hybridfree/eevblog-posts huggingface dataset:
Combining USB and buck converter power rails - Page 1
Forum section: electronics / beginners

author: mbless
author_rank: Regular Contributor
timestamp: January 18, 2017, 10:50:09 pm
content: Hello,I'm working on a BLDC motor controller using a STM32F446 for the MCU and a DRV8301 (http://www.ti.com/lit/ds/symlink/drv8301.pdf) for the gate driver. The DRV8301 has a built-in buck converter that I'm using to bring the motor source (24V) down to 5V or 3v3 depending on the best solution. I'm will be communicating with the MCU via an embedded FTDI chip. I want to be able to flash the MCU and test some peripherals without hooking up the 24V source needed for the buck converter, so ideally I'd just use the 5V from USB with a 3v3 LDO. But when the 24V source is plugged in, I want the buck converter output to take preference. Given that, I think these are my two options, but I don't fully understand how to implement either of them.1. Set the output of the buck converter to 5V, and run the USB 5V through a Schottky diode connecting to the buck converter 5V. That combined 5V rail would go to a 3v3 LDO. I think this would work because the forward voltage of the diode would drop the USB 5V to 4.5-4.7, putting it below the buck converter output which would then supply all the power. What I don't know is if it is bad to apply the USB 5V to the output of the buck converter when the 24V isn't present.2. Set the output of the buck converter to 3v3. From the perspective of powering the system independent of USB this works because the only 5V peripheral is the Hall effect sensor which can run off the 24V source. The issue I see with this method is that I don't see how to make the 3v3 preferential to the USB 5V. Is there some sort of "switch" that can automatically activated when the 24V source is present?Hopefully I explained my dilemma well. Please offer any suggestions or corrections to my assumptions! I'm here to learn
Combining USB PowerBanks - Page 1
Forum section: electronics / beginners

author: prashsax
author_rank: Newbie
timestamp: November 03, 2014, 07:55:13 am
content: Hi Experts,I have two 2600mah power banks.Is it possible to increase output current, if I join output terminal of both circuit together in parallel.As both these circuit board gives out 5v/1Amp each, would I be able to get 5v/2Amp output.Similarly, I will also connect USB input terminal together in parallel, so both cells will charge simultaneously.Does, joining output harm my powerbank circuit or my device?Please advice.ThanksPrashsax

author: German_EE
author_rank: Super Contributor
timestamp: November 03, 2014, 09:45:54 am
content: Joining the outputs together to double the load current will not be a problem. Use either a 0,1 ohm resistor or a schottky diode on each battery so that the current draw will be better balanced.The batteries should however be charged individually.
Comfortable tool to calculate resistors: EqResistors 2.0 - Page 1
Forum section: electronics / beginners

author: LEECH666
author_rank: Frequent Contributor
timestamp: December 08, 2012, 12:40:52 am
content: Hi, I just thought I provide a backup mirror of this nifty tool.The original source of this tool has been gone for several month now, and there seems to be no other mirror. Luckily I still had a copy on my hard drive.It's comes in handy when you want to calculate a specific resistor value which you don't have in your inventory.Anyway here is the download link:'http://www.mediafire.com/?m6x3kz39p05zwhgOriginal source:http://www.electronics-lab.com/blog/?p=16210http://pamarvin.ucoz.com/(currently dead)All credit for this tool go to the original author.Cheers,Florian
Comments on Breakout board for STM32 - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: April 23, 2016, 12:23:43 pm
content: I have made a schematic of breakout board for STM32F205RBT6.I will make a square board with all pins from MCU coming out to outer 2.5mm headers.1. Symbols in schemtaic with name "Nx", are bascially are small jumpers with 0805 size.2. I have some odd debug connector here. I have made this kind of connection for other boards so that's not a problem.Any comments/suggestions on ckt.
Commercial Advice on Import of Scientific Equipment - Cabling Standards - Page 1
Forum section: electronics / beginners

author: dankind
author_rank: Newbie
timestamp: April 03, 2019, 09:48:05 pm
content: Hello,As a total newbie i am unsure whether i can post this or whether it is in the right location.Essentially i am seeking to obtain contact details of an engineer or engineering company that can assist with professional services/advice in relation to the requirements in Australia for equipment cabling (power) when items are imported for resale from overseas.An example for us is the import of scientific equipment for sale, where equipment power leads require a new AU style plug, yet the lead itself has euro color codes (L=Black, N=Black, E=Green) or more frequently three phase where L1=Black, labeled L1, L2=Black, labeled L2 etc.Thanks in advance!Dan
Commercial Current source application and customer modification - Page 1
Forum section: electronics / beginners

author: Excavatoree
author_rank: Frequent Contributor
timestamp: September 21, 2012, 02:32:30 pm
content: Our company uses a "black box" current source to control a proportional solenoid valve. (controls hydraulic flow proportional to solenoid current.)The black box is a module built into a control grip, with a thumb switch. The current output is proportional to switch position. The current out is 0-1.4 amperes.The solenoid valves are about 3 ohms each, so the module must supply 4.2 volts at full current. The power supply to the module is 12 volts, so this is no problem.We have a customer that doesn't want full hydraulic flow. He has inserted a resistor in series with the solenoid valve, bringing the total resistance to 11 ohms. Now, the module will attempt to produce 1.4 amperes, but this would require 15.4 volts. This is greater than the supply voltage, so the current drops.The customer loves it, but our service guys are worried that it will "burn out the module."I say if the module is well designed, it should be no problem, even though the correct solution would be to buy a module with a lower output current. The vendor never considered this, and didn't provide a trimmer for such occasions.Does anyone have any thoughts/advice?

