Fluke and the settings on Auto hold and the voltage range set to 6.000vthe results I got were 0.1114v. As I understand it that with using the 1000:1 HV probe that would equate to 1114v or would I be incorrect?Thank you for your help with this[ Specified attachment is not available ]

author: MosherIV
author_rank: Super Contributor
timestamp: October 16, 2020, 07:59:26 am
content: I think 0.104V on the dmm means 104V.The probe is 1000:1 meaning divid by 1000. You need to multiply by 1000 which means move decimal point to right by 3.BTW the Fluke87V should easily be able to take 1000V and a bit more. The input protection will stop damage from happening.

author: tooki
author_rank: Super Contributor
timestamp: October 16, 2020, 08:55:49 am
content: Quote from: Turttle2013 on October 16, 2020, 07:05:02 amPlease use punctuation and fix your typos, so we can easily figure out what you mean instead of trying to decipher a huge run-onsentenceparagraph.

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 16, 2020, 08:59:41 am
content: A DVM would integrate the input voltage for a certain period in order to get a reading. I'm not too sure using a DVM to measure a spike would give meaningful readings as spike is usually of very short duration. The proper instrument to use is an oscilloscope.
Question about Frequency Tripler Circuit Using Complementary Transistors Pair - Page 1
Forum section: electronics / beginners

author: FurbulousFox
author_rank: Newbie
timestamp: June 15, 2024, 02:38:51 am
content: Hello everyone,I'm an electronics hobbyist currently learning about microelectronics. I've been trying to understand this Frequency Tripler circuit (image below) operates, particularly on how the transistors go to saturation. From the oscilloscope readings (yellow trace for Vin and blue trace for Vout), I could see that Q2 (NPN) reaches saturation during the positive cycle of Vin, and Q1 (PNP) reaches saturation during the negative cycle of Vin.What I don't understand is how each transistor goes to saturation once at the time and not both, especially when Vbe for Q1 is always negative and Vbe for Q2 is always positive? When I measured the base currents, I notice that:- During the positive cycle of Vin, ~130uA went into the base of Q2 and only ~3uA went out the base of Q1.- During the negative cycle, ~3uA went into Q2 and ~130uA went out of Q1.Why aren't the base currents more or less the same if both transistor are conducting?This is my first time posting here so I apologize in advance if I made any mistakes in my post. Please let me know if there are ways I can make my question clearer. Thank you for your help!

author: ArdWar
author_rank: Frequent Contributor
timestamp: June 15, 2024, 03:46:19 am
content: Because basically (heh) speaking, NPN conducts when current are pushed into its base and PNP conducts when current are pulled out of its base. Ergo the two transistors will never conduct at the same time, and base current will never be the same. Except at zero crossing when both are zero...With this configuration there will also approx 2Vbe band near midpoint where base is positive but not positive enough to make NPN conduct, or negative but not negative enough to make PNP conduct. That what's causing the "dip". This circuit is basically exploiting the crossover distortion of a class B output. Just that I didn't expect the transition region to be this clean.

author: MarkT
author_rank: Frequent Contributor
timestamp: June 16, 2024, 08:12:42 am
content: The transistors don't switch off, both conduct at the same time. The circuit works by saturation limiting the output swing.Its a high gain inverting amp but the saturation limits the swing relative to the input, so the swing direction reverse every time each transistor enters or leaves saturation.

author: eblc1388
author_rank: Frequent Contributor
timestamp: June 16, 2024, 02:23:37 pm
content: That is a very interesting circuit.If we fed the output to a comparator and reduce the input voltage amplitude to around 0.7v, then we will get a very decent tripler output waveform.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: June 18, 2024, 03:14:59 pm
content: Interesting...so I built the circuit. There is a lot of phase difference in thethree peaks which can be varied by adjusting the V+ and V-. Lots of Phase noise.
Question about function generator output level. - Page 1
Forum section: electronics / beginners

author: OilsFan
author_rank: Regular Contributor
timestamp: January 23, 2016, 08:20:07 am
content: I hope this isn't too silly of a question but I have a Tenma 72-5015 function generator and there is just a knob for the amplitude that is not marked in any way. So to set the amplitude I want I have just been using a piece of coax and running it right into my CRO and using that to measure it. Any problems with using that method?