author: SeanB
author_rank: Super Contributor
timestamp: September 21, 2012, 03:13:41 pm
content: Should not harm it, though a more elegant solution would be a shunt resistor across the coil, so that only a portion of the current flows in the coil and the rest in the resistor. You might have to make the resistor out of copper to have a similar TC to the coil, though using a nichrome wirewound 10W resistor will do the job, with only a slight difference in flow between hot and cold. This will give the control the full range of operation again.Add the 8R2 resistor instead of in series to be in parallel with the coil. This should give nearly the right full scale value, and will allow you to control ther flow using the full range of control, as opposed to now where you only use about 2/3 of the control before it stops responding.
Commercial name for common headers  - Page 1
Forum section: electronics / beginners

author: Back2Volts
author_rank: Unknown
timestamp: September 14, 2016, 07:55:26 pm
content: Just curious. I am having a hard time searching on Mouser / Digikey / Newark for common headers which in eBay/Alixpress are normally referred to as male/female pin headers, likehttp://www.aliexpress.com/item-img/10PCS-16-Pin-1x16P-2-54mm-Long-Leg-11mm-Single-Row-Female-Straight-Header-Pin/32720206598.html?spm=2114.10010108.1000017.1.otUPryI know in a purist sense, the female would not be pins, but again...

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: September 14, 2016, 07:58:17 pm
content: try -http://www.mouser.com/Connectors/Headers-Wire-Housings/_/N-ay0lo?P=1yzmo3uZ1yy4gdp&Keyword=header&FS=True

author: Back2Volts
author_rank: Unknown
timestamp: September 14, 2016, 11:37:24 pm
content: Quote from: Jeff_Birt on September 14, 2016, 07:58:17 pmJeff, thanks for helping, but it is odd. If I select "Stocked" and "Socket(Female)" for Gender, and then do "Apply filters" I get only 12 parts, and if I further narrow it to 2.54mm there are only 2 parts. It does not make any sense to me.

author: Jeff_Birt
author_rank: Regular Contributor
timestamp: September 15, 2016, 12:43:33 am
content: Sometimes the filters do goofy things. I'll sometimes find the part type I want and try to figure out what category it is in and search that category. If that fails I pull out the printed catalog which is much easier to search by picture

author: Brumby
author_rank: Unknown
timestamp: September 15, 2016, 05:14:54 am
content: Quote from: Jeff_Birt on September 15, 2016, 12:43:33 am+1.... and I've seen this on more than one site.
Commodore Amiga 2000 power supply RIFA capacitor value?  - Page 1
Forum section: electronics / beginners

author: Sanxion
author_rank: Contributor
timestamp: July 18, 2024, 05:27:06 pm
content: Hi all,I heard the all too familiar "pop" sound whilst using my A2000 today followed by that dreadful pungent aroma...upon further inspection, I discovered a RIFA capacitor in a very sorry state. From what remains, I can see the lettering "RIFA PME 271 M"...the problem is, I can't see a value.I can't find any schematics that I could use to determine it's value, so my question is, what value capacitor should I replace it with? I do have some TENTA 0.1uF 40/100/21...Thanks!

author: Vovk_Z
author_rank: Super Contributor
timestamp: July 19, 2024, 04:10:19 pm
content: If it was placed across mains then accurate value doesn't matter, so you may use a cap of a similar size.

author: MarkT
author_rank: Frequent Contributor
timestamp: July 19, 2024, 07:47:42 pm
content: This a known problem called "RIFA madness" - this style of RIFA cap absorbs moisture, swells and then explodes - it uses a paper dielectric. If you see any in equipment replace them before this happens!
common base PNP attenuation? - Page 1
Forum section: electronics / beginners

author: electrolust
author_rank: Unknown
timestamp: November 07, 2015, 07:31:30 am
content: http://www.electronics-tutorials.ws/transistor/tran_1.htmlAbout 1/3 down the page, "current gain for this type of circuit of “1” (unity) or less, in other words the common base configuration “attenuates” the input signal."Um, when we talk about attenuating a signal do we care about the current? I thought attenuation was related to voltage? In the following section, "Common Base Voltage Gain", they go on to say that this is an amplifier circuit, used in mic pre-amps and RF.uh, so which is it?

author: Whales
author_rank: Super Contributor
timestamp: November 07, 2015, 10:03:36 am
content: A signal is a concept. Voltage is one method of representing a signal in real life, as is current, light intensity (fibre optic) and so on. Attenuation == reducing.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 07, 2015, 10:28:54 am
content: A reduction in current means little, just as a reduction in voltage means little:The impedance (ratio of voltage to current) is vastly different on both sides (by a factor of perhaps 10^4), and so the power gain can be quite high.If you have a situation where the impedance ratio is needed, this is an appropriate circuit to use. An example might be, an RF amplifier front end, going from a 50 ohm transmission line, to an internal ~kohms impedance which might be part of a frequency-selective filter.So, it is what it is. Do you *need* current gain? Do you need voltage gain? Do you need some of both? These are the questions that drive the design process.Tim

author: mikerj
author_rank: Super Contributor
timestamp: November 07, 2015, 12:22:29 pm
content: Quote from: electrolust on November 07, 2015, 07:31:30 amWe care about power, which is a combination of voltage and current (or equivalently voltage and impedance). If only voltage was important then you could use a transformer to amplify signals, which of course you can't.

author: Zero999
author_rank: Super Contributor
timestamp: November 07, 2015, 02:14:52 pm
content: Emitter follower = voltage attenuated, current amplified. If the load is a low impedance and the input fairly high impedance then there will be plenty of power gain.Common base = voltage amplified, current attenuated. If the load is a high impedance and the input a low impedance then there will be plenty of power gain.
Common BGA stencill size and ball soldier size? - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: March 08, 2014, 08:32:20 pm
content: For a beginner, if I'm going to reball some notebook video chips and computer south bridges. What reballing stencil size do I need -- width length, hole size? What size ball soldier do I need? What is the most common chip sizes I'll encounter, as far as width and length?I'll buy stuff as I go, I guess. But I need something to start with.
Common Cathode Diode? - Page 1
Forum section: electronics / beginners

author: Axtman
author_rank: Regular Contributor
timestamp: June 26, 2023, 03:24:54 am
content: I recently bought a bunch of components in a parts lot. As I was sorting thru the components I cam across something I have never encountered in my electronics hobby.What are common cathode diodes and what are they used for? Thanks.

author: BillyO
author_rank: Super Contributor
timestamp: June 26, 2023, 04:50:09 am
content: There is no such thing as a single common cathode diode. Are you talking about some sort of diode array or an LED array?How many pins do these things have?Can you provide a picture and/or part number?

author: Zero999
author_rank: Super Contributor
timestamp: June 26, 2023, 08:14:02 am
content: It's common to find two diodes connected common cathode in a TO-220 package. They're often used with a transformer, to make full wave rectifier. Nowadays his is more often used in a switched mode, than linear power supply.

author: mengfei
author_rank: Regular Contributor
timestamp: June 26, 2023, 09:25:34 am
content: Just did a bunch of them for our svndblib both common K & common A in an SOT-23 package
Common Emitter gain and frequency response video - Page 1
Forum section: electronics / beginners

author: w2aew
author_rank: Super Contributor
timestamp: November 21, 2012, 05:39:14 pm
content: Here's a little video I did, by request, to briefly discuss the common emitter amplifier. Specifically, it addresses the gain and bandwidth calculations and bench verification of the calculations. Please note that this video is not intended to be a tutorial on BJT amplifier design, but just to briefly present these topics. For a more detailed design-related video, please check out Shahriar's excellent video on the topic on TheSignalPathBlog youtube channel.Here's my video, for those interested:
Common ground between ATX power supplies - Page 1
Forum section: electronics / beginners

author: bitman
author_rank: Unknown
timestamp: December 05, 2020, 11:30:34 pm
content: On my bench power supply I have common ground. I even connect one bench supply + to another's - to get multiple voltages for the same project. It works, I know how and it's very helpful.But I'm in the need to temporary add a second ATX power supply to a computer while I add more drives to migrate off the existing ones. The current supply is too small to handle this, so my plan is to just power the new drives temporarily from a second supply, move the data, remove the old ones and go back to just one PSU. But I need the two supplies to have common ground as the drives connect to the same motherboard. Is there anything on a standard ATX power supply that would prevent this from happening? Ie. if I connect the ground lines from one to the other, will this cause some safety in the ATX supply to go "nope - cannot do that"?Perhaps the better question is: How can I tell without risking blowing both supplies up in the process?

author: msat
author_rank: Regular Contributor
timestamp: December 05, 2020, 11:50:52 pm
content: It should work "in theory". I wouldn't rely on the grounds being shared strictly through the IEC power cables, though. Instead, find a better way to bond the PSUs together. Then check the resistance through the ground terminals on drive power connectors between the supplies, to ensure there's no unusually high resistance. But I wouldn't try it on my word alone because I've never tried it myself.

author: golden_labels
author_rank: Super Contributor
timestamp: December 06, 2020, 01:08:22 am
content: For short tests: I was doing that many times in my life with no issues. As a permanent solution: I would be careful, but this is not a “will not work”.For power hungry components the current goes through the same plug both directions, so each of them is always powered from a single PSU. The ground connection is there mostly to provide common reference for signals. The main concern are motherboards with multiple connectors and PCI-E cards, as they share power lines. Be sure to connect them all to a single PSU.