author: Rerouter
author_rank: Super Contributor
timestamp: January 23, 2016, 08:30:24 am
content: If the function generator is rated for a 50 ohm output, you will need to either use a 50 ohm termination right at your scope, or turn on the internal termination if its supported

author: tautech
author_rank: Super Contributor
timestamp: January 23, 2016, 10:19:41 am
content: Quote from: OilsFan on January 23, 2016, 08:20:07 amNot at all, however actual output may be affected by the load it drives so if different to your CRO input take care to start low and adjust to suit your requirements. This is when a BNC Tee comes in handy so you can monitor the output with your scope while adjusting the FG to your needs.Often older analogue FG's had substantial drive capabilities so check your documentation.
Question about GRF2133 LNA module - Page 1
Forum section: electronics / beginners

author: jk99345
author_rank: Newbie
timestamp: September 24, 2024, 08:46:02 pm
content: Hi,I am designing a low noise amplifier board using the GRF2133 LNA module. Ideally, I would like to power the LNA using +5v on the RF line from the bias tee on the RTL SDR. However, I am getting a bit confused by the datasheet. Based off the pin definition for the RF_OUT/Vdd pin, it seems that it is possible to power the module by applying the RF signal combined with the +5V directly to the pin. However, it specifies that a DC blocking capacitor is necessary for the pin and there is also one in the application schematic (reference number M12). This is obviously quite confusing because the circuit as pictured would block the DC and prevent it from powering the module. I was hoping somebody could clarify and maybe give me an example of a schematic I could use to power this module.Thanks
Question about ground and potential PE - Page 1
Forum section: electronics / beginners

author: Darlington
author_rank: Contributor
timestamp: June 25, 2024, 02:26:38 pm
content: Hello Everyone,I have some questions about wiring the boards of a pcb. I have 3 different pcb's as per the diagram attached.1. The pcb named "slave 1" has a USB connector and Ethernet. For instance, the USB connector has a SHIELD pin. Should this be connected to a chassis and then connected to the potential PE? Should the SHIELD be connected to GND (common to all pcbs)?2. Should the USB port on my pcb have ESD protection?3. In which case is it better to connect the pcb ground together with the PE potential or leave the pcb ground floating?

author: BennoG
author_rank: Frequent Contributor
timestamp: June 25, 2024, 06:49:33 pm
content: in most applications (industrial) you see the GND connected to PE as close as possible by the PSU.Benno

author: selcuk
author_rank: Frequent Contributor
timestamp: June 25, 2024, 10:00:54 pm
content: 1. If your board doesn't have a special requirement about isolation (medical device etc.), your USB connector shield will touch the chassis. The chassis should be connected to PE at some point for human protection. And you will connect USB connector shield pins on your board to DC ground return plane. So all of them will be a short on the schematics. But the exact shorting points in the layout need some experience.2. Yes. USB, ethernet and other connectors as well. You need to connect ESD protectors close to the connectors, and their ground pins close to the shield. So that the ESD transient path will be very short to the chassis.3. Generally you can connect them. Be careful about the isolation requirements if any. If you have a desktop computer, you can check the ground and PE connections with a multimeter (when the PC is not energized) and apply the same rules if you are not sure what to do. Computer hardware usually complies with many international standards.

author: Terry Bites
author_rank: Super Contributor
timestamp: June 26, 2024, 06:51:52 am
content: Although the circuit "ground" or 0V and PE perform separate functions its normal to connect them together near to the PSU common.In general, all exposed metal parts need to be tied or "bonded" together.The enclosure also connected to PE if its made from metal.There are situations in which the circuit 0V is left floating with respect to PE. This is often seen in high end instrumentation for measuring very low level signals.
Question about grounding - Page 1
Forum section: electronics / beginners

author: baoshi
author_rank: Regular Contributor
timestamp: December 21, 2012, 03:16:30 pm
content: Hi,I'm routing a simple system, as attached diagram.There is a mcu control system and a motor controller. The motor controller is pretty high power (6-8A).The MCU system will output a small voltage (0-2v) to the motor controller to adjust the speed of the motor.Taking many of the advise online, I use "star grounding" to separate mcu ground with motor ground and they meet only at battery terminal.Now I'm puzzled whether the control voltage will be affected by the ground potential difference, i.e., I'm expecting the ground difference between both system will be around 10mV and mixed with high frequency pulses from the motor. How can I clean up these?Thanks in Advance

author: IanB
author_rank: Super Contributor
timestamp: December 21, 2012, 05:50:22 pm
content: I think the idea of separate grounds is to separate the signal ground from the power ground, so that disturbances from the power systems don't get into the signal path.However, in your diagram you have (apparently) electronics with signal processing on the motor control side, which seemingly would be a bad idea. As you have foreseen, if the motor control section floats at different voltages from the MCU section it will interfere with the control voltage levels between the two.Maybe you should try to put all signal processing on the same star ground, or if this is not possible investigate something like a differential pair to communicate the control signal between sections--the differential voltage would cancel out common mode voltages on the signal path.

author: Psi
author_rank: Super Contributor
timestamp: December 21, 2012, 08:42:29 pm
content: Yep, star ground reduces the effect where your mcu switches on a high current load and the MCU ground jumps from 0V to say 0.5V for example. So all the mcu I/O now has moved up by 0.5V with respect to true ground.If it's communicating with some other device using analog signals or using some I/O as feedback then this is now offset and wrong.It gets more annoying if your doing PWM or switching of a high current signal because the ground keeps moving around at the switching frequency due to the continuous change in voltage across the ground cables

author: PA0PBZ
author_rank: Super Contributor
timestamp: December 21, 2012, 09:17:04 pm
content: So basically you want the MCU, regulator and controller grounds as close as possible, and from there one fat track to the power input.Then use the star for the positive supply, giving the regulator its own track to the positive power input.
Question about gyrator implementation of active inductor - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: March 30, 2018, 09:14:20 am
content: I am working on a gyrator-based active inductor as described inhttp://www.seas.ucla.edu/brweb/papers/Conferences/LK_ISSCC15.pdfI have done a more detailed analytical analysis on Gm2 circuit block as attached with help from others.For the gyrator-based active inductor, I still have problem obtaining inductor-based behaviour, with unexpected frequency response for a series LC filter.With S11 measurement result, I am getting NEGATIVE inductance value forhttps://github.com/promach/frequency_trap/blob/development/test_active_inductor.netBesides, I have also measured transconductance (using AC method, please seehttps://github.com/promach/frequency_trap/blob/development/Makefile#L19-L23) of both Gm2 circuit block and CMOS_Inverter circuit block.By using the obtained transconductance measurement results with the equation below to calculate the active inductor value, the calculation result (which is not negative) does not really match what I have for S11 measurement.Inductance = load_capacitance / [(transconductance of Gm2 circuit block) * (transconductance of CMOS inverter circuit block)]Could anyone advise ?
Question about high-frequency signals.  - Page 1
Forum section: electronics / beginners

author: andrew_salinas_
author_rank: Unknown
timestamp: March 21, 2020, 04:50:17 pm
content: I was messing around with highish frequency sine waves of 60Mhz (this doesn't happen with lower frequency waves). I had them coming out of a frequency generator and into an oscilloscope. When I grabbed the insulated wire the signal looked like it gained some DC offset (~1-2mV, the pk-pk value didn't change of around 23mV) and then lost it when I let go. I assume this has something to do with the fact that the capacitive reactance between me and the wire was way less than usual since the frequency was so much higher, but I don't know why the signal gained a couple mV. Maybe I had some voltage on me and transferred to the wire or something?Any answers are helpful and even if you don't have the exact answer but resources for me to learn more that would be super helpful (Freshman EE)