author: m k
author_rank: Super Contributor
timestamp: December 07, 2020, 11:08:14 am
content: I've temporarily used second PSU by just putting it on the floor of a standing metal case.It should be totally ok if you bolt metal cases together, with or without the decent wire.
Common ground for 2 eval boards with different powering - Page 1
Forum section: electronics / beginners

author: raff5184
author_rank: Regular Contributor
timestamp: May 18, 2019, 01:38:49 am
content: Hi,I have two eval boards. One for an FPGA and the other for an ADC. The two devices communicate via SPI. The FPGA board is powered from a PC to which it is connected via USB; the ADC board is powered with a DC voltage supply.1. I think that the two different grounds might create a problem since the SPI signals are not referenced to the same GND. How should I connect the two boards and reference them to the same ground?2. The FPGA has an analog GND and a digital GND, and I saw that they are at the same potential. So I deduced that they are connected together. So is grounding either the AGND or the DGND the same?Thanks

author: sokoloff
author_rank: Super Contributor
timestamp: May 18, 2019, 01:43:29 am
content: I’d power the ADC board from a floating battery-based supply.

author: raff5184
author_rank: Regular Contributor
timestamp: May 18, 2019, 01:49:19 am
content: Thanks, why is it better?

author: sokoloff
author_rank: Super Contributor
timestamp: May 18, 2019, 04:20:55 pm
content: It requires the least amount of thought, testing, and precaution to provide a ground-potential-free system.Without looking at the boards or knowing anything about them, you know that an isolated supply will float to whatever the PC/USB ground is. You can then safely tie the grounds together and not have two different earth-references that might be pulling their respective ground to a different reference. (Now, in all likelihood, you'd be fine to just naively hook up any two old supplies and tie the grounds together, but by using a battery, you take one variable out of the equation entirely.)
Common ground for voltage doubler and low voltage system? - Page 1
Forum section: electronics / beginners

author: peter123
author_rank: Newbie
timestamp: October 27, 2014, 10:37:12 pm
content: Greetings,I'm building a system with high voltage supplied from a voltage doubler, and a lower voltage DC supply. The plan is to use a transformer and a rectifier bridge to provide the low voltage DC (see attached schematic). The circuit will be connected to mains power.The output of the voltage doubler and of the rectifier bridge needs a common ground point, because the high voltage will be controlled by the lower voltage using a transistor. Is it okay to hook up the negative terminal of the voltage doubler to that of the rectifier output? I'm scared it will create some kind of ground loop since the potential difference is really high if the nets aren't connected.Regards,Peter

author: vk6zgo
author_rank: Super Contributor
timestamp: October 28, 2014, 07:24:45 am
content: Well,it would work,----- BUT!!If it is designed to be hard wired to the Mains Supply, enclosed in a double insulated enclosure,& dedicated to supply power to some device with no wired connections to the rest of the world,other than the incoming Mains,it would be OK.----,of course,all dependent on the approval of the Regulating Authority.Somehow,though,as it is in the "Beginners" section,I doubt if that is the case.As a bench power supply,it has several problems:-(1) Mains Active & Neutralcanbe transposed at power sockets.If they are,Active is connected to your "common ground" on each negative half cycle of the Mains,making it "hot" with respect to Mains Earth------you can get "'zapped"(2) If the situation in (1) exists,& another device with its "common" connected to Mains Earth is connectedto your power supply,the bottom diode of your doubler shorts the Mains supply on negative half cycles ----Goodbye diode!!!(3) If you manage to get your Mains connections correct,& connect another device as in (2),you will short out the bottom capacitor of your voltage doubler---"zap"

author: peter123
author_rank: Newbie
timestamp: October 28, 2014, 07:20:57 pm
content: Thanks for your reply!Do you have any suggestions on how to build a circuit like this in a more proper manner? I'm trying to build a capacitor charger circuit, where the caps of the voltage doubler are charged. Hence the current through the voltage doubler will be quite high (I'm using a current limiting resistor).
Common ground Power supplies vs Power Suppy and DC-DC stepdown converter - Page 1
Forum section: electronics / beginners

author: gefidalgo
author_rank: Newbie
timestamp: August 20, 2025, 05:10:45 pm
content: AS described I am trying to understand if there are any difference or benefit on this two configurations. I have a CNC control board "AXBB-E" that requires two power supplies (one 5V PSU that powers the internal logic of the device, the other 24V PSU powers the isolated ports and the devices connected to it,. On the 24V supply i have also 2 steppers drivers connected and 3 more on a separate 48V PSU. due to space and basically because the 5V power supply only requires 1 amp I added a DC-DC converter at the 24V power supply.My question is if my decision was actually Ok or if I should have added a separate 5V PSU. also if I need to set a common ground between all 3 Power supplies (I understand my 5V PSU now has a common reference point to the 24V PSU as its input is the 24V GND output.

author: BeBuLamar
author_rank: Super Contributor
timestamp: August 20, 2025, 05:39:41 pm
content: Are the 3 GND inputs of the machines connected together internally? If they are then there is no problem if they are not I don't thinks it's a problem either.

author: Seekonk
author_rank: Super Contributor
timestamp: August 21, 2025, 03:36:13 pm
content: There is a lot of junk converters out there with poor regulation. Most DC to DC converters only have enough capacitance to keep them from oscillating. Sudden loads on the 24V can transmit thru to the 5V. Current spikes in the common lead can cause issues. In most cases you are fine. I always add extra capacitance right at 5V load. Extra capacitance on the 24V would be good. If there is a problem. you will find out soon enough.

author: Buriedcode
author_rank: Super Contributor
timestamp: August 22, 2025, 03:32:18 am
content: Quote from: Seekonk on August 21, 2025, 03:36:13 pmI'm quoting the full reply to highlight how important this is. Whilst the actual converter IC's on the DC/DC boards that flood the "cheap" market tend to be rather good, the rest of the circuitry is an after thought and woefully inadequte for any kind of reasonable current application. A 1206 ceramic - or worse, a 0805 - just won't be enough for a reasonable output ripple or sudden load changes.
Common Ground vs Earth Ground in Power Supply - Page 1
Forum section: electronics / beginners

author: Adam60
author_rank: Regular Contributor
timestamp: February 21, 2016, 01:11:33 am
content: I have a quick question regarding voltage measurements on a power supply in a stereo receiver. If I look at the diagram, there is a pin 7 which goes to chassis ground, which I assume means Earth ground in this case. If I look at the rectifier, I would assume the point between Pin D1 and D3 to be the most negative point of the circuit.So the question is, to arrive at the voltage values that they have given, do you use the negative side of the rectifier as a reference or do you use Pin 7.On another note, lets say it is an SMPS. Same question although the unit is similar to a laptop adapter. Where do you reference for the COM lead of your DVOM.http://www.kallhovde.com/pioneer/sx-1010sm.pdfPage 57

author: IanB
author_rank: Super Contributor
timestamp: February 21, 2016, 02:00:34 am
content: When voltages are given on a circuit diagram these are referenced to the common rail or "circuit ground". This is where you should put the black lead of your meter when making measurements.Often the common rail will be connected to the chassis (but it doesn't need to be), and sometimes the common rail will also be connected to the earth safety ground (e.g. for noise rejection and signal quality), but it doesn't have to be.Typically, anywhere on the schematic that shows the chassis ground symbol will be a suitable place to put the black meter lead.

author: Shock
author_rank: Super Contributor
timestamp: February 21, 2016, 07:11:47 am
content: GRD (7) is connected to the negative side of a reservoir/smoothing capacitor C18 on the 13.4v rail (8.) So using that same technique see if you can deduce from the schematic if GRD is common to all those voltage rails. You can verify this using your mutimeter as well, keep in mind this circuit has high voltages.Another way of looking at it is you should see 112v and 48v DC across the +/-56v and +/-24v rails, indicating they are tied by a common point (assuming that power supply is running and functional). Wondering if +56v and -24v have a common point? If they did take a guess at what voltage you would see between them.For an SMPS on the output you can use the same technique to look if the negative side of the filter caps are common. When you don't have a schematic you can can "ohm out" (discharge and disconnect your circuit first) and trace that side of the circuit right to the DC plug or connectors. If you get sensible measurements between that and voltage rails you can deduce if it's common.Some SMPS may need a load or be started before you can measure their output.

author: Adam60
author_rank: Regular Contributor
timestamp: February 21, 2016, 11:41:53 pm
content: Thank you. Both answers seem sensible and I will approach circuits using these ideals. I know that voltage is a pressure difference netween two points, but I just wasn't sure what they would use for a reference point in an older unit like this.
Common ICs, Caps, and Other Components? - Page 1
Forum section: electronics / beginners

author: Brown
author_rank: Contributor
timestamp: December 01, 2013, 08:50:27 pm
content: Hello All! I have a questions to ask, what are some common components I should have in my parts bin? Thanks!

author: mariush
author_rank: Super Contributor
timestamp: December 01, 2013, 08:53:53 pm
content: Please search the forum, there were at least 3-4 threads where people talked in detail about what parts everyone should stock in their parts bin.

author: Brown
author_rank: Contributor
timestamp: December 01, 2013, 08:56:43 pm
content: Thanks, I will

author: mariush
author_rank: Super Contributor
timestamp: December 01, 2013, 09:11:28 pm
content: See at least these two threads :common-generic-cheap-easy-to-find-parts :https://www.eevblog.com/forum/beginners/common-generic-cheap-easy-to-find-parts/msg286033/#msg286033what-parts-to-get-at-the-store :https://www.eevblog.com/forum/beginners/what-parts-to-get-at-the-store/Just don't want you to think we're ignoring beginners here, or that we're rude... it's just something that was thoroughly discussed before.

author: Stonent
author_rank: Super Contributor
timestamp: December 01, 2013, 09:12:29 pm
content: Tayda electronics is a good way to stock up once you have your list. Usually the latter part of the month they post a 15% discount code on their facebook page.

author: Brown
author_rank: Contributor
timestamp: December 01, 2013, 10:17:41 pm
content: I LOVE Tayda! That's where I started to buy my components. Also I love the EEVBlog community, I don't think they're rude in anyway. Thanks guys!
Common Inductor Values for Switchmode Regulators - Page 1
Forum section: electronics / beginners

author: nathanpc
author_rank: Unknown
timestamp: July 28, 2013, 06:00:42 pm
content: I'm going to start working with some switchmode regulators in the couple weeks, just playing around, taking some measurements under different loads, in other words learning how to properly use them. For this I'll need some inductors, so I would like to know which are the most common values of inductors in these circuits so I can play around with different values and see how they affect the efficiency and other things. Most of the designs I'm going to try are boost for voltages like 3.3V, 5V to 9V or maybe a bit more.Any suggestions?