author: bob91343
author_rank: Super Contributor
timestamp: March 21, 2020, 08:48:32 pm
content: When operating at high frequency, everything gets important. For instance, the cable between the generator and oscilloscope will have standing waves unless you terminate it properly. Standing waves mean the cable length will become important and the voltage at the generator will not be the same as that at the oscilloscope.Many 'scopes have input impedance selection; if not, put a terminating resistor on the receiving end.If you see a dc offset that occurs when you touch part of the system, you are probably rectifying the signal somehow.High frequency techniques are an important subject and require extensive study. Read books on transmission lines and learn about skin effect and propagation velocity and all the rest.

author: vk6zgo
author_rank: Super Contributor
timestamp: March 22, 2020, 05:08:47 am
content: Quote from: bob91343 on March 21, 2020, 08:48:32 pmOr perhaps it is ac pickup at Mains frequency which is so much lower in frequency that you are observing your HF signal partway along one Mains half cycle, & through blind luck, the two signals are close enough in phase, that this state of affairs continues for a substantial length of time.If this is the case, the polarity of the offset may reverse over time.Fortunately, this is easy to check by increasing the time/div setting to around 5ms /div & retriggering at that rate.It it is Mains hum, you should see your HF signal "riding" on a 50 or 60Hz waveform.Quote
Question about isolation on pcb  - Page 1
Forum section: electronics / beginners

author: little_carlos
author_rank: Regular Contributor
timestamp: October 16, 2015, 03:54:16 am
content: Hey guysAfter i saw some pcb, a big question came into my mindIve seen that when some optoisolator is used to isolate a signal on a pcb, a track is cutted below the ic, why is this being done ?

author: Neilm
author_rank: Super Contributor
timestamp: October 16, 2015, 02:40:23 pm
content: Quote from: blueskull on October 16, 2015, 04:17:33 amCreepage also applies across the body of the component. However, materials have a different tracking indexes (which determines how much creepage is needed). This is called the comparative tracking index (CTI). It is expressed in volts due to the way it tends to be measured (what voltage causes it to track). PCBs tend to be lower values of tracking index - usually about 175V. Components tend to be better tracking which means the designer needs less clearance.
Question about laptop - Page 1
Forum section: electronics / beginners

author: Jane
author_rank: Frequent Contributor
timestamp: December 01, 2020, 08:48:46 am
content: f I connect a charger, to a laptop , must the laptop start if battery is flat ( or disconnected) and charging circuit is damaged? Or the working charging circuit is necessary for a laptop to start?

author: Zero999
author_rank: Super Contributor
timestamp: December 01, 2020, 10:34:31 am
content: Quote from: Jane on December 01, 2020, 08:48:46 amNo, the battery doesn't have to be flat. The charging circuit in the laptop will only charge the battery, if it needs to be charged. The laptop will be happy connected to the mains power supply, whether the battery is fully charged, or flat.If there is a fault with the charging circuit, the battery will most likely not charge. There is a risk it could overcharge, in which case, the battery should have a protection circuit, to prevent fire and leakage. Some laptops won't work without a battery, which indicates the battery charging circuitary is part of the internal power supply. If you suspect the laptop's internal battery charging circuitary is faulty, you shouldn't attempt to charge the battery with it.

author: Jane
author_rank: Frequent Contributor
timestamp: December 01, 2020, 12:01:52 pm
content: Thanks for your reply.But not sure I fully understandQuoteSo if I connect power supply and laptop is without battery, the laptot usually starts. But is working charging circuit necessary for a laptop to start without battery?