author: lgbeno
author_rank: Frequent Contributor
timestamp: July 28, 2013, 07:23:44 pm
content: This is probably going to be highly dependent on your switch reg and switching frequency. Just a quick swag but I'd say for a low MHz freq, 1uH to 15uH would be a good start.Truthfully though physical hardware is nice and all but unless you want to spend a ton of time building and measuring stuff, this is something better to experiment with in simulation.Sent from my iPhone using Tapatalk 2

author: c4757p
author_rank: Super Contributor
timestamp: July 28, 2013, 07:34:06 pm
content: I'd probably go with a factor of ten lower frequency and a factor of ten higher inductance.Sent from my living room using my keyboard

author: szhighstar
author_rank: Contributor
timestamp: July 28, 2013, 11:08:22 pm
content: is it commone mode choke or difference mode choke or storage emergy inductor or filter and so on? pin through or SMD configuration?

author: jebcom
author_rank: Regular Contributor
timestamp: July 28, 2013, 11:24:42 pm
content: Have you checked the data sheets? For example, the LM2596 data sheethttp://www.ti.com/lit/ds/symlink/lm2596.pdfdevotes a lot of space to selecting appropriate components -- not only the inductor, but input and output capacitor values and more importantly ESR, catch diode considerations, and even tips on board layout.
Common <1 Ohm resistor to have in stock - Page 1
Forum section: electronics / beginners

author: Moriambar
author_rank: Unknown
timestamp: October 02, 2023, 07:09:41 pm
content: Hi there.Tricky question.I built my resistor stockpile mostly via a 1% amazon kit, and then I replenish them as needed when I use them. They span from 1R to 10M. This was awesome: I always have the right resistor value for my project.I see, though, that many SMPS/Dc-dc converters ask for some shunt feedback resistors of various values but all less of one ohm. I'd like to have a few in stock, but I don't know which values are commonly used or even which power ratings I should choose*. I know that those will mostly depend on the voltages involved but I never work outside the 3.3V-12V range (which is large, I know).I guess I'm asking whether it's possible to build a small stockpile of some of the most used resistor values in that range.Can you help or should I go the "I need it now, buy a ton of them for later use" way?Cheers* Unless there's some standard there, I think I'll have to post a specific question on this

author: u666sa
author_rank: Frequent Contributor
timestamp: October 02, 2023, 07:20:31 pm
content: You should try searching aliexpress for resistor book. You get an entire book with mostly everything.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 02, 2023, 07:27:48 pm
content: Shunt resistors for current limit vary quite a lot, not much standard value there. Some kind of common values are around 0.22 to 0.33 ohm as the emitter resistors used with 2N3055 and similar size transistors when using some of them in parallel (e.g. in a linear power supply of audio amplifier). These usually need to be a little higher power to carry a few amps.

author: Zero999
author_rank: Super Contributor
timestamp: October 02, 2023, 07:38:13 pm
content: Just go for E3 values, 0.1, 0.22, 0.47, or the nearest ones you can get i.e. 0.1, 0.2, 0.5.

author: CaptDon
author_rank: Super Contributor
timestamp: October 02, 2023, 08:15:06 pm
content: I keep the old standard .1, .15, .18, .22, .27, .33, .39, .47, .51, .56, .68, .75, and .82 on hand in 1/2 watt, 1 watt, 2 watt and 5 watt. All in the flameproof packages! I have an inventory list to know what is on hand and what I need. When I can find them at ham radio hamfests I stock up usually at cheap prices. I mostly need them for amplifier repair but I am also an experimenter and it is just handy to know I have them. I lucked out several times when companies I worked for decided to downsize their inventories (at the suggestion of the six sigma dimwits). One of the places I worked for closed our local shop and moved to North Carolina. They didn't want to pay to move most of the gear and everything marked with a red tag (dispose) went home with me including thousands of pre-sorted resistors. I emptied each drawer and divider one by one into individual plastic 'snack bags'.
Common mode chokes for signal lines and comms lines - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: July 19, 2021, 05:22:45 pm
content: Hi,For helping to pass radiated emissions to EN55032...When you've got comms and signal lines exiting/entering a PCB via connectors, which is your favourite family of common mode chokes?I am thinking of something with NiZn ferrite, or nanocrystalline.

author: Terry Bites
author_rank: Super Contributor
timestamp: July 21, 2021, 03:29:18 pm
content: It depends on your current and voltage rating and the frequency range you'd like to supress. I usually go to coilcraft or first because of their useful calcultion tools. But then I'm not in mass production.Its always a bit wierd that makers of these devices specify them with 50R source and load- which is not very likely!You need to understand your sources of EMC before you can squash them. There's is no easy fix.
Common Mode filter Values - Page 1
Forum section: electronics / beginners

author: alhoop
author_rank: Contributor
timestamp: April 16, 2015, 05:02:23 am
content: I need to know what values to change the capacitors to in the pictured filter so that it would filterthe same Freq(s) if the inductor values were changed to 12 mhys.Is there a program to find different values in such a filter?TNXAl

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 16, 2015, 06:50:37 am
content: The X type (line to line) caps don't affect the common mode response, and there's no common mode path indicated back to your circuit. Is that little connection point thing actually connected to circuit, chassis or output ground..??Also, those resistors are miliohms..??Tim

author: alhoop
author_rank: Contributor
timestamp: April 16, 2015, 11:52:53 am
content: Tim:Thanks for the response. Corrected/added info to the drawing. I just assumedthat this was a common mode filter. Actually Tektronix lists every component inthe drawing as being part of a RFI filter.Al

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 16, 2015, 06:32:45 pm
content: And the caps in uF?So this goes between the line (or perhaps a power entry module?) and something inside? Why does the one cap go to +5 and not circuit ground??Very crudely speaking, the caps can all be increased proportionally, but the X (line-to-line) caps depend on the leakage inductance of the CMC part, which in general can vary independently of the common mode inductance value; and the Y (line-to-ground) caps can't total more than about 0.01uF or the line-to-ground leakage (at line frequency) can be dangerously high. And the performance of the filter depends greatly on the impedances in the circuit, so that any random component choice may work or not...If you're replacing things, the consequences are not fatal; you would need a test lab to verify if it's doing its job within decibels or not. If you don't have sensitive equipment around, you might not even notice a complete lack of filtering components altogether.Tim

author: alhoop
author_rank: Contributor
timestamp: April 17, 2015, 02:15:32 pm
content: Quote from: T3sl4co1l on April 16, 2015, 06:50:37 amTim:I think you are correct - after further study it seems that the choke(s) in the circuit are wired on a common core as a differential filterand not common mode. In my 60 years in electronics(no transistor study in my first electronics school, too soon after Roswell -first transistor I saw was in an intercom on a P2V Neptune) I have always taken line filters for granted.You are also right in assuming I don't have any means to test their effectiveness. Guess I will go with 12mhy and hope.PS- I have seen x capacitors with a value of 0.1 ufd.Al
common mode filtering - Page 1
Forum section: electronics / beginners

author: sdouble
author_rank: Frequent Contributor
timestamp: December 23, 2016, 04:56:03 pm
content: Hi Guys,I guess , I'm in the newbie section. Perfect, here is a newbie question /I power (really sensitive) preamps with a positive and a negative rail : + 6V and -2V.I have a DP832 to provide me with the 2 voltages. I connect the DP832 to a 2 wire Lemo cable. THe cable is properly shieded. I fix the ground directly at the DP832 output : 2 poles of the PSU are connected to the braid of the cables. I need to mention that the cable and the preamp will operate in a crapy EM envronment : RF cavities, Primary and Turbo pumps everywhere.. really dirty.THe cable will reach my equipment motherboard and I would like to proceed to a common mode filtering there.I'm interested in the frequency range : 50kHz -> 5 MHz.Now, my question :should I use 2 common filters (1 rail and ground for each) and just one filter connecting direcly the 2 rails.I guess that the 1st option is correct... but not really sure.Any suggestion on the part I should use ?THe current sucked is pretty low : less than 1 Amp.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 23, 2016, 05:37:22 pm
content: One could use two separate filter (the more normal current compensated inductor) or one special common mode filter made for three lines. This a single core with 3 coils on it. They are available, but not very common and not so much versions to choose from.

author: tatus1969
author_rank: Super Contributor
timestamp: December 23, 2016, 08:29:42 pm
content: In such a noisy environment you'll likely have noise on the cable shield as well, which means that you don't have a reference that you can eliminate incoming RF against. I would realize all communication with differential twisted pair signaling, use one additional twisted pair for the two supplies, add common mode chokes for all pairs at both ends, and add additional low pass filtering (C - Ferrite - C in a PI configuration) on all ends where possible.

author: sdouble
author_rank: Frequent Contributor
timestamp: December 23, 2016, 09:47:49 pm
content: thanks to both of you for your answers.I'll look for a 3 line common mode filter. Could not find any yet, but we'll see.The preamp outputs are filtered. RF should not be an issue.However, I admit that moving to diff pairs could help.Currently , my output are just single ended LMR240 coax. Those are good quality cables with braid and foil. In addition, I usually wrap the output cables with aluminium foils all together.That way, I could never see on the scope any RF pick up.
Comms cables may carry an earthed ground? - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: July 13, 2021, 05:28:16 pm
content: Hi,Which are the modes of communication (USB etc), that are likely to comprise an earth connection?I mean, supposing you have an offline SMPS on a PCB with an isolated secondary, and this secondary comprises circuitry that receives incoming comms lines from off the board…and suppose that those comms lines involve an earthed connection. -Then what that means is, that the secondary GND of the SMPS has been connected to earth ground…which in turn means that the offline SMPS will need sufficient common mode filtering to manage this….because as you know, offline isolated SMPS’s with earthed secondaries are far more noisy than those that don’t have earthing to their secondary.