author: BravoV
author_rank: Super Contributor
timestamp: December 01, 2020, 12:11:38 pm
content: Laptop will work with and without the battery.And if the laptop is turned on without the battery, powered from the adaptor of course, it wont damage the charging circuitry, with or without the battery (full,partial or dead flat).This assuming the laptop is the one with detachable battery designed from manufacturer.

author: PKTKS
author_rank: Super Contributor
timestamp: December 01, 2020, 01:23:11 pm
content: Well ..... that depends on the circuits itself..and they do vary a lot across age, manuf., model..I have seen more recent models with "devices"in the schematics I can not readily recognize..Some symbols that hopefully implement somebetter (hopefully) logic in the charging portand prevent damaged things to go weird.Fortunately these "new" symbols (devices) mostlycome with some code hint to try (i said try) to spottheir datasheet..Although each day I find myself spending more timetrying soPaul
Question about learning PCB-design - Page 1
Forum section: electronics / beginners

author: siyar
author_rank: Contributor
timestamp: March 18, 2025, 10:27:25 am
content: Hi,I'm trying to learn PCB-design. I believe i know the basics. I am able to create a PCB from schematic to generating gerber files.I was considering learning about IPC-standards. Would you guys recommend this or should i just practice by doing more projects? if so which stadards should i learn?

author: Picuino
author_rank: Super Contributor
timestamp: March 18, 2025, 10:37:47 am
content: You can read the application notes of the chip manufacturers of the type you are building. It is not the same to make a low current and low frequency PCB (for example a keyboard), than to make a PCB of a switched-mode power supply (high currents and induction loops) or a PCB of a high speed digital circuit (high frequencies).EDIT: Practice, of course, teaches a lot and nowadays it is relatively cheap to build PCBs from Chinese suppliers.

author: Picuino
author_rank: Super Contributor
timestamp: March 18, 2025, 10:44:05 am
content: Some links (oriented to switch-mode power supplies):2. POWER SWITCHING APPLICATION NOTES2.1. TISwitching Regulator Fundamentals2.2. TIFive steps to a great PCB layout for a step-down converter2.3. TI AN229.Simple Switcher PCB Layout Guidelines2.4. ROHMPCB Layout Techniques of Buck Converter2.5. EDNBandwidth of a signal from its rise time2.6.Powder Material for Inductor Cores2.7. LT AN137.Accurate Temperature Sensing with an External P-N Junction3. PCB DESIGN AND EMI REDUCTION3.1. TI. AN-1149Layout Guidelines for Switching Power Supplies3.2. NXP AN10912Switched-mode power supplys EMC and layout guidelines3.3. TI AN2155.Layout Tips for EMI Reduction in DC/DC Converters3.4. CUINCElectromagnetic Compatibility Considerations for Switching Power Supplies3.5. FairchildElectromagnetic Interference (EMI) in Power Supplies3.6. PericomEMI Reduction Techniques3.7. AVXParasitic Inductance of MultiLayer Ceramic Capacitors3.8. EETimesThe 13-Step EMI Mitigation Program for Switching Power Supplies3.9. ROHMPCB Layout Techniques of Buck Converter3.10. TIMinimizing Buck-Boost High-Frequency Switching Noise3.11. LT AN139.Power Supply Layout and EMI3.12. LT AN136.PCB Layout Considerations for Non-Isolated Switching Power Supplies3.13. LT AN70.A Monolithic Switching Regulator with 100µV Output Noise3.14.PCB Design Guidelines For Reduced EMI

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 18, 2025, 10:52:19 am
content: I'd say first practice with some more designs. Give yourself some constraints, like trying to minimise size, avoid minimum track/feature sizes, layers, specifically do it as 2-layer with groundplane and as few as possible tracks breaking up the groundplane.being able to visualise how the placement will enable easier routing will be a general skill applicable to pretty much all designs, whearas most IPC stuff will likely be more of a niche thing.Don't forget, placement is everything. Don't be afraid to rip it up half way through.
Question about LM317 - Page 1
Forum section: electronics / beginners

author: bogdan2013
author_rank: Regular Contributor
timestamp: April 21, 2013, 09:08:33 pm
content: I have an adjustable power supply with LM317 . I can increase the maximum current by putting in parallel more LM317 ?