author: dmills
author_rank: Super Contributor
timestamp: July 13, 2021, 06:32:59 pm
content: FFS Treez, you been doing electronics work for HOW many years now?Pretty much anything non fibre fits into this category.USB/RS485/GPIO/HDMI/ certainly all fit, even audio ports sometimes fit into this category.Oh and surprisingly, ethernet, it is transformer coupled, but the centre taps on the line side are taken to frame ground via a 1000pF 2kV cap and 75R resistors, negligible at power line frequency, but possibly not up where the diode reverse recovery dances with the leakage in a cheap and shonky switcher....I would argue however that at the point this becomes a concern you should be looking to make a class I product anyway, with mains earth and the comms line screens all bonded, at which point the circulating currents should follow the path of least impedance (smallest loop area) which will likely be some combination of class Y cap on the power supply board and the loop involving the negative output, the chassis and the RFI filter.I have not found that connecting one side of a switcher to ground to be a noise source particularly, but then I don't do completely cost driven design, so I can afford to specify grown up power converters, filtered IECs and pretty much everything I do is class I.
Comms giving EMC failure? - Page 1
Forum section: electronics / beginners

author: Faringdon
author_rank: Super Contributor
timestamp: September 29, 2022, 03:51:28 pm
content: AYK, comms switching edges give EMC fails...Why dont people slow down the transmission frequencies as much as possible, and also use comms protocols where the switching edges are deliberatley damped....by the way, what are those comms protocols wherein the bit edges are damped (slowed up) for EMC reasons?...there must be such a comms protocol?

author: exmadscientist
author_rank: Frequent Contributor
timestamp: September 29, 2022, 05:56:06 pm
content: AYK, it's edge speed that matters most, not frequency....Most people just limit the edge rate with either a capable driver or small filter and it isn't an issue for speeds up through USB High Speed or so. Protocols don't damp edges, drivers do.

author: tggzzz
author_rank: Super Contributor
timestamp: September 29, 2022, 06:05:36 pm
content: Classic treez word salad confusing/conflating several concepts.There are also many concepts he neglected to include. He should start by reading any decent comms theory book; I quite like Sklar'shttps://www.academia.edu/43182727/Digital_Communications_Fundamentals_and_Applications_2nd_Edition_by_Bernard_Sklar

author: Faringdon
author_rank: Super Contributor
timestamp: September 29, 2022, 11:29:46 pm
content: QuoteThanks, though i thought the driver is always "inside the micro" or whatever, and realistically you have no access to it?...Or say, for USB, the driver is in the offtheshelf "USB device", and its not cost effective to make your own driver?...so your stuck with the offtheshelf drivers?

author: coppice
author_rank: Super Contributor
timestamp: September 29, 2022, 11:44:25 pm
content: Quote from: Faringdon on September 29, 2022, 11:29:46 pmThis is why many MCUs now have selectable drive strength on some of their I/O pins. It can really help with EMI when a signal is attached to a long trace that can't be routed very well.
Communicate with an Webcam Chip? - Page 1
Forum section: electronics / beginners

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 14, 2016, 02:49:57 pm
content: HiMy USB Webcam have an OV5640 Chip onboard.It say:Quote from: PDFSo any way to use that?THX!

author: claudevdryst
author_rank: Newbie
timestamp: December 14, 2016, 03:18:30 pm
content: I have searched around on the web and it looks like you can use a standard I2C bus on a microcontroller to communicate with a SCCB interface.Here is a link to to the application note of the SCCB:http://www.ovt.com/download_document.php?type=document&DID=63and I have came across this implementation:http://embeddedprogrammer.blogspot.co.za/2012/07/hacking-ov7670-camera-module-sccb-cheat.htmlHope this gives you some where to start.Claude

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 14, 2016, 03:36:49 pm
content: This is how the Cam Module look like.

author: daveshah
author_rank: Unknown
timestamp: December 14, 2016, 05:19:26 pm
content: What are you trying to do with the camera? The SCCB interface - which is I2C compatible at least from my experience - is only used to set up the config registers in the camera (resolution, format, timings, etc). The OV5640 and other similar camera modules also have a parallel interface (or MIPI CSI-2, a high speed serial interface) which is used to transfer image data.

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 14, 2016, 05:50:41 pm
content: I want play arround and see and learn what is possible to do.And or play with IR (whats why I got the Cam without an IR Filter).And I want to turn the fffuuhhinngg LED off by Software. I hate LED on a Cam. Maybe its possible to turn it off soon so in some days I travel arround and I will get some live stream with the firework on 31.12.

author: fable
author_rank: Regular Contributor
timestamp: December 14, 2016, 07:01:08 pm
content: Quote from: Lord of nothing on December 14, 2016, 03:36:49 pmIt's camera module from laptop ?All of them are USB you just need to figure pinout but that is not a problem.I use two them one as webcam for my desktop pc and other as microscope.Sorry for my bad english

author: Lord of nothing
author_rank: Super Contributor
timestamp: December 14, 2016, 07:08:43 pm
content: QuotenopeQuoteI have an USB Cable vor and it run with the VLC Player.But I hope its possible to send the Data for example to switch for B/W over USB.

author: Lord of nothing
author_rank: Super Contributor
timestamp: January 03, 2017, 09:47:39 pm
content: So I am back home now.Is there any way to control the Camera Chip over USB?Thanks!

author: Lord of nothing
author_rank: Super Contributor
timestamp: May 10, 2017, 01:08:20 pm
content: No idea?