author: Simon
author_rank: Unknown
timestamp: April 21, 2013, 09:13:49 pm
content: No, You will need to use one or more parallel transistors, look around the net and you will find a schematic no doubt, or check the datasheet of the LM317 and it may have some hints, this is a common technique to get higher currents from the same regulator particularly when more current that the package could physically handle anyway.

author: bogdan2013
author_rank: Regular Contributor
timestamp: April 21, 2013, 09:22:41 pm
content: I found something :http://www.reuk.co.uk/OtherImages/lm317t-pnp-pass-transistor-voltage-regulator.jpg

author: Paul Moir
author_rank: Frequent Contributor
timestamp: April 21, 2013, 09:27:59 pm
content: That's the idea.If you're still in the design phase, you might think about something like the ancient LM723, which has a wimpy pass transistor but is pretty easily setup for external ones. Plus current limiting is simple.Have a look at:http://www.thebackshed.com/forum/forum_posts.asp?TID=2249&PN=2&TPN=1

author: mariush
author_rank: Super Contributor
timestamp: April 21, 2013, 09:33:38 pm
content: Seehttp://www.ti.com/lit/ds/symlink/lm117.pdf(it's same datasheet for lm117 and lm317)Typical Applications, page 17-25, you have several designs that all do more current than a single lm317.

author: bogdan2013
author_rank: Regular Contributor
timestamp: April 21, 2013, 09:41:19 pm
content: @PaulIs a old PSU and I want to modify it .
Question about LT3081 - Page 1
Forum section: electronics / beginners

author: TiTanerCZE
author_rank: Contributor
timestamp: September 27, 2017, 08:49:19 pm
content: Hi, I have a question about LT3081. Set pin is connected to internat opamp. Set current is on this pin, fixed current is 50uA, but i dont want to control this circuit using resistor, or digital one. I want to control this IC using DAC, or using uC.I cant find any simple project done using this LT3081.Is it possible?This is what i came whit:

author: TiTanerCZE
author_rank: Contributor
timestamp: September 27, 2017, 08:52:13 pm
content: OPAMP is random...

author: BU508A
author_rank: Super Contributor
timestamp: September 27, 2017, 09:38:54 pm
content: Have you seen this?http://www.linear.com/solutions/1256Maybe you'll find something in the related documents on the LT website.

author: newbrain
author_rank: Super Contributor
timestamp: September 27, 2017, 09:53:33 pm
content: Page 18 of thedatasheet:QuoteIt's possible, and works as expected: Dave'sµSupplydoes just that (with a 3080) and my home built PSU also (with a 3083).You will need to provide some gain (using the op-amp) to scale the DAC output (usually 3.3 or 5V) to the desired range.

author: RustyShackleford
author_rank: Regular Contributor
timestamp: November 18, 2017, 06:50:11 pm
content: QuoteI've done it this way, and it works fine. It also sidesteps the issue of leakage around the SET pin (discussed on p.12 of LT3081 datasheet).I'm curious why you don't want to use a digital resistor though (though I guess the quote explains on likely reason :-) ). I am building a multi-channel digitally-adjustable current source around an LT3081, and am torn between using a digital pot or a DAC (on the SET pin). The DAC has the aforementioned advantages, but in addition to needing to scale the voltage, you probably will also need to buffer it (to sink the 50ua from the SET pin); of course a single opamp can do both. A digital pot (e.g.http://www.mouser.com/ds/2/268/22059a-51937.pdf) sidesteps this, and all you need to drive is an SPI interface.
Question about matching network - Page 1
Forum section: electronics / beginners

author: promach
author_rank: Frequent Contributor
timestamp: October 06, 2017, 05:25:28 am
content: I am trying to apply circuit (c) tohttps://www.um.edu.mt/__data/assets/pdf_file/0010/113500/Matching_Networks.pdf#page=7using the formula Re(Zin) = L1/(C1*RL) computed below with RL = 75 ohm and Re(Zin) = 150 ohmHowever when I did the calculation, it does not fit with the values of L=6.12 nH and C=0.73 pF given, meaning the antenna impedance is not matched with transmitter side. Which part of calculation did I mess up ?

author: Benta
author_rank: Super Contributor
timestamp: October 06, 2017, 04:02:03 pm
content: Your screenprint unfortunately uses a font where there's no difference between "1" and "L" (lowercase)

author: promach
author_rank: Frequent Contributor
timestamp: October 07, 2017, 09:05:19 am
content: @Benta: Modified as requested.

author: promach
author_rank: Frequent Contributor
timestamp: October 07, 2017, 09:50:45 am
content: the formula needs to be modified for the case ofcomplex load.Do I just put R=a+%i*b which implies complex load into the Zin equation ?

author: Benta
author_rank: Super Contributor
timestamp: October 07, 2017, 11:02:53 am
content: This is a long way back, but IIRC, the matching network has to provide the complex conjugate load to the output (for maximum power transfer).You have 150 + j75, so the input impedance should be 150 - j75. Same goes for the antenna.
Question about MCU USB connection - Page 1
Forum section: electronics / beginners

author: baoshi
author_rank: Regular Contributor
timestamp: November 27, 2012, 05:33:44 am
content: Hi,Recently I'm building a CNC machine. There are two PCBs involved, one being a PIC18F4550 micro controller and the other 3-way step motor driver. For the original design the PIC18F4550 connects to computer via USB, and also get powered from there. The PIC connects to step motor driver using opto-isolation to avoid any interferences from the high power step motors. This configuration works. (Original.png).During a later thought I wish the PIC can run by itself using a simple control pad, so I added a 24-5V DC/DC switch regulator (TPS40007) and tap into the bulky 24V meanwell SMPS which also powers the step motors. I assume I did proper filtering with a Sanyo solid cap and MLCC. The original 5V from USB was disconnected. My test was on a desktop PC and the whole system works just fine. (Desktop Working.png)But when I try control the same system using a laptop (running on battery), the USB communication fails frequently and the program on the MCU seems to run into mass. (Laptop Non-working.png)I have learned ground loop issues with USB peripherals but I didn't expect it to happen for battery powered host.So what 's wrong with my design?Thanks

author: mazurov
author_rank: Frequent Contributor
timestamp: November 27, 2012, 06:55:00 am
content: By USB spec, you must have VBUS connection between USB host and peripheral. If you want your PIC to be self-powered, see the PIC18F4550 datasheet starting at page 186.

author: baoshi
author_rank: Regular Contributor
timestamp: November 27, 2012, 09:28:46 am
content: Quote from: mazurov on November 27, 2012, 06:55:00 amThanks mazurov.But a look at the datasheet seems the only thing I'm missing is an indication line to inform the MCU that USB is connected, which in my case I do not think I need that line.The current issue is that the results between desktop USB connection and laptop USB are inconsistent, where the only difference I can see is that the desktop is grounded while the laptop not.

author: Baliszoft
author_rank: Frequent Contributor
timestamp: November 27, 2012, 10:19:15 am
content: Quote from: baoshi on November 27, 2012, 09:28:46 amUSB is easy for the end users, but not for the developers. At first, if you are using the internal VREG of the PIC, then you have to connect a cap (f.eg 220nF to gnd) to the VUSB pin for its VREG to work properly. Then you should check the firmware (if not written by you), if this attach sense signal is used in it, because if yes and you do not provide this signal that's a problem. VUSB pin *should* be connected to an input pin (with current limiting & pulldown) and the firmware should act accordingly its state.